Manufacturing Concepts of Lead Acid Batteries by Vikas Kapre

“This Book is Dedicated to My Wife Eva, Daughters Rumeli, Rajashri " - Ranabir Chakraborty

Manufacturing Concepts of Lead Acid Batteries

By - Ranabir Chakraborty

Manufacturing Concepts of Lead Acid Batteries Copyright@Shree Sai Research Lab. No Part of this Publication May be Reproduced in Any Form Without there Prior Permission of the Author.

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Preface _______________________________________________

There are numerous books on battery technology, quality improvement, but hardly anything on Manufacturing. I have tried to cover this aspect in the book. Every person involved in manufacturing needs some knowledge of battery making. It can be technology, quality systems, equipment and their limitations. Manufacturing anywhere, has huge scope for improvement in efficiency, Quality Standards, Cost, Environment, using bookish knowledge and practical experience. What is given in the book can help in this respect, as I have tried to share my experience too. Managing people is key to success of an organization. With the knowledge on battery making, one can train people and also understand time to time changes. Training people makes them understand their job functions and need not do a job blindly. Every one working in a factory has to contribute to its improvement, continuously. I am sure, the book can further be improved, as time progress, with feedbacks received.

Manufacturing Concepts of Lead Acid Batteries INTRODUCTION Lead-acid battery has been the most commonly used secondary battery i.e. rechargeable battery. While the primary usage has been in automobile, but it has been used for various other applications, including Standby, Motive Power, Un-interrupted Power Supply (UPS), Inverter etc. The reasons, for it to sustain against other battery types are mainly because of: – Higher cranking power needed for starting application – Lower initial cost – Easier to make – Recyclable material Various other battery systems have been developed and are in use also, but lead-acid flag is still flying and would continue to do so in future Technology of making it has changed from pure manual operation to automated systems. Further the material used for making it has undergone changes to give better performance and make it user friendly. The designs of all components have been advanced. There are enormous amount of Research work and published papers on Lead-Acid Battery and various theories have been put forward over the years. The advancements are still continuing. The following pages basically outline the manufacturing process and also include some excerpts from relevant technical papers, as well as some simple tables / guideline, notes for the help / guidance of people associated with its manufacture. While it is very difficult to acknowledge various people / makers from whom many things have been learned / read / taught / practiced, but this book has been made to pass on knowledge gathered during working for more than three decades with Lead-Acid Battery Industry. It is for readers who already have basic knowledge of lead acid battery. I have tried to make it simple. Hope it will be useful. There are names of various Companies, with whom I have come across during my work. I have missed out those with whom I have no experience. So I may please be excused for their omission. During my visits to various factories, I have come across many things good and not so good. Each such visit has given many inputs to enhance understanding the product and how best to make it. Manufacturing Concepts of Lead Acid Batteries

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I started my career with Exide, India, from its factory at Shamnagar to Central Projects to Manufacturing head of all 8 units. Modernizing its plants and doing green field projects were major activities during Projects. Closely worked with Japanese Companies like Shinkobe and Furukawa. Learning from masters of Lead acid battery of Japanese companies and Indian Technologists, Managers, Engineers have been a great opportunity. Have also worked for Exide Srilanka. I am indebted to many learned Technologists, Engineers from many well-known companies from whom I have taken inputs. Post retirement I have worked as consultant with numerous companies in India and neighboring countries. Done few greenfield projects too. The book tries to summarize my thoughts, experiences with some added bookish inputs. Many inputs have been taken from technical papers, to make the book comprehensive for the benefit of battery making people at large. Technology of battery as I understood is how efficiently one creates active surface area in the battery plates. While cranking operation needs millions of micro-pores which gives the highest surface area, but can get choked as sulfates are built up due to discharge reaction. For discharge longer duration plates need to have macro-pores. These pores do not easily get blocked by sulfates and so discharge duration is sustained. Once this is clear along with various inputs needed to achieve these, the battery making is much easily understood. Grid alloys plays an important role and one needs to understand impact of various alloying elements. The book should be useful for all people engaged in battery Industry and can help them to improve from present status. I will be happy to have inputs from readers to enhance my knowledge and do correction where needed. There are likely to be some mistakes and the Reader may please let me know for correction.

- Ranabir Chakraborty Email : chakraborty02@gmail.com Cell : +91-9831425007

Manufacturing Concepts of Lead Acid Batteries

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INDEX Sr. No.

Chapter Name

Page No.

Manufacturing of Lead - Acid Battery, Introduction ________

Alloy Manufacturing ________________________________ 15 l Alloy Making l Blending of Alloys l Pot Construction l Heat Source l Input l Furnace Construction l Pollution Control - Pot l Casting of pigs / ingots l Layout l Calcium Blending

Manufacturing of Oxide ____________________________ 24 l Oxide Making l Red Lead l Pot Oxide Plant l Process l Control l Pot Construction l Oxide Collection & Pollution Control l Oxide Collection & Storage l Mill Oxide l Brief Description of Mills of Various Makes l Sovema l Lih-Shan l Huebach / Pennoroya l Mills From China l Oxide Storage And Conveying System l Mill Sizes l Oxide Quality l Pulverisor l Hazards l Start-up Oxide l Off Grade Oxide l Comparison of Ball Mill Oxide With Pot Oxide l Change In Oxide Parameters in Mill a Alpha and Beta Oxides

Casting of Grids __________________________________ 41 l Gravity Casting l Process of Casting l Hand Casting l Auto Grid Casting Machine l Main Features of The Machine l Casting Machine & Mold l Casting Parameters l Planishing Die l Casting Speed l Grid Collection And Storage l Grid Aging l Cork Spray l Wirtz Mold Spray Coat Procedures l Feed Line & Metal Delivery l Lead Pouring l Mold l Lugs l Ejection And Venting l Gate Portion l Issues in Grid Casting

Continuous Grid Making and Pasting System _____________ 53 l Multi Alloy Strip Caster l Rolled Strip Caster l Expanded Grid Production l Slit & Stretch Type l Progressive Expansion l General Comparisons Between Two Systems l Concast

- Con Roll System

l Continuous

Punching Line

l Issues With Casting Process l Volume

Manufacturing Concepts of Lead Acid Batteries

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Paste Mixing ______________________________________ 63 l Muller Mixers l Paddle Mixers l Constituents of Negative Mix l Constituents of Positive Mix l Temperature Control l Mixing Issues l Basic Mix Calculation l Additives l Expander In Negative Plate l Barium Sulfate l Carbon/ Graphite l Lignin / Sodium Lignosulfonate l Sulphasion Inhibitor l Amount of Expander l Carbon Additives l Tetrabasic Crystal Addition (TBLS) l Addition of Red Lead In Positive l Other Additives l Tubular Positive Additive l Gel Additives l Battery Internals l How to Know Sulfate Start Stop Battery D26 content ? l

Pasting __________________________________________ 76 l Pasting l Grid Feeder l Hopper l Operation l Other Points l Orifice

Paster

l Steel Belt

Paster

l Double

Sided Paster Roller l Cleaning l Skids For Pasted Plates l Flash Drying Oven l Oven l Vertical or Horizontal l Post Flash Drying l Stacking of Continuous Plate Making l Scrap l Drum Paster l Acid Wash l Finishing

Curing and Drying __________________________________ 86 l Curing And Drying l Curing Oven Conditions l What Are Desirable Conditions In Curing? l Post Curing l VRLA

Formation of Plates _________________________________ 91 l Formation of SLI and MC Plates l Soaking l Formation of Negative Plate l Formation of Positive Plate l Crystal Growth l Alpha & Beta PbO2 l Charging of Plates l Tacked And Tackless Formimg l Temperature Control l Charging Amount l Formation of VRLA Plates

10)

Plate Cutting and Brushing ___________________________ 97 l Plate Cutting And

11)

Brushing l Shearing l Brushing

Tubular Plates ____________________________________ 100 l Manufacture

of Tubular Plates l Grids l Tubular Battery of Tubular Plate l Common Tubular Plate Sizes l Spines Can Be As Long As 610mm. l Active Material l Dry Filling l Ammonia Dipping l Application l Construction

l Pickling

Manufacturing Concepts of Lead Acid Batteries

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l Test Results

of Tubular Plate With Different Parameters Filling Paste Filling l Gauntlet or PT Bags l Charging l Formation l Washing & Drying l Wet Filling l Slurry

12)

Assembly of Plates _________________________________ 111 l Assembly

( All Types) l Battery- Wise l Separator-wise Stacking l Machine Stacking l Group Making l Manual Group Burning l Rotary Cast On Strap TBS Cos 5 Or Equivalent l Basic Operation l Automatic Loading And Unloading (Cos-8 Type) l Stacking l Manual

13)

Assembly Line _____________________________________ 120 l Assembly Line (Continued) l Heat Sealed Lines l Short Circuit Tester l Inter Cell Welder l Tip l XY - Weld l Basic Stages of Intercell Welding l Weld Defects l Causes of Weld Failures l Weld Splash or Spit Out l Cold Weld l Cover Fixing l Heat Sealing Machine l Basic Features l Requirements l Variables l Auto Set-up l Criticality l Stages In The Process of Heat Sealing l Effect of Additives In PP Container And Lids l Temperature l Post Sealing Check l Pole Burning l Leak Testing l Epoxy/Glue Line for VRLA Assembly.

14)

Understanding Battery ______________________________ 137 l Understanding Reactions In Automotive Battery Making l Control

of Positive Plate Quality (Tribasic / Tetra Basic) In

SLI. 15)

Jar Formation _____________________________________ 138 l Effect of Sulfuric Acid Reduction In Paste After Jar Formation l Charging of Battery l Key Issues l Acid Filling l Acid Gravity l Charging Area l Charging Method l Completion of Charging l Post Charging l Charging with Acid Circulation System l Two Shot Charging System l Gel Charging System.

16)

Testing of Batteries _________________________________ 146 l Testing of SLI Batteries l Testing For VRLA Types l For Small VRLA 7ah Type, The Testing Can Be l For Automotive Batteries CA And CCA l Reserve Capacity l Shop Floor Quality Management

Manufacturing Concepts of Lead Acid Batteries

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17)

Lead Properties ____________________________________ 150 l Lead l Lead - Antimony Alloy And Its Compounds

18)

l Some

Properties of Lead

Various Metals and Their Influence _____________________ 154 l Cadmium l Antimony l Zinc l Silver l Iron l Silicon l

Bismuth l Nickel l Aluminum l Selenium l Barium l Leadcalcium - Tin Alloys l High Calcium Alloy l Low Calcium Alloy l Observations of Study 19)

Sulfuric Acid _______________________________________ 158 l Storage / Mixing l Specific Gravity of Acid For Different Climates l Typical Material List For A Battery Factory (Small Plant) l Container, Lid, Vent Plugs, Handle, Float Guides l Buffers l Gauntlets l Bottom Bar l Separators l Cork Powder

20)

Energy Management ________________________________ 166 l Charging/Forming Considerations

21)

l Other

Operation Areas

l General

Failures of Battery __________________________________ 171 l Failures

In SLI l Failures In MC l Failures In Inverter In E Rickshaw l Failures In VRLA l Premature Capacity Loss l Positive Plate l Changes In PAM l Alloying Additions To Grid Alloy l Antimony l Tin l AM Density l Plate Structure l Corrosion Layer l Gel & Crystal l Passivation l Failures

22)

5 S _____________________________________________

178

l 5S l Elements

of 5S- Very Simply l PDCA of Improvement Plan l Implementation Follows a P-D-C-A l TPM l 8 TPM Pillars l Benefits of TPM l How To Go About It? l Implementation

23)

SHE, PCB Norms, Ventilation ________________________ l She -

In Lead Acid Battery Industry

184

l Safety l Health

l Environment l Domestic Effluent l Excess Treated Effluent l Plantation & Gardening l Rainwater Harvesting l Pollution

Control Norms In India For Lead-acid Battery Industry l Effluent l Noise Level l Sewage l Emission Air l Ambient

Manufacturing Concepts of Lead Acid Batteries

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Air l Hazardous Land Fill l Exhaust And Ventilation l Design Considerations l Some Guidelines l Effluent Treatment l Lead Poisoning - Physiological Effects 24)

Cost Reduction ____________________________________ 192 l Elements

Costs l Optimum Design Increase l Lead Related l Manufacture On Throughput Basis l Cost Is Often Compared As Cost / Kg or Cost / Ah l Basic Profit And Loss Statement. l That Is What The Business Is About. Making Money l Material Handling And Storage l Storage of Inprocess Materials l Input Materials l Output Items l Labour

25)

of Cost

l Other

l Productivity

Quality Control ____________________________________ 198 l Concepts

of Quality Control l Data Collection l Data Analysis l Tools of Quality Control l Analysis of Histograms l Abnormality Types l Other Statistical Techniques 26)

Battery Sizes ______________________________________ 207 l SLI Batteries

27)

(Nomenclature)

Maintenance Management ___________________________ 209 l Production Plant & Equipment l Utilities l Civil l Disaster Management l Selection or Right Equipment l Installation l Manufacturing Plant And Equipment

28)

Manufacturing Plant _________________________________ 214 Some Summery Points l l Material Plan l Points To Ponder

29)

Edifice Science (Vastu) ______________________________ 218 l East l South -

East

l South -

SW l West - NW l North &

North East 30)

Basics and Key To Achieve That ______________________ 219 l Battery Design l Manufacturing Has A Major Role To Achieve Designed Performance of the battery l Paste Weight Control l Plate Thickness Control l Curing of Plates l Physical Size And Shape of Plates l Strap Casting l Pole Heights l Formation l Jar Formation l Some Summery Points l Key Concepts

Manufacturing Concepts of Lead Acid Batteries

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31)

Some Key Conversion Items _________________________ 222 l Needed

Frequently In Battery Industry

l Conversions

l Volume l Flow l Linear l Weight l Temperature l

Distance Travelled l Duct Diameter l Discharge rate of Battery Gravity C20 at 80’F l Density of Lead and its compounds l Key Concepts 32)

Lead Acid Battery use in Environment Friendly Vehicles ____ 225 Use of l

Gases l Start Stop Application Vehicle l Electric Vehicles E -Rickshaw Rickshaw l Additives l Concern Areas. 33)

Hybrid l

Electric Batteries for El

Layout of Battery Plant _______________________________ 229 l Lead And Alloy l Casting l Aging l Pasting l Curing

And Drying l Plate Cutting And Brushing l Assembly l Charging l Finishing l Packing l Layout l New Plant a basic Issues. l Existing Plant. l Some Basic Concepts. 34)

Manufacturing Plant With 100 / 200 / 500 / 100 Batteries Per Day 233 l Assumptions l Manufacturing Facilities

35)

Lean Management ________________________________

235

l Lean Philosophy l Wastes l Elements

36)

Application Related Inputs __________________________

237

l Equalising Charge l Design Life of 12V Monobloc PP Batteries l Temperature correction factor for Capacity calculation l Battery Capacity Selection

37)

Manufacturing of Quality Products _____________________ 243 l Oxide l Alloy l Antimony( Sb) l Tin (sn) l Copper (cu) l Arsenic Test l Procedure l Grids l Mixing Pasting l Curing l Drying l Assembly l Small Parts

38)

Battery Application Related Question and Answers _______ 253

39)

Battery Application Related Question and Answers _______ 253

Manufacturing Concepts of Lead Acid Batteries

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1) Manufacturing of Lead - Acid Battery, Introduction The manufacturing is basically a BATCH process. Although newer equipment have tried to combine some of the activities but the basic steps in making a FLAT PLATE battery are. ¨

Alloy making

Oxide manufacture

Casting

Mixing

Pasting

Curing & Drying

Forming (other than container formed Batteries)

Washing and Drying (Dry Charge# included)

Plate finishing

Assembly

Charging*

Testing

Packaging

Dispatch to customers *For Container formed batteries, it is with uncharged plates (called green plates). The plates/panels after “Curing & Drying” go to “Plate Finishing” straightway. Further in Formed plate batteries, if it is with “Dry Charge” processed plates, then the Batteries post Assembly goes to packing without any acid inside. Generally on pouring acid at the time of sale, batteries develop sufficient charge so that it can be used directly. In some specified cases it may need charging.

For Tubular batteries the process of making positive plate is different. Can be seen in later chapters. v v v

Manufacturing Concepts of Lead Acid Batteries

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2) Alloy Making Alloy Making : What is Alloy in Battery making? It is what all metallic and non-metallic items composed of and used within a battery. It is used in Grid making, for Top lead and for Lid inserts, burning sticks and interconnecting parts for some design/ applications. The purpose of alloying is to enhance certain properties of lead by addition of various elements: metallic and non-metallic Basic purpose : -

To enhance physical strength of lead to with stand rigors of manufacturing process

Improve bonding between the metallic grid with active material / paste.

Improve corrosion properties.

Alloy consists of Lead with desirable elements and it does have some undesirable elements too. Various alloying elements have different functions and they are discussed in brief below. The most common alloying elements are Antimony (Sb) - hardening agent, bonding Arsenic (As)-anti-corrosive and hardening Tin(Sn)- conductivity and fluidity Selenium (Se)-grain refining Copper (Cu)- grain refining Calcium (Ca)-hardening agent, bonding Cadmium (Cd) -hardening agent, bonding Silver (Ag)- anticorrosive, hardening Sulphur (S)-grain refining Barium (Ba)- anticorrosive Lead with Antimony has been predominantly used. Over the years newer alloys got developed, particularly for low maintenance and maintenance free applications. Further application related alloys have been developed, such as cyclic duty, cranking application, higher temperature Manufacturing Concepts of Lead Acid Batteries

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application, start stop, hybrid etc. application. Batteries like VRLA, E bike uses specific alloys. Traction with Tubular plates still have high Antimony alloy. Plante positives are from pure lead. The trend is to make the alloys closer to pure lead particularly for continuous plate making. A very small percentage of any elements make profound impact. Based on the application the elements are mixed with certain percentage and proportion related to each other after years of study. There are hundreds of different alloys being used by various manufacturers. Some have been guarded with patents. Grain refiners Se, Cu, S come out of solution prior to solidification of Lead. They form the nuclei or center points round which lead freezes. So they needs to be contained during Alloy making. Some obviously gets lost. Selenium forms intermetallic compound Pb-Se. Melting points of Se 217 C. Below 450 OC, the dross formation of selenium by oxidation to Se O . So the molten alloy temperature during use, from pot to ladle needs to be kept 490OC to avoid its loss. The grain size of Alloy reduces with Selenium content even at 0.02% O

Tin (Sn) is needed for fluidity and also in bonding layer of Pb and PbO . It improves the Casting quality, and protects the molten lead from oxidation too. 2

Arsenic- It also has high resistance to corrosion and improves hardness, eliminates shrinkage cracks. It allows molten alloy to fill in the cavities. Too high Arsenic makes the grid brittle. Cracks can appear even after 24 hours. Lead Calcium Alloy is being increasingly used for both negative and positive grids. A hybrid battery consists of Lead- Antimony positive and Lead- Calcium negative. Calcium readily combines easily with Oxygen; as such its alloying is a difficult process. More about effect of Alloys discussed later in “various metals and their influence” in this book. There are some impurities like Nickel, Tellurium,Manganese, Iron, Zinc which have profound negative influence in alloy.Maximum limit is specified by users. Since a small percentage of non- Lead element makes a big impact in the Alloy, as such Alloy Blending is a very critical activity. Blending of Alloys : Lead is the heaviest metal in which much lighter Manufacturing Concepts of Lead Acid Batteries

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alloying elements are to be mixed. So it is a challenge to make the alloy with least amount of loss as vapor / dross. The Alloying is done at Smelters end or by Battery makers as per specification by a process called Blending. The blending is done in heated melting pots. It can be pure lead, “Refined Recovered” pure lead or by modifying “Recovered” alloy lead. Recovery means getting it from Lead based scraps e.g. batteries, cable sheathing, lead linings etc. Metallurgically, “virgin” pure lead is from lead ore. While in “pure” lead various additions are made to get the desired alloy, in case of “recovered”pure lead the process may also include removal of some impurities and addition of desired elements in the form of combination alloy or pure element. In some cases the elements are added with Aluminum based mixture of alloying elements in molten lead. One can also source already blended alloy with higher percentage of alloying element and Lead. The Blending operation is not a metallurgical operation and is done little above melting point of lead. Pot Construction : i) Material : Pots are generally round with hemi-spherical / dished bottom. Depending on size of pot the thickness of steel varies. It is better to use Boiler quality mild steel plates to fabricate the pot. For smaller pots it can be of cast iron also. ii) Sizes: It can be anything depending on requirements (say 1 Ton to even 20 Tons). Larger Pots are mostly used by Lead smelting plants for refining. The diameter and height of pot is also important. It is better to have lower height than diameter. That is L/D ratio < 1. iii) Method of discharge - Pots can be discharged by tilting, by use of pump or by tapping from bottom. While tilting and bottom discharge can drain out the pot fully, but for pumped discharge, a residual alloy remains at the bottom of pot. It can be a problem for making a different alloy next time. But having pumped discharge - saves construction and material handling cost. For higher output per hour pumping to moving ingot mold conveyor saves production time. iv) If the alloy to be made is of dissimilar nature then having a pumped discharge is a problem. Or have multiple pots for various alloys. The flow of metal to casting molds - should not be turbulent. Turbulence causes dross formation, which is not desired and can get on to the cast ingots, called pigs. Manufacturing Concepts of Lead Acid Batteries

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Often casting pot is separate from blending pot. In that case dross segregation from alloy is better The other feature is that, if the pump is placed into the pot after removing the stirrer (located centrally), further stirring is not available, it can affect the consistency of alloy for the entire batch. Lastly the temperature of the alloy being casted should be kept uniform throughout the casting period. Lead being heaviest, lighter metals tend to move up, creating differences in consistency of alloy. Keeping temperature constant during casting is very important to get uniform metal compositions. One can check the level of consistency by checking last ingots and compare with earlier ingots. Heat Source : Heat Source can be by burner fired by Furnace oil, HSD, LDO, LPG, Natural Gas etc. and generally the flame is tangential to the surface of pot. It is better to have automatic control for firing to conserve energy. Auto control can also help to restore uniform Temperature at minimum acceptable limit during casting. The burnt gas moves round the pot and is discharged to the stack from the side (top end) of Pot. Temperature in high. Can be used for pre-heating of air. Induction heating is another method of heating the pots and is more suitable for smaller pots. It is fast and efficient, but more capital intensive. Input : The inputs can be fed manually, or by gravity roller track, or by EOT crane, or by pumping from another pot, or by gravity flow from smelting furnace through launders. Generally Jumbo blocks post smelting/refining with steel hook are used. At factory level often pigs of 25 to 50 Kg. are used by roller track or by EOT/JIB crane with holding/grabbing device. Additions of various input metal to make the alloy are done at the appropriate time, post melting of initial inputs of lead/lead alloy. Some of the elements being mechanically mixed into the metal, it needs to be distributed evenly in the alloy by the stirrer. Further there is need to maintain certain minimum and maximum temperature so that these elements does not evaporate or segregate unevenly. Calcium, Selenium and Tin are mostly affected by the temperature. Furnace Construction : The steel pot is generally supported on a top frame. The outside of the pot comes into contact with hot gas and the passage is confined by refractory bricks, in mild steel casing. The refractory is designed to make the gas swirl around the pot and then discharged to the stack. Manufacturing Concepts of Lead Acid Batteries

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The bottom of pot is generally supported at the center by brickwork for support. Pots should have a provision to rotate on its axis periodically; this can extend the life of pot. Often the pot gets deformed with high heat in one side along with heavy load of metal. The top of the pot should be under cover with folded entry doors of material. During melting and blending operation, a mild negative pressure is maintained below the cover, so that lead-bearing air does not move out of pot to affect the surrounding atmosphere. Pollution Control - Pot : Pots are generally covered with an exhaust system. The top of molten surface is kept in negative pressure, so that people surrounding the pot does not inhale any gas / dust generated on the surface of molten alloy. It should not be again too high to cause high oxidation resulting into dross. But it should be enough to take care of heavy dust while charging any metal, powder, alloy etc. It is advisable to pass it through a cyclone and then Bag filter. Other option is to use a scrubber. Temperature of the hot air is important to decide the route. It is better to cool the Gas and use a Bag filter. The fan after the filter should be sufficient to move out the air via 30 m stack with an ejection velocity of around 25m/sec. Suction side ducts leading to Fan, can be with velocity between 15 to 20 m/sec of the hot air. It should also have provision for cleaning of duct from deposits of dusts at the bends. The ducting should be supported with flexible supports to take care of expansion and generally to move up. Some users take the duct under the floor to the pollution control device; generally a scrubber. cooling of the gas in important to get lower size of fan and ducts. The Fuel gas can be independently exhausted via stack. This does not contain lead. The norms to be maintained to meet air pollution control standards are specified, but it is always better to plan with stricter standards as the policy can change with tighter norms in future. Casting of Pigs / Ingots : ‘Pigs’ are basically ingots cast in casting machine, where molds are fixed on chains and move round on a long table. The metal is poured in a mold and then to the next one. The metal solidifies as it moves on the conveyor and while the conveyor takes a downward turn the pigs just come out and drop below. Often little tapping is required manually by a knocker. The metal is often cooled by water spray from bottom / top. Skimming device can be fitted or manually done to achieve a clean top surface. Ingots can be delivered to another conveyor and collected manually to Manufacturing Concepts of Lead Acid Batteries

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stack or can be collected by a jib crane to stack. Normally 1.5 to 2.5 tons of stacks are made for handling by Forklift truck / pallet truck. The ingots are shaped with stepped and taper ends, so that it can be easily handled during stacking. Alternately ingots can be cast in floor level cooled ingot molds kept in semicircle. A launder carrying molten alloy fills up one after another mold. It can be easily skimmed to have a clean surface. The alloy when gets cooled is uprooted from molds by a crow bar manually. For smaller pots, the moulds are simple and are filled by launder moving in semicircular way. Cooled ingots are crowed out for fresh casting. Layout : Often two pots are used to feed a pig casting line. In some cases there is a third pot where lead is pumped and then it is fed by pump or gravity to the pig casting molds. It is better to have a blending pot and casting pot in tandem. Post blending metal is pumped to casting pot and is free to do the next batch. The casting pot of same size is then used for pumping metal for ingot casting. This arrangement also helps to reduce embedded dross. (“Dross” is an undesirable impurity and will be discussed later in the book) Calcium Blending : While blending with Antimonial alloys with additives as Arsenic (As), Selenium (Se), Tin (Sn) etc. can be done as above to pure lead of desired specification, but for making calcium alloys (either for negative or positive alloy), the system is little different. It is added in nugget from as an alloy of Aluminum. Pure Calcium granules can also be used by feeding it in inert atmosphere of Argon or dipped below the surface of metal quickly. Inverted dome is often used over the pure molten lead for this. For fine globules, the same can be fed by pipe with mix of Argon, below the molten lead. The other option is to use Calcium - Aluminum alloy nugget and put inside the metal quickly by pusher operating vertically. Calcium alloys generally contains certain percentage of Tin, which can be added in pure form. Positive has more tin percentage than negative alloy. Loss of metal by evaporation, oxidation needs to be minimized. Common method is to supply alloying elements well below molten liquid level, having inert atmosphere at surface, preventing ingress of Oxygen, Air along with additives, using antioxidant. Aluminum is an important anti-oxidant and most alloying elements have Aluminum base. Manufacturing Concepts of Lead Acid Batteries

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The alloy made is sensitive to temperature and as such a close control has to be made. It is advisable to check alloying element input and what finally found in alloy. One can see extent of Ioss due to evaporation and think of improvements. Some typical Alloy specifications Alloy types

1.65 STA

3RT COS

CVN1202 (Cal.Neg)

Antimony (Sb)

1.65+/-0.10

3.0+/-0.10

0.005 Max

Arsenic (As)

0.20-0.25

0.10-0.20

0.002 Max

Tin (Sn)

0.030-0.045

0.08-0.12

0.3+/- 0.05

Copper (Cu)

0.05 Max

0.002 Max

Selenium (Se)

0.020-0.030

0.015-0.025 -

Calcium (Ca)

0.002 Max

0.120+/-0.02

Nickel (Ni)

0.005 Max

0.005Max

0.002 Max

Zinc (Zn)

0.002 Max

Bismuth (Bi)

0.030 Max

O.030 Max

0.010 Max

Cadmium (Cd)

0.001 Max

Silver (Ag)

0.004 Max

0.002 Max

Iron (Fe)

0.005 Max

0.002 Max

Manganese (Mn)

0.0005 Max

0.005 Max

0.0005 Max

Aluminum ( Al)

0.018-0.030

This is very basic, Each manufacturer has its own specification. Bismuth (Bi), is considered favorable element now and can be used up to 150ppm level. Nickel specs have been reduced to 0.0002 levels, to reduce water loss. Silver Specs for some Company are higher, claiming high temperature use. Barium (Ba) is also used up to 0.020 by some for corrosion resistance. In general Nickel (Ni), Manganese (Mn), Tellurium (Te) are harmful alloys. Aluminum (Al) is an antioxidant and suitable for all alloys. For Calcium positive grid casting alloy, it is better to take help from experts. Similarly for Pure lead, one can use primary lead 99.99, Refined Recovered lead of 99.985 Alloy, Recovered pure 99.97 Alloy depending on price, life, warranty, battery type etc. There are some alloys, which are called Master Alloy. These are used to take care of depletion of metals in melting pots due to oxidation or evaporation. Manufacturing Concepts of Lead Acid Batteries

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Pure Antimony Antimony

99.80%

Minimum

Arsenic

0.06%

Maximum

Bismuth

0.05%

“

Copper

0.04%

“

Iron

0.01%

“

Silver

0.04%

“

Nickel

0.01%

“

Cadmium

0.01%

“

Tin

0.05%

“

Tellurium

0.01%

“

Pure Tin

99.5%

Minimum

Arsenic

0.08%

Maximum

Bismuth

0.05%

“

Copper

0.1%

“

Iron

0.01%

“

Silver

0.01%

“

Nickel

0.005%

“

Cadmium

0.001%

“

Zinc

0.01%

“

Selenium Master Alloy -

“

Antimony

0.005%

Maximum

Arsenic

0.001%

“

Bismuth

0.03%

“

Copper

0.003%

“

Iron

0.002%

“

Silver

0.004%

“

Nickel

0.001%

“

Calcium

0.001%

“

Zinc

0.002%

“

Lead

- Balance

Calcium Aluminum Master Alloy -

Manufacturing Concepts of Lead Acid Batteries

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Calcium

75% +

Aluminum 25%

Antimony

0.05%

Maximum

Tin

0.05%

“

Bismuth

0.01%

“

Iron

0.05%

“

Silver

0.01%

“

Nickel

0.01%

“

Zinc

0.02%

“

Arsenic Antimony Master Alloy Antimony

10% +/-

0.5%

Arsenic

10% +/-

0.5%

Bismuth

0.03%

“

Copper

0.05%

“

Iron

0.005%

“

Nickel

0.005%

“

Tin

0.1%

“

Lead

Balance

v v v

Manufacturing Concepts of Lead Acid Batteries

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3) Manufacturing of Oxide Oxide

Making : Lead Acid battery is composed of Positive and

Negative plates. The plates have two basic components, Metallic Grid and Active Material (AM). The AM material undergoes chemical changes during charging and discharging process to either consume energy or provide energy respectively. So, AM is key item in the battery. The AM can be constituted or produced from various types of Lead Oxide. eg Litharge, Grey Oxide and

Red Lead. Their Chemical

Composition and other details are given below. Grey Oxide is predominantly used for Flat plates and Red oxide has major use in Tubular battery and also for positive AM for some flat plate batteries. Litharge,It is chemically PbO powder (called Lead Mono-oxide), reddish or yellowish, odorless, water insoluble, powder. The use in battery industry is limited and mostly used in stabilizers, pottery, enamels, Inks etc. Manufacture; primarily first Grey Oxide is produced in Barton pot from pure lead and same is fed to Litharge making Furnace, Grinder, Cyclone,Bag Filter, Silo etc in series. It can be two types either in granule form or in powder form. Later is used by some battery makers still. Some characteristics of Litharge: Density - 9.5 to 9.9 Apparent Density 1.8-2.2 Acid absorption -80 to 110 gm/gm Water absorption – 100 to 105 gm/gm Crystal structure – Orthorhombic +Tetragonal Composition 99% PbOwith very small amount of Red Lead (<0.06) and Free Lead (0.01-0.05) Melting Point 888 DegreeC. Thermal stability 297 to 897 Degree Red Lead : Lead tetroxide, also called Minium, Red lead or tri plumbic tetroxide, is a bright red or orange crystalline or amorphous pigment. Chemically, red lead is lead tetroxide, Pb O , or 2PbO·PbO . Lead tetroxide 3

is used in the manufacture of batteries, lead glass and rust-proof primer Manufacturing Concepts of Lead Acid Batteries

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paints. Properties Appearance - Vivid orange crystals Density

8.3 g cm-3

Melting point

550 Degree C

Crystal structure

Tetragonal,

This compound’s Latin name Minium originates from the Minius River in northwest Spain where it was first mined. Natural Minium is uncommon, forming only in extreme oxidizing conditions of lead ore bodies. The best specimens known come from Broken Hill, New South Wales, Australia, where they get formed as the result of a mine fire. It has a tetragonal crystal structure at room temperature. Lead tetroxide is prepared by calcination of leadoxide (also called litharge) in air at about 450 to 480 OC: 6 PbO + O u 2 Pb O 2

Red lead is virtually insoluble in water and in alcohol. However, it is soluble in hydrochloric acid present in the stomach, and is therefore toxic when ingested. It also dissolves in glacial acetic acid and a diluted mixture of nitric acid and hydrogen peroxide. Red Oxide is a mixture of Pb O and PbO . Its presence in positive 3

active material in plate gives rise to Sulphates of Lead with increase in volume. Upon charge it converts to PbO .The volume contracts leading to 2

voids. The use is in positive active material. For flat plates it can be for faster initial charging and also for higher Active Material utilization in thicker positive plates. Most deep cycle Tubular batteries use Red Lead in combination with Grey Oxide. Usage can be 0 to10% in Flat plate positive. In Dry Filled Tubular positive the mixture with Grey Oxide can be from zero to 100%. Mostly 50:50. In wet filling or slurry filling it is less than 25%. Often it is15%. Red Lead Furnaces can turn grey oxides to desired Red Lead in 20 to 22 hrs. Furnace are cylindrical, flat bed with stirrers fitted in two arms and Manufacturing Concepts of Lead Acid Batteries

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churning the bed. Initial start-up needs heat with open flame at top of bed. Some people convert grey oxide to a form called Massicot. It can be with water or fire. A tray of Oxide is put with fire from waste cotton, the fire catches up and slowly the entire mass is converted to Massicot. For water type, fire is replaced by water. It is then utilized for Red Lead making in furnace with open flame. Grey Oxide is the most common constituent of Active Material.It has Oxide of Lead known asPbOx (1<x<2) and certain quantity of pure lead, Pb, and the color is in various shades of grey. As such is called Grey Oxide. This oxide mostly becomes lead sulfate, during ‘Mixing. Certain amount of free lead is retained during oxide making and this Free Lead percentage progressively reduces during Mixing, Pasting, Flash - Drying. This balance lead is called RL (‘Residual lead) This RL gets almost fully oxidized during Curing, in presence of water, exothermically. Water acts as catalyst. Water becomes vapor and leaves the Paste, creating pores in active material. Pores increases surface area of Active Material. Creating pores is the basic technology of battery making process. Production of Grey Oxide can be done by various processes. Mill - Hardinge / Sovema / Lih-Shan / Huebach, Sanhuan Jintan etc. Reaction Pot - Barton Pot, Eagle / Linkater, CTL, Sanhuan etc. Smaller sizes up to 12 tons/day are made in India also. Oxide produced by both the systems, having certain ranges of free lead are different in their structure and properties. Pot Oxide Plant : The Plant consists of mainly: -

lead melting furnace from which molten lead is fed to a ‘Pot’

Pot (circular shell) with a stirrer. The flat top cover has arrangement

of ingress of air. Also water inlet from top for cooling. -

The duct connecting Pot to Cyclone and Bag filter for collection of

Oxide mixed with air post reaction inside the Pot, also located on top cover. Process : Molten lead is fed in to the Pot at regulated rate where this is stirred up inside vigorously. The Air which is drawn into the pot, gives the Manufacturing Concepts of Lead Acid Batteries

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oxygen for lead to react to form oxide. Oxide laden dust along with fine particles of unreacted lead particles released, moves up with the hot air into the discharge duct to Cyclone, where most of the grey oxide is collected. The Air also gets cooled and then enters the Bagfilter where further separation of oxide takes place from air. The air after passing through absolute filter moves to fan and stack. The fan is responsible for the suction of air into the pot. The bag filter has fresh air entry damper. The oxide produced is generally with around 75 to 80% oxidation level. Higher level is also possible for yellowish oxide/conversion to Red Oxide later, in Red Lead making. Pot Oxide plant is generally a part of Red Lead Plant. Control : Control is by metal feed rate, air flow rate, load of stirrer motor and also water addition (to reduce temperature if required). Automatic control of parameters results into very steady operation almost ±2% variation in oxide quality. The Control of 4 key parameters are key to its steady operation. Pot Construction : Pot can be slightly above floor with pre-heating burners at the bottom. It can also be installed in a pit with burners (removable) from the top cover. The pot needs to be heated up for starting the operation. It can also be with full electric heating, with ‘L’ type band heaters. Since stirrer is with heavy duty motor in rotation, either the Pot (Pit type) is fully bolted on its flanges with the concrete floor or the top driven pulley and frame are held firmly by additional supports, from the floor. V- belt driver generally rotates the stirrer. Bottom of the pot are generally flat keeping a small clearance with Stirrer bottom. For some pots the bottom is ‘W’ shaped for giving more surface area for the stirrer which is also shaped accordingly. The stirrer scatters the metal inside the pot shell where air reacts with the pure lead particles and oxidizes it. Pots are generally fabricated with thick boiler quality plates at the bottom. (A 15 Ton/day Pot can have 40 mm thickness of the shell.)

Manufacturing Concepts of Lead Acid Batteries

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The pots which are heated from bottom, needs periodic change of the base. Distortion takes place where the water drops and touches the hot plates. Various designs of Pot like ‘Linklater”, ‘Heubach,’ ‘CTL’, Sanhuan are there. It is a simple machine to operate, but needs good control equipment. The feeding of lead can be by gravity pump with special control valve to regulate flow to the pot from the top cover location. The control is basically with the load of the motor. Since the reaction is exothermic, so once the pot starts, with preheating, it needs to be cooled. Normally lower temperature of air entering the pot has the effect of taking away the heat, but if temperature exceeds a set limit water flow can be started automatically. Some pots have a steady water inlet and have a secondary line to flow in more water if required, by a controller. Oxide Collection & Pollution Control : Hot air laden with Oxide and lead particles moves up almost vertically by a duct and enters a cyclone. Almost 60% of solids are collected at Cyclone. There is dilution damper at the entry point of Bag Filter for control purposes. Post Cyclone cooler air enters the Bagfilter. Generally the temperature is around 100°C for air entering Bagfilter. Balance particles are collected in Bag filter. The Air then moves to the Fan. This Fan, before the stack draws the air through the plant from pot onwards. Control of this fan by damper or VFD is key control in Reaction Pot operation. To avert fine particles escaping to atmosphere it is prudent to have an absolute filter after the Bagfilter to have a very low emission level. Oxide Collection & Storage : Oxide is collected generally below the cyclone and Bagfilter and fed into a screw conveyor. Either it can be drummed or transported by bucket elevator or Sunekon Conveyor/tube chain conveyor vertically up to another horizontal screw conveyor for feeding silos. Silos should be capable to store about a day’s production giving time for the oxide to cool off. In some cases cooling can be done externally. The Silos should have a Bin-Activation with “Rotary air lock” for controlled out Manufacturing Concepts of Lead Acid Batteries

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feed of oxide to a screw conveyor. Bin-Activators are circular devices which are sharply tapered and bolted below silos with a rubber bellow joint. The eccentric movement of the Bin-Activator helps oxide to move to the discharge hole as well as prevent agglomeration of oxide in the Silos. The pot oxide plant Includes : A lead melting pot with pump or gravity flow of lead into the pot. It has to be regulated depending on electrical load of Pot. The lead ingot is fed to the melting pot by a conveyor. The POT. As Described above, has flanges and is firmly bolted with Concrete. Top of the Pot has cover with provision of -

Molten lead entry

Provision of reaction air entry from atmosphere. Adjustable damper or gate.

A duct moving up angularly containing hot air with oxide and lead particles to cyclone.

A cooling water entry port from top frame to cool pot when needed. Oxidation is exothermic reaction.

A central bearing housing for a shaft to enter. It has a stirrer fitted at bottom. Top end of shaft has a pulley, driven by a Motor firmly anchored.

The stirrer bottom rotates inside the pot just over bottom surface with a fixed gap. The stirrer basically throws/ sprays the molten lead inside the pot exposing the surface to the air for oxidation. The oxide so formed along with some fine particle of lead moves up the duct to cyclone.Lead Level is above the stirrer blades.

Cyclone, separates the solids from hot air and there after it enters the bag filter. Post bag filter, it goes to a suction fan leading to chimney. There is a screw conveyor connecting cyclone and bag filter to a collecting bucket elevator. Hot solids comprising of oxide and lead particles stored in Silo for further use. It can be used in paste making just after getting it cooled to Manufacturing Concepts of Lead Acid Batteries

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atmospheric temperature. No aging in needed. The oxidation level for paste making is around 75+/- 2% level. For litharge/ Red lead making it is above 95%. When the pot is started initial half hour the oxide produced is off grade. This oxide can be collected by extending the conveyor, it is blackish in color. It is better to operate POT oxide plant with less out stoppage, to avoid off grade oxide. If need be, one can have a bigger silo.

Fig.01 : Elevation of Pot Oxide plant, 15T/hr.

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Volume Distribution 100

Accumulative (%)

Differential (%)

0 0.2

0.5

100

200

500

Diameter (m) µ Diam ()µ

Diff (%)

accum (%)

disn (%)

diff (%)

accum (%)

diam (µ m

diff (%)

accum (%)

0.20 0.24 0.29 0.35 0.43 0.52 0.63 0.76 0.92 1.11 1.35 1.63 1.97 2.39

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.37 1.10 2.46 2.21 2.40 4.85

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.37 1.47 3.93 6.41 8.54 13.39

2.89 3.50 4.24 5.13 6.21 7.51 9.09 11.00 13.31 16.11 19.50 23.60 28.56 34.57

8.65 12.90 12.66 10.96 9.60 8.12 6.19 5.15 5.05 3.82 2.15 0.84 0.42 0.10

22.04 34.94 47.60 58.55 68.15 76.27 82.46 87.62 92.67 96.49 98.64 99.48 99.90 100.00

41.8 50.6 61.3 74.2 89.8 108.6 131.5 159.1 192.6 233.1 282.1 341.1 413.1 500.0

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00

Fig.02A - Particle Size Distribution Typical chart of particle size distribution of a Pot Oxide. The apparent density (AD) is high close to 1.5. The particles are in spheroidal from very fine to large as shown in graph above. The voids between lager particles are filled in by smaller ones to make AD higher. The operation of plant depends on effective control of airflow, pot temperature, load current of stirrer, air dilution before bag filter. The storage of oxide may be for a shift or so for use. One can store more too. The oxide can also be moved up the mixer from silo by air blowing instead of mechanical conveyors. At the end of the pipe, bag filter is provided to collect the dust. Particle Size of Pressurised Mill Oxide The distribution curve shows two humps. Second hump is bigger than first. This curve is for a high AD plant. For automotive applications, first half is bigger than second. The mean particle Size is also lower. Around 3 microns. These distribution is for mills with Forced air inlet. For mills with air entry without pressure, the chart Is with ALMOST straight Gaussian curve. Like Sovema or S type plants. Manufacturing Concepts of Lead Acid Batteries

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Fig. 2B Particle Size Distribution of a Mill Manufacturing Concepts of Lead Acid Batteries

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Mill Oxide : The Mill oxide basically utilizes frictional heat generated between the lead pieces / lumps rubbing against each other and also internal wall of the shell (cylindrical / cylindroconical) to convert lead to lead oxide powder in presence of air. Here the oxidation takes place at much lower temperature than a Pot oxide, where molten lead is used. The pure lead is fed into the system can be small cylindrical pellets 55 gm to 120 gm or even large ingots of 25 Kg. (like in Hardinge Mill). For a particular Mill design the weights are specified. The shape of the Mill is generally cylindrical. For a Hardinge Mill it is cylindro-conical with largest diameter around middle and variable tapered cone at each end. Air can be force fed (eg.Lihshan of Taiwan / LS type of China) or by air suction from the main fan located after the bag filter. In a German mill air which cools the shell is fed into the rotating shell. So air gets pre heated. The Air can be at Room temperature or pre-heated. Pre-heating of air either by shell heat or by electrical heater. Pre - heating is better, as it reduces the variation of temperature of entry air due to ambient air changes, seasonal day / night changes. Major makers of Mill are Sovema, CAM, from Italy, Lih-Shan from Taiwan, Huebach from Germany and various Chinese makers as Sanhuan, Jinfan, etc. Indian companies are also making both Pot and Mill oxide plants. The speed of rotation varies from manufacturer to manufacturer, as in case of Lih-Shan the speed and diameter are such that the pellets do not turn round with Shell-but tumbles down. In other types the pellets goes round with the shell inside. Brief Description of Mills of various makes : Sovema : Mill shell is a cylindrical shell with small dished ends. The metal is fed from rotary caster casting cylindrical pellets of 55 to 65 gm for 14 MT and then storing in a Silo via a bucket elevator. Regulated flow to the inlet hole, located centrally at feed end, based on load on the motor. Air also moves ‘in’ from the same hole. The speed of Mill is about 32 rpm. The pellets tumbles against each other as the Shell rotates by gear drive generating heat. Air reacts with heated pure lead surface making Oxide and lead dust. The shell is externally cooled by water spray with the help of temperature controller. The 24 Ton mill has higher pellet size. The air laden with oxide and free lead dust moves out from the other Manufacturing Concepts of Lead Acid Batteries

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end of shell centrally. Arrangement of returning coarse particles is there at the exit end. The oxide and lead particles move upto the Bagfilter for collection at the bottom and into a serew conveyor. The Oxide transported to Silos via bucket elevator and screw conveyors. Water can be fed inside to cool the air inside. Some Chinese maker’s uses similar principle and calls as S type Mill. Lih-Shan : This design of Mill is of similar cylindrical shape, but with air forced through via an inlet blower, through a central Pipe fitted with numerous branches fitted with injection nozzles over to the bed of the lead pellets. Diameter of shell is also higher. Lead Pellets are heavier (110-120 gms) and are made by Shearing from Cast pure lead strips produced on a circular or straight channel in which molten lead is pumped from a lead melting pot. The Channel is water cooled. The pellets move up by conveyor Silo with regulated feeding at the inlet of shell. The Silos for pellets generally be for day storage. The pellets move up the Shell as it rotates but tumbles/slides down over other pellets. The Central Shaft has 3 thermocouples to control temperature zone wise along length. The Shell is externally cooled by water spray in 3 - zones with solenoid valves. The Mill, has provision of dross feeding at the entry end of Shell. Oxide, so produced enters the Bagfilter in straight or goose neck way and collects at the bottom. There is a micron filter to further arrest dusts and also meeting pollution norms. Suction blower, there after moves the clean air up the stack. The control is by temperature of Shell, load of motor, airflow, damper setting etc. Some Chinese maker’s, make on similar principle and term as LS type mill. For same capacity specified Lih Shan gives higher output per day. Huebach/Pennoroya : The Mill is similarly cylindrically and is placed on load cells. So the control is by physical weight moment. The air is flowed over the Shell within a cylindrical jacket before entering the Shell at the inlet hole. This preheats the air. The design is robust. Mills from China : Have features like above Mills, but with various improvisations. Generally they are placed closer to the floor. There are many makers of Mill, having various features. They classify them as S or LS type.Sanhuan is leading maker. There are many other companies. Some make from 4ton/day level.

Manufacturing Concepts of Lead Acid Batteries

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India - there are few Indian companies as well and sizes are 12 ton or less per day Oxide Storage and Conveying System : Mill Oxide is generally aged for 72 hrs. For some cases even upto 6 days. As such unlike Pot Oxide, it has multiple silos. The silos are placed on load cells and have a “Bin activator” at the bottom to discharge the oxide via a rotary air lock. Lih-Shan uses Sunekon / Snake chain conveyor for oxide conveying with Screw Conveyors at the top and bottom of Silos. The conveyors are robust and need very little maintenance. Screw conveyors have reversible drives if required. If the oxide is conveyed to a distance, then it is better to have a stock pot near Mixers, to reduce frequent movement of the main conveyor. Most of other Mills uses a combination of bucket elevators, screw conveyor, tube chain conveyors. A new conveyor extends in length after few months of use. So it is advisable to check for same every 3 months and adjust the length otherwise a sudden break down cam take place. Mill Sizes : While there are small Mills of 1 to 3 Tons per day, Mills of bigger manufacturer are for 8T, 12T, 18T, 24T, 36Ton etc. Control system is better on higher sizes particularly 12 ton and above. Oxide Quality : Key feature of oxide quality are: a) Oxidation level b) Apparent Density c) Acid/water absorption d) Particle size distribution Generally oxidation level is 70% level, but it depends on users. Some users have even 60% level also. Apparent density(AD), varies a lot from make to make as the particle shapes and sizes have a major role to play. The AD varies between 1.11 to 1.45 depending on design of Mills. Acid absorption is over 200 gm/cc and is generally around 220 - 240 gm/cc for Mill Oxide. Particle size distribution, with a median about 3 microns are common. Some makers have two peaks in the particle distribution. The two peak heights can be different depending on design of manufacture and requirement of battery maker. The forced air entry hits the surface of lead pellets via nozzles and gets the products move into the flowing air to Bag Manufacturing Concepts of Lead Acid Batteries

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filter/s where air is separated. A suction fan moves the warm air to chimney. Pulverisor : Oxide can be made finer by using Pulveriser to make it finer. Apparent Density is low. Major use is for some types of VRLA and also for use in orifice pasting. Pulverised oxide needs to be stored in different Silo. Hazards : Mill Oxide is very much susceptible to fire. Presence of moisture starts exothermic reaction. As such Silos to have automatic Nitrogen purging system to purge nitrogen sensing temperature of oxide. The air inlet should also be via silica gel breather to take out the moisture from entering air. Periodically the gel needs to be heated up to drive out the moisture. Bagfilter - bags should have anti-static feature. Generally needle felt polyester bags are used temperature of bag filter be above 90OC. Start-up Oxide : During commissioning some amount of Iron can get in. If the content is high then the same is not to be used. Another way is to coat the internal of Silos so that the entire Oxide can be used in process. Off Grade Oxide : For every start up after a rest period, when the Mill is started, first 30/40 minutes the Oxide produced is off grade. This can be collected in an extra small silo and used up in every mix. Better in Negative Mix. It can be collected in drum and be used similarly manually feeding the conveyor or Mixer. The Oxide is blackish. Comparison of Ball Mill Oxide with Pot Oxide : (1) Oxide particles are generally smaller for Mill Oxide 0.8–1.0 m²/gm to 2.63 m²/gm (2) Ball Mill Oxide is more reactive. Typical acid absorption values are 220 - 240mg/mg H SO for Mill and 180 – 200 mg of H S0 /gm for Pot. 2

(3) Space required for Ball Mill is much higher (4) Mill Oxide enhances initial discharge capacity of pasted plates. (5) Ball Mill more expensive to buy,consumes about 30% more power. (6) Process Control - Ball Mill is easier to control, but slower response to change. It is also more difficult to store. Fire hazard is an issue in Silos. (7) Ball Mill Oxide needs at least 48 hrs.Aging. 72 Hrs is advisable. Pot Oxide can be used, as soon as it is cool enough. So, number of Silos or Silo capacity for Mill oxide plant are more. Aging makes sharp edges rounded for further operation. It also increases oxidation level by 1-2 percent. Manufacturing Concepts of Lead Acid Batteries

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(8) Pasted Plates made out of Mill Oxide are mechanically more stronger than pot oxide,in general. (9) Ball Mill has high noise and potentially higher dust emission. (10) Ball Mill Oxide generates more heat during mixing in Paste Mixer compared to Pot Oxide. Greater surface area and shape of particles are responsible for this and with greater reactivity of the Mill Oxide, it drives off some extra water & gives a stiffer paste compared to Pot oxide. (11) Finer particles of ball-mill oxide pack more densely than those of Pot Oxide. Therefore to achieve same paste density, further water needs to be added to the ball-mill paste towards the end of mixing. But the Mix recipe should be such that, addition of trimming water post mixing to adjust the density is not usually required. (12) The paste of Pot Oxide is much easier to paste. Pastability is much better. (13) Pot oxide particles are close to spherical. As finer particles fill the voids, the AD of Pot Oxide is better. Its Movements for Dry filling of Tubular plates is much better then mill oxide. (14) Mill Oxide is tetrahedral in shape and the paste is bit crunchy. Change in Oxide parameters in Mill 1. Low Free Lead

Increase positive pressure Increase Mill load Decrease Mill temperature Increase negative pressure

2. High Free Lead

Decrease positive pressure Decrease Mill load Increase Mill temperature

3. High Apparent Density

Decrease negative pressure Decrease Mill load.

4. Low Apparent Density

Increase negative pressure Increase Load.

Mill Construction a. Making of lead lumps. There are various options. -

Casting in rotary dies with ejection from molten lead fed by pump from melting pot

Cutting continuous cast rods cooled after pumping into channel from melting pot

Manufacturing Concepts of Lead Acid Batteries

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Similar arrangement but the casting in a circular table for cooling.

Sheared lumps from ingots processed in extruder.

b. Lead lumps of desired size and weight are then stored in lead lump hopper, for feeding into the Mill. Normally the storage is more than one shift. It is quite possible, to have one pellet making unit for two identical mills. c. The Mill shell needs lead lumps and air. Also can have a dross feeding arrangement. The Air can be forced via a blower or just enters by negative pressure created by Suction blower. d. Post oxide production it goes to silos via Bag filter. The Suction blower sends the clean air to the stack. Two arrangements below gives schematic arrangements for two basic type of Mills. Forced air and Suction air.

Fig.03 Schematic arrangement of mill with naturally aspirated air via a suction fan. The suction blower is responsible for airflow through the mill shell

Manufacturing Concepts of Lead Acid Batteries

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>> System Flowchart

Fig.04 The arrangement above shows a forced draft fan before the mill shell. This air enters the mill through a central pipe and then it flows at various segments by extended nozzles. Lead lumps cast and fed inside through air lock gate into the shell. The pellets moves up along the shell and again slides down, instead of rotating with shell. The friction between pellets results into heat and with high pressure air hitting the surfaces oxide and lead particles are picked up. The air laden with powders, enters the bag filter where the powders get separated. The oxide moves to a conveyor through a rotary airlock device and then moves to the silos for aging. The conveyor system can be a combination of screw conveyors with bucket elevators or it can be by snake or Sunekon conveyor. There are multiple silos to cover 3 days output or a single tall silo. Basic aim is to ensure proper aging of oxide, needed for smoother pasting operation. 3 silos helps to store day wise. The storage system can have fire, if moisture is present. Reaction with air in presence of moisture is exothermic. Normally facility of nitrogen gas purging is made inside silo/s, with temperature sensor for activating the gas. Mill oxide is conveyed by mechanical conveying system, as uncontrolled oxidation can take place with flow by air. One should have a small silo to collect the start up/ off grade oxide, to store and use in small quantity in negative mix. Initial bag filter collection can go to this small silo. Manufacturing Concepts of Lead Acid Batteries

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The oxide from this silo can have a feeding system connected to main feeding line to mixer/s.

Fig.05 Author’s experience is pot oxide gives better performance in deep cycle applications. Dry filling of Tubuler plates is much smoother with pot oxide. Mill oxide is best suited for automotive applications and VRLA. Some manufacturer of oxide fills 25 kg. bags manually. It is extremely dangerous for the person working. De-bagging equipment with good pollution control measures should be used. v v v

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4) Casting of Grids Gravity Casting : Grids are on which Active Material (AM) are pasted and it holds the AM during service. The Grid also acts as conduit of electricity from and to AM. It is also having lug to get connected with other grids through strap. Generally the height of internal grid wires are lower than surrounding frame. The grid wires near to the lug are of higher cross section to increase current carrying capacity. Bottom corners are rounded, as this area practically does not take part in reactions. For small-scale production it can be ‘Hand Casted’. For larger production Automatic Grid Casting Machines are used. (GCM). Process of Casting : Molten Alloy of desired specification of composition and temperature are put inside the pouring channel of Grid Molds. It consists of two halves. One is fixed half and other is moving half, so that when grid is formed upon solidification of alloy in the cavities/spaces provided in the molds, the cast grid can be taken off - manually or automatically, after opening the movable half. The important parameters of Grid castings are : Alloy composition Solidification range Alloy temperature at various places Mold temperatures Coating of mold by spray Grid design including its venting system Timings of each activity Cooling water temperature Vent passage cleanliness Time since last spray/touch up Control of these variables are some with automatic and some manual way and are skill dependent. The variables in Casting of grids are many. It also varies for Antimony based alloy and Calcium based alloy. As far as practicable control of variables by means of control system, Manufacturing Concepts of Lead Acid Batteries

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independent of manual control is desired. Some items are operator dependent and skill of operator is very important. Hand Casting : Generally employed for low volume products and some Industrial products with large and complicated grids. Plante type positives are generally hand cast. Arrangement of pre-heating of mold is also required with gas / electricity. Fine chalk powders are used as coating. Lever action ejection pins are provided to eject the grid from the mold cavity. For some cases one has to use pincers to grip the top gate and pull the grid out from fixed half.Grids cast has a top gate -which is almost close to the weight of the grid itself. It needs to be trimmed thereafter. In better designed hand molds the gate is sheared automatically. Hand casting is suitable only for Antimony based grids. Calcium Grids are not hand casted. The range of solidification is narrow. Auto Grid Casting Machine : GCM The machines can be designed for both Calcium types and Antimonial types. Generally two sizes of machines are available. One is for grids up to 350mm and other above that. Later is called Industrial type. For small sizes eg. Motor Cycle and small VRLA it is multi panel. Normally it is twin paneled for all automotive types. Main features of the machine : Lead Melting Pot: It is either gas heated or with submerged electrical heaters. The lead delivery can be by centrifugal pump, pneumatic hydraulic cylinder acted reciprocating pump. Machines are also made with pot above for gravity feed to mold through a needle valve. Overhead single machine pots are of around 800kgs with less dross generation, as benefit. Cuttings and scrap are manually fed after collection at back end, which is cumbersome, in this case. Multiple GCM with same alloy can be from a common pot with pipeline supply. The pipes are heated by resistance/induction.The pot has manual or auto infeed system of lead pigs, chute for return of cuttings of gate and feet etc. The surface of the metal has ‘dross’ which is oxidation product of lead and metals. Dross must not go to the grid, so it needs to be skimmed out periodically by special perforated spoons. It is practice to keep some dross floating on surface to prevent further oxidation of metal surface. While top Manufacturing Concepts of Lead Acid Batteries

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of the pot be with a hood, the pot needs to be covered on all sides, to prevent ingress of air. Slightly negative pressure can be kept on metal surface. Higher air velocity cause more dross. There are various ways to control / minimize dross. Negative pressure be enough for air from pots do not come out to surrounding. Air on the surface of ingot /Air with grid trimmings, rotation of pump shaft generally accentuate dross formation. Flow of Air on the molten alloy surface also causes dross. It is better that ingot and trimmings get preheated above molten alloy before slowly submerging. It reduces dross significantly. The temperature of Pot is very important and needs to be maintained in close range, in spite of periodic ingot addition. Lower alloy temperature can segregate the alloying elements and get evaporated. These needs to be replenished with Master Alloy, after periodic checking of alloy composition. It is better to keep minimum temperature of 490 degree C, when machine not in use for 1 or two shifts, so that lighter metals do not move up with alloy becoming more viscous. Selenium, Tin, Calcium are more susceptible for evaporation. Pot is externally insulated. Gas pots can be single burner type or with air aspirated multiple row burners at the bottom of Pot. Electrical heaters are generally ‘L’ type or fish tail type and needs to be clamped properly to prevent its float in use. Cast heaters or tube type heaters are also used. Use of Nitrogen on top of alloy surface can reduce dross significantly. Casting Machine & Mold The machine has Mold (in two halves) mounted on a frame, with lead delivery ladle on top, so that as ladle tilts by cam mechanism - molten alloy drops inside the Gate of Mold. After a set time the moving half opens and grid is ejected to fall. The cast grid slides down a stainless steel curved sheet to become horizontal. It moves forward and then drops to the Trim-Die unit in an angle. Grid is received by the stacking device and stacked. For Calcium alloy types a soft receiving attachment is used by some, to avoid distortion, Water spray device can be installed before the grid reaches trimming device. The dies are lubricated, periodiocally. The control in the machine is by programming of various cycle time, speed of machine (that operation number of times/minute), Temperature controller for Pot, feed line, ladle, mold upper and lower etc. Often an Manufacturing Concepts of Lead Acid Batteries

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integrated system is used like ‘Cast Master’ of Wirtz for optimum use of various parameters. The grids, which have a solidified thick gate at the top end and feet at the bottom falls on to the trim die stopper where the feet rest. Based on this location the feet and gate are sheared off by trim dies. The cut grid, then get collected and stacked vertically on to the machine discharge frame so made. The cut pieces like gate and feet drops below in a conveyor to return to the lead pot/or collected at back of machine for addition to pot. Trim dies can be adjustable type or fixed type and needs to be changed for change in Grid size. A grid is actually twin plates, for SLI application for ease of handling and working upto plate parting/cutting stage. For Motor cycle a grid may have 4, 6, 9 panels. For VRLA medium it is like SLI, but for small it is like MC. For larger grids be in VRLA / Industrial types it can be single grid with single panel. For such cases generally a false lug is kept for handling. Casting Parameters Low Antimony (1.65%) O

Calcium Alloy

Lead pot temperature

480 to 500 C

500 to 520OC

Lead pipe temperature

490 to510OC

540 to 560OC

Ladle temperature

530 to 550OC

540 to 560OC

Lower mold temperature

170 to 190OC

190 to210OC

Mold cooling water temp

35+/- 5’C

38+/-5OC

Machine Speed

13/min max

15/min max

(Above is just a guideline and machine type, mold etc. will determine actual usage values) With CCS and higher water temperature one can achieve better figures. Plannishing Die Thisis a hydraulic device fitted with trim die to flatten the grid while trimming to a maximum permissible size. This flattened grid helps in pasting and also controlling pasted plate thickness. The planishing die is to be obtained with the machine. This is a must for use of orifice paster. Also VRLA grids of same maximum thickness can give uniform plate thickness leading to uniform compression of AGM. Casting speed It varies due to alloy composition, mold design etc. For SLI 12 to 18 casting/machine are generally achieved. For Industrial machines it is Manufacturing Concepts of Lead Acid Batteries

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between 4 to 10 per minute. For heavier and large grids, it is on the lower side. SLI grid output can be between 4000 to 6000/8 hr. shift. For Industrial, it can vary between 2500 to 3000/shift. But it depends on alloy /design/grid thickness. Calcium grids can be casted at higher speed than antimonial grid, as its solidification band is lower. Grid Collection and Storage : SLI Grids are generally kept on racks/skids vertically or on pallets horizontally. Normally a bunch of 50 grids are lifted together. Keeping horizontally is good for softer grids. Collection and placement are manual, but some also use auto collection device mounted on rails. Grids before stacking, it’s all sharp edges must be scrapped with a scrapper. The outer frame has to be smooth for better pasting and later plate cutting, this is very important. Grid Aging : Aging is a very critical process in plate making. When freshly cast, grains are large and grows perpendicular to the face which got cooled first. Grids are soft and not suitable to withstand rigors of mechanical pasting. For an Antimonial alloy, the hardness of cast items goes up sharply after 5/6 hours to a hard level and again drops to a steady lower level after 72 hrs, but much higher than original hardness level. (This is the reason, use the straps casted within hours of casting or after 72 hours, with higher compression level). Antimonial grids are air aged for 3 days minimum. Grid stacks be tagged to identify date of casting. Grids excess to requirement should not be produced. Such grids adds to inventory. During the aging process grains become smaller and cohesive. Grain boundaries are the places where active material joins the grid. Closer the boundaries, better are the joints. Active material does not join with lead, but the additives in alloy. Calcium based grids needs to be oven aged as it does not get adequate hardness even after few days of storage, in air. Oven Aging is done in small ovens of low height. The time for aging is after the grid mass has reached about 80 OC. A 2.6 % Sb, freshly cast grid can be done in about 12 to 15 hrs at 80 OC, and generally it is not done, as grids post casting gets into aging process as it is and how much to do aging in oven is not easy to determine. If it is stored outside more than 12 hrs, then it can be done in 6 hrs treatment time. 1.65 % Sb alloy can be oven aged for 6hrs. This is treatment time. Calcium grids can be aged at 80 degree C for 3 hrs treatment time. Over aging is not good for grid and not necessary. Grids kept in storage Manufacturing Concepts of Lead Acid Batteries

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for more than two weeks are not to be used. Grids become too hard, almost brittle. There is surface oxidation too. It is better to melt these grids back in pot than trying to use. Cork Spray : This is an important activity for grid production. The spray is prepared from Cork dust and other ingredients (varying with various users) processed/stirred etc. They are then sprayed on to the mold face and gates by a spray gun. Spraying is a skillful technique and is done to: a) insulate the surface to prevent pre-mature solidification b) to give a surface roughness on the grids Generally a mold is first cleaned thoroughly and then sprayed all over. Some parts are penciled and then final spray is done. The movement of gun has to be quite precise for better result. It is a very skilled job. Venting is kept open during and after the spray. Technique of spray and no. of timeof spray are user specific. Periodic touch up once or twice is done on this coating during casting per shift. When the casting is started after initial spray, its weight is on the lower side. Slowly the weight goes up. If it reaches a higher set limit, the mould needs to be touched up. Keeping weight record in graph is helpful. Wirtz mold Spray coat procedures : The operation of applying mold coat to the grid mold is very important, the technique used and the care taken in the operation has a large bearing on successful grid casting. There are three basic methods used to apply mold coat.Each requires the mold to be machined differently to account for cork build up and to obtain correct weight and thickness of finished grids. It is always better to know the spray details from mold makers, when they certify a particular grid mold. Following are three types can be tried out. An example of 0.05+/-0.003 inch grid with weight about 50gms +/- 3gms has been considered. Heavy or light horizontal spray is accomplished by 20 to 25 horizontal passes from side to side. Heavy or light vertical spray is accomplished by 20 to 25 vertical passes from side to side. The difference between light and heavy coats is time. Heavy 15 to 20 seconds, light 7 to 10 seconds or about half. This varies by how fast the Manufacturing Concepts of Lead Acid Batteries

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spray gun moves across the mold face. In addition, the coarseness setting of spray head can vary the amount of cork applied. A determination of too much or too little cork applied can be by checking the cast grid thickness and weight and then adjusting accordingly. In each corking procedure, the mold is designed to produce grids at the low end of the tolerance, that is minimum thickness and weight, thus allowing the maximum running time after each cork job. With any corking procedure, grids will increase in thickness and weight after several hours of casting. Following is an aid to help understand what is happening when using the different procedures and decide which procedure would best meet production requirements. 1. Spray and Run. No wipe and no scrape Approximate amount of cork build up Frame

0.004 inch(approximately 0.1mm)

Wires

0.004 inch

Surface

0.004 inch

Cast thickness

0.47 inch

Approximate running time

3 hours depending on design and skill

Advantages

Easy method of operator

Disadvantages

Hard to control thickness and flash

Procedure

Spray 4 heavy horizontal coats and 4 heavy vertical coats. Begin casting.

2. Spray - scrape - Spray and run Approximate amount of cork build up. Frame

0.004 inch

Wires

0.004 inch

Surface

0.002 inch

Cast thickness

0.047 inch

Approx. running time

3 hrs depending on design and skill

Advantages

Easy to touch up, control weight, Thickness and flash

Disadvantages

Requires good operator skill

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Procedure

Spray 4 heavy horizontal coats and 4 heavy Vertical coats. Remove cork from Surface by Scraping with large putty knife. Spray light Coat. Begin castings.

3. Spray -Scrape- Wipe-Spray- Run Approximate amount of cork build up Frame

0.002 inch

Wires

0.006 inch

Surface

0.002 inch

Cast thickness

0.48 inch

Approx. running time

6 to 8 hrs with touch ups

Advantages

Easy to touch up, longest running, Improves thickness and flash control

Disadvantages

More time and operator skill.

Procedure

Spray 4 heavy horizontal coats and 4 heavy Vertical coats. Remove cork from surface by scraping with large putty knife. Wipe out frame,lug and foot area with wooden stick. Brush same areas with a firm bristle type brush. Spray 4 light horizontal coats. Begin Casting.

Procedure #3 can be varied by Spray-Wipe-Spray-Scrape and Spray. Equipment needed are: 1. Good quality Spray gun- say with 30 nozzles 2. Large putty knife 3. Wooden stick 4. Small wooden stick 5. Small firm bristle type brush with short bristles 6. Wire brush- used for removing old cork off the mold and clean surface 7. Small putty knife Manufacturing Concepts of Lead Acid Batteries

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8. Cleaning chemical for mold. The cork spray should be prepared much before spray and to be kept stirred before filling the spray gun. Older cork material above 6 months should not be used. Viscocity of Cork spray - 11-13 cp (falling sphere) / 12-14 cp(B4 cup) Specific gravity of final spray 1.025- 1.035. It is better to get experienced mold spray person to train the casting operators. Mold heating system, cooling system and right cork spray are fundamental to quality casting within UCL and LCL. If the mold needs frequent touch up for shrinkage, flash, short run, one should delve deep into cork spray. Molds need to be cleaned of sprays after weeks of use. Best way is to clean ultrasonically. Feed line & Metal Delivery : For pump delivery the feed line is heated by electrical heater encased with insulation blocks or if it is bare pipe then by open flame/ribbon burner. For overhead pot for single machine the line is straight to the pouring valve. For overhead pot with common feed line - the lead flows through about 50 mm size pipeline with “impedance heating” system. No. of machines can be easily fed with same pot, if the alloy is same. The scrap conveyor at back end or at the bottom conveys the cuttings back to the pot. It can be into a lower pot and then pumped overhead or straight to overhead pot. For overhead pot pig feeding arrangement has to be made to the pot, based on level control. The feed line temperature is generally little higher than pot temp. (5 to 10 C) and is controlled by temperature controller for electric heating. O

At the end of Feed line is a valve to feed the alloy to the ladle. For single machine, dispense valves with ceramic ball is common practice where the feed line is fed by centrifugal pump. For reciprocating pump, it is straight to clamped mould (e.g. spine casters) or to the ladle for over flowing to the grid mold, when needed. For overhead pot or common pot a gas heated needle valve can do the job. Provision of cleaning and gas entry nozzle are to be kept. Manufacturing Concepts of Lead Acid Batteries

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Lead Pouring : For Gravity Cast, the alloy is poured to the cavity of grid molds clamped together by tilting of the ladle. The ladle has holes (depending on alloy, rectangular / elliptical / semi elliptical) with or without notch are in use. Tilting of ladle is automatic and by mechanical rotation of a cam drive. It is quite fast and the lead moves very fast inside the Cavity / Gate of two mold halves brought together. The pouring is never in the center and generally it is in loose half. In GCM’s, as soon as the moving half closes the fixed half - the alloy is poured by tilting of the ladle. Post solidification the loose half opens and the grid is ejected out by ejector pins located at key locations. Ejector pin height, clearance with the hole are key focus areas. Ejection marks appear on the grid, if seen closely. Solidification time depends on alloy composition, temperature of alloy and temperature of mould halves, which has water cooling arrangement. The cooling water temperature is different for Antimonial and Calcium grids. It is better that coolant be via CCS (closed circuit cooling system). This gives higher productivity and less defects. Keeping a constant cooling water temperature is very important, particularly, when cooling tower is used for cooling. Mold be at temperature specified by mold maker. Where cooling towers are used, the water line to have temperature controller, for controlling fan operation, for near uniform temperature. Also intelligent use of cold and hot well where large variation of ambient temperature is there. Mold : Basically approximately each half of mold casts half of the cast weight. The grid design is cut into the cavities. Generally Mehanite cast iron is used for Grid Molds. For hydraulic spine casting, steel alloys are used. Loose half of mold is rested on two horizontal supports and a pull system. In every cycle the loose half comes flat on the fixed half, before the alloy is poured. The mold cavities and pouring channel are generally sprayed with a liquid / slurry which has fine ground cork powder and some additives. This is sprayed on to the hot mold surface very skillfully. The spray movement/angle of spray etc. are very important. Some areas like flow channel, mold gate, lug areas are penciled also for keeping different cork thickness. The tools used are wooden pencil and brass scrapper and brass wire brush. Cooling is by water channel inside the molds and is regulated by temperature controllers. There are also heaters fitted on to the mold or inside the mold in drilled holes. Manufacturing Concepts of Lead Acid Batteries

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Mold design is very detail subject. It has to take care of flow properties, current densities across cross section, strength of grid for handling, holding of active material corrosion tolerance; expansion possibilities (positives) post usage etc. Generally the internal wires are kept little lower than frame thickness for better paste coverage of these wires. Exposed positive wires leads to early corrosion. Grids can be with rectangular features for horizontal and vertical wires, inclined, radial, complex step / radials etc. are used by various makers. Lugs : Length of lugs are depending on the handling of grid / plate stack, amount of cutting for COS operation etc. For hand burning it can be at the same final size and need not to be cut. But for COS the lugs have to be cut to expose fresh surface for fusion. Before the cut face oxidizes it has to be used in COS. Position of lug in grid is very important. It can be side lug, shoulder lug, mild offset, large offset. Based on lug, positive vertical wires / their inclination etc. are decided. The lug should be minimum required. Cut pieces of lug are waste and needs recycling. Ejection and Venting : There are ejection pins inside the fixed mold operated by a small length cylinder at the back. The pin locations are generally at thicker areas (so that grid wires does not get damaged) and as it comes out the cast grid gets dislodged from fixed half. Ejection pins be lubricated once in a shift at least. Loose ejection pins must be replaced or renewed. Venting of air is key to proper fill of mold cavity. Gate Portion : Dimension of gate portion varies between users. The Gate is necessary to give hydraulic head for filling up the grid mold. Just below the inclined gate there are small channels, so designed to guide the alloy to the mold frames/cavities for fast fill up. Generally the alloy is poured into the loose half. To prevent erosion of cork spray (consequent premature cooling) angle of gate is important. Some use a grilled surface to keep the cork spray in place. Issues in Grid Casting : The cast grids can show up with some defects. While cork spray and touch up after certain intervals should maintain grids within a specific weight range. UCL / LCL. So when the weight nears the upper control level, the mold needs attention. Other defects are Short Run, Crack, Flash, even if venting is ok. Short run, is due to some unfilled wire spaces in grid cast. Most of the time it can get corrected by touch up spray and maintaining proper temperature. Manufacturing Concepts of Lead Acid Batteries

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Crack, is something most dangerous as might go undetected to battery. Usual method is to fold the grid lengthwise in a 2 inch diameter pipe. If there is a crack, it should show up. Quality of alloy and temperatures play a major role in crack formation. Flash, this happens by visible flashes besides wires and frames. Generally high alloy temperature can show up as flash as metal become much thinner. But it can be corrected to some extent by touch ups. Flashes in the central portion could be due to bowing of mold. Cork Spray and touch ups. Generally one spray is needed per shift with one touch up. As the weight goes on increasing to upper control limit, a touch up is needed. Periodic cleaning of mold and its cooling water passage is very important. Use of soft water or solid free water is desired via CCS. Best way is to have cooling by use of mineral oil. Cleaning of Mold by ultrasonic method in a box is good way to keep grids in new condition. CCS - that is closed circuit cooling system maintain uniform temperature and improves output also. One CCS be used for two grid casting machine. Record of grid weights via computerized graphs can not only lead to better control of weight, but can give an estimate of Alloy consumption with out put charted out. v v v

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5) Continuous Grid Making And Pasting System To improve productivity and reduce weight of grids various continuous grid and plate making system have evolved. Broad classification a) Expanded Grid b) Concast and Con Roll grid c) Punched grid system Expanded grids They are basically two types a) Slit and stretch - Called ‘Rotary’ also. b) Progressive expansion - Called ‘Reciprocating’ also. Both systems accept rolled strip coil for making the grid profile. The former can use multi-alloy strip caster for the operation, instead of rolled strip coil. Grids by Various Systems : In the figures below : left to right. Brief features. 1) Progressive expansion or reciprocating system. No side frames. Narrow bottom frame. Diamonds near top frame be closer vertically. Generally thickness of grid is about 0.2mm less from twice strip thickness. Say with 0.8mm strip thickness, one can get 1.4mm grid thickness. The lug thickness remains 0.8mm. 2) Punched grid can have any profile suiting application and lug position. Same looking grid have been in gravity cast too. Generally thickness of grid is same as thickness of strip. It has frame in all sides. 3) Stretch expansion or Rotary system. It has wider bottom frame to grip the slitted strip. No side frames. Grid thickness as in 1 above. The stretch induces stress at nodes, the places where diamond joins. The failures in positive happens due to stress corrosion. So mostly used for negatives. 4) Concast. The grids are continuously casted. It has side frames and lugs can be outside, making it suitable for container formation. But otherwise lugs are inside like expanded grids. 5) Cast. This is gravity cast grid. Frames all sides. Vertical / horizontal, diagonal wires, current carrying paths possible. The paste is locked in the profile of grids.

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Reciprocating

Punched

Rotary

Concast

Cast

Fig.06 Multi Alloy Strip Caster : In this system various alloys made are extruded into strip Coil in drums and the required thickness of strip move through cutters to required widths and coiled in multiple coiler stations. Advantages are use of various alloys. But antimonial alloys are not possible. Disadvantages are the strip is not rolled from higher thicknesses, so as to align the grains in line with strip. Strips rolled in multi stand rolling from say 12mm thickness to desired thickness have superior grain structure than cast grids or multi Alloy strip caster and coilers. The grains are aligned along the strip. Rolled strip caster : This system - casts strips with higher thickness from alloy made in the pot and fed to casting wheel. Post casting strips are of about 12 mm thick and then the strips passes through a series of Rolls ( 5 to 8 sets) to roll it down to the required thickness (0.65 mm upwards). After going through a finishing roll to reach the exact thickness, the sides are trimmed and then coiled in the form of Rolls. The Rolls formed from either system are generally aged in air/oven to the required hardness for the grid making operation. The cut edges/scraps of strips goes back to the casting pot. The alloy for positive and negative alloy are different and separate pots are used. Some makers have an alloying pot and then a casting pot. There are 3 pot system also, where one is alloying pot and two are casting pot. Cut pieces and blanks are returned to the respective pots by series of conveyors. The strip width requirement is within 55- 85 mm. Strip thickness are from 0.65 to 0.9mm. Output ranges available are 1.5 ton per hour to 3.5 ton per hour. For one expanded line installation, 1.5 tons/hour is ok. Manufacturing Concepts of Lead Acid Batteries

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The strip coming out of final roll and cleaned of excess coolant from surface are coiled in double coiling machine. Once coiling is finished in one set, the strip is moved to next set. The coils are generally less than 800m and weighs about 800 kg. length of strip depends on thickness and which is between 0.6 to 0.9mm. Aging period- for positive it is 3 to 7 days. For negative 7 to 30 days. Two coils are generally kept per pallet for storage. Issues : The strip coils made be clean of coolant and of uniform thickness across. The tolerance is specified by the maker. Length of coil of 5m be spread on floor to see if this is straight and within specified tolerance. The coiled surface of a roll, be flat and smooth to touch from outside. Most important control features are, preventing any dross to get into initial cast. Also the water temperature should be constant and cool equally both halves of casting. Alloys for expanded grids, typical. Positive

Negative

Antimony

0.005 max

Arsenic

0.002 max

Tin

1.10+/-0.05

0.25+/-0.05

Copper

0.002 max

Calcium

0.06-0.07

0.090-0.095

Aluminium

0.018-0.030

Nickel

0.002 max

Zinc

0.002 max

Bismuth

0.005 max

Cadmium

0.001 max

Silver

0.002 max

Iron

0.002 max

The Bismuth value can go high upto 100 ppm level. The Nickel value if obtained at 0.0004 level or less is better. Expanded grid production : Generally expanded grid production is in line with pasting line. But some users can have it done separately and stock Manufacturing Concepts of Lead Acid Batteries

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the expanded coils. Later as required the expanded grid coil are fed to pasting line with a decoiler station. Although storage is cumbersome, but there is no major time loss of pasting operation, during tool/type change. As Mentioned above there are two distinct ways to make expanded grids. Slit & Stretch type : This system originally with reciprocating type and later with fast Rotary system are available. In both systems, the strip coil is fed through, strip coiler, coil joining, to the Expander. The coils are slit by the die and then expanded to the required height of grid. The expansion is done on both sides with lugs in the middle. That is one gets two plates per width of grids. The central unslit portion is then ‘blanked’ to form the lugs. The two halves remain joined at lug top with top frame of the grid. After a flattening device - the expanded continuous strip enters the Pasting machine. Post Pasting, the pasted grids enters a ‘Divider’ where the joints of lugs are cut and also the width of the plates, producing two plates per width and goes via conveyor to Flash Drier and then to stacking device. In short the process is: Decoiler

(To decoil the strip coil)

v Strip joiner

(To join by tape or butt welding)

v Accumulator

(To make the feeding to expander Continuous) OPTIONAL

v Expander

(make the slit and stretch to required width)

v Tab Blanker

(To cutout the central strip to make the lugs)

v Flattening Device (For thickness and width) v Pasting machine v

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Divider

(To separate out the plates)

v Flash Drier v Stacking This operation is in one continuous line. Before and after pasting ‘dancing’ spaces are kept for balancing of speeds of the continuous expanded strip. The pasting can be with or without paper on the pasted surface. Progressive Expansion : In this method the expansion takes place by shaped cutter dies to cut and expand one half of the diamond. The next teeth cuts and expand the next row - the same continues one after another till the top frame. Difference between each row of cut and expansion with the next one is the node width. As the process is completed a net of diamond shaped grids are formed and hanged on two sides of middle portion of strip. The net of the diamonds are then made horizontal with the central uncut portion and then moves through the ‘Tab Blanker’ to blank out material to make the lugs - similar to the previous system. After a flattening (to required thickness) and edging operation - the expanded strips move to the pasting machine. Essentially the lineup of the continuous chain of machines is same for both Systems, with major difference in the expansion process. General Comparisons between two systems : a) Grid Profile - The diamond size for progressive expansion can have lower height of nodes towards the top - giving more metal presence, where flow of current required is more. The pitch is lower. While the stretch expansion has a wider bottom frame, owing to process of expansion, the bottom frame of progressive expansion is much less. The extra frame of stretch type has not such relevance to the grid except to add some rigidity. b) The stretch expansion twists the wires at the nodes, giving rise to a stress area and as such it is not advisable to long life positive grids. Some battery makers use it for positive, but for 1 year plus batteries. c) Height variation is generally higher in progressive expansion compared to stretch expansion. Manufacturing Concepts of Lead Acid Batteries

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d) While progressive expansion can have cuttings at node, by combined operation of Tab blanker, but in stretch type it is not at node. But this is not a key feature in terms of puncture failure, if the plate handling upto Assembly is more automated. e) Alloy & grains - With rolled strip, the grains are aligned in line with wires and as such internal resistance is lower and tensile strength is higher. In cast grids the grains are scattered and some almost vertical from the surface due to surface cooling. More grain boundary areas at the surface for cast grids than rolled expanded grids. f) Lugs - While one can have side lugs for use in negative, but offset lugs are essential for expanded positive use, as without side frames the top frame can bow up leading to top shorts. With thin strips - the lug cross section is much lower in expanded grid and as such it generally uses wider lugs to compensate the thickness area loss to some extent. This increases strap width. g) Weight saving - Weight saving of grid is key to such continuous processes, besides productivity. In about 70 million plate per year, 1 gm saved is 70 tons/year. So with about 15 gm/plate saved it is about 105 tons per year. Expanded line are typically planned for 5 to 7 million plates per month with 3 shifts running. h) Speed of operation - Stretch expansion units can be operated at much higher speed close to 45m/min, but generally the progressive types are less than 30m/min. But such speed can only help if the paste is available to match the grid speeds as well as Pasting line and plate stacking can match the speed. For high speed stretch types one can consider higher mixer size, twin mixers and also improve in mix time to gain the benefits of high speed. In general progressive expansion is more suited for units going for both negative and positive and stretch expansion for units who will do for negative only. Concast - Con Roll System : Concast: This is continuous casting process, where lead alloy is fed via a slitted shoe touching a rotating drum which has profile of grid cut on its surface. The internal of drum is chilled. As the alloy fills up the grid cavities made into the drum rotates, continuous strip of cast grids comes out from the bottom and are then coiled. The coils are stored for aging and then pasted via a decoiler operation, later. Manufacturing Concepts of Lead Acid Batteries

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The alloy melted in a pot adjacent to the casting drum is fed via pipe line to a block (pasting shoe) profiled to the drum curvature. The molten alloy moves out via slit in the block and fills up the grid cavities in the drum. Extra metal comes back to pot. One such unit replaces requirement of about 10 standard book mold casters. Grid Profile - The grid profile has frames all round, unlike expanded grids. One can get grid weights comparable to expanded systems. While grids can be with rectangular profile, but various other combinations like brick/diamond/radial/tree radial are also possible. One can have multi panel grids as well as tall grids, suitable for Inverter Battery applications. Alloy - It is generally meant for calcium negative, but if the grid profile is staggered ( brick or diamond shaped) some amount of Antimony can be used. It is basically to avoid piping. It is not very proven concept. Other features – Since the grooves are in the drum, so one half of the grid has triangular/trapezoidal feature and other half is flat. This can be little problematic in locking the pallets which happens in the diamond profile in cast grid, but with paste cover up from both sides – like in an orifice Paster, it is not an issue. The grids can be similar to twin plate type like expanded grids or can be in single row. Multiple grid profiles can be made but with same overall cutting width at divider, The lugs can be towards the center as in expanded grid or can be made on the outer side also. With lugs on outer side, it is possible to use the negative plates in formation operation as is done for cast grids. Lugs can be of regular shape too and not thin and wide as expanded grids. Since there is no tab blanking, as such metal returned for re-melting is absent. Wirtz USA are manufacturer of this system and is being use for decades in various parts of the world. Sovema and Chinese Companies are also in the fray. While an orifice Paster is a good system for pasting, but it can also be done in conventional paster or steel belt paster. Orifice paster has the best bottom coverage of wires. Drum paster is another option. Chinese double sided paster can also be used. Conroll - The system evolved to make grids for positive. This essentially is to Roll concast grids via a series of Rolls, thereby giving the Manufacturing Concepts of Lead Acid Batteries

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benefit of rolled grid (grain structure) and also flattening the grids uniformly with same profile. To make better adhesion of paste, the surface is not only finely embossed, but also has some pips which gets embedded in active material. It is an excellent grid for spiral batteries. While the performance claimed by Wirtz and cycle life proven by hot J 240 test, the system did not catch up well with battery manufactures, although a leading U.S maker has been using it very successfully. In general - For negative – Concast, stretch expansion, progressive expansion are all suitable and with comparable grid weight reduction. For positive - Con Roll and progressive expansion are suitable, although later is more popular. Continuous punching line : This is a more recent process, where sheet of lead can be formed to grid by punching out the pallet area. This essentially is to use calcium based alloys for positives and Negatives. The wide sheet of required thickness is rolled out of a casting and rolling equipment. The grid weight is comparable to other continuous plate making equipment. Grids of designed profile can be produced by punching out from sheet cast and then rolled. Calcium alloy is also used like expanded grids for both positive and negative. Generally the Rolled sheet is between 300-330mm. The grid can be made of many shapes and has frames all round. While some makers uses grid of same thickness as the sheet, but there are now designs with wires or nodes pressed out from node to node, to give greater thickness of grid overall. The process involved is to make wider sheet of rolled strip (to make multiple grid) and coil them. Thereafter Punch them and coil. The coils are fed to Pasting line. Aging is generally not required, from strip making to Pasting is like in expanded grid coils, which needs to be aged. The system of punching is not easy, but it can be by a long reciprocating punching tool or by a semi-rotary system. East Penn have been using this with Oak press and Wirtz. JCI, the US maker uses the punching system from early 2000.Sovema has also supplied to several companies. Chinese companies are also making the plant. The press needs strong foundation & vibration isolation. Issues with Casting Process : 1) Grain Boundaries : It is the grain boundaries which chemically bond Manufacturing Concepts of Lead Acid Batteries

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with active material.The grain of lead does not bond being chemically inert. The metals added to make the alloy, are between grains of lead. In a cast grid the grain boundaries are closeby and as such the bonding is good with active materials. In case of grids made with rolled strips, while grains get aligned in a line but the grain boundaries shift to longer distances. When the thick strip is casted, smaller grains are on surface and large grains at the central portion as the water cooling is from outside. As it rolls in multiple roll stands, bigger grains first gets flattened and finally the smaller grains. Some exposed grain boundaries can be on the surface of expanded areas and also at the nodes. For punched grids, grain boundaries get exposed at the cut ends, where ever it occurs. Use of taper edges at the cut portion is to make more areas exposed for bonding. In some cases a pip is also added. During curing, a corrosion layer is developed which bonds the metallic grid with active material.In the stretch expansion system with single roll casting, the grainboundaries are on surface well distributed. But the stretching action results into stress concentration at the nodes. So for using in positive, it can lead to early failure due to stress corrosion. For negative it is not an issue. Some people do use such grids for positive with 1 year plus life use. For Concast grain boundaries are naturally close by. Basically grains are perpendicular to the surface, which gets chilled. 2) Thickness: The grid thickness of punched grid made out of flat rolled strip is the strip thickness only. One can have from 0.65 to even 1.2 also. For punched grid, where nodes or wires are pressed beyond the flat surface, the overall thickness would be higher than sheet thickness. For Expanded grids nodes post expansion is twice the thickness of strip. After some flattening the thickness is reduced by 0.2 to 0.3 mm. Say with a 0.8 strip, one can get 1.3 to 1.4 as grid thickness. Further flattening increases load on the machine. For Concast thickness is not an issue and it can be based on grooves cut on the drum. While one face is flat, the other face has all the angles to increase surface area and ease of casting. One can have single large industrial grids or multiple small grids, in one go. 3) Lug width. Since the grids are made from thin strips, to get the desired cross section of lugs, they need to be made wider. This increases strap width.

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Volume : Continuous plate making, while being capital intensive, but factories with volumes of 1 million equivalent SLI battery/year, can easily go for it and the payback is quite fast. It is possible to have about 10- 15 gm. less plate weight than cast grids. It depends on design and machineries used. A B size plate can have weight of 17 to 26gms.compared to cast grid of 33 to 37 gms. Larger the diamond size capability available In the machine, greater is the weight saving vertical stroke length is very important. Another important feature is uniform thickness of plate, unlike variations in gravity cast system. Better electrical performance on high rate discharge is obtained too. Key Points in casting (Gravity & Concast) - Alloy Compostion - Temperature Settings - Aging - Thickness of Grids - Focus on scraps - segregation & checks Key Points in Continuous Plate Making - Operation at steady speed - Alloy composition - Check on wire breaking Environment : - Fresh air ventilation is required. So also low suction from melting pots to bag filter. Flame area need separate suction to scrubber. - Lighting of 200 lumen focusing on Moulds v v v

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6) Paste Mixing The Paste, which is the active material, is made in Paste Mixer for use in Pasting. Depending on plant capacity, various Paste Mixers are used. The penetration, temperature paste mixing, density are final parameters to check, but load current / kw of motor, temperature profile of mix and various timings of dry mix, water addition, Acid mixing, final mixing time, are variable which needs to be controlled/specified. The Mixing systems are of various types. Commonly used types are: a) Sigma Mixers/Z-blade Mixers - Mainly used for mixing capacity from 100 to 500 Kg/batch. Here two rotors in the shape ‘z’ move in tandem in horizontal mixer shell. The Mixer body is generally water-cooled. The Mixer can be rotated to discharge the paste in to any trolley or conveying system. The loading is from top with shell horizontal. A covered hood can be fitted for suction of air to cool the paste. Acid and water tanks can be hung on brackets or wall. The mixing is by shearing action of the rotating blades, through the wet paste. The paste quality is good with high degree of pastability

Fig.07 b) Muller Mixers - (Fig.08 B) In these mixers two rotating Muller’s move inside the round horizontal Mixer Shell. The Muller’s hang on supports and rotates as it moves with the friction of paste. A small gap is kept between Muller and the flat base. The action of mixing here is like kneading. There are scrappers to scrape out paste sticking to Muller roller side faces and also from the side of mixer shell, so that the paste is brought on Manufacturing Concepts of Lead Acid Batteries

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the way the Muller’s move, to knead them. For use of high Carbon and Graphite additives, muller mixer is much better than paddle mixers. Present day almost 2% Carbon and Graphite additives are used for negative plates for special application. The Mixer shell is water-cooled. The top cover can be opened. All oxide, water, acid, additives are added in measured quantity via various ports. There are duct lines for entry of chilled air and exit on the opposite side of the top cover. The chilled air from Heat Exchanger moves over the changing surface of the paste under mixing and sucked at from the exit port. Apart from cooling of mix by contact of chilled air, there is also evaporation of water from the mix by the air getting warm, thereby cooling the mix, as the water takes the latent heat to become vapor and go with air. This heat is taken from the mix to cool it. Purpose of chilled air is to negate variations of atmospheric conditions. The chilled air enters close to saturation level and as it gets warmed by the paste, it has space to take up moisture evaporating. So amount of air going through is important. For a one ton mixer it is about 5000 cu.m. per hour. The discharge should go to scrubber. The discharge of ready paste is from the side of mixer through a rectangular gate. Generally the drive is from the bottom of the shell to the Central Shaft connecting to an arbor. The two arms fitted with arbor holds the Mullers in suspension and also the scrapers. Side scrapers are meant to clean the vertical bottom faces of the mixer clean. Any residual paste sticking anywhere, post mix needs attention to the scraping system. Such paste once dried up can create pasting problems and performance problem of plate. Generally these mixers are mounted on a platform around 4 m high, so that the paste upon discharge from mixer can vertically go down to pasting machine hopper by a cone feeder. The Cone feeder is a conical device, with a rotating scrapper inside and a bottom gate (manually or automatically operated). The pastes are required for the pasting machine is delivered through the gate by the cone feeder. In Muller Mixer of ‘Simpson’ type the discharge is from bottom (side is also done for some cases) to discharge paste to trolley’s/bucket skids, which are then moved to pasting machine for manual loading to the hopper of pasting machine by shovel or drawing the paste from a lifted and tilted, bucket. Generally in Simpson mixers, the loading of oxide is by drums and cooling air is via multiple vertical pipes fixed on the wall. Supply air is on the periphery of shell internal, vertically down and from a blower fan. The air flow is only after start of acid mixing and can continue till mixer is ready with mix. Start of chilled air is based on temperature fixed in programme. Manufacturing Concepts of Lead Acid Batteries

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Paddle Mixers - (Fig.08A) In this mixer the basic construction is above, but instead of Muller it has paddles (inclined to axis of movement) and scrapers to push the paste around the shell internal vigorously, thereby mixing it. There are multiple paddles and scrapper, so that the paste is thrown over each other, moved up and down to do the mixing.

Fig. 08A Paddle Mixers

Fig. 08B Muller Mixers

Oxide addition in both cases is from a conical bin with a gate below. The bin is auto weighed and stores oxide for the next mix upto the quantity required. The oxide is generally fed by conveyors from Silos to this bin. Acid addition and water addition is from Acid and Water tank with respective feeding pipes, supply pipe to mixer with valves and weighing system. So for a mixer oxide, acid and water are stored in respective tanks and are fed in the sequence as programmed in the control panel PLC/Computer. The additives can be added, manually via an operable slot at top or via a hopper with screw feeding. Water and acid is generally sprayed inside the shell via distributor pipes over oxide/paste. The Mixer motor load (KW/Amps), temperature of mix are key operating parameters to control, to arrive at desired density and penetration of paste. Temperature is auto measured from the side of the Shell by a Thermoprobe fitted with self-cleaning facility. Generally for Mix for tribasic sulfate - the temperature of paste is kept below 60°C or lower. Better be below 55°C. Manufacturing Concepts of Lead Acid Batteries

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While the water addition should be as fast as possible, the acid addition should be slower to around 4 to 5 lit/min for a 1 Ton Mix. The chilled air circulation can be set with temperature for starting. Additives can be added by making water slurry. Reuse of Sump paste is via a feed pipe through an opening and only for Negative mix. Better to keep this quantity below 12%. The Acid and water addition quantity are revised when sump paste is used. Some manufacturers use lower acid density than 1400 gravity normally used. In mixing process some battery makers’ use waters first, then 400 kg oxide, then additive and finally the balance 600kg oxide. Generally these Mixers are for mixing of about 1000kg of oxide plus water, acid etc. So final mix is generally above 1150 Kg. per batch. Mixers of 500Kgs.oxide / batch are also available. The density of mix is generally physically measured post acid mixing/ final mix and if one needs to do adjustment, and then the mix is prolonged with or without trimming water. Besides density, penetration figures (which are an indication of paste ability) are also measured. For same density, there can be different penetration values. Higher the penetration better is pasting. Values of density and penetration are specified for a particular mix with upper and lower control levels, to get as uniform paste as possible for pasting. Constituents of Negative Mix : For negative mix, besides the oxide, water, acid, fiber, various additives like Expander (a mix of Barium Sulfate, Carbon black, lignin), LSA (Stearic Acid) etc. are added as specified by the process, battery design requirements. Also the negative mix can utilize up to 12% of mix with sump paste slurry. The sump paste is generated at the Pasting Machine, Paste Mixer cleaning, Wet paste recovery from Plates, sump cleaning of acid wash tanks. The slurry so collected / settled/cleaned with DM water/adjusted to proper density is to be fed to the negative Mix. Consistency of its density is very important. It is around density of 2gm/cc. Constituents of Positive Mix : a) Grey oxide of desired specification and quantity b) Sulfuric Acid of desired gravity, quantity and quality Standards c) Water of desired quality and quantity Manufacturing Concepts of Lead Acid Batteries

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d) PP/Acrylic fiber of required type and length. e) Red Oxide as part of overall oxide. Generally less than 10% f)

Carbon black / Graphite in specific cases.

The mix proceeds in following steps · Dry Mixing with Oxide and Additives · Water Addition and Mixing · Acid addition in regulated manner · Final Mix with or without addition of the mixing water. Temperature Control Generation of Heat : it can get generated during the paste - mixing process from four possible sources. i)

Wetting of Oxide during initial addition of water

ii) Dilution of Sulfuric acid by wet paste iii) Reaction between the acid and the lead oxide iv) Mixing operation itself (frictional effects) Temperature control of paste-mixing is usually achieved by means of water jackets on the side of mixer shell and also at the base. But major amount of cooling takes place, by forced evaporation of water from the surface of paste by flow of chilled air. The upper limit of temperature of mix is generally taken between 55 to 60ºC. A reasonable practice is to cool the paste below 40ºC as soon as possible and complete the pasting within next 40-50 minutes. Chilled air circulation is the most effective means of cooling the paste as it gets mixed. A blower forces air through the Mixer, which flows over the paste under mixing. The air enters through a heat exchanger, where the atmospheric air gets chilled over the fins of heat exchanger. Temperature of air close to 18 degree C hitting the surface picks up heat from mix and also some water evaporates from the mix. The evaporating water takes the latent heat from the mix. The chilled air circulation can start immediately after dry mixing. Around 15 Tons of chilling unit is needed for a 1 Ton Mixer and flow rate of about 5000 cu.m/hr. In Vaccuummixing system, the mixer is sealed and the high vacuum created inside drops the pressure and water from mix evaporates, thereby cooling the mix. The vapor takes the latent heat from the mix. Such mixers can reuse/send back the vapor by converting it to water in heat exchanger and the air suction line. The Mix timings could be around 20 minutes. The Manufacturing Concepts of Lead Acid Batteries

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Mixer made by Eirich Germany, can be run in automatic mode. Quality of mix is very good, almost like butter. Some Chinese makers are also doing it. The Mixer is inclined type with a high speed rotating stirrer at the lower end. Mixing issues : Improperly treated paste will prematurely undergo the hydro-set reaction. That is the free lead will oxidize, the moisture content will fall and perhaps most importantly of all, large crystals of basic lead sulfates will start to form. These crystals cause the paste to become very stiff and sometimes become almost impossible to apply properly to the grids. In simple terms much paste is in a half way state between being fresh and fully cured. Faster acid addition also results in poor paste quality with formation of grits. Plates prepared with averaged paste are of inferior quality. - Paste unused can be kept for a shift inside cone feeder and be covered with wet cloth. - For changing from positive to negative mix, one need not wash the mixer. But from changing from negative to positive Mixer to Pasting Machine be thoroughly cleaned. paste

Periodically, scrapper blades may be adjusted or replaced if accumulation is seen on sidewalls or bottom.

Basic Mix Calculation : (from book of Prof. Prout) Some Key Figures: 1) Sulfuric Acid of 1400 gravity is 50% W/W. One liter of this solution can react with 1.593 Kg. of PbO to produce 2.16 Kg. of PbSO and 0.829 liters of water. 4

Density of Pb

11.3 gm/cu.cm

Density of PbO

9.5 gm/cu.cm

6.3 gm/cu.cm

Density of PbS0

3) Sample calculation for a mix w/o considering evaporation loss and some oxidation of Pb. 1 Ton Oxide (70% PbO + 30% Pb) 120 ltr water 60 ltr Sulphuric acid of 1400 gravity 4)

i) Wt of Pb Volume of Pb ii) Wt of PbO Volume of PbO

300 Kg.

30 ÷ 11.3= 26.55 lt.

700 Kg.

700 ÷ 9.5 = 73.68 lt.

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iii) Weight of PbO reacted with 60 l of Sulphuric acid

60 x 1.593 = 95.58 Kg.

Volume of PbO reacted =

95.58 ÷ 9.5 = 10.06 lt.

Volume of unreacted PbO =

73.68 – 10.06 = 63.62 lt.

Weight of PbO unreacted =

70 – 95.58 = 604.42 Kg.

Weight of PbS0 produced By Reaction = 60 x 2.164 = 129.84 Kg. 4

Volume of PbS0

129.84 ÷ 6.3 = 20.61lt.

Volume of water produced by Reaction = 60x0.829 = 49.74 lt. Weight & volume of starting water = iv) Total weight of components

120 Kg/120 lt. 300 Kg. Pb +

604.42 PbO + 129.84 PbS0 + 120 water =1 2 0 4 K g . + 4 9 . 7 4 water 4

v) Total volume of end products

63.62 (PbO)

+ 20.61 (PbS0 ) + 49.74 (water) + 120 (water) 4

+ 26.55 (Pb) v) Theoretical Wet Paste density

280.52 lt.

1204÷280.52=4.29 gms/cc

Above excludes additives, evaporation loss, hydration of lead sulfate, oxidation of lead in mix etc. But can be used as a guideline. Positive Mix for Car or heavy duty operation are different. Generally one uses around 16% Sulfate for Car types and 10/11 % for heavy duty types. Acid and water quantity is adjusted accordingly. Even the additives are different marginally. Additives : Expander in Negative plate : Expanders are additive to negative plates, to increase the electrical capacity and life. They increase the surface area of active material, produce and maintain fine grained crystal structure and prevent passivation when the battery is discharged. The addition of required expander is during paste mixing operation. The expanders are generally composed of Barium Sulfate, carbon and lignin. Each has different functions but complimentary to each other. Manufacturing Concepts of Lead Acid Batteries

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Barium Sulfate : It has a very similar crystal structure as lead sulfate. The Barium Sulfate crystals forms earlier, needle like, and lead sulfate crystals following it gets deposited on the needles of Barium Sulfate crystals, thus preventing its coating on the active material forming a nonconducting film called- passivation. So presence of Barium Sulfate makes active material surface much cleaner than without Barium sulfate. Quantity of Barium Sulfate varies with application requirement. The life cycle of negative plates increases considerably with addition of Barium sulfate. Carbon/ Graphite : It is inert and good conductor of Electricity as such its addition improves the conductivity of negative active material and aids in formation of plate. Various forms of Graphite are available, like expanded graphite. The types, prices are to be studied, used and then be incorporated. Lignin/Sodium lignosulfonate : VanisperseA ,HT/ Indulin AT are dark brown water soluble powders and are derived from spruce wood liquor. They are derived from Organic sources. It gets absorbed in tiny lead particles, so that these lead particles do not agglomerate to form hard solid mass. As such it increases the surface area of active material and Improves capacity. Batteries operating at high discharge rates and at low temperatures uses an expander with high percentage of sodium lignosulfonate, while those requiring moderate discharge rates but long cycle life use expander with high proportion of Barium Sulfate. In tank Formation some of the Lignin’s are lost in electrolyte. Both types improves cold cranking. Sulphation Inhibitor : It suppresses accumulation of Lead Sulphate on negative plates, thus better use of active material. Increase in discharge capacity, with reduction of internal resistance. Expander should be used Pre-Blended. In pre-blended expander with ready packs, there are several advantages. The dispersion in paste is much uniform, the particles sizes are smaller, with no lumps. The Active material strength increases with excellent dispersion. The diffusion of electrolyte is much better than using loose ingredients The chances of mistake by no addition or double addition in manual addition at Mixer eliminated, if it is nor pre-blended. It happens in manual addition. Even weights can vary. Weighing area needs space and is often dirty. They should be stored in cool and dry place. Amount of Expander : The amount of various constituents can vary depending on application. Generally 1% of the mix is used for high Manufacturing Concepts of Lead Acid Batteries

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discharge rate application with low temperature use. Mostly used on cranking application. A level of up to 2% can be used for moderate discharge rates - like Forklift/Golf Carts/Sweepers etc. A level of 1 to 2 % is used for Telecom, UPS, and Solar type of applications. The impurity level and ash content of the expanders needs to be checked. The impurities to check are Iron<200 ppm, Copper <170ppm, Nickel<10ppm, Manganese <10ppm The additions can be dry or wet depending on manufacturer’s recommendation, but it is always better to add by a screw feeder in Mixer or by spraying so that it evenly gets distributed in mix. Addition as a whole can be done with a good mixer, but spreading it across mix, is a better way. Expanders can be made into slurry in water and be added too. Pre-ground and mixed additives are better as the fineness is higher resulting its distribution evenly within paste. Carbon Additives : The enhancement of performance in modern day Lead -Acid batteries have been the focus area and newer products are available. Particular focus in recent years has been on Dynamic Charge Acceptance and suitability for PSOC. (Partial state of charge applications) - High rate discharge results in the deposit of lead sulfate on the surface of the plate. High rate recharge is not able to remove the lead sulfate buildup on the surface of the plate. As lead sulfate covers the surface capacity decreases. - Without carbon size and number of the sulfate particle deposition increases. - With Carbon the Lead Sulfate deposit as many small particles throughout the plate. High amount of Carbon greatly increases the time required to generate Hydrogen at the negative plate. - Carbon additions have pronounced positive effect on charge acceptance and cycle ability. - Carbon Nano Tubes offer great promise as NAM additives through endowment of high surface area and added electrical conductivity. The incorporation of high surface area carbon enhances the Hydrogen evolution reaction at the Negative plate. Particularly for HEV cycling. Carbon also improves the conductivity in active material, lead sulfates formed is an insulator. Carbon in the form of Graphite is very conductive. At about 2% level, it increases the conductivity of cured plate by 6 orders of magnitude. Graphite with much higher surface area than negative lead crystals serve as a nucleating source of lead sulfate. Manufacturing Concepts of Lead Acid Batteries

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- Carbon negatives operate well opposite PbO positive as a hybrid super capacitor. Negative plate with ‘’carbon only’’ has shown excellent performance in recent times 2

- Glycerene incorporated lead oxide as an active material in place of conventional Lead Oxide has shown enhanced capacity and higher over potential, compared to use of Carbon Black. Other Additives can be molybdenum disulfide and Boron nitrate. But use of such can only be done with expert advice and repeated trials. Molecular Rebar is also a performance enhancing battery additive. It comprises of discreate nano tubes . It can be used for both negative and positive pastes in aqueous dispersion. There is a relationship between amount of carbon and expander for optimum performance. The carbon additions be maximum up to 2%. Carbon has effect of super capacitor also. Although it increases water loss but increases CCA performance. All these performance improvement additions add to the cost. But the benefit be compared to cost and then be decided. With repeated trials these can be used and not just blindly as advised by the suppliers. Plain and simple Lead acid batteries of yester year are rapidly changing and one needs to experiment with various additives before deciding. Some critical batteries for motive power use like E- Rickshaw etc can surely get benefitted with these newer additives. Tetrabasic crystal addition (TBLS) : This is an additive required for positive active material where tetra basic crystals are required. One way to produce is to generate it with higher temperature during Mix / Curing, but it tends to form large crystals of tetrabasic, than required. By adding in fine particles in Mixing at normal mix temperature - its’ distribution in active material is more uniform and crystals are smaller and evenly distributed. The curing can be done at lower temperature with saving in energy. Curing and Drying time is also shortened. The crystals increases the porosity and have conductive presence in active material. The bonding of active material enhanced with the crisscross needle type crystal structure. The crystalline structure is stable. Reduces softening of active material. It can improve cold cranking ampere, reserve capacity, improves free Manufacturing Concepts of Lead Acid Batteries

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lead oxidation and reduces plate to plate variation. The life of battery is also increased. Major use is in Inverter, Cyclic duty operation. It can also reduce the total curing time and related high energy costs required otherwise, as these are formed at lower curing temperature. Addition of Red Lead in positive : Red lead is added in VRLA positive for specific sizes and varies between battery makers. VRLA has 3 distinct grades small, medium and large. Applications are different and as such mix specification and additives are technology items of various makers. In SLI red lead can be added. It reduces initial charging time. But with modern pulse charging system it is not relevant. Red lead can result into spalling of active material. Other additives : Sodium sulfate is used in positive mix to the level of 0.15 % particularly for deep cycle application. Sodium sulfate acts by common ion effect to prevent the harmful depletion of lead sulphate ions. In discharge battery solubility of lead sulphate can cause growth of dendritic crystals and cause short across the separators. The Sulfate ions gives added conductivity. With more sulfate of Sodium in electrolyte lead sulfate solubility decreases. The open circuit loss of battery is reduced by use of Sodium Sulfate. These are available in tablet form and also liquid form. It can be added in electrolyte itself at acid dilution plant. Some makers use Sodium sulfate in Positive Mix. Since it is highly soluble in water it comes readily to electrolyte. Use of Barium or Strontium sulfate to overcome self-discharge due to long idling. Barium Sulfate avoids Lead Sulfate blocking the pores. But negative point is extra shedding of positive active material. Use of phosphates/Phosphoric acid also helps in reduction of selfdischarge. Negative effect is capacity loss in initial cycles. Boric acid use is also possible, but such use be done only with expert advice. Tubular Positive Additive : For dry-filled tubular plates, the additive can improve back up time by a good marging.. This is again based on seeding dry powder of Tetra basic crystals. It improves the utilization of active material, which goes without taking active part in absence of additive. One can Dry at much lower temperature with reduced cycle time. It can be used @2kg per 100kg of Dryfillied oxides of Grey and Red lead. The best way is to try out and compare with and without additive. One should aim for 10% higher initial capacity and 6% average capacity Manufacturing Concepts of Lead Acid Batteries

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GEL additives : These are mainly used in Tubular and VRLA batteries. Although cost is increased but the performance of battery, particularly in cyclic application is enhanced. Colloidal silica is generally used. There is other type called Fumed Silica. Batteries be first charged in low gravity and acid is dumped for Tubular application. There after the Gel is added with electrolyte. It is better to do it in vacuum. Slowly Gel sets in and during charging, aim is to crack the solidified gel for movement of electrolyte and ions. The particles size of Silica is very important to decide what GEL to use. The near spherical silica crystals can be anything between 3 micron to 150 micron. Preparation of GEL. Add in Sulfuric acid electrolyte of about 1.28-1.33 gravity about 5-10% Phosphoric acid and mix. The GEL of about12% is added to mixed acid solution and stirred The same to be filled in battery and allowed to gel for 6-7 hrs. The battery can be put on charge thereafter. The level of electrolyte is very important and be limited to below group bar level, so that gases gets an escape route. GEL has a shelf life and better be used within six months. In VRLA application with AGM fume Silica is used. The procedure of addition and charging is best left to experts. GEL enhances performance. Greatly reduces stratification. Battery Internals : On same container, batteries can be with different internals for different applications. One example for a very popular battery is given below. 80D26 Battery (N50) variations for CAR/SUV/ISS applications 1.) Positive Plate 7nos/cell is heavier for SUV/ISS in same overall size and thickness 2.) Alloy is 1.6 % Sb based grid –same for all. 1.65mm thick grid 3.) Positive plate sulphate content 16% for car,10%+ for SUV/ISS. 4.) Active material same for car and SUV. Higher for ISS 5.) Negative Plate 8 no’s / cell and can be with continuous plate types 6.) Calcium negative grid of 1.15 mm thick 7.) Sulfate content of negative 15% for car / SUV and 13% for ISS. 8.) Active material same for car and SUV, higher for ISS 9.) Lignin same for car / SUV, lower for ISS 10.) Carbon same for car / SUV. Higher for ISS. Manufacturing Concepts of Lead Acid Batteries

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11.) Separator PE-GMAT for all 12.) Acid gravity 1.280 for car / SUV,1.260 for ISS This is just to understand the differences in design of same battery for different applications. The AM of negative plate is kept higher to delay Hydrogen generation, which starts around 90% of charge. How to know Sulfate Content ? PbO + H So u PbSo + PbO 2

223.2 98

303.2 18

i.e. 223.2 kg PbO + 98kg H So - 303.2kg PbSo 2

Acid - 84kg added in mix at 1400 gravity = 42 kg pure acid 98 kg H So u 303.2kg PbSo 2

So 42kg H So - 129.94kg PbSo 2

Total oxide mix u 1150 kg (approx) Therefore % PbSo u 129.94 x 100% 4

1150 % of PbSo

= 11.29% v v v

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7) Pasting Pasting : Pasting is the most critical manufacturing process in leadacid battery making. It depends on the nature and quality of paste, flowing to the grids moving either continuously or by a continuous flow of book mold grids. The purpose is to paste active material in the grid. It should produce l Plates with close tolerance in weight variability l Plates with close tolerance in thickness variability l Plates

with clean lugs, frames and clean area between the individual plates

l Plates without distortion/bowing/skewing l Low generation of slurry and paste waste l Minimal stoppages during operation l Plate generation matching paste generation l Plate generation matching downstream operation

Hand pasting of grids, is the best way to produce, but its output is very less as required by large capacity units. Around 600 grids per man per 8 hr. Shift. Whereas the Pasting machine can do 30k to 100k plates (SLI) per 8 hrs. shift. Hand pasted plates have good wire coverage on both sides and least variation on weight. There are several kinds of Pasting Machines in terms of hopper design, kind of paste application process, speed of operations, feeding methods etc. Broadly -

Belt pasting - Endless cotton pasting belt

Steel belt Pasting machine

Double sided Pasting machine (Feeding paste below the grid, with good coverage of wires)

Orifice Pasting - Can be used for both cast or continuous grid

Drum Paster - Used for continuous grids only

In both Orifice pasting and drum pasting, one can have good bottom coverage and typically 0.2 / 0.3 mm over pasting can be done. Grid feeder : Grids from stack are to be fed to pasting machine. Generally they are hanged vertically in the grid feeder. There are lower Manufacturing Concepts of Lead Acid Batteries

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speed Pasters (upto 60/minute)where grids are pushed to pasting machine from a horizontal grid stack by a reciprocating grid feeder, feeding the lowest grid out to the pasting machine. From vertical grid magazine to horizontal, to feed the machine, either a mechanical grid separation or vacuum pickup and feeding is done. The feeders can be ‘Roll-on’ type, i.e. can be taken out from its position for cleaning and maintenance of Pasting machine. Purpose of the feeder system for book mold grids, is to feed single grid at a time, one after another and move it over the pasting belt then to hopper inlet/in feed at set location. For continuous grid chain, the feeder is simple and is just to hold the grid strip down and guide at the set location. Hopper : Paste is fed to the hopper either by cone feeder of Mixer or shoveled from trolley/bin. Since they are in lumps, the hopper has various drives/rollers to make the paste move to the bottom, without voids and to the requirement of paste for pasting the grids. The design of hopper and its rotating paddles, rollers, serrated grooved rollers varies from maker to maker. The movement down below can be through two driven rollers of same size rotating in opposite direction or via serrated roller. The paste movement system is to generate sufficient pressure to fill the grids up to its bottom face. For serrated roller system (like Mac) the paste unused comes up from the delivery end of hopper via a pressure plate unit. The thickness of pressure plate or gap through which paste return back, can be changed by changing the pressure plate. This is to ensure required paste pressure on to the grid.This gives lowest variation of paste weight in plates. The moving belt below moves the pasted grid forward to the delivery end via a roller or squeeze unit, which is set to the required level to control plate thickness. The porous cotton belt takes up some moisture out of paste during pasting. The same is squeezed out as the belt returns back by a pressurized squeeze (adjustable pressure) - so that the belt is again ready to take some moisture as the plates get pasted on its forward path to the hopper. The belts are endless type and mechanism is there to adjust the belt tension below the bed plate structure of pasting machine. As the belt gets older, it is necessary to adjust the tension. Life of pasting belt depends on how well it is cleaned after mix and then kept wetted. Post hopper there is a piano wire diagonally across the belt to separate the pasted plate from the belt and move on to the finishing rollers. Many Pasters do not need Piano wire anymore. Present day pasting machines have VFD motors separately for hopper Manufacturing Concepts of Lead Acid Batteries

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and pasting machine. Best combination of speeds of both can be done by trials / studies, which can generate the best quality of pasted plate at acceptable speed for particular grid. Parameters to check are weight variation, scrap / waste / downtime. The hopper can be lifted forward or sideways by pneumatic / hydraulic / electric drives to clear out any problem due to double feed / grid distortion / jamming etc. Below the hopper there are fixed shoes and a center mark fixed so that pasting is clean and without smearing out on areas like lugs / frames / intervening portion of multi-panel grids. The shoe units are specific to grid types and its setting along with center mark is skillful job. Sometimes masks are composite. Material used is spring steel. Operation : Pasting machine as such has various adjustable setting means to get desired pasted plate quality. Normally to start with a zero setting, operation is done as specified in manual or shown by service engineers. Or follow as mentioned in manuals. Depending on feedback of weight/thickness data, various adjustments can be done. After FDO plates are weighed and feedback given to Pasting operator. It is better to weigh consecutive 10 plates to see any abnormal variations. The book mold grids are variable in terms of thickness, weight etc. and as such the pasting machine needs to be adjusted to get as uniform plate as possible. One of the key point is to see that twin plates out of a grid are almost same in its features and weights are balanced. Other Points : 1) Belt Pasting machine, as described above can also be used with continuous plate making by some modification in feeding system and also adding 4 paper roll units, so that the papers covers the paste plated area, from both sides. But speed is low. 2) Fallen paste collects in a space below and be reused by putting back into the hopper. The put back can be manual, with shovel or can be via a screw pump. Basically fallen paste is interior to original paste and as such its addition back is in small quantities and more often. It is done in bulk, pasted plate weights will change. One can try and see. 3) The hopper must have just enough of paste up in the hopper, so that it can be moved below by paddles and stirrers. Finally there are grooved rolls which exert a pressure below. Further paste sticking to hopper Manufacturing Concepts of Lead Acid Batteries

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sides at the top; be periodically put back into the active mass. To have paste full of hopper automatically either the conefeeder discharge be controlled sensing hopper weight or by level control with proximity switch. Sensors be so placed and adjusted that the paste is just enough. Grooved rolls needs to be replaced, when pallet missing is seen during pasting. Underfilled hopper gives lower weight and overfilled, higher weight. 4) Generally there is a gap about 5 to 15 mm between each pasted grid. The paste in between grids falls below as mentioned above, at the end of belt. It is possible to have a suitable system inter-linked with grid feeding with hopper and belt speeds together to achieve a zero gap pasting. This can avoid fallen paste. The fallen paste is inferior paste. It can also be pumped continuously by a screw pump with its inlet hopper below the belt drop area. Post operation these needs good cleaning. 5) Spring steel shoes can also be used by replacing fixed shoes. This can give a better finish of plates and also better bottom finish. 6) One of the most critical features of good pasting is to have good bottom finish or the wires of grid are covered with paste. This has a major bearing of performance of the positive plates and on grid corrosion. The design of grid, wire profile, its level with respect to grid frame, paste ability criteria of paste are other controllable features to get good underside finish. 7) Overpasting of the grid from its top face can be 0.1 to 0.4 mm, as required. In double sided Pasting machine one can paste both sides. But generally over pasting is more on top than bottom. 8) One paste maker has incorporated a lift up piece at infeed for paste going below grid. This is suitable for continuous grids only. Steel belt Paster or Orifice Paster have this feature. Orifice Paster In this the paste is fed through orifice on both sides of grid - be it book mould or continuous strip of grids. Since the paste moves through orifice, the essential requirements of its use are: l Uniformity of grid thickness. This can be achieved by use of planishing dies in grid casting machines. l Oxide of fine/uniform particle size often a pulverizer is used to pulverize the oxide or efficient screening of oxide through screen is required. Paste with Burton pot oxide is better for orifice Pasting. l Fibres

have to be of much smaller length as specified by machine

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Paste with good flowability and preferably softer paste. l Use of orifice paster can give excellent performance of the grids with good covering of wires from both sides. So overpasting is possible from both sides. Steel Belt Paster : This is with stainless steel belt in place of cotton belt in pasting line. It is generally used with continuous plate making system. Both side over pasting is good. Double Sided Paster : This is by having a two belt system by Sovema, providing a channel on bed plate after the first belt. A roller is also put in the channel. While pasting the paste goes into the channel and the roller smears the bottom grid face/wires with this paste. It just smears the grid and covers the wires with thin layer of paste, as such over pasting of bottom is limited. The Baoding double side Pasting machine has paste feeding close to entry point of grid, to go below grid. And then moves over to belt. The underside pasting is good. Full coverage of wires increases surface area of plate and also protect the grid wires direct contact with acid and get corroded. This is for positive. For negative paste coverage is good for increased surface area for reactions. Since active material is also mostly lead in charged condition, current conductance is not critical issue. Drum Paster : This is used with continuous plate making system. There is a rotating drum just below the pasting area. The paste has access to go below the continuous grid strip just before the pasting area. So this paste from bottom can smear the grid bottom face with paste. The Drum Paster has paper rolls fitment, so that the pasted plates have paper over the active material faces.Sovema is leading maker for Drum Paster. Acid Wash : Using of an acid wash system of plates is beneficial from the view of moisture retention is the plates.This is only used for cast plates. In modern production line, post Pasting ‘Flash Drier’ is installed, to quickly dry the surface of the plates, so that when they are stacked horizontally or vertically, and do not stick to each other. But by that process the plates loses between 1 to 1.5 % of moisture, during the flash drying. Retention of moisture in plate is very crucial for curing operation, particularly for large batch size oven, so that when the oven door is finally closed, the skids kept initially do not reach the high curing zone. Retaining higher moisture in plates is important from that point of view and acid wash helps that. Post acid wash, loss of moisture is less than 1%. So acid wash helps moisture retention. Manufacturing Concepts of Lead Acid Batteries

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For pasting machine without flash drier, plates can be picked and kept in skids with good gaps. Although it shows down pasting speed and needs good number of persons to do the job, but it does not need acid wash and more importantly with gaps available in between vertically stacked plate’s quality of curing is much better and uniform. Running of FDO in expensive, from energy point of view. Acid wash is primarily to spray/flood the surface of the plate from bottom and top. Plates move on a driven roller conveyor, rollers generally made of Teflon or UHMWPE material. The excess acid, drop- off to an acid collection tray below and pumped back to an overhead tank from collection tank. It need not be filtered. Little stay in tank makes the acid reasonably clean by settling. The tanks for negatives and positives have to be different as well as their gravities. The tank’s to have topup lines of acid/DM water. If a single Pasting Machine is doing both negative and positive, then it is necessary to have good cleaning of bottom tank during change over and use of separate acid tanks are required. Gravities are different for negative and positive. While acid reacts with lead oxide in active material to give a lead sulfate coating, the excess acid needs to be sponged out from the surface of plates, before entering Flash Drying oven. The sponge rollers of special grade are very effective for removing the extra acid from the surface. Another option is to use an “Acid Surfacer” where the acid just gets contact with plate top and bottom by a wet roller, where acid is put in trickle. The acid wash system should also have the facility to stop flow of acid with the stoppage of pasting machine, so that acid flow does not make the plate unusable. Acid washed plates also have less tendency to loose dust on plate surface in subsequent handling of dry plates improving environment. Hand pasted plates need not be acid washed and can be kept manually with gaps to prevent sticking. Finishing Roller : Finishing Roller has a major role to play for belt pasting machine. The Roller is kept wet by water drops falling via a pipe with holes. The Roller is wrapped with cheese cloth. The quality of various cheese cloths should be tried out. The gap between roller and the pressure of roller on plate surface varies with thickness of plate. Purpose of Finishing Roller is to make the bottom surface better with good wire coverage. Also Manufacturing Concepts of Lead Acid Batteries

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finish the plate surface with some undulations to increase plate surface area. The Finishing Roller is before acid wash roller. The finishing roller weight needs to vary for different plates. Generally both ends have a adjustable screw/Spring compressor. The finishing Roller needs just wetting. No flooding with water spray. Cleaning inspite of having proper masks below the hopper, some paste can stick to sides or for twin plate panel at the center. This can be blown out by airjet or airjet mixed with water. Clean plate edges helps in plate cutting and stacking plus loss of dried paste later. Skids for pasted Plates : Ideally, the skid, design and plate loading be such that there is clear gap between the plates, hanging vertically. This allows better and uniform plate curing. It can also be stacked horizontally (around 200 mm high) on flat skids. This is more so for continuous pasted plates with paper on both sides. For SLI normally two rows of plates are stacked vertically and skids can have 3 to 6 high rows. For Industrial plates, the placements should be with gaps and preferably with slots made to keep the plates separated. Generally for SLI panels, post placement in skids, an angled tilt 45 degree of plate stacks manually from bottom, can make some small gaps in between the panels. This is very important for uniform curing. Gaps are needed between plates. Stacking of plates can be done manually or also by overhead lifting device which can hold a full row of plates in its hooks and loaded to skids. The skids should have moveable support on one side to help hindrance free stacking. Staggered stacking in consecutive skids are better for large ovens with multiple rows for getting better air movement across plates stacked in line with air flow. Flash Drying Oven : The function of the oven is to just dry the skin of the pasted plates, so that, they do not stick to each other when stacked in skids. The drying should be optimum and too much drying is loss of moisture in plates, which is required for the curing stage. For different plates and as well as mix quality, the flash drying temperature be specified/worked upon. Even 0.1% additional retention of moisture is beneficial for the plate. If it is possible to paste upto 50/60 plates per minute, then there is no need of FDO. At this speed plates can be picked up stacked with gap of at least 2 mm without sticking. Semiautomatic Pasting machines can be Manufacturing Concepts of Lead Acid Batteries

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without FDO. This saves lot of energy. Oven : It is continuous oven, where the plates move from the pasting machine and to collection conveyor horizontally or vertically, in a heated air atmosphere, so as to dry the skin of plates. An atmosphere with carbon dioxide is also helpful as it forms some lead carbonate on the skid – which also helps the surface to be non-sticky. The oven can be : (a) Infrared type with LPG/Natural Gas, where ceramic burners are kept at highly radiated condition (almost yellow color) to radiate heat on surface of plates moving horizontally just below the burners. In just few seconds it dries the surface. (b) Electrically heated type – to do the similar function with radiated heat from the heaters as well as by convection air moved by the fans. Gas heating is generally dries the skin with convection heat as well as the carbon dioxide present in the flue gas. Some lead carbonate is formed over surface which is not sticky. The oven has got a primary heating zone, a recirculation zone of hot air and then a cooling zone. The circulated air post drying is moisture laden and has to be bled out in certain quantity. The manual of oven is to be studied in depth to study the settings of various dampers and controls to make the settings right. Too less exhaust means high moisture content in the air under circulation and one need to increase the temperature to prevent sticking of plates. Too much exhaust – on the other hand, can be loss of heat/energy. Speed of oven - is also very important - the traverse time is another variable to control to get better performance. It can be as slow to have one plate front is touched by others’ rear end. In this case the time the plate remains in the oven is longest. Generally a gap is maintained between each plate, based on collection and traverse time. The transfer of plates prior and post FDO has to be smooth. Vertical or Horizontal : Plates can traverse vertically hanging on a chain with its lugs. This is better way as air flow is uniform both sides, but good for thick plates/stronger plates, so that the pasted plate does not bow and fall out of the chain. Horizontal flash drying oven can be with a meshed chain or a multiple simplex chains. The latter is a better way as the chain is fully supported on channels and does not vibrate. Horizontal mesh chain can vibrate, leading to plates jumping on the chain and soft paste in each pellet has a tendency Manufacturing Concepts of Lead Acid Batteries

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to bulge out. Proper levelling of inlet, outlet and supporting rollers can take care of it. Horizontal ovens give rise to different flow and temperature profiles on top and bottom of the panel, unlike vertically moving panels. Post Flash Drying : Plates can be collected in Shingling conveyor either horizontally, one above other or turned vertically to hang on its lugs, and collected in a pack at the end of conveyor. Horizontal collections are to be collected manually and then stacked in skids. Vertically stacked panels, can be picked up by Material handling jigs to lift and place on skids. Often top and bottom of plate stacks can be brushed before pick up. Bottom row by a angled circular brush and top row by a reciprocating brush, to clear any paste sticking to the frames. It is better to brush the sides manually a group of plates before stacking manually. In high speed operation above 350 plates per minute one can have mechanized stacking with inching conveyor of stacked plates moving out. Generally it is close to 500 plates/min. Measuring of plate surface temperature at the exit and controlling the oven temperature is the best option. Generally experienced persons can feel the plates by hand and adjust the oven temperature. Sticking characteristics can also be seen by moving one’s finger across the plates on paste plate surface. Some collection system has auto collection system and once a certain height is obtained of stack the belt inches for ward. For large industrial plates, it can be collected manually from vertical or horizontal conveyor. Stacking of Continuous Plate Making : The plates are single after divider and after flash drying, they can either be collected in stacking machine or by hand. Machine collection is better as it does not damage any edges. There is vacuum belt pick and stacking also. Here any plate not right or in right position is dropped in a belt conveyor to move out 90 degree. Good plates are stacked one above other upto a certain height and dropped to conveyor below to a hand or robot pick up. Robot pick up has another stacking mechanism by which skids are loaded as programmed and skids in turn are stacked one above other for fork lift to lift out and carry to curing oven. Empty skid tacks are loaded on other side of stacking mechanism. Instead of Vacuum pick up stacking machines can stacks plates on inching conveyor or mechanized stack removal features. Scrap: Pasting machine area generates some amount of scrap, apart Manufacturing Concepts of Lead Acid Batteries

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from paste slurry collected from cleaning machines, tanks, sumps. These scraps can be categorized as startup /setting scraps, jamming below hopper, pellet missing, distortion, weight problems. Again good amount of rejects at plate cutting can be attributed to Pasting. They should be analyzed for corrective actions. It is possible to have zero rejection of cast grids in pasting operation. With a proper setting and speed it is possible. Some companies operate at high speed, with higher productivity, accepting some scraps as inevitable. v v v

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8) Curing and Drying Curing and Drying : The lead acid Battery technology is mainly based on creating required amount of pores in the active material, so that the surface area available is much more than what physical height X width X 2 side of a plate has. Chemical reaction of charge/discharge depends on total surface area available including surface area of each pore. The curing is different based on application of the battery. This is achieved by : l Retaining an amount of free lead in oxide and ultimately a percentage of this free lead as residual lead (RL), post mixing, pasting flash, drying. This RL is to be oxidized in curing process which is an exothermic reaction. l Keeping a moisture percentage in AM by adding in mix, evolving out of reaction of Acid with oxide. Some moisture is lost during mix cooling by evaporation, through the belt of belt pasting machine and then in flash Drying oven. Balance moisture is carried with AM to the curing oven.

The purpose of keeping the moisture in active material is to help the residual lead to oxidize. The moisture acts as a catalyst. Since the reaction is exothermic, the moisture gets vaporized and starts to come out, to the surface of Active Material. When this leaves the plate surface by the flowing air across the plate surface, new vapor start moving out from the place it is generated inside active material. Once the plates are cured and dried the pores left behind by the vaporized moisture are the ones which give the active material, the additional surface area to react in charging and discharging besides the basic plate surface. The moisture needs to come out of active material slowly, for this the external environment of plates have higher relative humidity and slow movement of air. So in short, during curing Residual lead u Moisture

lead oxide vaporized and leaves plate creating passages / pores

With RL & moisture coming down around 2 to 5% post curing, the plates are to be dried in separate drying oven or in the Curing cum Drying oven itself with changed conditions, so that finally we can get RL < 2% and moisture < 0.5% for green plate assembly and < 0.8% for Formed plate Assembly. Generally in Negative plate RL is bit higher and can be as high as 5%. Oven temperature rise be in slow gradient to avoid any crack in active material and particularly between grid and active material. At last 2hrs from Manufacturing Concepts of Lead Acid Batteries

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O 40 degree to 80 C.

Curing Oven Conditions : Since curing ovens are generally loaded with multiple skids, the time between first and last skid should be as low as possible. During curing the peak activity starts below a certain percentage of moisture in AM. So if the moisture in AM is kept higher as explained in Flash Drying, the first skid is not likely to enter the peak zone, when the last skid is kept inside and door is closed. The idea is to have uniform conditions available for all plates. While humidity inside oven is kept high, from the beginning of loading, but movement of air and temperature maintenance to come after the door is closed. During loading period humidity to keep high with no air flow. Generally a conditioning period is kept before first skid is loaded, which maintains high humidity and low temperature of around 35/40 degree C. There are some large curing rooms also in use, which have generally a fixed temperature, humidity and air flow maintained inside the oven continuously and skids can be loaded any time and taken out after a predetermined time. The Curing oven has an exhaust and also an opening with fans to supply outside air. The outside air replenishes the Oxygen consumed from the air already inside the oven. The RL needs Oxygen to get oxidized. For Automotive application, keeping high humidity and mild air flow inside oven, reduces both RL and Moisture progressively and almost with each other. One should try to achieve around 4% on both after about 8/9 hours from starting. Longer the period, the curing is better. The curing activity starts to peak from about 9% for positive and 7.5% for negative. The temperature shoots up and be limited within 60 OC for plates. Post Flash drying the moisture in plates for positive be about 10% and 8.5% for Negative. What are desirable conditions in curing? High humidity condition, so that moisture in the plates is retained for longer duration, to act as catalyst for oxidation of residual lead. Generally upto about 4% level the peak RL conversion takes place. So longer we maintain the period to reach this level, it is better for the conversion. Again we need Simultaneous reduction of residual lead and moisture in Active Material. If we have lower residual lead but with high moisture, then we will not have the desire pores, as the moisture removal during drying will give much lower surface area. l More pores with lower pore dia results higher surface area

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Less pores with higher pore dia results lower surface area l Former is for cranking operation and latter is for deep cycle operation. Generally a relative humidity level around 90 to 95% is adequate, but the optimum conditions are to be arrived after various trials for different plates. The air flow has to be regulated and uniform across height of skid. If the RH is low the loss of moisture will be faster from AM and one can end up with high RL in plate with lower moisture in plates. So balancing the drop of RL and moisture is key to successful curing operation. Further, during a curing oxidation takes place so availability of oxygen is required in the oven. With a small air space available in oven, the oxygen can drop to a low level hindering curing activity. Stagnancy : if the air flow inside the oven is too low then the atmosphere near the plates be at 100% RH level, resulting moisture remaining high in plate but RL going down. While drying, the levels of moisture will move out leaving large pore sizes. So some air flow is a must during the curing operation to avoid the stagnancy effects. Supply of fresh air is also required. Further it has been seen that temperature of curing oven plays an important role during curing. A lower temperature (35°C) increases the duration of curing and better plate conditions are achieved, particularly for PAM. There are many. who use higher temperature in curing to optimize curing conditions along with production requirements, while best of conditions can increase the curing time, but with some compromise ‘adequate’/’desire’ qualities of plates can be achieved at lower cycle time, by manipulating. l Temperature of oven l Humidity i.e. RH l Air Flow and Uniformity of Flow l Skid Placement l Plates Placement and Spacing

There are curing processes for negative where the high temperatures (about 80°C) is used in the initial period. It results into stiffer plates for subsequent handling and is again a compromise to suit production requirement. Since the reaction is exothermic the curing oven temperature can Manufacturing Concepts of Lead Acid Batteries

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shoot up beyond the limit, so the oven should be equipped to cool down the chamber, when required. For SLI, it should be maximum 60 degree, plate temperature. Oven will be at lower temperature If the ambient temperature is low, the oven should have heating arrangement to maintain the temperature. Below 30 C, Curing does not happen. O

For creation of humidity, basically Relative Humidity (RH), one needs to have the moisture/water in vapor form in the air. If the water has been sprayed in fine micro level, it can show high humidity, via wet bulb and dry bulb thermometer but since water is not in ‘vapor form’ that is ‘H 0 gas’, so the true RH of air is not increased as shown in the measurement by bulbs. Whatever water can evaporate by absorbing latent heat from air/plate/oven, only that part will add to Relative Humidity. Actually plates itself is evaporating moisture and in most cases that should be adequate to create the humid condition required for Curing, but if external means is required then it can be best done by generating vapor by Electrically heated water pot or supply low pressure steam from a steam boiler. 2

Once the peak curing operation is on way the moisture of plates released can give the required humidity level. The air flow should be just to avoid stagnancy and be as low as possible. During this period fresh air is to be supplied inside oven, as oxygen content depletes, due to oxidation of residual lead. The oven should be tried with various operating conditions to arrive at optimum condition from quality and manufacturing point of view. Plates to have uniform color and without any visible crack. Single row of skids in oven is the best. There are units, where a skid stacked with plates are just covered with a wet gunny cloth with some gap at the bottom. This simple way is quite effective also. But not suitable for places with lower than 30 degree atmospheric temperature. The humidity is created by release of vapor from plates and rise in plate’s temperature draws in air from bottom by convection and goes out through the cloth, so stagnancy and high temperature is avoided. This is possible in tropical climates as with low ambient condition, the curing of plates will not be good enough. One important aspect is about peak plate temperature. It should be aimed below 60 C and not exceed 65ºC for the positives surely. Generally the peak level comes after 5 to 7 hours from the start of operation. As O

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mentioned for negative some use high temp. (up to 80ºC) curing. But for gravity cast pasted plates generally same profile is maintained for Positive and Negative. Some curing ovens have designed to condition the plates about an hour, so that same conditions are prevalent for all. In some cases, particularly one may have to kick-start the operation by raising the temperature of oven. Post Curing - the same oven can dry the plates if it has the facility of l Raising oven temperature progressively to say 80ºC l High air flow across plates l Bleed off facility of high humidity air l Reduce humidity of circulating air to zero setting.

The reduction of moisture should not be very fast, which may cause crack.The rise of temperature be steps in 2 hrs or more, if it has PLC. Proper curing and drying of plates is key to the performance of battery, as such this is an area where most attention is to be given. As explained use of Acid wash post pasting can reduce moisture loss in flash drying. For hand pasting on Cloth - moisture reduction is not an issue. So also collecting plates pasting and stacking in skid with spacing is another good way to retain the moisture, but one has to sacrifice the speed of operation and productivity, as man-power required is high. Drying is carried out to about 0.5% moisture level for jar formed / green plate battery. For tank form it can be 0.8 % or less. VRLA plate curing has very exact specifications and it is a technology item varying between manufacturers. Production process up to plate making is same but curing and drying operation vary a lot. Expanded plates are also used in VRLA batteries, to reduce cost. In some cases better electrical performance has been seen. It is also possible to have tunnel type curing oven where skids can travel on chain and pass through various atmospheric conditions. Individual panels can also be cured in continuous curing oven. Here the total operation time is essentially shorter, and plates are all uniform. But it needs much longer oven space. Gap between plates for gravity cast plates is the best created by tilting the vertical plate 45 plus. So when released, it creates the gap. If plates are sticking to each other, air flow gets hampered. O

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9) Formation of Plates Formation of SLI and MC Plates : This is for dry charge battery for SLI or Motorcycle battery. Also for small VRLA In a lead-acid battery both lead dioxide and lead are on a higher energy level. In order to arrive at this state energy must be added to the plates with grid and active materials. The Basic Formation reactions are: Pos.

PbS0 + H 0

= Pb0 + H2S0 + 2e + 2H+

Neg.

PbS0 + 2e¯+2H+

= Pb+H S0

The hydrogen ion (H+) travelling from the positive to the negative plates close the electric circuit and leave the plates in an almost electrically neutral state. Soaking : Pores of active material created during ‘Curing’ operation gets filled by capillary action once in contact with sulfuric acid. The acid should be sufficient, so that we get acidic pH in electrolyte for electrical conductivity. This period takes some time and is between 30 minutes to 2 hrs. Depending on plate types and thickness. The acid which penetrates the pores react : 3Pb0. PbS0 + 3H S0 4

= 4PbS0 + 3H 0 4

The basic lead sulfates are converted to neutral sulfate PbS0 . This is an Exothermic reaction. 4

The acid entering the pores is diluted to almost water. The grid and active material contact points must be wetted by electrolyte for sufficient conductivity, as the active material at this stage is almost a non-conductor. The lead sulfate is slightly soluble in sulfuric acid - but this is very much required as further reactions can take place in dissolved state. This is called ‘dissolution precipitate mechanism. The lead sulfate must first be dissolved and then lead and lead oxide got precipitated in the active material. During initial soaking period, the sulfuric acid immediately reacts with free lead oxide on surface, so the liquids going into capillary is not acid as it has already reacted with free lead oxide and the status is slightly alkaline. The solubility of lead is fairly high in absence of sulphasion. So if one starts the current, the condition is good for producing alpha Pb0 . So it is 2

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necessary to provide some rest period so that sulfuric acid can penetrate by diffusion. The reaction is exothermic and it is necessary to keep the temperature down below 55 C. O

As the soaking is being done the porosity decreases as density of leady oxide is 9-5 and of sulfate 6.9 gm/ml and weight increase from 223 to 303 gm/mole. So volume increase = (9.5 x 303) / (6.9 x 223) = 1.87 times. If the soaking period is too long, the conversion with such increase in volume can create mechanical stress, which is not desirable. Even with long soaking time and with excess sulfuric acid available, the conversion of lead oxide and the tribasic sulfate to neutral lead sulfate will remain incomplete. This results from the change of porosity. The changes are not as drastic as in negative as the former is more voluminous from the beginning. Post charging the Pb0 and Pb0 balance is not drastic as lead oxide having 9.5 gm/ml and weight 223 gm/mol compares well with lead dioxide of 9.4 gm/ml and weight of 236 gm/mol. 2

Formation of Negative Plate : The basic reaction is PbS04 = Pb+ S04 Free lead ions are available directly on the interface between metallic grid and the electrolyte. The ions pick up electrons there and are precipitated as metallic lead when it is being charged. The deposition of crystals is needle shaped/dendrite structure with many branches and have large specific surface area, which is very much essential for the active material utilization. The resultant acid will further react with lead oxide and basic lead sulfate present and continue till all basic components are converted. Till this continues, the specific gravity of electrolyte does not increase and no additional heat is generated. As can be seen about 25% of theoretical charge the lead sulfate content rises after 70% only the lead oxide portion becomes negligible. Porosity - Lead oxide has density of 9.5 g/ml and the lead as 11.3 g/ml, with weight reduction from 223 gm to 207 gm per mole, so the volume of solids in percentage terms Manufacturing Concepts of Lead Acid Batteries

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V = 100 x 9.5/11.3 x 207/223 = 78% For Lead sulfate the weight losses are higher and the volume reduction is about 75%. Actual porosity is much higher than theoretical due to crystal structure. But point to be noted, that metal sulfate is of lower density and so, till 25% charge and also during soaking period, the pore volume reduces. So during this period it hampers further penetration of acid. The lead content in 100 Kg. of oxide used, is about 94.6 Kg. of lead. With 53.6 Ah, being equivalent to 1 Mole of lead (207 gm), the 94.6 Kg. of lead represents the theoretical formation requirement = (53.6) x (94,600 ÷ 207) = 24,500 Ah. Using Dry AM as a base this result in the weight specific theoretical charge requirement = 24,500/108.1 = 226.6 Ah/Kg. Formation Efficiency of Negative plate formation is high and close to 90% say, about 200-210 Ah/Kg, thereafter the hydrogen evolution can take place 2H + 2e = H . +

Almost 95% of active material can be formed with 100% theoretical input. Formation of Positive Plate : While the reaction of the basic lead sulfate with sulfuric acid the neutral lead sulphate is formed, but while charging the lead dioxide Pb0 is formed. Lead dioxide is semiconductor. There are two modifications of lead dioxide in terms of crystal lattice - alpha and beta. 2

Alpha is comparatively compact and generally formed in alkaline conditions, preferably at low concentration of sulfuric acid and elevated temperature. Discharge is possible in low current density, because of compactness and low specific surface. Beta modification has loosely attached small crystals. It is formed in acidic condition at low temperatures. It can be discharged with high current density. It has tendency for active mass shedding more than alpha. Generally in service it is about 20% alpha and 80% beta are in equilibrium, alpha acting as glue. A couple of cycles is necessary to come to the equilibrium. So alpha/beta problem is more important for the initial performance of lead acid batteries. Manufacturing Concepts of Lead Acid Batteries

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Crystal Growth : Lead Oxide tends to grow over the normal oxide and once the surface is covered, it is difficult for further reaction to proceed. For tri basic whose crystals are small, it is not that serious, but much larger tetra basic getting covered early, the formation is difficult to complete. So for production of positive plates i.e. paste mixing, curing etc. It is better to keep temperature below 55 C (Maximum 60 C). O

Alpha & Beta Pb0 : As the electrolyte throughout the plate is nearer neutral, so the initial lead dioxide formed with charging is of alpha type and acid is liberated. Initially it is absorbed by Pb0 and 3 Pb0. PbS0 present, thereafter Beta is generated. This happens around 10% of theoretical charge. Final percentages would depend upon acid concentration. Generally lower gravity of electrolyte is to give higher concentration of alpha Pb0 lower cranking power. Again higher temperature can give more alpha Pb0 . 2

High alpha has a gluing effect and with reduction of shedding. Lower quantity of acid in mix - can give higher PH of plates for a longer period and consequently higher alpha Pb0 2

Charging of Plates : The positive plates show a significant difference after 50 to 60% of the theoretical charge, with evolution of oxygen according to 2H 0 = 0 + 4H + 4e 2

Generally positive has less of AM compared to negatives, so the positive plates determine the charge amount. Almost 85% lead dioxide content can be achieved with 120% of theoretical charge, depending on quality of oxide, mix constituent and plate thickness. Even after 200% of theoretical charge, still some lead sulfate will be present and oxygen deficit in the Pb0 . 2

As the charging progress from outer to inner, the accessible lead oxide or basic lead sulfate decreases. Simultaneously specific gravity inside the plate rises. This is called polarization. So the charging voltage has to go up. The transformation of lead oxide and of the basic lead sulfate initially to basic lead sulfate gives out heat about 45KJ/100 gm of active material. Basically the electrolyte temperature goes up, as heat capacity is much less in grid/active material. Manufacturing Concepts of Lead Acid Batteries

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The gravity inside active material is much lower than electrolyte outside, because of neutralization and conductance is poor also. Maximum current density can be used is about 25mA/cm2 of surface. Measuring Cadmium voltage for plates can give indication of status of Formation. When the readings remain flat for 3 hrs, one can conclude that Formation is over. PbO level of plates is another indicator of level of Formation. 2

Tacked and Tackless Formimg : In Tacked Formation panels are inserted into grooves of Forming Furniture. Multiple plates are there for flat plates. For tubular positive generally one plate per slot. For 6mm tubular, it can be two. The lugs of panels are soldered to a banding strip and connected to next or previous tanks. Banding strips are of pure lead. The charging current flows via the banding strips. Generally 40 to 110 tanks are in series and voltage drop per circuit is taken as 3 Volt plus per tank. After Formation is over the banding strips are removed but it leaves a joint between plate lugs, which needs to be removed before plate cutting. If plates are properly tacked/connected, the formation of all plates happen, without miss. Banding strips can be flat or round. It can be reused few times . In tack less, panels are put vertically over conducting V type lead bars below. Lug corners touch these bars. The bars are connected to next tank by a vertical and horizontal bars. Since lugs are not soldered it remains clean, but care has to be taken that contact is good. Periodic cleaning of bars are important. In another tackles method panels hang on v type slots. One end is conducting and other end non-conducting. Conducting grooves are connected to conducting bars, which in turn gets connected to next tank. The plate with lugs on two sides are horizontal. Multiple plates can be put in each slot, which is trapezoidal. This is best way to do. Tackless obviously needs much less manpower than tacked. With clean lug ends no problem of cleaning of solders. But tackless needs regular cleaning of contact faces. Generally under formation is more in tackless. Non uniformity of plates are also seen. Temperature Control : Loss of heat from container wall is insignificant compared to heat loss in the air by keeping suction over the formation tank. Cooling by water / chilled water inside tanks is another option. Maximum temperature of electrolyte be 55 C and if it exceeds, a rest period needs to be given. O

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Charging Amount : Typically about 320 Ah/Kg of dry positive active material be used for good formation. It can go upto 360 Ah/Kg, if plate quality is poor. (Quality of oxide, cracks, high RL). It also depends on plate thickness and for thicker plate the Ah/Kg will go up. Getting 85- 88% PbO be the target. Prolonging formation can weaken the bonding between grid and corrosion layer, reducing life of battery. It is better to give a rest period of 1 hr after about 70% of charge input. This helps the gases inside plates to move out, exposing fresh surface. 2

The current, timings of charge, rest etc. are based on temperature, charge acceptance can be programmed in chargers. For SLI plate about 20 hrs. Total formation time is generally done for tank formation with about 1 hr. rest after 17 hrs. Extended formation cycles can be done for enhanced performance, but it is a matter of cost vs. performance. Some white patches of sulfate may appear in some positive plates. If it is below 10% of surface it can be passed. Otherwise it is to be reformed. Formation of VRLA Plates : Other than small VRLA and MC plates most of the Medium VRLA batteries have shifted to container/Jar formation. Multi panel plates of small/MC VRLA are formed almost same as MC plates. Some makers also have additional hot acid dipping system at a fixed temperature to improve the plate quality. This is mainly for UPS application for smaller sizes. v v v

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10) Plate Cutting And Brushing Plate Cutting and Brushing : Now to make individual plates from multi-panel, the operation of cutting/shearing is required. In a machine generally the cutting operation is along with brushing also. For manual cutting it can be by guillotine shear or sawing and then hand brushing. If the grids are multi panel, then for both formed and unformed type’s plate cutting and brushing are required. Plates can also be parted after flash drying to stack one over another. Sawing generally removes 2 to 3 mm of lug length. It is convenient, but results into higher environmental problem including scrap/dust generated from the portion removed by saw. For cutting by saw, as such a margin of 2 to 3 mm are kept in the grid. The other option is slitting / shearing. The slitting is generally by thin rotating disc separating two parts without removal of any metal. It can be done with a circular knife at top and a flat bottom with small clearance between the two so that, the edges come out clear without residues. Shearing can be with rotary disc or by punch press. The latter is more suited with more than 12 panels per grid, but it is very sensitive to plate shape/thickness etc. The shearing is by having two shearing edges from each side to move across the, edgns come at clear With good design and minimum allowable clearance, one can have clean edges at the cut portion, but variation can lead to sharp edges, which can create problem with separator/plate handling etc. A machine for doing any of the above needs l Feeding magazine to hold full finished grid with multi-panels (If the lugs are welded in Formation, then need to have clean cut the metal sticking to lug) l Plate segregation (mechanical / vacuum) and feeding mechanism.

Gen-erally the panels are vertical in magazine, but for slitting / shearing, they are to be made horizontal. For sawing - generally a bunch of panels clamped together and sawed when moved to it and then back after sawing for removing finished plates to storage bins. The plates after slitting / shearing, then move through the machine horizontally by moving chain with flags to take the full panel forward for the Manufacturing Concepts of Lead Acid Batteries

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brushing operation. For twin panel, there are two brushes on arbor and for more than two panels there are multiple rows of brush. Brushing - should just polish the surface and not actually remove the metal. In order that the brushing does only skim the surface, the lugs must be of good quality. If the lugs have a deposit of paste from pasting machine or have deep pencil mark in grid mold or have embossed marking in grid casting - then such brush will not work to make clean surface. Use of harder wire brush which makes the surface look shiny, but actually creates deep grooves. Flux sticking to these grooves, very often results into large bubbles in COS. For hand burning such brushing can be tolerated, but for COS burning, such hard brushing is detrimental in COS fusion. Flux sticks to grooves and make bubbles. Post brushing the panels move through the circular knives / shear tools and at this stage the panel needs to be firmly positioned to avoid dislocation/vibration. Generally instead of pushing the panels by the flag below lugs - the panels are pushed by its trailing rear edge. Change from lug pushing to this is done by another set of chains overlapping the former chain. Another reason is that lugs have a corner radius where pushing by lug may not center the panels properly. Panels additionally need to be held by long spring plates, so that the cut is better and without variation without proper positioning, poorly cut plates results - rejection. Post brushing and cutting each plate is then dropped on a stacking conveyor either one above the other and inched periodically in a bunch or dropping one above the other like a pack of cards, stretched. The plates are then grouped by hand and after check (and some hand brushing) are then kept on bins for Assembly. Generally a brushed and cut finished plate is used within a shift, so that the clean surface does not get oxidized. In COS fusion , basically top edge of lug gets fused, in side of lugs surfaces rarely melt and is seen as fine lines in a cut strap with etching. Fusion at the lug top is generally good enough, but for fusion of sides there are many actions including higher strap alloy temperature, good fluxing, pre-heating of lugs etc. are required. For more than 2 plates per panel, generally two stage work is involved

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i.e. X and Y cutting. So output of ‘X’ cutting has to go through Y-cutting. It can be a combined machine or two separate machines. The second stage involves more number of panels to cut than the X-cutting, so adjustment of speed / multiple row cutting can be considered. Generally at plate cutting the scraps are - cut lugs/false lugs / spruces and they need to be collected in bins below. While using same machine for different alloy grids, separate collection bins have to be provided with proper color code, so that mix-up is avoided. Plate brushing and cutting machines need good air pollution control system. Generally rejects at plate cutting is little higher than other areas, as defects happening at Pasting / handling are more visible here. Cut lugs can be used in melting pots. Generally center parting is done for SLI plates, but for complete feet removal it is better to have 3/4mm feet, total 6/8mm gap. Cutters can cut the feet fully. It is better that for such feetless cutting, mudrib is located away from feet in container. There are feetless grid design with 0.6 mm gap with 0.2 mm contact between two halves. If the plates are pasted clean, it is better way to separate the plates. Alignment is key issue. The cutter is generally with 25 degree disc cutter on flat anvil with 0.2 mm gap. There are also hand brushing and guillotine cutting machines. Sawing of multipanel plates are common practice. But the there is good amount of sawed material to collect and dispose. Sawing is done with multiple plates together located firmly on a moving platform. The same is then pushed through multiple saws in one arbour for cutting. Post cutting the platform returns back. Good ventilation is needed. X-Y cutting / slitting, these machines cuts multi panel grids in consecutive two operations. The y cutting is 90 degree of X cutting / slitting. Cleaning of individual plates on all side is very important, manually or by machine. For specific battery types (particularly small VRLA and MC) of plate are segregated by weight manually or by machines. Similar weight plates are used for making a battery. v v v

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11) Tubular Plates Manufacture of Tubular Plates : Tubular battery has tubular positive plates and flat pasted negative plates. Manufacture of negative plates uses same facility as SLI plates, if its height is within mold size. If the plates are taller, like traction batteries the casting and Pasting are of larger sizes. Called Industrial type. They need Industrial size pasting machine. Most batteries are designed with some duration of discharge and some being for deep cycle application with 80% depth of discharge (DOD),unlike automotive or Motorcycle batteries. Further, batteries can be 2 V to 12 V and their multiples. Eg for 36/48/110V systems Tubular plate essentially uses a perforated bag put over a spine/rod with one end closed and other end open. Closed end has a shape matching the bag end. This is called carrot. Open end is the place, where from, powder/paste /slurry is inserted and closed by a plastic bar. Called bottom bar. The plate has a lug to connect to a strap by fusion. The bags are called Gauntlet or PT bags. They can be with round tubes, elliptical, rectangular tubes with taper edges. Can be one per spine or for the full set of spine. Grids : They are mostly of Antimonial Alloy. They can be made by gravity casting or die casting. Gravity casting can be in manually filled mold or can also be machine cast. Calcium grids are also done for MF types. While casting the Spines are kept vertical with Lug at top. The bars are joined at bottom. Post casting the Grids are trimmed with cutting off material not needed. Post cutting the PT bags are inserted and stacked. Tubular Battery : Application Depending on application it can be l 2 V cells - as used in Motive Power, large capacity standby l 4V/6V/8V/12V individual batteries for some specific application Being a battery where it can withstand deep cycling and varying environment condition, the use is mostly where SLI / AGM cells finds difficult to operate. l Motive Power, Forklift, Pallet Trucks are major application area

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Power Plant standby - many with transparent SAN containers in 2 V l l Standby for UPS & Inverter l Telecom

towers exposed to poor electrical power and harsh

environment l Miner’s Cap lamps l Train lighting, Air Conditioning, Signaling in Railways l E- Rickshaw, Electric Vehicle, Electric Sweeper, Mower etc.

Its deep cycle feature and also ability get charge faster than flat plate types have made it the choice for above. It has longer life also comparatively. But for same ampere hour it is costlier than flat plate types. Heavier too. Further the cells can be with flooded electrolyte or GEL types. Stratification is common issue in flooded batteries. For gel type it is practically avoided. It can be better used where higher temperature and vibration are prevalent. Tubular Battery essentially uses tubular positive plate with flat negative plate. These batteries are meant for generally non-cranking operation unlike SLI batteries and have been in use for both Standby and Motive Power range as broad classification. Construction of Tubular Plate After gravity casting the bottom is cut to expose open ends for PT bag insertion. The bags / tubes can be inserted and stacked in skids. Grids cast have a rough surface with grain boundaries encircling the lead. It can join much better with active material than pressure die casting, but has higher electrical resistance as the grains are scattered. Machine Casting: The molds are generally made of Steel and the two halves are held together during casting by Mechanical or Hydraulic pressure. The mold has an entry point on lug side, where a nozzle seats. Through this nozzle the molten alloy is inserted into the mold. The insertion is by high pressure of hydraulic pump. In simpler machine high pressure air cylinders are also used. Post casting, the mold is taken back to other end and the mold opens up. The spine with all feeding bars are taken out in one piece and then trimmed to the required size. Some machine casting machines are fully automatic. The grid is taken out by lifting arms, Lubricate the mold surface by spray device. The cast spine with false lug are stacked in magazine. Further automation is automatic trimming the grid and gauntlet insertion. Manufacturing Concepts of Lead Acid Batteries

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Hadi, Austria are very known machine in this field. Chinese Companies are also making similar casting machines. The trimming is in a shearing tool. Common Tubular plate Sizes : Inverter is very common application where 6mm / 6.2mm gauntlet with 22 spines are used. Some use 21 spines too. 8mm 15 spines are also used for inverter. For Solar application 9mm 14 spines are generally used. The tubular spine given below has 3mm spine with carrot diameter of 8mm, the place where gauntlet/PT bags are fitted tightly. Other end of spine is designed and cut to fit into a bottom bar. The spines have a fin to centrally position the spine inside gauntlet. There is a taper top bar and the lug is generally at side. The length of spine can be cut to required size for particular active material capacity.

Fig.09 Typical drawing of a 15 spine finished casting. Manufacturing Concepts of Lead Acid Batteries

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The round spines are provided with fins at distances so that it is centered within PT bags. For wet paste filling the fins are lower height for the tubes to get in. Also the spine ends are shaped to fit within the bottom bar. The spines can also be flat, or half round. There are cast spines with two thin spines close together inserted into elliptical bags. While the carrot portion is to match the internal diameter of tubes, some designs have plastic carrots too to save cost. Alloy: For FLT battery it can be anything between 5.5 to 11%.Antimony. Higher antimony gives deep cycle capability, easy to cast, longer life, but water addition is high. For lower duty applications 1.65 to 2.55 percent Antimony is used. There are other alloying elements too. Size of spines: Thin spines of 1.8 mm diameter for lower duty application and maximum around 4 mm for bigger batteries. Generally BS and DIN standards are followed. While BS spines are in general with 15 spines and maximum width of 156 mm of grid, the DIN’s are with 19 spine and width of 260 mm The 2.25mm spine are of 22 spines, but there users with less or more spines. The spine diameter and numbers vary for various applications and designs. Length of spines for traction / Batteries can be as long as 610MM. Casting : The Spines can be cast single or two spines per mold. It depends on machine capacity and mold width available. With a single spine mold one can do 900 plus single grids from single mold in 8 hrs. shift. For automatic machines it can be close to 1250 plus/shift. The casting speed is 4 per minute, but stoppages for cleaning, lubrication etc. Reduces the output. Special grade of Lubricating medium is used. Output with twin molds can give almost double output. But machine capability is an issue The tubular plate consists of a top frame with lugs and below the frame several spines (rod like) are there of equal length. During casting the spines are joined by a frame and after casting the bottom frame is cut to expose the spines. A tubular bag, with specially treated cloth (woven or non-oven) are inserted through these spines up to the top frame enclosing the spines. The top frame where the spines start has a taper (called ‘carrot’) on which the cloth gets tightly fitted. The spine dia. is smaller than internal dia. of the tubular cloth and in this Manufacturing Concepts of Lead Acid Batteries

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annular space the active material is filled in. Post filling - the bottom portion (through which active material is inserted) is sealed with a plastic piece which has taper matching the internal of cloth and has a hole in center where spine gets located. So we have a tubular plate, which has a spine, a tubular cloth encasing the active material filled and a bottom bar sealing the active material. Active Material : The active material is generally oxide of lead with a combination of Red lead (Pb 0 ), Grey Oxide with some free lead. Use of Pot oxide is better. Even hundred percent grey oxide or 100% Red lead can be used depending on requirement. The density of the active material is very important for various oxide types and application. The mixes can be 25/50/75 % depending on design. 50% ratio for Dry filling is common. The Mixing is best done in ribbon blender. Mixed oxide should be dry and easy flowing. 3

Dry Filling : The empty plate with spine and gauntlet fitted in filled in inverted condition with the PT bag opening at top. The filling can be a single piece at a time or multiple pieces. The dry filling system can be: l By magnetic

vibration of the plates at various frequencies with dry oxide in a funnel at top. l By mechanical vibration of the plates with funnel at top. l By jolting of the plate bunches together with the funnel containing oxide at top l By combined magnetic and mechanical vibration.

Each has somewhat different end result in terms of packed density, uniformity across the length. By mechanical vibrations with eccentric drive gives the best result for plates up to height of 450 mm or so. For taller plates Jolter / Vibration can be used but Jolting tends to have more density at bottom and top than center. Vibration system if correctly done can give uniform filling. For small plates - it can be done manually by simulating jolting action when plates are encased in wooden box with a tunnel at top. Unless the extraction system of lead dusts are good, the lead-in-air in machine vicinity is high. Also plenty of oxide drop out to base while filling and must have various means to collect and flow back to the top. So essentially the equipment have an oxide storage (coupled with Manufacturing Concepts of Lead Acid Batteries

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mixing also of various oxides), supply to a top horizontal conveyor (screw type) and then chutes down below to filling station(s). At the bottom collection system of the mixed oxide and sending back by conveyor system back to the top. The oxide mix should be free flow type so that its movement is uniform. In some case heating/fluidization is necessary to keep the oxide in free flow condition. Use of Ribbon Blender to blend Grey and Red oxide before transferring to top feeding conveyor is good in terms quality and also fluidity. Post filling plates are taken out, weight checked and bottom bar is snugly fitted. Ammonia Dipping : Generally oxide particles are also sticking to the outside of the tubular cloth or gauntlet. As such it needs to be cleaned/wetted for subsequent handling. A process called ammonia dipping is done by which apart from cleaning the layer of loose oxide, it improves the shelf life for the next process. Post dipping plates for 30 seconds maximum, they are stacked on skids to dry at least for 24 hrs. under shed. During the process lead as Pb also gets oxidized in presence of water, which acts as catalyst. This operation is optional. It is generally done when plate have to be stored for maximum 2 months or have to be moved at a distance for acid Pickling/Assembly. Ammonia Dipping is not pickling. The dried plates can be straight way used in Assembly. Need to store in open for at least 24 hrs for reduction of lead and moisture. It can then be dried post reduction of RL and moisture. Pickling : Dry filled tubular plate’s needs ‘pickling’ for Sulphasion of oxides. (For wet filled process this is not required.) This can be done in Formation tank or outside by immersing in sulfuric acid before forming. If it is dipped in 1400 gravity acid, then 6 hrs. be the time. For 1200 gravity acid it can be upto 12 hrs. During the dipping process air bubbling is to be done. Adequate amount of acid be there so that gravity does not dip below 1300 or 1150 respectively. Post pickling, the plates are to be thoroughly washed and dried in oven. One can keep for air drying for 12 hrs. And then dry in the oven. The free lead becomes lead oxide in presence of moisture. By pickling process one generates rough surface on metallic grid for better bonding of material. The lead sulfate conversion to above 60% is usually made. The PbSO made inside active material by pickling changes to PbO , on charging with reduction in volume. This creates pores for acid to penetrate better inside active material. 4

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For doing it in Forming tank - initially with low current (say around 50Adepending on plates / tank) to build conductive structure in active material. The circuit will not take high current at the beginning due to high resistance. For Acid circulation charging also needs about 6 hrs. of Pickling charge before actual charging. Why Pickling? : The packed material is Red oxide, Grey oxide and some free lead. During charging volume increases to Pb0 so it will prevent diffusion of electrolyte inside the active material. It can result in more current / more time to form the plate. More of alpha Pb0 will be formed, reducing capacity of plate. So by doing pickling at low current, the active material is much more conductive for charging at higher current. By pickling it, it becomes PbS0 so there is decrease in volume while charging and acid ingress to active material takes place. 2

Pickling before putting in circuit in tank, is labor intensive, but eliminates the circuit time taken for pickling during charging. This reduces total cycle time of Formation Circuit or charging the battery. But post pickling - while ‘Forming’ or ‘Charging’ the plates, in tank formation, acid gravity will go up and after charging, some of it have to be taken out as effluent and compensated by DM water. Effluent with acid leads to - additional chemical for neutralization, additional effluent and additional sludge for disposal. Adds to ETP volume. Without pickling with only oxide present, the charging is not efficient. So if it is to be done in charging stage a period of low current charge is given for 6 hrs. The Pickling acid attacks the smooth surface of spines which gets corroded enlarging the surface area of contact between Metallic grid and active material. A chart of a Pickling study is given below with both 1400 and 1200 gravity acid and duration of 6 hrs. and 16 hrs. respectively. The ratio of Grey and Red Oxide in trial was 50:50 and 70:30. The amount of red lead is to grey oxide can be 100%: 0% to even 25%:75% depending on the design specification. The volume changes to sulfate, to lead oxide and also oxidation of free lead are critical factors in the formulations. Basically the plates need to be quite porous - so that acid can ingress deeper, giving deep cycle capability. Test results are from an actual study at a factory. The Sulfate content of plates be seen. Manufacturing Concepts of Lead Acid Batteries

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Test Results of Tubular Plate With Different Parameters

Wet filling : In the wet filling there are generally two processes. -

Slurry filling

Soft paste filling

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Slurry Filling : Here the mixed oxide is treated with sulfuric acid solution to form a slurry of required density and kept in such condition by continuous stirring. The density of slurry is between 2 to 2.2 gms/cc. The Red lead : Red oxide is between 15 to 40%. Sulfate conversion is much better than dry filling and pickling. The slurry moves in a pipe over to the slurry filling station and enters the annular space of Gauntlet with spine. Porous Gauntlet allows water/some slurry with air present to move out, thereby filling the plate. The slurry is fed with pressure, uniformly into the annular space between gauntlet and spine and the water moves out of the pores outside for collection and reuse. Size of pores in gauntlet is very important. Use of non-woven gauntlets are better. Post filling plates are cleaned in situ with water jets and taken out for sealing with bottom bar. They are then stacked for further operation of Curing/drying. Although the excess slurry flows back to the system, but still the operation area is wet and gets dirty easily. The tubes sometimes are not uniform if the nozzles are not well maintained and cleaned. The plant consists of red lead and grey oxide silos at top level. Measured quantity of both are taken into next level and mixed with acid to make slurry. Slurry is stored at lowest level and pumped to filling units by double diaphragm pumps. Recovery and reuse of water, mixed with solid particles are built in and collected in other tanks for reuse. Generally there are two filling stations side by side. About 1500 plates can be made in an eight hours shift. Soft Paste Filling : In this case, soft paste with density around 3, made in mixer, is pushed under pressure in between the annular space. The typical system is where multiple tubes (same as number of gauntlet holes) enters the annular space between spine and gauntlet and goes upto the top carrot area. Paste enters under pressure through the tubes inside the gauntlet and as the paste fills in, the carriage tubes moves back. When the tubes are out the annular space is filled with soft paste. The process of filling is horizontal. Paste filling open end is sealed with bottom bar. The bottom bar can be for individual plate or can be from a continuous strip. After fitment - it is cut to the required length. In automatic machine, the gauntlet and bottom bar are heat imprisoned, so that the bar cannot slip out. Paste filling the plates are washed/cleaned and weighed to check the Manufacturing Concepts of Lead Acid Batteries

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filled weight. Thereafter it is stacked and goes for next operation which is basically a curing and drying operation. Any variation in weight can be programmed in PLC. The wet paste can be of only grey oxide or a mix of red lead with grey oxide. The curing and drying is of 3 days duration and programmed. Generally red lead used is about 15%. The bonding of grid and active material is achieved by the curing process. The spines required for the soft filling system is different from dry or slurry filling. In later case the spines have staggered fins the centrally locating the spines inside the gauntlet cloth. For soft filling system the fins are not raised so high, to facilitate the tubes to go in, easily. The bottom of spines are also having special design for snug fitment with the plastic bottom bar. In wet, paste filling also some amount of effluent is generated and also paste waste. There are semi-automatic machines with manual feed and also automatic machines even connected with Spine casting machines as a single machine. Hadi, Austria are makers of these. China, also have manufacturers doing wet paste filling. Dry filling has been banned, to check environment pollution. Gauntlet or PT Bags : The Gauntlet as mentioned above are broadly two types -

Woven

Non-woven

They can be of individual single tube type or can be stitched/joined together in the cloth making system. Very simply two layers of cloth are joined at specified intervals, so the partition not joined can be shaped to a round shape (square tubes are also prevalent) by inserting rods within and curing to retain the tubular form. Non woven gauntlets have finer pores and uniform distribution. Its use can give higher capacity, upto 5% than woven type, although it is costlier. Charging : The Tubular Battery can be made with ‘formed’ plates or by ‘green’ plates for charging after Assembly. Formation : They are formed in Forming tanks. Smaller sizes can go in standard SLI size tanks, but larger sizes need bigger height tanks. The plates need to be tacked with a pure lead bar. For taller plates, the electrolyte needs agitation by air from the bottom to prevent stratification.

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If the pickling, washing and drying has been done earlier, than the charging can be done straight way. If the plates are to be pickled in the tank, then the acid gravity has to be higher and a small current of about 50A is needed to ‘pickle’ the plates for 6 hrs, as already explained. The formation temperature be kept below 55 C. Tanks may need either cooling by lead pipes inside with flowing water or by ventilation arrangement connected to scrubber. If the temperature goes high, a rest period is to be given. Based on temperature and the stages of charging e.g. soaking, ohmic resistance, polarization etc. The programme can be devised. Generally 360 Ah/Kg of dry active material is charging requirement. By measuring Cadmium voltage of positive and negative can standardize the process. 3 hrs of constant reading of gravity gives indication of end of Formation. Further charge weakens the plates. O

Washing & Drying : After formation, the negative plates be washed and dried in ‘Dry charge oven’. The positive plates will need thorough washing in wash tanks with flowing water and bubbling air. Post washing they are to be dried at 80 C. Since they are without the lug at other end to hang like for negative plates, either they can be kept flat crisscross or can be kept on skids in inclined way with bottom corner resting an angle. 4/5 layers of tubular plates in 2 rows can be kept in each skid. Post drying false lug of negatives are to be removed and both positive & negative plates needs cleaning of the lugs. For longer lugs than required, lugs are to be cut in guillotines. O

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12) Assembly of Plates Assembly : Generally, tubular batteries are made with Jig burning, instead of COS. For large mechanized plants, COS both semi-automatic and automatic machines can be used. Depending on the size of the plates jig boxes are made. For low height it is more like SLI batteries, but for tall plates, the jigs are stationary and have facility of stacking the plates and stackers in inclined formation and then made vertical with fitment of center bars and combs. The straps with crow feet are placed and then burned manually. Post burning and declamping the cells are lifted out by hoist for placement inside container. For Inverter / E- Rickshaw / small height batteries jig burning is done with burning boxes and combs. Small parts are casted and used for straps and poles. Casted items should be used within 4 hrs. or after 3 days. One can do in Cast on Trap machines. But as the lugs are thicker, they need to be tin dipped for proper fusion with strap. Which increases the cost. But manpower reduction with output rate increases. Assembly ( All Types) Assembly operation in a battery plant depends on type of battery and its components. Battery - Wise : a) Heat Seal types - like MC both DC & VRLA types, SLI and some VRLA types with PP Container and Lids, Tall, Tubular, Traction b) Epoxy type - like in VRLA either for small VRLA, EBike battery, non PP types, large VRLA Industrial OPZS types c) Pitch sealing - Ebonite/HR types, with individual lids, Plante, some 2V types, FRP container Batteries etc. Separator- Wise :

w PE & PE – Glass mat w Leaf Glass mat w PVC type

Machine stacking SLI, MC

Hand/machine stacking

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AGM types w w Sleeve type w Rubber types

Hand/machined stacking

For tubular plates

hand or machine stacking.

w Separator thickness, ribs, pores, application needs are decided by the designers. Any change of separator, should always be with all tests. Separator have high pores, while it separates negative and positive plates, but allows free movement of electrons. Dry and wet glass mat. Features DRY

WET

Advantages over wet

Compression

Prevent shedding of positive

Conformability

Adopt surface profile

Pores

Big

Small

Acid absorption higher

Fibre orientation specific angles randomly dispersed Easier gas permeability Wicking

Fast

Slow

Better

Stiffness/Rigidity

Ease of assembly

Thickness measured

20kpa

3 kpa

Stiffer product

Plate types-wise a) Flat plate

MC, SLI, VRLA Small, Medium- large, Cap-lamp, large Industrial types, EV etc.

a) Tubular

Small and large for Inverter/Motive Power

b) Plante

Generally 3 sizes

STACKING : In the operation of Assembly line, the first item is stacking. Manual Stacking : It can be just manual stacking with flat separators, some units also do with ready PE envelopes for small volume, Inverter types, large Industrial sizes etc. Often PE is used with flat glassmat separators also. AGM types are also hand stacked be with manual folding/semiautomatic machines for folding. Automatic machines are available for AGM stacking also. Machine Stacking : While machines are there for flat separators like PVC, leaf glassmat, but generally manual stacking is there where labor is cheaper. Manufacturing Concepts of Lead Acid Batteries

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Major machine stacking is for PE envelopes often only PE or PE with Glass fleece or PE with glassmat. While PE along with Glass fleece together can be used either in combined or via separate rolls, but PE with leaf glass mat needs separator feeding stations post enveloping of plate. Depending on design either negative or positive is enveloped. Ridges / ribs on PE always face the positive plate, be it negative or positive enveloped. Glass fleece or mat is also facing the positive plate. PE enveloping machines are of various speeds depending on the COS capacity. Some units do ‘offline’ enveloping of plates stacked manually later or may be feeding different assembly lines based on battery types. For online feeding, it is kept before the COS. It can be manually loaded to COS jigbox or to COS infeed conveyor with loading to COS mechanized. With Auto loading system there is a need for buffer table fed by stacker with robotic pick up. This is to take care of loss of time due to small interruption of either stacker or COS. Stacking machines often have stoppages at various stations in stacker for few seconds/minutes. Generally uptime of stacker is less than COS, so stacker output needs to be higher than COS. Also have buffer table. While COS -8 Type can be fed with one high speed stacker, COS-6 will need two with bigger buffer table. PE envelopes are fed in rolls of required width. The internal and external dia of Rolls are to be specified to stacker suppliers, along with plate details and separator details. A good stacker will have following components: t PE Roll station with easy move out of PE strip. t A PE strip joining station to join previous and new roll for quick change over of rolls t PE feeding unit through a cutting device, to cut the PE to required length up to a stop. t PE folding station generally in the middle of the cut PE piece. t Plate

feeding unit from stacked plates generally with vacuum pick up from magazine or vertical stack t PE sealing station to seal both sides of folded PE with plates inside.

The sealing can be by mechanical crimping or by heat/ultrasonic sealing. Generally PE width is higher between 10 to 14 mm than SLI plate width Manufacturing Concepts of Lead Acid Batteries

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depending on plate thickness, size and area of crimping. This also takes care of some variation as specified in plate shape. For small plates like MC, it can be of lesser width. t Some makers have a separate plate for doing the fold and retract where a single plate then moves in. This can give a uniform/designed fold with addition of additional mechanized unit. It can also take care if the forward edge of the plates are not square and smooth. t Post folding, there has to be a detecting station, if the PE is short in height or folding is not proper. Some users often put in an image comparator to locate any abnormality beyond specified tolerance. t The enveloped plate is then stacked with plate different from the one enveloped. t The plate feeding can be by one or two feeding stations depending on even/odd ratio of plate groups. The feeding method is similar as above. If a glassmat has to be fed separately (It becomes a combination stacker) then it will have stations to feed. Feeding station can also have lug cleaning device, as an option, particularly for plates made in continuous way. t The plates then move into either a magazine via Geneva wheel to make a complete group and it then goes to outlet conveyor slot, which moves forward by one step so that next group can be stacked. t Feeding of glass fleece can be with PE roll with already glass fleece in it from PE supplier or by a separate roll and both joining together at the feeding point before folding.

Stackers are sensitive machine and must have good air extraction system. It needs to be cleaned every shift of dust etc. The machine adjustment is skillful job. Change of plate types/PE types also needs perfection and experience. Modern enveloping units also have panels to record output, stoppages due to various reasons, yield etc. etc. which can help the supervision to improve. No. of rejection of plate/separator is a permanent loss and needs a focused approach to reduce/eliminate But generally if the plate quality (dimension, thickness, trueness) are good stackers have least problems. So primary focus is in plate quality. PE can also have problem of waviness, bents, holes etc. leading to rejection. Pin holes are generally marked in suitable color spots by PE separator maker and are detected by the machines before folding. If the PE cut piece is rejected due to this, the plate feeding also does not take place. All sensors/proximity switches for detecting faults must be in order always to get the best output from the stackers. There are several such Manufacturing Concepts of Lead Acid Batteries

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items. The fault due to a stoppage is detected by light pertaining to the location of stoppage or an annunciation panel. Post group stacking, there is often use of color by spray or pen to mark on the group top off center, so that it can be detected, where any manual boxing is there to prevent reverse boxing. In assembly line, color sensors can also detect if there is reverse boxing. If the group is incomplete with desired number of plates, stacker itself can detect and reject via a reject station, so that defecting groups do not go to COS. This is often given as an option. For large Industrial plates, tubular sleeving and stacking machines are there before the group burning station or COS. AGM can similarly be used like PE in stacking machines, specially provisi-oned for AGM. For E-bike batteries, generally AGM is folded in wave form fold with plates in between each wave. In other words, there are two AGM pieces between the plates. Separator comes from a roll and crimped to facilitate operator for quick stacking manually. For small VRLA, plates are mechanically inserted from plate magazine to fold the AGM separator, cut from roll. They are then stacked to form groups. For large VRLA, stacking can also be with mechanization. Generally AGM sheets are cut from roll and stacked automatically between the plates. A ) Group Making A cell is generally composed of number of positive and negative plates with separator in between. All plates of one type are joined together by fusing the lugs with alloy in the form of a bar, called straps. So, positive plates are with positive strap and negative plates are with negative strap. If it is a 2V cell then there are posts on the straps which comes out through the respective holes in the lid fitted with alloy lid inserts. Posts are then joined with the inserts by melting with addition of alloy to the correct size for ultimate external connection. In some cases, there are molded pieces with built in feature (like holes on it) put over the posts and melted together. This operation is after lid fixing to the container by heat or gluing. The Cast posts are often with fingers (crow feet) in which lugs slides in and then burned manually in group burning jigs. For 2V batteries, like monobloc type each cell is connected to the next cell in series. That is +ve strap of one cell with negative strap of next cell. The end/last cells have posts to connect/protrude through the lids. Say in a 12V battery there are 6 nos. of cells connected in series. The terminal on lids Manufacturing Concepts of Lead Acid Batteries

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can be several types and are generally the standards are specified by customers / OEM. The cell or group making can be by - Manual group burning jigs or mechanized as in cast on strap machines called COS. Manual Group Burning : In single group or multiple groups, the lugs of the plates are clamped in combs. The combs have slots matching the lug sizes on which the lugs get fitted and clamped by another piece to create a space where the strap can be made with fusion of lugs with gas flame with suitable connector. These connectors are also positioned in the combs slot ; so that finished strap has the connecting piece to connect with next cell or go up via posts. These cast pieces are designed suitably for the intended purpose. It can be a w Post of either negative or positive w Flag which can be welded through partition w Small posts which can be joined by up and over the partition or above the lid with connection pieces. These small parts can be manually casted in molds or in strap / connector casting machines. For VRLA types the group burning jig has features to compress the cell to the required width / pressure and then the straps are made. After the burning, the pressure is released and groups are taken out for boxing in cells, manually or mechanically. The alloy used is different for different applications depending on the alloy composition of grids. It can be antimonial alloy or tin based lead alloy depending on the specification/design. While, 2 V cells are group burned in single station, but 6 or 12 volt cells are group burned in multiple jig boxes for higher productivity. The operation involved, are placement of groups in the jig box and clamping the lugs in combs and dams, then placement of cast pieces at respective places on to the comb, then group burning. Post group burning are de-clamped and taken out for boxing. The jig box is ready for the next cycle. For high volume multiple jig boxes are in rotation amongst a group of workmen, each doing a part of activity. For quality jig burning, the jig box, combs have to be well designed and well maintained, so that there is no run through. It is skill dependent and gas burning should be such that it fuses the cast pieces with lugs uniformly. Manufacturing Concepts of Lead Acid Batteries

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For VRLA, groups are also strapped by thin plastic strips to keep the plates and separator together for ease of insertion to the cell box. Group burning makes the lugs fully fused with strap alloy and are generally with lower weight than carton straps. Manual COS : This is mostly for VRLA small types or E-bike with up and over intercell joint. In this case the molds are with a handle and are dipped in the alloy bath and after taking out, the top surface is scrapped to level. It is placed on a table and immediately the jig box is placed over it with lugs facing the cavities containing the molten alloy. Pre-casting, the lugs can be trimmed, aligned, cleaned, fluxed, preheated depending on the facilities installed. It can be done manually by shifting the overturned jig box from one station to another or by a machine where the jig box moves automatically from one station to another. Since the molds are not thick enough to have posts or flags for welding, generally “up and over” intercell joint type batteries are made by this process. Such COS operation is difficult to do for straps with flags and posts. The jig boxes, post placement on mold are cooled by air either at the same place or on a conveyor with cooling air flow. The COS mold comes back after removal of the jig box via a conveyor for a conveyor cooling line. Semi - Auto COS These can be rotary with 4 Stations or linear. Linear - Group loading and take out at front end of machine. The COS mold is at the back end. Mold has lead feeding system by pump from a lead pot, mold heaters and cooling water flow with temperature control. The groups are loaded in front and also aligned by a separate attachment and pushed to a conveyor, which brings the already COS cast groups in the jig box. The groups are then taken out and boxed. Rotary Cast on Strap TBS COS 5 or Equivalent This came into being for increased productivity and here the lugs after preparation are dipped in molten strap both in a cavity, enabling the lugs to get fused with the molten alloy. Post solidification, the straps are already with either post, flags, pillars for further operation.

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Generally in the COS mold, both negative and positive straps are cast at the same time with entire stacked groups / cells fixed in a jig box are dipped into the COS Mold. Basic operation n Loading of stacked groups in jigs manually or mechanized. The jig boxes having spacing to load at particular only. n Alignment of the stack groups and also the lugs by vibration as well

as shifting device. n Cleaning of lug and fluxing n Lug pinching - generally last lug is bent little inside, so that it does not gets molded almost at the end of strap. n Lug pre heating - if needed. n Bring in the jig box over to the COS mold n COS

mold cavities get filled up to the required level and the lugs dipped into it to the required depth. Groups can be held over the molten alloy to get the lug end pre heated called double dip. n Post solidification is taken out from the mold, by rejection pins from bottom. For manual COS - groups one taken out of jig boxes are taken out manually. n Post Strap Casting - the jig box comes to the station where groups can be manually or automatically lifted out, for boxing. Color marking is done on straps to detect wrong boxing visually. n Boxing be done manually or automatically in the battery case.

This is the simplest Rotary COS with manual loading and unloading. Jig boxes and molds are to be changed for each type of battery. Output varies with type of battery. For smaller NS40 type one can get 900/shifts and N70 type around 700/shift of 8 hrs. The COS can do truck types also, sometime two times for 1 no. 12 Volt truck battery. Some makers have larger jig box, where either one truck battery can be done per cycle or two car types / cycle. There are linear type COS also, where loading and unloading is from one end. Rest of the operation are similar. The jig box moves in chains. Cooling water system is automated with generally low flow of water Manufacturing Concepts of Lead Acid Batteries

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continuously and a high flow during casting period. The temperature of mold is maintained by round heaters fitted in molds and also by the amount of cooling water flow. Accurate adjustments of Water flow, temperature setting, cycle time of each operation is required. Entire system is controlled by suitable PLC. Molds need to be sprayed with suitable cork spray. The flux for fluxing the lug is various. Generally oil or water based. Later it is used mostly with CaCa batteries. Automatic Loading and Unloading (COS-8 type) An online stacker in connected with these groups from its conveyor can be picked up. 6 groups at a time and then loaded in a buffer table. From buffer table a robotic pick up loads another conveyor with slots for each group. Basic top & side alignment is done on this conveyor. Six groups from the end of conveyor are picked up and loaded in Jig box. Post alignment, brushing, fluxing it turns by 90 to top of mold. Double dip is done with heating before going into molten alloy. O

COS - 8 molds are designed differently and gives higher output than COS-5. Post casting the groups lift up and moved by 90 to unloading station. All six groups are picked up 1, 3, 5 are boxed and then the case rotates by 180 to load 2, 4, 6. Battery container with six groups then move up to assembly line. O

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13) Assembly Line Assembly Line (Continued) Assembly line differs a lot due to type of batteries. n 2 V cells - Heat Sealed - no intercell weld

- Epoxy Sealed - Pitch Seal n 12V cells - Heat Sealed

- Epoxy Sealed Then nature and speed of Assembly line - Semiautomatic lines - Automatic lines By type of cell to cell connection (12 V) - Up & over - Intercell weld - Over the lid - for Hard Rubber types Heat Sealed lines Essentially an Assembly line consists of following in series. -

Short Circuit Tester

Intercell welder (other than 2 V)

Lid placement (Manual or Automatic)

Heat Seal

Pole burning and building to Insert (Manual or automatic)

Leak tester

No punching / coding

There are also some reject stations to move out a battery which did not pass the particular tester test. Short Circuit Tester : This is done generally by applying a voltage across the straps in a cell, commonly between 1 to 1.5 KV. This can detect, if there is short between negative and positive plate or between straps with corresponding opposite plates. Generally puncture of separator is not detected. If the separators are Manufacturing Concepts of Lead Acid Batteries

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wet, then also the battery can get rejected. Separator can get wet if there is high moisture in the plate. The pointed probes fitted in a frame, fixed or adjustable distance and are connected electrically to the tester unit applying high voltage. Some makers also use color detection sensors to detect, reverse boxing by sensing the colors marked on the top of separators. Inter cell Welder : This is needed for cells inter connected by welding of flags connectors through the partition of the container. The container has hole round / elliptical at the designed location, at the center of the flags. The flags touch flush with the container wall. The welder has two jaws, coming down and positions themselves just outside the flags and then move to grip the flags. The jaws have trapezoidal tops and press the flags, so that the resultant metal from two ends touches together. High current is then passed for few cycles, causing the small contacts melt due to high resistance, melting the metal; the pressure of the jaws makes the molten metal to fill up the void in the container hole fully. This is a very simple description of the welding process, but it is a very complicated operation including the -

Design of tips, contact area

Void space volume

Current to pass in several KA

No. of cycles

Pressure exerted by the jaws/tips

Hardness of flag material

This is when flags are with manual burning with pre cast pieces burned with lugs. The cast piece age hardens and if an old casting is used, the hardness will be higher needing additional pressure. One can do inter-cell welding immediately after group burning with freshly cast lugs and store for balance operation. Tip Weld tips are designed, to force metals out of flags to touch and then post melting to move forward to make a full joint feeling up the hole of the container wall. Tips are generally trapezoidal round section and some are also Manufacturing Concepts of Lead Acid Batteries

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designed with a pip. For low height DIN types with offset lugs - elliptical tips are also in use to care of the short height available. The diameter, height, taper of the tips are designed depending on the hole size, container wall thickness etc. Tips need to be changed periodically, but needs to be checked 2/3 times in a shift and particularly in case of ‘Flash’ during weld. Flash : Normally ‘Flash’ occurs when the contact of both halves are not there or inadequate, resulting a spark. It is generally visible. Resultant liquid metal flows out of the joint. This weld is not good and be rejected. Cold Weld : This occurs when the pressure of the jaws makes the contact but the weld current does not flow and very little current to make fusion. So although mechanically the two halves are touching; but it is not a fusion weld to take care of the current which is required to flow through the joint during operation. This defect generally gets detected at the High Rate Discharge (HRD) station post charging. No Weld : This can occur even the jaws don’t get activated to squeeze material between the gaps. This can happen, during power disruption very commonly, when the batteries move out of ICW machine without welding. It can also happen, when batteries are moved manually for welding and operator missing weld/s. Cross section of weld area, when dissected, one can see, how the joint has been It is not uncommon to see a hole at the joint, result of solidification of liquid to solid and contraction. Shear Test : Weld strength can be checked by shear testing. Although it generates a stress at the joint, but can do periodic tests to see at what N-m the weld snaps. For various joints there is a minimum value in N-m. Some makers do shear test of all joints, by applying pressure without snapping the joint. Weld Controller : Generally electronic weld control systems have replaced such system, where the actual KA utilized is compared with ‘Set value’ to check if the welding is OK or not. Such controllers need to be calibrated also, periodically. In this respect study of ‘Robust Parameters’ is a good way to study and set current values/cycle time. The two main variables are KA and no. of cycles. Fixing KA and varying cycles - weld strength are checked in N-m as above. Then with fixed no. of cycles - KA is varied and similarly data is noted. These are then plotted in graph with KA and cycles as X & Y axis, Manufacturing Concepts of Lead Acid Batteries

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marking the good welds and poor welds. The good weld range is then joined by lines to draw the upper and lower ranges. The place where, two curves have the widest range is marked vertically and the center of such line giving a particular KA and no. of cycles are then programmed in weld controller. The margins available can take care of various aberration in welding parameters. XY – Weld For a battery with 2 x 3 layout, one of the weld is in Y axis and other four are in ‘X’- axis. The weld head rotates by 90 to take care of the ‘Y’ - axis joint. Some welders have one weld head, so to do all five welding it has to rotate for the weld. For two head weld station, the division is 3 in one head and 2 in other head. It is so programmed, that with battery movement time taken between one weld to other, the load is evenly distributed to get the lowest cycle time for the complete battery. O

There are machines with 3 - weld heads also and the last head can be set to do the Y welding only. The important point to note that each weld head is connected to individual transformers, with single transformer, there is a possibility of two welding occurring at the same time. By suitable interlock it can be avoided. Where multiple assembly lines are there, the supplies to the ICW’s are from separate units of Distribution box, so that possibility of simultaneous weld occurring at same time affecting weld quality. Weld heads are generally water cooled and periodically it needs to be checked if the heads are getting hot or not. A hot head can buckle reducing weld strength. Weld Control : Weld control as described about is based on constant current. There is software where it can be on the basis of constant energy also. Further the actual weld firing can be based on actual physical contact based on set mechanical movement of jaws or it can be based on sensing electrically - the contact and then the current is paused Movement of Jaws is another variation. Some manufacturers have a fixed jaw and a moveable jaw. Some have both jaws moving with toggle device. Further the movement of jaws can be hydraulic or pneumatic. Jaw pressures can be adjusted based on robust study. For COS line normally the connectors are of equal strength, but with manual burning and cast connectors the hardness can vary, depending on when the casting has been done. Some manufacturers have a system of control to keep the Manufacturing Concepts of Lead Acid Batteries

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variations within a short band and one can use a higher jaw pressure to take care of the variations. It is better that post group burning the welding is done within six hours from the time straps are cast in hand or machine molds. Hardness of such cast parts tend to move up and after 48 hrs tends to come down. If welding has not been done within first six hours then it is better to weld after 72 hrs with higher jaw pressure, when the hardness of straps are fairly constant but at higher level than initial hours. Stoppers : The position of stoppers for the batteries is important, as time taken for the batteries to move from one station to another is the major portion of total cycle time. So when the first welding is taking place, the next battery to go in should be as near as possible to reduce movement time. With multiple welds by a single head, the batteries need to be positioned quickly between one weld to another. It can be by a set of stoppers or the batteries moving in a carriage. The later system is better, as for former it needs de-clamping, movement of battery and then re-clamping of the battery. Where only one weld head does all 5 welds, the position of table is generally changed to suit. Online hole punched containers are best for ICW. As the hole positions can be programmed to suit. Otherwise it is better to do hole punching with reference to bottom surface of container. For fully manual operation it is better to mark the hole location on container surface by a pen for easier location. During welding the conveyor should not be running. Either it should stop or be lifted up by the table on which battery is resting. It is better that battery conveyor is stopped during weld or be on a carriage where battery bottom does not touch the moving conveyor. For all welding activity battery has to be kept clamped and stationary. There are machines, where weld heads quickly positions itself for the set of welding’s with battery clamped at a fixed station. Manufacturers specify the cycle time based on battery sizes. The speed of welding machine should be little higher than COS output, so that the later does not stop for the welding machine not able to cope up. It is better that there is no accumulation of battery between COS and welder/short circuit tester. This can help to detect any COS problem quickly and in less number of batteries. Manufacturing Concepts of Lead Acid Batteries

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The cast straps are post COS and it needs to be cooled with air blast, otherwise the hot metal touching the plastic container can create distortion of the partition or can cause plastic film to come within the weld joint. There are few important things to check before welding is: a) Burr free hole in plastic partition b) Hole located at correct height c) Hole located at correct location horizontally d) Both connectors of the straps are flush with the partition wall naturally with correct location of partitions in jig box or correct location in burning jig as the case may be. If the vertical faces have to be dragged to the partition wall by the jaws, post welding there can be a narrow gap, through which acid can sip in by capillary action to cause corrosion of the joint. Basic Stages of Intercell Welding : Basically there are two types of connectors for ICW. a) Formed projection type i.e. extrusion type b) Cast weld tips on connector. ‘Cast projection’. In the first case connector faces are flat and can be cast in COS. The electrodes have tips. As the jaws come closer, it pushes lead through the partition to make initial contact - called ‘squeeze’. The current then applied generates intense heat as the resistance of small contact face is high, the partition hole starts getting filled with the molten lead called ‘Weld period’. This is between 3 to 5 cycles for SLI types. For larger batteries it is more. In the next stage the lead is heated to final temp and the partition hole is filled with lead. Weld area then gets cooled and solidifies. It is ready to withstand the compression forces of partition. This is called Hold time. Periodic check with dummies be done, 2/3 times a shift. The parameters are set by a robust parameter study. At various values of KA and cycles welding is done and the weld strength is measured. The selection of the parameters which are generally in the middle of boundaries drawn by connecting good welds. Weld defects : Cold Weld - The fractured face is smooth without a feel of having wrenched off. Manufacturing Concepts of Lead Acid Batteries

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Spit Out - Molten lead having jumped out of the circle, also referred to as scattered lead. Weld strength is very low Crack - Micro -fine cracks can be seen by magnifying glass. Net - Very fine needle like grooves formed. Blow Hole - Air bubbles, void in nugget. If it is large size, (20% of area) it can lead into decrease in weld strength. V- Shape - Similar phenomena as blow hole but bubbles are not trapped and escaped out of circle. Shoulder - A state that a meniscus-like portion in the circle, like half moon is not welded, but rest is welded. Causes of Weld Failures : 1) Misalignment of connector over the hole 2) Misalignment of electrodes 3) Hole with burrs/plastics 4) Badly oxidized connector faces 5) Supply voltage variation 6) Equipment failures. Leakage of electrode to earth 7) Worn or wrong size of electrodes 8) Electrodes touching the top of group bar 9) Lead splatter & leaking out from weld joint 10) Variation in partition thickness 11) Wrong programmed. Robust settings not there. 12) Wrong hole diameter for the battery 13) No periodic check of weld strength 14) Unfilled castings, blow hole 15) Lack of instruments for initial set up 16) Flat faces away from partition, resulting clearence post welding for acid in-gress 17) Contacts for initial flow of current is inadequate 18) Hardened connectors due to long aging.

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Weld Splash or Spit Out : If the spit out is large and substantial the reason most likely - very high number of weld current cycles. The excessive weld cycle time leads to over-melting and subsequent lead flow. t Secondly it can be due to higher lead volume - generally attributed

to design of weld tip or variation in partition thickness of container. t Porosity in the strap, with venting getting blocked. t Misalignment - i.e. the weld is at one edge of strap t Not upright strap - resulting insufficient squeeze t Aged or hardened straps

Cold Weld : Occurrence of cold-welds are due either of the following causes I)

High cycle time of weld

ii) Large mating area of squeezed straps iii) Poor insulation of weld head iv) Interruption in power v) Fault in circuit/program Issues - 1) Torque testing of weld joint after initial startup is must. 2) Weld checks at beginning, middle and end of shifts with dummy straps 3) Quarterly check of weld controller with spare controller if available 4) Check of weld tips after any splash. 5) ICW of two lines should not be from same breaker. Cover Fixing : The Cover or lid placement can be done automatically by machine. Stock of lids are kept in magazine. For manual operation, lid is placed and with wooden mallet it is correctly located with respect to container and poles. Heat Sealing Machine : The heat sealing machine comes after ICW, short circuit tester and cover fitment. The machine can be for sealing a 2V cell, 12V battery and basic design being same but sizes vary. They can be for a single unit or 2 units at a time. Machines with 3 units are also there. Manufacturing Concepts of Lead Acid Batteries

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Basic features : Conveyor t

leading to machine and then conveyor of heat seal

machine t Cell/battery stops and clamping t Battery

can be on the conveyor itself (with conveyor stopping during the operation) or it can have a feature, where the Battery is lifted above the conveyor. t Cover

pick-up device by either grippers on side/through the vent hole or by vacuum pick up. t Platen, with electrical heating with proper temperature. t Mirrors

on top and bottom with profile to match with lid and container respectively. t Platen movement and stop devices. t Lid movement device to the mirror after the platen in position. t Heating and control panel with timers, temperature controllers. t Platen retraction after lid and container mating faces heated to the

desired level of melting. t Lid placement

device on container and then holding at fixed level for polymerization to take place. t Post sealing release and placement on conveyor (if container was lifted), declamping/stopper retraction and moving out. t The next battery ready to move in with the stop going back and then

following the same routine. Requirements Post heat Sealing, the joints should be strong enough to prevent any leakages in testing / handling / movements and during service. The joints at the corners and various places can be cut and to see/set required parameters for a strong joint. The cuttings done are generally two near each corner, partitions one per each and 4 side’s one each. The joints should not break open while trying to open up the joints manually. Variables Variables can be many, but some key items are mentioned here. t Level of container and lid

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Container faces be square and without inward or outward bowing t beyond specified tolerances. For 2 V cells, taller type, some machines are fitted with vacuum devices at sides to pull out the concaved faces to make the edges square. t Partitions are straight. Care be taken at COS and ICW operation to prevent any distortion of the partition mating faces. t Accurate positioning and container and lid faces. t Lids be without bowing beyond specified limits. t Platen temperature and its control. t Clean mirrors. t Heating time for container and lid. t Polymerization time. t Melt depth.

- Total interference depth. t t Positions of stops.

There are several things to check t Surface temperature of mirrors by infrared thermometer t Consistency of air pressure, if pneumatic cylinder is used. To keep an interlock for low pressure. A large display of air pressure is better. t Stoppage of machine if any heater fails. t Cleanliness of mirror surfaces. It should be clean and smooth as mirror. Some manufacturers use Teflon coating. Such coatings need to be renewed periodically. t Location of Stoppers and its firm fixing matching the battery type. It

is better to use some slip gauges to set the machine. t Flatness of platen and mirror faces, so that no air gap is there. This needs to be checked outside with steel scale. Fixing of mirrors is important. For some makes the final tightening up is after heating up of platen. Some makers have combined mirror and platen in one piece. Heating is more uniform.

Auto Set-up Some machines are equipped with a second set of platen which can come in place automatically. The pre-heated platen reduces the total tool change time.

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Some machines have total platen and mirror package delivered by conveyor and changed automatically with planned program. It is better to have two machines in series to reduce change over time or auto change over machine. Criticality Heat sealing is a very critical activity and its failure renders rejection of battery. Any rejection at leak test station in Assembly - can still be reworked by using up the plates, but post charging, the entire battery gets rejected. A failure at customer end is very serious and can result into high claim in terms of damages caused by spillage. For a Jar Formed battery - it is essential to have a high voltage leak test machine to detect minor leakages which the Assembly leak tester cannot detect and also post assembly defect developing in handling. Such tester be used with fully cleaned and dried battery. A better option is to put the HV leak tester before packing. Stages in the process of Heat Sealing : 1) Battery loaded into machine, clamped in set position, ready to start operation 2) Cover holder engages with cover and to pick it up 3) Cover picked up & makes room for heating platen to move in. It has mirrors on both sides matching the container and lid surfaces to be sealed. 4) Heating platen in position heat the mating surfaces of cover and container 5) Cover and container in contact with respective mirrors and are melted first to ensure flatness and then to reach the stops to remain in contact with hot faces for the heat to penetrate and melt to a depth of 1 to 2 mm. 6) Cover raised, heating platen raise and with draws back to its start position. 7) Cover and container are brought into contact under pressure, until stops are reached. The polymerization takes place and slowly they solidify with pressure relieved by the stops. Time lapsed from heating to mating should be less than 2 seconds. If not one should look for ways and means to reduce the time. 8) Process completed - cover holder moves up, battery de-clamped and move on. Manufacturing Concepts of Lead Acid Batteries

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Effect of Additives in PP container and Lids : Heat Seal joint strength reduces with additives like color, talc, glass filling, percentage of recycled PP being used etc. For high recycled PP material heat seal surfaces needs to be frequently applied with Silicone spray. A decision on hot plate temperature is made before hand, so that the design can incorporate. Basically, higher temperature for larger type of containers to take care of expansion and as such design should take care of that. Temperature A temperature between 350-400 C of hot plates is generally employed. O

Some use Teflon quoted mirrors, some with silicone spray (every 30 to 50 units). Teflon coating can last about 3000 seals and if needs with longer time for heating up, but at reduced temperature. It is always better to heat seal at lowest possible temperature. Initially time and temperature settings needs to be set. Cleaning of sealing surface at higher temperature will be more frequent. The two mating surfaces need different heat content and temperature. Container side is much narrower than lid side. Post sealing plastic portion spreads on both sides and gap at end surface is kept for that. For Teflon quoted a temperature below 250 C is desirable otherwise PP can stick to Teflon. O

For direct metal surface >360 C is better as so sticking on polished mirror surface is minimal/absent. The surface can be periodically wiped by cloth. O

Some machines need silicone spray intermittently. Particularly if Plastic material has good amount of recycled material. Post Sealing Check The gap of lid with container ledge should be uniform. Sample sealed unit be cut at 12 points (each corner - 2 Nos., partitions 4 nos.) to see the joint strength and extent of bonding. Just mechanical adhesion will leak on handling and also induce capillary action of acid. The polymerization has to take place between the joints.

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Picture of a Heat Sealed joint given below (Fig.10)

Fig.10 Pole Burning Poles are the items in a battery from which external connections are made. It is of various shape and sizes and are generally following international standards. Basically it can be with simple flat metal piece on which external connections can be clamped - like in small VRLA’s. The metal piece has some spring action when pressed with flat contacts or it can be done by clips. Poles can be at top of battery or at sides (mostly US types). The Poles at the top can be ‘bolt on’ types, circular types with taper, angle types with nut and bolt connection with cables. Poles generally emanate from the end straps of a battery and it protrudes the lid. Some poles have inserts made of brass with thread types for fixing connections with screws. The portion protruding out of it is joined with lid inserts, to make the connections and battery leak free. While pre-cast pieces are placed on the protruding pole and are then burned with metal fill from burning sticks. Manufacturing Concepts of Lead Acid Batteries

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The poles of taper and round types are the ones which are often burned in a pole burning machine. The longish poles, goes through the taper lid insert. While for hand burning, extra metal is added, but for machine burning no extra metal is necessary, but the pole length is longer, so that finally one gets the correct height of poles. This must be taken into consideration for hand or machine burning in earlier stages. The pole heights have to be different. For hand burning, small steel cups are placed surrounding the round, taper lid inserts and the operator burns the lid insert with poles and then makes it to the desired height. The cups are cooled in water thereafter before using. The pole burning is a skillful job and is to ensure that depth of burning is adequate, height and dimensions are OK and top of pole is uniformly rounded. The same can be done by machine. They are basically of two types. Only with gas burning torches or TIG type. Induction heating system can also be done, but not very popular. a) Gas Pole Burning - The action is similar to hand burning, where post clamping, the water cooled burning cups comes down to keep the lid inserts fitted well with its inside profile. The burner is automatically ignited and comes down to provide heat from the flame to melt the joint between lid insert and poles, in a circular motion. Post melting the burner moves up and again stops to smoothen/or rounding the top face of pole. Finally it moves up to its original position and burner gets switched off. For burner ignition there is sparking provision, which lights the burner, as it comes down. The cups are water cooled and as such, batteries one after another can similarly be burned. Car types can be burned, with minimum - 3mm fusion. b) TIG Type Burning - In this a heated (almost red hot) high alloy electrode surrounded by inert gas flame comes down and goes into the post, thereby melting it and lid-insert to occupy the shaped tapered Cup Volume. Inert gas can be replaced by reducing flame of Acetylene. Once the fusion is over, the electrode moves up. Depending on the programming, the electrode movement is regulated with stop before going down the pole or just tapping for some time just after the fusion. The Cups are water cooled. The depth of fusion is much higher than the only Gas type fusion. Electrodes are costly and have limited life. The surrounding gas prevents oxidation of metal also. Manufacturing Concepts of Lead Acid Batteries

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Pole height checking is very important to see the heights are within specified limits. Sometimes it is by pneumatic cylinder touching the pole or some mechanical arrangement with micro-switch. For 2 V VRLA batteries the pole burning is by moving an electrode surrounded by Argon gas round the weld joint and again reversing the path. It is best done by robot or by servomotor controlled device. It can also be done manually, with Argon gas cover during joining, from a cylinder. Leak Testing Post connection of end strap with lid inserts, leak testing can be done. For VRLA types post burning and cooling epoxy is poured to take care of any minor leakage left over post burning. Leak Testing is generally done to check if the heat sealing and pole burning operation is okay and not leaking by pressure of air. The battery compartment is pressurized through the vent - cap hole. The testing heads have rubber ends to seal the air pipe with the vent cap hole. Upon pressurization by air (say about 5 bar) the airflow is stopped and the drop in pressure is measured a pressure recorder. There will be some drop as some air gets into cracks/voids slowly, but any drop beyond the specified drop limit the cell will be considered leaky. There are various ways to pressurize. 1-3-5 or 2-4-6 and then full pressure to all the cells. It is to find out which cell and which partition is leaking. Any rejection is pushed out to reject table. The good cell/battery is generally marked with Sl. No / month / Factory / line etc. either by embossing/by bar code/by laser printing/by test punching, to identify the battery in case one wants to find out. For batteries to be jar formed, normally a bar code is ok. Some makers mark bottom of lid by pen, for later identification. This is quite simple. A sample leak battery should be kept for check at shift beginning. For side vented lids attachment for closing the side vents of lid to check for leakage. For kamina types side holes in each vent plug hole are closed by bellow in leak testing probe. For VRLA, the leak testing is by high voltage testing for ABS types and normal SLI system for PP types. Any failure of leak testing should be immediately studied by cutting it open, so that corrective actions are taken. Cell groups of such batteries can Manufacturing Concepts of Lead Acid Batteries

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be used back by buildup of straps and poles. The weld flags are built up with alloy stick burning and pressed by hydraulic cylinder to make the surface flat and smooth for welding. Only one such cell may be used in a new battery. Pole build up is via joining a new pole in a mold by fusion. Leak testing of large VRLA, 2 volt type can be by Helium leak detector. It is expensive machine and the best for detecting minutest leak. Unless specified by buyer, it is not necessary. Epoxy / Glue Line for VRLA Assembly : This is primarily for ABS batteries of VRLA. The plates and AGM separator stacking is first operation. The stacking can be done manually with cut separator lengths or by machine. For smaller types 4/7 Ah both negative and positive can be enveloped, popularly known as W type. The group with positive and negative consisting of a cell are inserted in special jig box. The groups post insertion inside the jig are clamped with a set pressure. Usually it is 20kg/decimeter square. It is higher for MC types. The lugs are then cleaned, fluxed, and placed upside down in a mould with cavities filled with group bar alloy. The lugs fuses with group bar. Posts are there in each group bar. In manual operation burning of lugs and fusing with alloy stick is above the comb. Post above operation cells are released from burning box and inserted inside ABS container. For a high speed line movement between each stage is by a central conveyor. The posts are then joined by mechanical gripping and burning above the partitions. This is called up and over welding. Then there is cleaning and short circuit test. A lid kept up turned horizontally is now filled with epoxy glue of required quantity. This can be done skilled person or by robotic dispenser. The container with cells already interconnected is now firmly placed on the lid. Epoxy glue makes container with lid into one piece. The semi-finished battery moves into a oven singularly or in multiples for curing of glue. The electrically heated oven can be 5.5 m long for smaller types and 9.5m long for bigger types. After exit from first oven the terminal location are cleaned, O-ring and external terminals are placed into the group and burned at the top of internal post to make the joint. Epoxy/glue is then filled inside groove and the batteries now vertically up moves singularly or in multiple inside another oven for curing the epoxy of terminals. Manufacturing Concepts of Lead Acid Batteries

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The glue over the top terminals are further filled with colored epoxy to identify positive and negative. Red and black.The battery then moves to another oven for curing the glue. For larger types similar process is followed. For all ABS types. In most cases there is a checking station for compression. If there is need for a thin plastic packing it is done and inserted to container. Compression of required strength is very important for VRLA batteries 12 V VRLA batteries of larger sizes, say above 26 Ah to 200 Ah can be done in heat sealing route, very similar to automotive lines. Even acid is also filled online with weight check. The epoxy/glue sealed batteries are then taken to acid filling and charging operation. The entire operation described above in labour intensive. Fully automatic lines are also available. Automatic lines need more perfect plates. As much the quality of plates improves with actions upstream. v v v

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14) Understanding Battery Understanding Reactions in Automotive Battery Making A. Control of Positive Plate Quality (tribasic/tetra basic) in SLI Positive quality is key to battery performance. In order to understand how and what are example is given below.

What is quality problem of 4PbO/PbS0 ? 4

a) BET surface area is less than 3PbO/PbS0 /H O 4

b) Chemical reaction cannot occur easily c) Charging efficiency is low d) Initial battery performance is low, due to surface area of PbO is less. 2

Low temperature curing is at around 40 C, and 95% RH (3BS 63.2%) O

High temperature curing is at around 80 C, and 95% RH (3BS 38.6, 4BS 40.2%) O

Other purpose of curing process is to make good contact between grid surface and active material. So in general for SLI batteries tribasic sulfate is important and as such during mixing temperature needs to be kept below 60 C and curing is done at lower Temperature. O

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15) Jar Formation 1. Acid filling (soaking reaction = exothermic) ‘It is better to fill in with chilled acid so that electrolyte temperature does not exceed 55’ C. Basically acid reacts with active material to form lead sulphate’. 2. Formation 2PbSO + 2H O <--> 4

Pb+PbO +2H SO 2

PbO is of two types 2

áPbO

dark brown

âPbO u

Reddish brown

Should keep á/(á+â) < 10^% What happens if á - PbO is high. 2

Battery Capacity is low. If can happen due to a) Acid temp. is high b) Acid S. G. is low c) Charging current is high d) Paste density is high e) Acid volume in paste mix is less Various characteristics of á - PbO2 and â - PbO2 á - PbO2 (Orthorhombic system)

â - PbO2 (Tetragonal system)

Generation place in AM

Central Part

Surface layer

Size of Crystal

Big

Small

Surface area

Small

big

Discharge Potential

low

high

Capacity

Small

large

Endurance

good

bad

Speed of self-discharge

speedy

slow

Effect of sulfuric acid reduction in Paste after Jar Formation Paste density high, penetration high á - PbO u high, â - PbO u crystal size high, PbSO low. 2

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Charging of Battery Battery assembled with uncharged plate or called “green plate” needs to be charged after Assembly. It can be called Jar or Container Formation. Some battery made with DC plates are also charged, particularly VRLA batteries. If DC is not perfect then also a small degree of charge is needed post addition of acid. Batteries after Assembly is to be filled with required gravity acid and then connected in series with other batteries of same size and charged. The process and equipment varies a lot from small scale to large scale. Key Issues Acid Filling – It can be done manually or by a even by single head filling pipe from overhead tank to a set level -

Acid filling machine :

- It can be by level or volumetric. In filling machine with level, acid is filled by nozzle and as the level reaches/more than the nozzle bottom, the top acid is sucked back. This makes the battery filled to a level of nozzles. In volumetric type, there can be two ways. The acid is premeasured in cylinders’ and then transferred to filling cylinders. The acid is then delivered by opening of valves. The second method is by timer. Sophisticated timers open the filling pipe for set duration and cells get filled by gravity. This is faster method. - Acid filling for VRLA is done by vacuum. First the vacuum is created and then measured quantity of acid is filled in by pumps/cylinders’. The vacuum takes away the entrapped air from plates and separators. For small VRLA it can be 3 machines in series. For larger VRLA amount of acid filled is also measured by weight. Mostly on line. -

Acid Temperature

- The 55 degree rule applies here. As soon as the acid is filled the temperature shoots up. In order to keep the temperature of electrolyte within cells below 55 degree C, the acid is chilled before the acid filling. The temperature between11-13 C should be ok. Filled batteries should be put on charge preferably within 70 minutes. Otherwise all the batteries be allowed to settle down to an uniform temperature and then charging started. The batteries may be cooled in the water bath or by circulating cold air from top. O

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Acid Gravity - Acid gravity varies a lot. Even for flat plate automotive the gravity differs for car and trucks. Tubular has different gravity. The VRLA gravities are much higher. The gravities are specified by the designers and process people. Charging Area - Charging be done in well ventilated area or by water bath. For Air circulation it can be by air circulating across with batteries kept isolated by 2 inches at least. For water bath it can be on floor tub with acid proof lining or on tanks at a height. For former, one has to put the battery in place manually and take out. For later it is by roller or plastic conveyor up to tank and then on rollers. Water inlet and outlets are provided for maintaining the temperature of electrolyte inside cells. The temperature should be below 55 degree. Generally the charging tanks are hooded with extraction system leading to a scrubber. It has several functions. Keeping acid fumes out. Cooling the batteries. Not allowing Hydrogen gas to accumulate, which is dangerous. The lower explosive level, LEL is 1%, for Hydrogen. - Often batteries are also charged within water cooled rectangular ss tanks, multi-level (up to 5 high) and well connected by cables and water lines. - The charging tanks are generally 1200 mm wide. It is better to have a partition in between along the length, so that each part can operate independently. A gap between tanks be around 800 mm for people movement and safety. Length can be from 8 m to 16m. Tanks can be with mild steel lined with 2mm vinyl, or SS 316, or PVC fabrication. Smaller tanks of FRP are also possible. - Charging area be with acid proof lining. Vinyl lining of 5 mm is better. Lining with tiles/bricks/ Epoxy grout has limited life. Once it cracks anywhere, the entire lining can go bad. - It is essential to have mist eliminator in each cell. Not only it checks the fumes but also acid collected again goes back to the cell. - For VRLA batteries of medium this needs tight fittings, as during charging acid moves up the fittings, till it is absorbed by the plates. For larger batteries, the fittings are bigger and taller. Transparent. - VRLA batteries are charged at a fixed temperature. For larger batteries like telecom need charging at 60 degree plus for certain period. only.

Acid mist eliminators for gang plug batteries can be by gang plugs

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Charging Method - The chargers are of various types. Simplest is constant current types. The DC voltage can be 200 V for 12 batteries in series or 360V for 20 batteries in series. The chargers are with simple Diode Bridge, or 6 pulse Thysitors. Present day chargers are with more sophisticated power electronics. When multiple chargers are from a panel, one needs to have short circuit protections too. IGBT technology is good technology and does not need short-circuit protection as response time is in microseconds. - Simplest charging can be with series parallel system. Here a bus bar is connected with series of batteries in parallel. Each individual lines can have a controller too. - The batteries initially accepts charge easily. During this period one can pump in more current, temperature of electrolyte permitting. In a constant current charging after midway, the voltage across cells move up and charge acceptance is poor. Further during the period the pores get choked with bubbles. A rest period or a discharge helps to continue with charging better with reduced cycle time. -

For SLI charging method can be

- a. constant current only or constant current with rest period, as programmed. Rest period is given after about 70% of charge, -

b. consant voltage then with constant current.

- c. constant current with various steps, high or low or nil depending on electrolyte temperature Very good way. The programme to set after trials. - d. constant current with pulse stoppages or pulse discharge at low current. This appreciably reduces cycle time too. For discharges or stoppages of 5 seconds or so, one has to depend on IGBT types, as the waves are cut vertically. Without IGBT, 10 second rest is better. One can do 5 minutes charge, 10 seconds rest as one cycle. Around 135 cycles can do charge of a small SLI battery. 40% C10 A 45 cycles, then 30% C10 A for 45 cycles and then 20% C 10A for 45 cycles. Based on results obtained modify, number of cycles, Amps. The Ah, total time will vary with respect to battery type. Cycle time and Ah is lowest by pulse charging. - e. Constant current with discharge even up to 80%, post about 70 % of charge. This is generally used with VRLA and helps to check on quality of batteries and also for pairing. In VRLA, individual batteries are also monitored by data loggers. -

Some times there are two discharges.

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- Almost 30 % of electrical energy of a battery factory is used up in charging. More efficient is the system better for conservation and improving quality too. Most charging systems try to utilize the period when charge acceptance is high. If temperature is kept within the maximum, one can pump in any current. Temperature probe can be kept logged in a pilot cell. Measuring gravity and temperature during the charging period is a good practice. Seasonal temperature variations can be utilized. Most connections are with copper multi-strand wires and inter-battery either by cable connectors or lead bars. Water cooling has to be efficient and at constant flow based on temperature. Palletized charging: There is charging system where batteries after acid filling are palletized. They get pre-connected before they enter the water cooled tanks. The pallet as a whole gets into charging tanks on rails or can be lifted by EOT for placement. Small VRLA charging is done in air-cooled rooms maintaining constant temperature. Connections are mostly by alligator clips. -

Careful evaluation is needed while getting new chargers,

- One key point must be noted that turnaround time of charging tanks and chargers. Shorter the idle period, it is better utilization of investment. Acid filling machine speed is key to reduce cycle time. Completion of Charging - For a programmed charging, end of charging is already predetermined. Other charging system, one has to measure gravity in each cell of battery to see it is charged. Basically it is taken that if three consecutive hourly gravity readings are same, Battery is fully charged. Bubbling from all cell is also an indication of completion of charging. Bubbling means electrolysis of electrolyte has started with evolution of hydrogen and oxygen. Generally Oxygen evolves at about 70% of charge and Hydrogen at 90% of charge. Top of charge (TOC) voltage achievement is not target. - Overcharging of a battery means weakening the contact point of active material with grid. In a car, batteries get charged at constant voltage. Some float charge is there after battery gets fully charged. If one does Manufacturing Concepts of Lead Acid Batteries

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overcharge in factory itself then it is loss of life. So one has to be very careful about over charging. Post Charging - Post charging battery needs to be finished. The batteries are discon-nected and then series of actions happen for a mechanized line. - Acid leveler- it levels the electrolyte. Excess is taken out and less is filled in with the same gravity of electrolyte. For vented batteries, the vent channel be cleaned with air jet before leveling. Also magic eye if specified is to be fitted. - Acid level checker- This is optional. Some OEM insists on it. Acid leakage due to over fill can damage a costly car. -

Vent plug Fixing-It can be manual or automatic.

- Battery Washer and Drier- This is a long tunnel where battery surface is washed with waterjets, brushes, Air, and finally hot air. It can also be done manually with cleaning material and wipes, for lower volume of production. - High Rate Discharge Test- The battery poles are subjected with high voltage for 4 / 5 seconds and discharged at set current, specific for a battery. The current reading is noted in computer and data logged. There are tests with Delta V. Where rate of fall of voltage is also compared. - Barcode / Code Printing- The accepted batteries are given QC sticker and can be physically marked with needle with codes of year, month, date sl.no etc. The bar coding can be done on its basis at packing. QR Code is also possible. - Pole Brushing- Optional. Machines are there to brush the poles. Quality of brush is an issue. - HV leak Tester- This is for checking of leakage of battery peripheral sealing joint and also any leakage from molding at bottom. The batteries need to be dry for this test. -

Pole greasing - This can be done manually or by machine.

- Bar Coding and Packing - Final bar coding can be done here and stuck to guarantee card and carton. There are various stickers pasted on battery manually or by labelling machine. Battery can be put inside polythene envelope to prevent damage of carton and guarantee card, in case of accidental spillage. Manufacturing Concepts of Lead Acid Batteries

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- Shrink wrap - One can shrink wrap the battery post carton packing. Shrink wrap can be done on battery itself, if carton packing is not there. - Guarantee Card- Can be separate or can be with stickers with month/date/year marking on battery. It is put inside the carton or shrink wrapped as the case maybe. - VRLA - small and MC are generally tested on HRD, HV leak testing and OCV either singularly or integrated machines. Packaging is done after various stickering in multiples in one carton. For larger sizes packaging is as per customer requirements. 2V telecom or Railway items also packed as 48 Volt system in racks or 110 V systems in situ. Various connectors are needed. Charging with acid Circulation system. - Acid circulation charging originally was used for 2 V motive power cells, now it has spread to E-Rickshaw and inverter batteries as well. - Chilled acid at low gravity is circulated through each cell fitted with dual nozzles for in and out. Heights are different. Acid cools the heat generated during charging and gets into collection tank for adjustment of gravity and getting cooled automatically. One can use Chilling system but normal cooling water cooling works too with increased time. The acid also cleans up internals. - High current can be passed than any other charging method as the temperature of electrolyte is under control. Post charging by low gravity acid, the acid is changed to high gravity after 70 to 80% charging. The gravity is such that final gravity post charging is the required gravity. Cells gets levelled too. Normally the 2 V cells are clubbed together to increase the voltage of charging. Charging period can be between 16 to 24 hrs depending on cell sizes. The energy saving is high as charging is done at low gravity. This is for pre-pickled plates. - For Tubular plates if not pickled, then the ACS takes additional time to pickle the plates on line with acid in circulation. The entire system is computerized. Key issues are leakages from cell connections, which have to be very accurate. Often adopters are used if the lid hole is not good. Quality of Lid molding has to be good. - The other important thing is that evacuation of hydrogen gas. There are exhaust fans connected to scrubbers by ducting. They must not stop under any circumstances, otherwise devastating fire and explosion can take place. It is prudent to fit an UPS with the fan, so that it runs even if the power trips. Devastating fire can take place if the Hydrogen is not evacuated. Manufacturing Concepts of Lead Acid Batteries

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- There are systems where the acid preparation system is centralized, but nowadays it has become modular. Just connect up with Acid, Water, Air and electric lines. - The system is now made suitable for 12 V system batteries with almost 180 batteries charged per module, 90 batteries on each side. Time taken for charging varies but generally within 24 hrs. The connection and disconnection period are long. - Space requirement is low and no need for acid dilution facility, for modular system. Inputs are pure acid & DM Water. -

Two shot charging system

- This system is mainly flat plate batteries, where the batteries are charged with low gravity acid to almost 80 % level and the acid is taken out or dumped by a dumping machine. Almost 60-65% acid can be dumped. Then a high gravity acid is filled and charged for a short duration of about 3/5 hrs for mixing of the acid and its spread to all pores. Some company do maximum charging in first phase itself 90/92%, PbO and then dump it. The high gravity acid is filled and battery is dispatched to customers. In the vehicle during use the balance charging and full mixing takes place. Maximum charging in first charge may reduce the life. The benefits are in energy saving and duration of charge reduction. Problem is with some glass mat coming out with acid and frequently filters are to be cleaned. Generally dual filters are used to clean glass mat out of acid and utilized in making acid for charging. 2

GEL Charging System

- Here also batteries are charged in low gravity and dumped. The gelled electrolyte is filled into the batteries subjected to vacuum. The batteries are then fully charged. v v v

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16) Testing of Batteries When a battery is made with certain specifications/design, it needs to be tested for finding out conformance with standards or not. There are various standards eg JIS (Japanese). DIN (German) BS( British) IS ( Indian), IEC etc. Testing of SLI batteries. SLI Batteries can be Sb-Sb types, Hybrid, Ca- Ca types and test parameters vary for each type. The battery: Dimensions, dry weight, filled weight to note down before charting the following tests -Capacity, C5 and C20. In Ampere Hour. Generally actual capacity is more than nominal capacity. One can repeat the test 3 times to see improvements possible. - Reserve Capacity at 1280 gravity in Ah. Reserve Capacity (RC) is defining a battery’s ability to power a vehicle with an inoperative alternator or loose fan belt. - HRD at -15 degree C. items to check are 5 Sec. Voltage and 30 Sec Voltage and Duration in minutes. - CCA at -18 degree C. Items to check 10 Sec Voltage, 30 Sec Voltage and Total duration. This is to indicate ability of battery to start an engine in cold temperature. Higher the CCA rating, the greater is starting power of battery in any operating temperature. - Charge Acceptance Test. Post full charge, discharge to 50% and then charge at 14.4 volts for 10 minutes. The Amps to above 15% of C20’ ‘Test patterns vary a lot. Inverter batteries, the capacity test and duration at 400 Watts are important. The test patterns are application specific, for VRLA, tubular, MC etc. But most tests described above also holds good for others. Only crancking application needs to be tested for CCA. Life cycle test is very important to launch a new/changed product..’ - Water loss test - 4g/Ah or 1g/Ah in 21 days. - Life Cycle test - Varies with respect to battery sizes - Internal Resistance - In micro Ohm. Manufacturing Concepts of Lead Acid Batteries

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Testing for VRLA types Depending on sizes and applications tests are specified. For small VRLA 7Ah type, the testing can be -3 C test, 200W Test, C20 test, IR test For Automotive batteries CA and CCA Cranking Amps (CA) are the numbers of Amperes a Lead-Acid battery at 0’C, can deliver for 30 seconds and maintain at least 1.2 volts per cell ie 7.2 Volt for 12 V battery. The basic job of a battery is to start an engine, it must rotate the crank shaft, while at the same time maintain sufficient voltage to activate the ignition system, until the the engine starts and maintain rotation. The requirement involves a high discharge rate in Amperes for a short period of time. Since it is more difficult for a battery to deliver power when it is cold and since engine requires more power to turn when it is cold, the CCA rating is defined as the number of Amperes a Lead-Acid battery at 0’F (-17.8’C) can deliver for 30 seconds and maintain 1,2 V per cell. The CCA rating helps to see how good the battery is OEM buyers insists on meeting CCA rating. Reserve Capacity Reserve capacity is the time in minutes that a fully charged battery will deliver it is with 25Ah at 80 F. O

Shop Floor Quality Management If we need to keep good health, we need to do periodic checks. Periodic checks g Earlier Treatment g Good health Same concept be considered for shopfloor Actions before g Production under Process check g defect appear g good condition How? By QC check QC Check - Identify the areas where we need to check i

Sample Check i

Final Product check i

Review - Modify what needs to be checked. This is to be done jointly Design, QA and Production. Manufacturing Concepts of Lead Acid Batteries

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UCL & LCL The checks are to be within some bands called upper control limit (UCL) and lower control limit (LCL). The parameters to check be seen/plotted in charts to see where it is and what the trend is. These are narrower than upper and lower specification limits. Reaction Is the data out of limits? If yes, who is responsible to take action for the particular item to be clearly defined, including reporting system if it is not taken care off immediately? Responsibility Matrix There are generally layers in Management Process. Supervisor, Section-In-Charge, Production Head, General Manager. The job of taking care of a particular out of limit or specification by clearly defined in a Responsibility Matrix Chart. Without a clear role - one cannot have a Quality Management in Practice. For each process what are the QC checks be done by production people and by QC people be clearly defined, including frequency. It is best to display this at a prominent visible place in shop floor. Sometimes a single defect, although being take care of, but getting repeated quite frequently needs attention. It is better if the number exceeds 5, it should get reported to next higher level. Some examples of ‘check’ items While input ‘Quality’ needs to be checked for the operation, but during operation some items need to be checked to ensure good quality. Some points for SLI production given below:a) Oxide Making

Input lead Impurity check, weight check, AD Check, Oxidation Level check

b) Grid Casting

Input alloy check, pot composition check, weight, Thickness checks, defects (crack, flash, short run)

c) Mixing

Paste density, % moisture, penetration check

d) Pasting

Pasted plate weight, percentage of moisture, Thickness, weight balance, pasting Defects

e) Curing

% residual lead, moisture, drop test, strength

Alignment of groups, burning height, group bar

Assembly

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Thickness, bend Test of poles, fusion check (all start of shift), flash. Short circuit (Nos per shift), ICW – alignment, weld quality, torque value, splash, sealing depth, 12 point heat seal check, pole height, leak test etc. The numbers of check points, frequency, and responsibility level will be different for different products, while taking action - always take one action at a time. Depending on final product quality, QC checks with responsibility matrix be clearly defined and understood. The tests needs to be done basically to check things in order are 1) Oxide AD and free lead content. 2) Test for moisture and residual lead during pasting and Curing & Drying stage. 3) Checking of Lead sulfate content. Multiple tests from various location of skids is also required to see the consistency of process. Test equipment like weighing balance be at site. For pasted plates, it is after FDO. Weighing 10 consecutive plate gives better idea of reasons of variation. The feedback to pasting operator, leads to immediate correction. Grid casting area to have weighing scale. Weight can be recorded in chart by operator or it can be put in computer with machine no. and nos. of castings made. A Small chemical laboratory is essential for various analysis as AD, oxidation level, residual lead, moisture etc. A spectrometer helps to measure alloy in casting pots to adjust the alloy level. v v v

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17) Lead Propeties - Lead Lead has many properties, which makes it suitable for the battery. Lead sulfates in active material in positive and negative plates become lead oxide and spongy lead when charged by electricity. Since this is reversible reaction - so when the battery is connected to load, Lead di-oxide (PbO ) in positive and spongy lead (Pb) in negative become lead sulfates by supplying electricity. On charging they are again back to PbO and Pb. So Electricity can be stored and retrieved many times. The Electrolyte is Sulfuric Acid. 2

Lead is recyclable - so major source of new product is from recycling. Lead resists the corrosion in battery electrolyte. The acid is also inexpensive comparatively, with respect to other electrolytes. It can be easily be fabricated or cast for making use in the battery. It can also easily be allowed to enhance various physical properties to meet the requirements of modern production technology. Lead is soft and not rigid enough, so it needs to be alloyed to make it suitable for handling in fast moving machines. It is cheaper than other battery types per unit of Power. On the negative side it is heavy and so delivery per Kg is lower than other rechargeable batteries. It is poisonous and needs careful handling and protective work in the factory. Lead - Antimony alloy Alloying with Antimony makes the molten lead more fluid and can be easily casted in various forms e.g. grids, straps, posts, inserts etc. Antimony melts at 631 C and lead at 327 C. On cooling, it follows a pattern. Pb-Sbgraph be seen in books. The two ‘eutectics’ are at 12% and at around 3% of Antimony. O

As Antimony content has been decreased over the years in battery grids, the Arsenic content has been increased to assist in the hardening action. Tin was added to aid flow as production rates rose, plus it has some beneficial effect in grid corrosion. Later to make maintenance free battery calcium substituted Antimony. Calcium and Antimony cannot be used together in an alloy. Manufacturing Concepts of Lead Acid Batteries

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As an Alloy it is used to support the active material of the battery and as a conductor to allow the electrons to move to and from any part of the cell. ‘The depletion of elements can cause major failures. The molten alloy is to be topped up with required master alloy, to make the percentages right. Many Companies do not have test equipment of alloy in use and fail to detect depletion. This is very critical. Many failures like grid, strap corrosion, pole melting have been caused by depletion of alloying elements. As soon as it is detected, master alloys be used to correct the situation. Even whatever is added does not go 100%. There are losses too. This problem mostly happens where the melting pot is used intermittently’ The horizontal bars and vertical ribs must be of such dimensions so as to cast easily. Thickness has to be within a limit, so that a cell can be made with multiple plates. The volume of the grid should be such that it has space for desired quantity of Active Material, which is generally of higher weight than grid, although densities are quite different. The grid wires/bars of positive normally corrodes and so the design of life is of battery is depended of the cross-section of these. Generally for hybrid batteries 1.65 Antimony with Selenium, Arsenic and tin are used. Here the negative grid is of calcium. For both grids with antimony alloy, 2.5 to 2.7% Antimony is used with other ingredients for automotive. For motive power higher Antimony percentage is used, generally 5.5% and above. For cast on strap alloy 3% Antimony alloy is common. The lid inserts also are of lead-antimony alloy. Properties of some metals used with lead Metal

Specific gravity

Melting point Hardness (Moh’s scale)

Aluminum

2.70

660

2.0 - 2.9

Antimony

6.68

630

3.0 - 3.5

Bismuth

0.85

271

2.0 - 2.5

Cadmium

8.65

321

2.0

Calcium

1.54

810

1.5

Lead

11.34

327.4

1.5

Silver

10.5

960.5

2.5 - 2.7

Tin

7.31

231.9

1.5 - 1.8

Zinc

7.14

419.4

2.5

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Density of Lead – Antimony Alloys As the Antimony percentage increases, the density goes down. So a mold designed with high Antimony alloy when used for lower Antimony alloy will give higher weight grids from the same cavity. Percent Antimony

Density in gm/c.cm

11.34

11.26

11.18

11.10

11.03

10.95

10.88

10.54

Same mold with different Antimony content will give different weight. Some properties of lead and its compounds Lead has atomic number of 82. It is residual element of series of radioactive degradation. So the Atomic weight can vary for different isotopes. It is generally being taken as 207.21. It has two main divisions -

Primary or virgin lead (made from ore - concentrates)

- Secondary lead. (These are from reclaimed lead from scrap battery and other lead based products). Secondary lead may contain some unknown impurities coming from battery scrap and not easily detectable - so for certain applications designers recommend use of only virgin lead. Atomic volume at 20 C

18.27 Cu.cm

Density, Pure Cast at 20 C

11.344 gms for Cu.cm

Rolled Sheet at 20 C

11.35 to 11.37 gms for Cu.cm

At 327.4 C just solid

11.005 gm/cu.cm

At 555 C

10.382 gm/cu.cm

Melting point

327.4 C

Boiling point

1700 C

Specific heat 0 C

0.0303/gm

50 C

0.0309 cal/gm

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327.4 C(solid)

0.0340 cal/gm

327.4 C (liquid)

0.0333 cal/gm

0.0240 cal/gm

5.91 calories/gm

To melt 1 Kg. of lead from 20 C

15760 calories

Thermal conductivity 100 C

0.081 cal/cm/second

300 C

0.074 cal/cm/second

500 C

0.037 cal/cm/second

Vapour Latent heat of fusion O

Decrease in volume due to solidification

3.1%

At melting point

6.35%

Relative electrical conductance

8.15 (copper = 100)

Relative electrical resistance

1230 (copper = 100)

Increase in volume from 20 C to liquid O

Brienell hardness (1Cm ball, 30 Sec, 100 Kg.) = 3.2 to 4.5 It becomes soften with increase in temperature, and tensile strength also goes down. Eutectic Melting Points Metal

Percent by wt.

Temperature p C

Silver

2.3

304

Arsenic

2.5

292

Barium

4.5

290

Bismuth

54.9

125

Calcium

17.4

249

Antimony

3.04 & 12.5

251.5

Tin

6.2

183

Zinc

0.5

318

PbO is semi-conductor, almost four times less than Pb. All others PbO, PbOx, PbSO , tri and tetra basic lead sulfates are non-conductor. 2

v v v

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18) Various Metals And Their Influence Cadmium It gives strength to low Antimony Positive grids and has better effect in PCL (Premature Capacity Loss)1. Cadmium with Zinc can reduce water loss. Deep cycling capability improvement with low antimony alloy. Antimony has been used with lead for the grid. Over the years, its percentage has been reduced. Higher Antimony increases resistivity. Lower Antimony performance have been improved with various additives. Antimony is attacked by Sulfuric acid at the grid surface and forms soluble Antimony Sulfate Sb (SO ) , finally reaches negative plate. Here localized cells are formed and increases water loss and self-discharge. Antimony is more electropositive than Lead. So both together forms cell at negative. 2

4 3

Zinc being electronegative, alloying to the level of 20/30 ppm reduces water loss/gassing. This can be accentuated 108 ppm in electrolyte is equivalent to 340 ppm in AM, by using ZnS04 in solution with electrolyte. Silver has been considered beneficial for higher temperature operation in positive grids. But using without cadmium; can have higher water loss/gassing 100 ppm can be level off figure. In Pot oxide, output can go down with higher percentage of Silver. Generally silver is present in 2040 ppm in metal. For higher ppm, it has to be alloyed specially. Iron reduces oxygen evolution level in +ve. It is an impurity. Potassium Magnesium Sodium

Reduces sulfating and short circuit through separator

Silicon Forms gel with AGM Bismuth Allowing upto 100 ppm is common. It comes with metal. It has life cycle improvement property <300 ppm. Nickel

This is an impurity. Lower the better. Should be below 0.0004. For improving water loss this impurity should be minimum

Aluminum to protect Calcium from oxidation during melting and casting. Too much Aluminum can enhance grid corrosion and too little can enhance Calcium loss. Generally be between 0.01% to 0.02% by weight. Presence of Aluminum also increases the melt temperature of alloy. Tin : Mechanical and corrosion properties improve with addition of Tin, Manufacturing Concepts of Lead Acid Batteries

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for Calcium grids. Re-chargeability improvement is with high Tin content. Above certain percentage - it has no extra benefit. Since it is much more expensive than lead, the usage be at the optimum level. The fluidity of molten alloy is improved with Tin. Selenium : It is a nucleate to avoid cracking during solidification. Low Sb alloy ‘Se’ is key ingredient (0.05 to 0.13%). Gassing is minimized at negative plate. It improves cold start, being better conductor of electricity than Antimony. Barium : It improves cycle life and reduces corrosion. These are general observation. The usage percentage will vary with various alloys and application. Each metal singularly or in combination has various effects. A very small presence of such metal can have major implication on the performance of battery. Not only it has to be blended within the specified range, but maintenance of same in casting state is very important. Consistency in alloy composition gives a major impact on battery performance. Lead-Calcium - Tin Alloys “Use of Ca from 0.03 to 0.13% wt Sn from 0.30 to 1.50 % wt The appropriate levels of elements involves consideration of: a) Grid-production capability b) Economic feasibility c) Metallurgical and electro chemical properties of the alloys For casting in Gravity Cast addition of Aluminum in the range of 0.015 – 0.025% wt to maintain level of calcium in molten alloy, otherwise loss of calcium due to oxidation is high. High Calcium Alloy Calcium 0.09 to 0.13% and tin level 0.3 to 1.0% wt. The tin to calcium ratio varying between 2.31 to 11.11 (Micro structure can be prepared chemically polluting with 3:1 (by volume) acetic acid; 30% hydrogen peroxide solution, followed by a wipe etch with solution containing 7gm Ammonium Molybdate and 15 gm citric acid). Low Calcium Alloy Calcium level 0.06% wt and tin varied for 0.3 to 1.5% wt. Tin to calcium ratio from 5 to 20. Observations of a Study t Increase in grain size with increase in tin.

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Grain boundaries serrated at low tin and becomes smooth with t higher tin% t Above

0.8% tin. Grain sizes becomes very large (100 to 150

micron) t The micro structure differ a lot of a critical tin to calcium ratio of 9. t In lower value Pb Ca in cellular form is seen and at high ratio, tin is segregated in intercell regions and calcium precipitation in the form of more stable (Pb, Sn) Ca. 3

t Solubility of calcium is decreased by addition of tin.”

Calcium : Calcium metal combines readily with Lead. Solubility of Calcium in Lead is maximum at 0.10% weight. At lower temperature solubility decreases appreciably- permitting precipitation. Formation of Pb Ca compound happens at about 0.07% weight of Calcium. 3

Calcium if comes into contact with Oxygen it readily oxidizes. While blending good amount of Calcium can be lost, as it is also light in weight. Calcium is highly corrosion resistant, rapid age hardening with fine grain structure. In Lead-Calcium-Tin alloy precipitates are fine compound of Lead- Calcium and Lead-Calcium-Tin. These strengthens the alloy. Rolled strip of alloy are now used to produce automotive grids. Lead Antimony, Lead- calcium, Lead- Arsenic alloys must not get mixed in liquid state. Resultant dross can give rise to poisonous gases Arsenine, Stibine, if it comes in contact with water. Calcium alloy is used in MF types due to low gassing, low selfdischarge ,high charge retention, less over charging, low corrosion rates, possible to charge at lower voltage than Lead- Antimony grids. Higher Hydrogen over voltage on lead, so that evolution of Hydrogen is arrested even at higher charging voltage or float current, (Hydrogen over voltage means the difference between theoretical voltage at which the gassing should actually start and voltage at which it actually starts). Pb Ca crystals start forming earlier to freezing of Lead/Lead-Calcium alloy with corresponding increase in strength and hardness. Size and distribution of these crystals are effect of time and temperature. In improving properties of grid. Solubility of Calcium in lead is 0.10% at 328 3

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degree C and 0.01% at room temperature. The freezing range is narrow and solidification is fast. So the mold needs to be kept above a certain temperature so that casting is complete without forming any crack. Freezing range of Led- Antimony alloy is wider. Say for 4.5% Sb the range is 44 degree C. Lead-Calcium alloy melts at 25 degree C higher than LeadAntimony alloy and solidifies at 54 degree C higher. So to cast Calcium Grid it must be poured at higher temperature and mold must remain heated, so that alloy reaches all corners. Calcium is much softer to handle and to develop adequate strength for pasting, it is generally oven aged. Molds for calcium alloy are different from antimony alloy. The heaters on mold are also more for calcium alloy casting. v v v

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19) Sulfuric Acid This is the key ingredient in Lead-Acid Battery. First requirement is in Paste Mixing, where gravity from 1.265 to 1.400 are in use by various makers. This acid converts a portion of oxide to sulfate. The next requirement comes at Forming, Jar Forming or from Pickling. Basically, at ‘Forming’, the acid which has been put in Mixing comes out of Plates post ‘Forming’. A small percentage is carried forward. If we do ‘Jar Formation’ from green plates, then we need to add dilute acid close to 1200-1220 gravity, so that post charging we get the required acid gravity in the battery/cell. Acid is also needed at the selling point for dry charge batteries. Some key features of the acid are given below. Some typical sulfuric acid gravity at 60 F O

Sp. gravity

% by weight

% by vol.

1.400

50.0

38.0

1.300

39.1

27.6

1.260

34.4

23.6

1.200

27.2

17.7

1.140

19.6

12.1

1.040

5.9

3.3

Freezing point of Sulfuric acid is lowest around 1.280 gravity

1.160 gravity acid can freeze at – 18 C and 1200 gravity at – 29 C O

Gravity

Elect. Resistance Ohm-Cm

1.139

1.55

1.218

1.28

1.260

1.34

1.305

1.49

So lowest here is at 1.218 gravity - Further Electrical resistances of sulfuric acid changes with temperature. Say for 1260 gravity acid the temperature changes are Temp. p C

Resistance in Ohm-Cm

1.140

1.231

1.334

1.602

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1.998

– 10

2.600

So, with increase in temperature, resistance is lesser. Permissible Impurities These are limits of impurities of concentrated acid (of 1.833 gravity) Iron

0.0005%

Sulfurous Acid

0.004%

Arsenic & Antimony -

0.0001%

Manganese

0.00002%

Ammonium

0.001%

Nitrate

0.0005%

Chloride

0.001%

Platinum

nil

Organic Matter

Trace

Fixed Residue

0.05%

Zinc

0.004%

Selenium

0.002%

Nickel

0.0001%

In the event that acid is purchased having sp.gr. Lower than 1.833 at 60 F, the impurities contained therein shall be calculated on the weight content of 1.833 sp.gr. of acid and must not exceed above stated limits. O

Change in battery capacity with different electrolyte specific gravity. Electrolyte sp.gr.

Percent Capacity At 3C

At C/20

0p F

80p F

1.310

108

102.2

1.300

105

101.3

1.290

100

100.0

1.280

98.5

1.270

96.6

1.260

94.4

1.250

91.9

1.240

89.4

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1.230

86.7

1.220

83.5

Storage / Mixing Generally the fully concentrated acid is transported in mildsteel (ms) tanks. It can be stored in ms tank, but it should have proper moisture free air space and venting. It is highly Hygroscopic. The dilute acid floats on surface and can corrode the ms walls. Use of silica gel breather is must. It is to be maintained. For mixing ALWAYS add acid to water and not vice versa. The mixing results in heat. The solution should be agitated as acid is being poured and cooled by water cooled pipe. Acid unless kept stirred can stratify at the bottom. Dilute Sulfuric acid is easily stratified and kept without disturbance the gravity at the bottom of tank is always higher. If it is a storage tank, it is better to have a pump taking out from bottom and supplying to top to keep it under agitation. One can use dry air also to agitate, by bubbling. Sp. gravity is to be adjusted 27 C level from the gravity Vs temperature chart or by electronic meters which can convert directly. O

Use of eye-shower, protective glasses in eyes, hand gloves, shoes and apron are a must with first aid facility. Good house-keeping at acid storage and dilution area can prevent various accidental damages. Concentrated Sulfuric acid with 98.072g/mal and specific gravity of 1.833 at 15 C. Temperature correction of gravity is 0.0094 per degree centigrade. O

Dilute acid can be kept in lead lined or plastic tanks. Corrosion chart be used for such application. There are some expensive plastics which can also withstand Corrosive effect of fully concentrated acid. Further since the gravity is higher, so strength for dimensional stability is also a factor for tank specification and design. While for smaller operation batch-wise dilution can be done, but now a day’s continuous dilution plants with auto feed with proportion of acid and water to a mixing chamber then heat exchanger and then to specific storage tanks. The feedback obtained from ‘online check’ is used to vary the ratio of inputs to get the desired acid gravity (corrected by temperature compensation). The programmed unit can produce and store acid of various concentrations in the identified storage vessels.

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Specific gravity of acid for different climates Most batteries used in temperate climates have fully charged specific gravity in the 1.250 range. A fully charged electrolyte specific gravity of 1.210 to 1.230 is used in tropical climates. A tropical climate is considered one in which water never freezes. The lower strength electrolyte does not deteriorate the separators and grids as fast as higher specific gravity electrolyte, thereby increasing the service life of battery. However lower specific gravity decreases -

Electrical capacity of battery

CCA performance

The loss is offset by the fact that the battery is operating at warm tempe-ratures, where it is more efficient and cold cranking performance is not critical. For very cold climate even specific gravity of 1.290/1.300 is also used. CCA maximizes upto 1300 gravity. The self-discharge rate of the battery at sub-freezing temperature is so low, that it will not require a recharge for many months. Typical Material List for a Battery Factory (small plant) Lead Alloy is = Lead, Antimony (Sb), Selenium (Se) Alloy. Available in 25Kg ingots. Used for making Grids and small parts. Calcium-lead alloys are different for Negative and Positive. Oxide is = Grey Oxide, made from pure lead, available in 25Kg Bags. Used in both positive and negative paste mix or produce in house. Red Lead is = Red Lead, made from purelead, available in 25kg bags. Used in tubular positive plate or in some positive mix. Fibre is = PP(PolyPropelene) fibre available in 3mm long cut fibres. Used in both positive and Negative paste mix. Moda acrylic fibres are also used. Barium Sulphate is = part of Expander used in Negative paste. It is in powder form. Carbon Black is = part of Expander used in Negative Paste Mix. It is in powder form. Vanisperse is = part of Expander used in Negative paste mix. It is in powder form Manufacturing Concepts of Lead Acid Batteries

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Graphite is = Additive in Negative and/or positive Paste Mix. It is available in powder form Sodium Sulphate is = Additive in Sulphuric acid for charging. It is available in powder form Sulfuric Acid is = Used in Paste Mix (generally at 1.40 gravity) and charging. It is liquid form. Normally supplied in Concentrated form (1.84 Gravity) in Ceramic jars or in mild steel tankers. In dilute form,it can be supplied in Plastic Jerry cans or plastic tanks of stronger walls. Container, lid, vent plugs, Handle, float guides are plastic (PPCP). Recycled plastics can be used. Buffers are = packing’ of various thickness are used with plate groups insertion in containers to make them tight. It is bought in rate of square meters. It is rectangular molded items of sizes close to plate sizes in dimensions (length x breadth). Gauntlets are multiple tube bags (called PT bags or gauntlet) can be woven or non-woven types and will be as per designed plate spines and length. Top portion fits into carrot of spines and bottom portion is sealed with bottom bar after powder, paste or slurry filled in. Bottom bar is fitted into the tubular plates after filling the Oxides to seal. They are plastic items and are available in numbers for different types of PT bags. Separatorsare, either in PE envelopes or glass mat sheet of required size for Automotive. For VRLA types it is AGM of different gram-age / compression requirement, thickness. Can be obtained in Roll form or Sheet form. AGM separators have shelf life less than 6 months and it is better to store in rooms with low humidity and temperature. There are separators eg rubber type, PVC types Cork Powder is used in making spray for grid casting. There are few additives, depending on spray quality specified. Other items eg Thermocole, Carton, Sticker, Warranty card, Pouch, Petroleum Jelly are packing items. Basic Sizes of Batteries.(dimension in mm. battery with cast grids, weight kg) Dimensions and weights vary than what are projected below in each type of container size. There are many varieties and nomenclature with

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varying internals. The weight mentioned are on higher side. Thinner plates or with plates made in continuous process, weights are much lower. Type of Battery Volt Length Breadth Height Filled Weight Automotive 12 V Battery - nominal sizes. (LXWXH) Weight in Kgs. NS 40/38B

197

129

227

11.

NS60/N40Z

230

129

227

13.

N50/60

260

173

225

18.

N70/N75Z

305

173

225

N100/90

410

175

235

N120

505

182

257

N150

508

222

257

N200

521

278

270

DIN44/50

209

175

190

DIN 55/60

240

175

190

DIN 66/74

351

175

190

Flat Plate Inverter Application of N150 / N200 sizes Internals are different on above container sizes. Jumbo Tubular from 100 to 200 Ah in 515x270x245 mm Tubular Tall 500 X 505 X 471 with two more heights 394mm and 343mm OPZS in SAN container and ABS lids. Nominal figures for 2 V cells . AH (10hr) Length Width

Height

Weight W/O Acid

100

105

208

420

7.90

2.65

200

105

208

420

12.20

4.05

250

126

208

420

14.60

5.00

300

147

208

420

17.20

5.75

350

126

206

535

18.90

6.45

400

147

208

535

22.20

7.45

450

168

208

535

25.20

8.80

600

147

208

710

31.90

10.40

800

215

193

710

44.20

13.80

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1000

215

235

710

52.30

17.90

1200

215

277

710

62.10

20.90

1500

215

277

855

80.40

27.35

2000

215

400

815

102.5

39.50

2500

215

490

815

129.80

50.95

3000

215

580

815

159.40

60.55

VRLA Sizes 12 Volt in ABS Container. Nominal sizes Battery

Length

Breadth Height

With Terminal

7 AH

152

63.70

84.5

94.00

20 AH

181

158.50

172.00

24 AH

176

164.50

105.50

125.00

38 AH

198

163.50

142

170.00

65 AH

349

164.00

158.00

190.00

90 AH

307

165.50

197.50

211.00

100 AH

331

167.10

194.40

218.00

200 AH

522

231

199.50

219.00

Motor Cycle Batteries Flooded Types All 12 Volt Battery

Length

Breadth

Height

2.5 AH

80.5

67.5

107

5 AH

128.5

56.50

130

7 AH

158

57.00

129

9 AH

136

73.00

140

Motor Cycle VRLA Types All 12 VOLT 3 AH

120

4 AH

120

5 AH

120

105

6 AH

120

130

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E- Rickshaw / Electric Vehicle Batteries (C5 Capacity) 90 AH

362

172

260

100 AH

362

172

260

100 AH

331

172

290

110 AH

415

176

210

120 AH

415

176

210

The lids of batteries have various design, so also handles for automotive and inverter batteries. There are spill proof design, gang plug design etc. Also colors. Terminals as per requirement of application. Venting’s are also from side and top. There are double lid designs too, where the 2nd lid is heat sealed after charging. It in fully spill proof application. v v v

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20) Energy Management Like any other manufacturing Industries, while there are standard energy management actions, some items particularly related to Battery Industry are being mentioned. The energy used are: a) Predominantly electrical b) Gas (LPG/Propone/Natural Gas) c) Oil (Diesel, Heavy oil, HDO etc.) Some of the points related to Energy Management in Battery Industry a) Charging / Forming - This takes almost 1/3rd of total electricity consumption. Further it has detrimental effect on Power factor and Harmonics. If 6 pulse thyristor’s are in use then 5th and 7th harmonics are often very high - which creates lot of nuisance in quality of Power supplied to various software, controllers etc. So actions can be : -

Study level of Harmonies and use Harmonic filters

Keep power factor above 0.95

Have efficient charging regime. Stepped charging on the basis of temperature, pulse charging, charging with stops are various options. It can reduce major input power.

Having controlled temperatures of electrolyte during charging

Use of proper size cables/wires

Use of proper isolation

Monitoring of leakage currents, in Formation, being wet area.

Use of star and delta windings on alternate panel of chargers can cut back harmonies to some extent.

Avoiding use of transformers in series as overall efficiency is multiplication of efficiency at each stage

Full loading of transformers with programmed loadings.

Full loading of chargers, as far as practicable.

Casting Use of common pot to supply lead to multiple casting machines by pipe line with impedance heating system. Manufacturing Concepts of Lead Acid Batteries

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Use of proper temperature of mold cooling water to reduce higher temperature of Alloy.

Minimum gate size/weight to reduce wastage of heat

Gas less casting wherever possible

Other operation areas For each area there are many ways by which energy can be saved. Curing and drying is one area. Efficient Curing system with proper humidity and temperature can not only give good quality but also have reduced energy consumption. Drying at lower temperature can also reduce energy consumption. Both flow of air and temperature are responsible for the Drying operation. General considerations 1) All Bagfilters / scrubbers use high power motors. The motors generally are loaded less during actual operation, than during initial periods. VFD drive should be used for all such installations. Damper control is very inefficient control and must not be attempted Design be based on winter conditions. 2) Sizing of pumps are, often not correct, as various factors (pressure, flow, specific gravity temperature etc.) influence the selection and then have pumps which are not in use at peak efficient period. Also use of proper type of pumps for various application, e.g. -

Pumping of water - U/G, bore-well, cooling tower

Pumping of acid/acidic water

Pumping of effluent with some solids

Pumping of Alkali/dosing chemicals

Pumping of Slurry

Many are continuous running - e.g. in Cooling Towers, Chilling Plants, as such great importance be given for its selection. Use of gravity can eliminate some pumps. Throttling is inefficient way to control. VFD drives can be effective solution, once it is turned over size. Use of lower horse power motor of same frame size is also another option. 3) Reduction of Scrap, Dross etc. While molten baths should be adequately enclosed, but a small negative pressure is also required to prevent fugitive emissions. Often these negative pressures are higher than required, resulting higher dross. Manufacturing Concepts of Lead Acid Batteries

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Reduction of dross is one key way to cut back energy loss. All pots/hot and cold pipes to have adequate insulations and needs periodic checks. The surface temperature should be such that one can keep his fingers on surface for at least 10 seconds. 4) Use of less and less of water pumped/received from its start and its ultimate end be as effluent, be as vapor, be as with acid in battery, be for human consumption needs very careful analysis and water balance be seen. Recycling / Reuse be focus area and preventing its contamination by acid / dust / paste / oil / grease, can make it reusable. For high TDS water use of RO & DM is efficient and RO rejects can be utilized for toilet/ablution. Spillages of acid during charging should be prevented with mist eliminators. Use of ion exchange system to reuse water and taking off mild acid contamination can reduce requirement of fresh water and its multiple pumping cost. It is possible to have near zero effluent in a Battery manufacturing plant. Compressed Air : While compressed air management essentially starts from going for efficient compressor and load management. - Having a high uptime of compressors ‘on load’ is key to save energy. The demand fluctuates, and depending on demand compressor/s to come online with load. It calls for auto ‘start’ & ‘stop’ facility - Compressed air pipeline sizing should be adequate so that drop in pressure is less. Pressure gauges at various places help - Use of a receiver at end of line, than having ‘ring main’ system is better. - Compressor location and its ventilation is important. Lower the intake air temperature, higher is the efficiency. Often it is better to take air from outside, than from the warm compressor room. - The Air pressure requirement of machines varies. One need not run a 100 PSI rated compressor at 100 PSI ‘cutoff’. Every 5 PSI drop is about 2.5% improvement in efficiency. If majority consumption needs between 70 to 80 psi, then, it is better to use booster units at location where higher pressure is needed. Also for operations where compressed pressure is sensitive use of booster is required also. - Study air leakages periodically on a off day, fill up receiver and note time taken to drop from peak to 50 psi, which can indicate extent of leakage. Further, leakages can be heard at various places. Manufacturing Concepts of Lead Acid Batteries

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- Where low pressure air can serve the purpose, never to use compressed air e.g. for acid agitation one can use high pressure blowers to agitate instead of using compressed air. Also later may have oil, if it is not oil free compressor. Similarly for agitating water for plate washing air blower be used. - For Reciprocating Compressor, with high no load period, VFD drive be used. - Please remember no load power consumption of screw compressor is more than reciprocating compressors. Maintenance of plant, equipment, air controls, driers etc. play a major role in reducing energy consumption. Only some major points have been highlighted above. In general 1) Use energy efficient motors, some motors which have been rewinded 2 times, be replaced 2) Use correct size motors. Higher size motor can be replaced with lower size of same frame size in few cases. Any motor having running time more than 10 hrs in a day be investigated for correct sizing. For some centrifugal fans it is better to have VFD drive, as density of air changes between winter and summer. 3) Use energy efficient general lighting and localized high lumen lighting where required only. Auto switch in and out, segregated switching are other options. Switches can be with string operation by operator so that the lights can be switched off by operator when needed. Further for all lights lumens drop as it ages. Maintenance of reflector for better lighting is also important. Cleaning of reflectors periodically be done. 4) Natural lighting be the only general lighting source in the day time. So the building be planned that way. It is better to use translucent sheets on sides of building than on roof, if feasible use of north light kind of shed is another way to utilize day light. 5) Rejected heat eg Flue gas heat can be source of preheating air for another area. Monitor Flue gas temperature. 6) Flue gas temperature be as low as possible and wherever high temperature exists there is possibility of using it for refrigeration, thermic fluid heating etc. Manufacturing Concepts of Lead Acid Batteries

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7) Where natural ventilation is possible it should be utilized. Roof ventilators natural types be used also. Roof ventilators are not to be used in lead dust area. 8) Majority of Bag filter can be inefficient or have reduced action level if the area from where it is sucked is not supplemented by adequate fresh air. 9) Transformers be efficiently loaded. If huge imbalance of load is there in various transformers, it needs to be corrected. Various energy efficient systems are there for transformer load management. 10) Discharge from battery is fed back in line instead of dissipating in resistors. 11) In general leakage of anything water, air, electricity, oil, gas be taken care by efficient maintenance system. 12) Maintaining load factor above 80% is also very good and power factor near unity. M.D. controllers can also be effective. 13) Use of Power at correct voltage is important. Heaters will heat less at lower voltage. 14) Saving of energy is purely be based on DATA. Collect DATA and analyze it with respect to production is very important. 15) Electrical energy is major energy in battery facory. KWH/TON of lead usage is key comparative figure 16) Month to Date figures/ Year to date figures/ Target based on best figures are very important to see the effectiveness of EMS. 17) Use temperature, pressure, vacuum gauges and mark in red when it is in best condition. Any deviation will indicate some inefficiency. 18) Link output at various stages with energy consumed. Daily the kwh readings can be taken at fixed time. v v v

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21) Failures of Battery Here there are two aspects. End of life period post the warranty and premature failure. Premature failure is the key focus area to know where to improve. There are abuses of battery in various forms. Also the dealers have friends to please. In most cases failures just near guarantee period is seen. In general one can consider any failure within 6 months of usage be manufacturing related. Key issue in battery performance is use it as fresh as possible. During storage the OCV, Gravity drops. Many dealers do not follow FIFO (First in And First Out) principle. It is better to recharge the battery if the drop is higher than specified and then put into use. This will give a much better performance. Batteries if cycles in low peak gravity (post charge) by the user equipment fails much faster. If the same battery is given a conditioning charge periodically it will perform very well and last long. Sulfuric acid tends to stratify with lower level having higher gravity. Sulphasion of Negative and Corrosion effect on Positive grids are major issues. Timely top up with distilled/DM water is very important too. Normal tap water should not be used. Battery upkeep with tight connection and terminal lubrication with petroleum jelly is very important. For battery on the move, tight fixing to its base is very important. During replacement of a battery a full data sheet covering all aspects eg gravity/voltage/physical condition, charging particulars, Manufacturing date, Guarantee card details User equipment details etc be noted for feedback. Often a battery if given a conditioning charge by dealer, revives. Failures In SLI : The manufacturing faults are generally weld failure, separator puncture, Leakage, short circuit due to loose metal piece, grid crack, pole disconnection, gravity drop in particular cell. Loss of active material by shedding within 6 months. Even when grid alloy is not correct, one can see corrosion of grids within 6 months. Positive active material shedding at bottom within a short period indicates poor adhesion of active material. Usage failures can be identified, with level of parasitic load in (leakage current), Use of additional equipment in car for which proper size of battery Manufacturing Concepts of Lead Acid Batteries

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not used, Idle car for months, vibration, too much of cranking needs. It has been seen if a battery getting discharged by more than 30% due to some reason, the car on its own cannot charge back the battery. Sometimes one needs to start and stop battery many times in a jam, lowering its charge level below 30% It is better to get it charged by a vendor. If a battery shows signs of low crank, it should be given to vendor to charge it fully. Keeping regular data of gravities are very important, as specified in guarantee card. In many cases it has been seen the failure is sometimes due to poor car electricals. While replacing battery car electricals be checked. Over charging setting be checked. Over charge can charge battery quick, but the useful life gets shortened very Fast. After a car starts, the battery gets charged and even if charge is complete some overcharge current is there always. If change of battery is from non-MF to MF or vice versa, voltage settings of charging needs change in vehicle. Failures In MC : MC batteries are both flooded and VRLA types. Apart from failures mentioned above, MC batteries can suffer from OCV drops, if the cells are not equal. In some battery failures the reason could be over or under charging, as the diodes or other devices are not of correct specification. While replacing battery, car electricals be checked. Wrong charging voltage is key issue. MC batteries are subjected to lot of vibrations, it should be clamped well. Failures due to leakage of acid in flooded type can happen, due to faulty chamber sealing inside lid. Keeping charged batteries upturned on papers, can reveal any possible leakages. Impurities in alloy and acid can cause early failures. Often poles can get disconnected, due to melting of pole. The cause is basically depletion on alloying elements in casting pot of poles. Failures in Inverter Batteries : Most failures are due to high sulphasion of negative plates. The quality of Inverter and charging system are also causes for failures. Over charging can be seen, if water addition is frequent. Under charged battery cycling, severely reduces life. Lead acid battery needs to come back to original condition post charging. But if it does not happen, there is memory effect and the battery is not likely to reach original level of charge. Cycling an Manufacturing Concepts of Lead Acid Batteries

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undercharged battery reduces life considerably. If the inverter has facility to give equalizing charge, the life of battery gets extended. Bursting of batteries can take place, if there are sparks anytime at the connections to cables outside. Secure fastening is very important. Failures in E-Rickshaw Batteries : Basically low life due to its daily use with several starts and stops. There are 4 nos of batteries in N100 container size. Batteries can be flat and tubular types. Cycling at low charge is another cause. Batteries need to be fully charged before using with water topped up. Using with partial state of charge, reduces life. The charger provided has also some issues. The charging regime are different in many makes. Making them cheaper has been the motto. Shedding of positive active material due to vibration. Needs higher density paste and better curing. Key causes of failures have been due to positive grid corrosion. Higher antimony grids can reduce corrosion. But water top up will be high. This application is continuously being improved. Failures in VRLA Batteries : VRLA (also called to SLA - Scaled lead acid or AGM Battery) batteries have similarities. They are sensitive to temperature and charge conditions compared to flooded cells. Most VRLA batteries are charged at a fixed voltage of 2.27 volts per cell. Over voltage during charging, say 2.3 volts/cell for example, will cause electrolyte to produce more gas, then the recombination chemistry can cope with. Over time the gases will escape from safety valve, making the batteries dry. Temperature also plays an important role. Although the batteries are designed with 10 years plus life, if the ambient is high and above 30 C, the cell will overcharge and the moisture is lost. O

Other problems of failure are early sulphasion, poor connection between the posts and the grids, poor adhesion of grid with active materials, and accelerated grid corrosion. If it is a bought out container, it is better to ensure that molder is using virgin Inputs. Recycled ABS can have presence of metal. If a cell anywhere becomes dry, leading to open circuit, then the battery Manufacturing Concepts of Lead Acid Batteries

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cannot supply current. If one cell becomes weaker in a group, other cells get overcharged. Thermal runaway is another failure mode, where higher float charge current over time, causes the cell to take more current and the process accelerates, resulting into fire/explosion. Leakage at terminals and then leakage current across terminals is another reason for early failure. Early detection is difficult, without discharge tests, which is not practical. Regular measurements / monitoring of impedance / conductance / resistance - can show cells which need further attention - But by the time a significant change is detected, the cell has significantly deteriorated. Various detection/monitoring systems are commercially available. In a group of cells / monoblck, it is always better to have matching cells / batteries. Higher terminal voltage can lead to accelerated positive plate corrosion and lower voltage cells can cause accelerated sulphasion. Keeping the batteries within a specified temperature environment, can give much better performance / life of the batteries. Costly monitoring system can at best be suited for expensive / critical installations, but having uniformity in cells in a batch and good ambient conditions, correct charging voltage are better way to get good service out of the cells / batteries. Premature capacity loss Positive Plate (Research Paper of Dr Pavlov) a)

Lack of certain alloying elements e.g. Sb, Sn in positive grid.

High utilization co-efficient of PAM

Low AM density

No stack pressure

No capacity limiting role of H2 SO4

Discharge reaction PbO + 2H++2e ¯

Pb (OH)

Pb(0H) + H S0

Pb S0 + H O

(PbS0 (Sol)

PbSo (crystal)

(1)

(2)

For reaction to proceed equivalent amount of H+ions from bulk of Electrolyte AND electrons from GRID should reach PAM. Manufacturing Concepts of Lead Acid Batteries

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It has been established that PCL is due to the IMPEDED transport of electrons when passing from the grid through the corrosion layer and PAM. Changes in PAM a) IMPAIRED contact between Pb0 crystals in the structure of PAM 2

b) Changes in intrinsic electrochemical activity of PAM (Formation of PbS04 barrier layer). c) Changes in á / â - Pb02 ratio (formation of a-Pb0 semiconductor layer) Sb (antimony) lowers the critical value of density thus prolongs life of the plate. Sb ions get into the polymer chains improving conductivity of gel zones. So for deep cycling Pb-Sb grids are superior to Pb-Ca. Pb-Ca plates may look good and fully charged - but capacity is reduced. The capacity loss precedes softening and shedding of PAM. So PCL is also mentioned as ‘Antimony-free effect” - More pronounced when Sb<1.5%” Alloying additions to grid alloy Antimony Strongest effect on PCL linear cycle life reduction is with reducing content of Sb from 6 to 1%. Tin Higher capacity compared to pure lead grids. But only Sn is insufficient to eliminate PCL effect. AM Density Cycle life is enhanced with increasing PAM density and plate thickness but with smaller capacity. With higher stack pressure in Pb-Ca, the life is improved substantially (VRLA). H2S04 The life of Positive plates (Pb-Ca-Sn) is reduced when H2SO4 concentration is increased. Decrease in amount of H2SO4 in the cells causes batteries to exhibit longer cycle life (VRLA) Plate Structure Me - Metal grid

Inner, dense layer covering Metal surface

CL - Corrosion layer PAM - Pb02 Mass

Outer, porous sub layer in contact With PAM

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Metal

Coros ion Layer inner

Outer H2S04 Solution

PAM

H2S04 c

Reaction 1e

H+

PbSO4

Reaction 2 h

H2O

Fig. 11 a) The ion transport gets impeded when 50 to 60% of the PAM has been converted. (20 h discharge) but PCL occurs much earlier i.e. when 20 to 40% of PAM is reacted. So Electron transfer is the key to PCL. PbO crystal size growth in cycling also leads to PCL. This is with Pb-Ca and pure lead mainly. Sb in grid increases Pb0 nucleation and slows down crystal growth thus prevents PCL effect. 2

Size of crystals and agglomerates determine area and properties of CONTACT between them. PCL is due to irregular growth of electrical resistance in the NECK zones. There are many theories of Hydrogen presence in the crystal structure of Pb02. á & â ratio affects the cycle life of positive plates. Greater á - Pb0 is longer life of Plates. Though it decreases in cycling but those remaining are higher in Pb-Sb than Pb-Ca grids. Sb has strong effect on the amount of á Pb0 in the PAM and strengthens the skeleton structure. 2

Corrosion layer Sb & Sn slow down reduction of the corrosion layer to PbS0 . On cycling the CL grows in thickness and form two sub layers. On discharge the sub-layer that Faces the PAM is converted to PbS0 . 4

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Lowest corrosion layer resistance in Pb-Ca alloy is with 0.6% Sn. Hence PCL is not only due to lack of Sb but of deficiency Sn in grid alloy due to, formation of Pb (Sn) Ca. This is a good conductor. Cracking of CL PbO is 20% more in volume than Pb. This leads to cracking of CL and impedes the contact. With Sb no much phenomena is deserved. Pb with 4% Sb is softer (54 Kg/mm2) than Pb with 0.9% Ca. (88 Kg/mm2) so former is more elastic and less susceptible to cracks. 2

Gel & Crystal Crystals are Pb0 , gel composed of mixture with hydrated form. Both are needed for optimum conductivity. 2

The volume of PAM grows on discharge to PbS0 and shrinks on charge. But it is not 100% reversible so the PAM volume grows. Apparent density decreases. If it is below critical limit PCL effect appears. Gel zones try to absorb this and restrain. It acts as hinges. 4

Passivation Another cause of PCL a) Formed plates are dried for longer at > 100 degree C (thermo passivation) b)

Battery kept on store for a long period (Storage passivation)

c) Sb-free grids is kept on floating mode at 2.24 V without discharge (floating passivation) d)

A battery is discharged with weak current.

Warranty figures be studied with months in use. Cut open analysis of early failures can reveal what actions are needed in manufacturing. Standardized feedback from service is a must. v v v

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22) 5 S 5S Elements OF5S - Very simply 1S - Segregation

deciding what is required/not required and disposing the non- required Items continuously.

2S - Sorting

Marked storage for all required Material i.e. “a marked place for everything and everything in its place only at all times”

3S - Shining

A clear environment without any Garbage, dust, water, etc. Keeping the area and equipment shining.

4S - Standardize

A state where shifting, sorting and spic and span stage is maintained all time.

5S - Sustain

Developing customs for correct

Practice of work place regulation and rules. Following above 5 S steps, one can significantly improve Manufacturing activities. For problems identified there are procedures like PDCA, which can lead to solution’.

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PDCA Implementation OF Improvement plan Implementation follows a P-D-C-A PLAN

Evaluating awareness and training needs Identifying areas of implementation Identifying members of implementation Identifying the coordinator

Find areas requiring immediate improvements Implement task force activities Prepare area-wise check sheets Impart required training Carry out 5-S Audit

CHECK

Evaluate the effectiveness of action plan implemented Check the status of area requiring improvements Check 5S score vis-à-vis earlier score

ACT

Make further action plan Standardize improvements Evaluate further training program.

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Control Cycle The control cycle can simply be by a PDCA cycle, which is repeatedly turned to make improvements for upgrading the products, equipment etc. Post improvement it needs to be standardized. Basically the ‘control’ means to turn PDCA and SDCA cycle continuously. PDCA Plan: Plan means full mapping of requirements a) Selection of Project - identity the problem b) Collect the facts c) Determine the targets d) Establish the goal and time target e) Plan the activity - items, schedules f)

Analyze the factors, which cause the problem

g) Plan the counter measures Do a) Study of the counter measures b) Study prevention of recurrence c) Confirm the counter measures, based on data d) Study method of implementation e) Implement counter measures Check a) Confirm the effect of counter measures b) Make comparison between effect and the goal c) Identity the tangible and intangible effects Action a) Standardise the new procedure b) Determine method of control c) Make all people involved, aware of the changes d) Train personnel e) Confirm that the effect is maintained f)

Identify any remaining problem for subsequent plan

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g) Conclude the problem h) If the result is sustained for a month congratulate the team. If not, start again. PDCA is a very good technique to solve a problem. The Small Group Activity (SGA) teams should follow the PDCA. A Single page progress chart be there. Most Important - ‘Defining’ the problems is the most difficult step. Spend more time initially to ‘define’ the problem.

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TPM TPM 8 TPM Pillars Focused

That is improvements on machines / Improvement equipment’s to remove abnormalities, Reduce losses and improve Overall Equipment Effectiveness (OEE)

Autonomous Maintenance

That is maintenance by the people operating the machines / equipment on a daily basis through cleaning, lubrication, inspection, tightening and adjusting activities (CLITA) to guard against deterioration.

Planned Maintenance

That is to institute preventive and predictive maintenance according to a schedule to avoid breakdowns and Reduce cost of maintenance.

Quality Management

That is Quality Maintenance to see how to reduce defects due to machines / equipment and go towards zero defect.

Development Management

That is how to reduce the design, development and fabrication time of machines / equipment and its spare parts and ensure stability of running Machines.

Office TPM

That is implementation of service support functions to production departments, like administration, stores documentation, MIS

Education & Training -

This is establishment of skills and Knowledge needed to implement the TPM

Safety & Health

For safer, healthier, environment friendly work place.

Benefits of TPM Tangible

Increase in production

Increase in Overall Equipment Effectiveness (OEE)

Reduction in scrap and defects

Reduction in spares and repair cost

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Intangible

Reduction in Inventory levels

Decrease in Mould and Punch change times

Saving of space and better layout

Rectification of abnormalities in machines / equipment

Removal of hand to access area/parts. Maintenance and repairs easier and faster

Stoppage of contamination sources like leakage, spillage, dust

Reduction of actual and potential unsafe areas.

Improvement in housekeeping and organization through 5S

Improvement of all people in autonomous maintenance and kaizen activities

Improvement of morale and motivation

Transparency and visibility of results through shop-floor displays

Accountability of results linked to efforts.

How to go about it? -

Declaration by management.

Introductory education & campaign.

Build TPM organization & Pilot Study.

Setting basic policy & target.

Master plan for improvement.

Kick off. v v v

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23) SHE, PCB Norms, Ventilation SAFETY, HEALTH, ENVIRONMENT SHE - in Lead Acid Battery Industry Lead-acid Battery manufacturing plants needs to have a focused SHE – programme. Hazardous substance like lead and its alloys, sulfuric acid need to be handled very carefully to prevent any hazards for safety, health and environment. The following outlines various programmes which can be implemented / targeted in a Battery Industry to minimize the negative impacts due to battery manufacturing operation. Safety v Identification

of various hazard like Fire from Gas, oil etc., use of lead and alloys, acid, Electrical Installations.

v People

Involvement - in all areas, including temporary and casual workmen - by various training on safety, first-aid etc.

v Implementation

of TPM - accident possibility from each machine / work area be focus area on the Audits.

v Accident Trend monitoring and actions thereof. v Introduction

of Poka - Yoka in all accident cases, to prevent future occurrence. Poka - Yoko is fool proof system.

v Use of personnel protective appliances

- Have safety manuals, as prescribed, with emergency measures v Have

identified and trained people for first-aid / emergency measures and display. This also includes periodic retraining.

v Installation

of safety equipment’s, hydrant system, fine exiting wishers, safe escape for Hydrogen.

v Periodic/specified

checks on all oil and gas storage systems, pipelines, fire exiting wishers, lifting tackles & cranes, pressure vessels.

v Safe storage

and use of sulfuric acid and collection of waste with acid proof linings of drains/pits etc.

v Use of barriers, railings, near all pits, high level platforms, Electrical

Installations. v Color code

use for identification as specified for all electrical and safety appliances.

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Use of oxygen and acetylene gas storage and handling as in safety v standards along with use of safe equipment’s, pipes, burners and their periodic inspection / replacements. v Use of

mechanization at all areas where lead is handled in all forms, pigs, plates, batteries, scraps etc. to reduce fatigue and back-aches.

v Focusing or Safety Awareness by having ‘Safety week’ celebration,

safety exhibition, safety competitors in posters and essay. Safety incentives, demonstration activities on fire alarms, mock drills etc. Safety signs on roads, shopfloor and equipment’s. A Safe work place - Has Direct impact on employee morale and Company benefits from rise in productivity, reduce costs etc. Health Health of all people working in factory is key to wealth creation. It should have v Pre-employment

check with various tests. Blood sugar, HIV, lead in Blood must be covered other than general health checkups. Casual / temporary workmen should also be taken care off.

v In-house

medical facility with first-aid, periodic health checkup (lead in Blood, Dental checkup). Depending on size of unit specified facilities be provided, as per acts and rules.

v Covering

each employee with ESI (Employee State Insurance), Medical Insurance as applicable.

v Advice on family planning v Distribution of calcium tablets v Meals with Garlic rich, low fat diets. v Health

and hygiene check, nails, washing of hands, feet and bath before leaving factory.

v Physical

exercise collectively at the start of work every day, is a good way to improve health and energize the people.

v Blood lead level must always be checked periodically

< 40 microgram/dl - safe > 41 <50 - Acceptable > 51 - Environmental Intervention, Workplace transfer >60 – Medical recourse Manufacturing Concepts of Lead Acid Batteries

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Environment : Being red-category Industry it has already norms in air, water, noise by various standards. The basic needs are: v Having 30 m high stacks at all lead emission areas with appropriate

control equipment’s. v Covered

pots and extraction system with applicable control measures as Scrubbers, Cyclones, Bag filters etc.

v All hand

work areas must have extraction system from top or

bottom v Fresh air

ventilation – at work place with minimum 9 changes of air/hour. Input of fresh air also helps the extraction systems.

v Acid mist areas to have covered extraction system with scrubbers. v Ambient air quality monitoring as specified and also periodic stack

monitoring is a must. v Noise

- All generators must have noise shields and so also compressed air systems adjacent to work place to maintain noise level standards.

v Cool atmosphere by fresh hair supply from top is very important for

fatigue and prevent lead dust inhalation. A drop down of 3m/sec. from 3m height is good. v Floor scrubbing

- is one way to reduce lead in air. For some equipment like plate cutting, grilled base to collect dust particles and its periodic cleaning.

v Keeping a moist floor is good way to reduce lead in air. v Industrial effluent treatment and Domestic effluent Treatment must

be there. v The aim

for Industrial effluent treatment is to have zero discharge from the factory by use of facilities like :

v Recirculation / reuse wherever water is used v Settlement and use of paste slurry

in negative paste

v Mildly acidic DM water be reused with ion-exchange treatment v Higher

acid concentration can be used for acid dilution/Jar Formation with adequate filtration / acid-recovery plant

v Jar Formation facility to have good venting traps to avoid acid mist

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The effluent v

after all above needs to be collected, neutralized to required pH to precipitate the lead and post treatment be reused, use of RO with sodium based salt can provide higher recovery, but the High TDS (above allowable) water needs to be evaporated in Solar ponds/evaporation tower.

v Use of micron filtration, for further reduction of treated effluent. v More use of Jar Formation reduces acidic effluent. The acid used in

Paste mixing is the quantity which comes out in Formation. Since it is low gravity - it can be limitedly used in acid-dilution. So if a good part of the unit is with Jar Formation, this acidic effluent be cleanly collected without contamination and then with filtration, cathodic filter, activated carbon filter - can be used in Jar Formation. v Formation

tanks if covered with fume extraction system need not use surfactant

Domestic effluent – From Ablutions, Toilets, Canteen be covered with sewage treatment plant. Solid wastes can be used for composting. Excess treated effluent – meeting in-land water standards can be utilized for gardening and plantation. Use of micro filtration can recover some more usable water, but final effluent gets concentrated. Plantation & Gardening - must cover 30% of area with leafy plants/trees. Areas near walls and also between factory and offices be with barrier – plantation. Tall trees be on south side. Trees beside drains must have vertical roots, so that drains do not get damaged. No open area be without grass, to avoid dusts getting into environment. Rainwater Harvesting - Must be there to collect in ponds and reuse as it has low TDS. Groundwater can be recharged with percolation pits and directing all rain waters to pits located at convenient locations. In general: a) Any battery/component units/vendors supplying to the units be with ISO 9000, ISO 14000 standards & OHSAS 18000 standards. b) Besides checks by PCB’s, units to have its own checks periodically. c) Use of fresh water per ton of lead input is a good way to measure and improve. Manufacturing Concepts of Lead Acid Batteries

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Pollution Control Norms in India for Lead-acid battery Industry Effluent PH

5.5 to 9.0

SS (Suspended Solids)

100 mg/lt

COD

250 mg/lt

BOD

30 mg/lt

Oil & grease

10 mg/lt

TDS (Total Dissolved Solids)

2100 mg/lt

Chlorides

600 mg/lt

Sulphates

1000 mg/lt

Lead

0.1 mg/lt

75 dBA

6.00 am to 10 pm

<70 dBA

night time

Suspended solids

100 mg/lt

BOD

30 mg/lt

SPM/TPM

150 mg/Nm3

S02

50 ppm

Acid mist

10 mg/Nm3

Lead

10 mg/Nm3

HCL

100 mg/Nm3

NOX

50 ppm

100 ppm

Noise level

Sewage

Emission Air

Ambient Air Lead

0.015mg/Nm3 on 24 hrs basis

Hazardous land fill Sulphate

1000 mg/Kg.

Chloride

1000 mg/Kg

Mixture of heavy metals Lead

1 mg/kg

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Exhaust and Ventilation Some Thumb rules and Guidelines given Design Considerations: Equipment / Arrangement

Pressure drop

1. Bag Filter

150mm water gauge (max) < 100mm under clean conditions

2. Outlet from Bag Filter to 30m Stack50mm wg (water gange) 3. Exhaust hood for collection

5mm wg

4. Ducts a. Straight length

1mm wg/m

b. Bends

3mm wg/m

Some Guidelines Air flow requirements

Exhaust requirements

1. For Dry filling operations a. For Non-toxic Dusts

400-500 cfm/point

i.e.700-850cu.m/hr/point b. For Toxic Dusts

1000-1500 cfm/point

1700-2500cu.m /hr/point 2) For Collection through hoods

Q= 1.4XPXDXV Q= Air volume in cfm P = Area of hood D = Height above work in feet V = Capture velocity in fpm

3) Duct Velocity a. For Dust extraction

20 m/sec

b. For Fume extraction

10 m/sec

4) Fresh Air Ventilation : Vertical laminar flow at ceiling

Clean Air >local exhaust ensures

Height (max 8ft) should be

dilution and pressurization

Installed as low as possible to

Critical velocity = 100-125fpm

Ensure piston like effect.

for minimum entrainment

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Most of these be seen in ACGIH- American Conference of Governmental Industrial Hygienist. Most production equipment have ventilation needs specified. While acidic fumes like in Formation, Charging Tanks, need Scrubber, most other places can be with Bag Filter with or without cyclone. Grid casting area ventilation be lead to Scrubber, as hot flints can burn filters. Where dust level is high eg Plate brushing, Cutting, Stacker, Group burning can be fed to bag filter. Alloy blending can be with cyclone and scrubber. 30m stack is standard. If various areas are to be clubbed together, pressure and temperature balance is key. A duct with positive airflow must not join a duct where the air is being sucked. There are two streams of effluent. Leady and Acidic effluent. Both can go to same holding tank. From Holding tank effluent to be pumped to neutralizing tanks where pH is to be increased to around 9 and then be clarified in circular type Clarifier with resident time of 3 hrs. Lamella clarifiers can be used instead. Size will vary with effluent volume. Post settlement where flocculants can be added, the effluent is to be filtered in sand or pressure filter. Sludge from clarifier be dried in sludge beds or via plate and frame filter press. This is to be disposed of to authorized land fill sites. The treated effluent can be discharged post filtration. Where restriction is there on TDS, the treated effluent volume can be reduced by converting the solids to Sodium salts via Softener and then do RO filtration. High TDS portion needs to be evaporated. Improvement can be done if non lead bearing effluences regeneration water of softener, DM plant, Replacement water of cooling towers are mixed after ETP in treated water tank or before filter. Maximum possible reticulation be done at each stage, Even DM water, Acid can be recycled by treatment plants meant for recovery only. For small set up neutralizing pits, settling tank and then filtration in sand bed be enough. The designs can be varied. But basic principle is same. Neutralization, precipitation of lead is needed to meet the discharge standard of lead in water < 0.1mg/lt.

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Lead Poisoning - Physiological effects When inhaled, lead tetroxide irritates lungs. In case of high dose, the victim experiences a metallic taste, chest pain, and abdominal pain. When ingested, it is dissolved in the gastric acid and absorbed, leading to lead poisoning. High concentrations can be absorbed through skin as well, and it is important to follow safety precautions when working with lead-based paint. Long-term contact with lead tetaroxide may lead to accumulation of lead compounds in organs, with development of symptoms of acute lead poisoning. Chronic poisoning displays as agitation, irritability, vision disorders, hypertension, and also a grayish facial hue. Lead tetaroxide was shown to be carcinogenic for laboratory animals. Its carcinogenicity for humans was not proven. Display of daily position of air and water standards, and quantity of chemicals used, power consumed be done at plant. v v v

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24) Cost Reduction There is no end of cost reduction. It is the key to Manufacturing efficiency. Elements of Cost v Cost of input material, price, taxes, transport, handling. v Conversion cost. v Fixed cost v Cost of wastes

Other costs v Sales and Distribution cost v Warranty cost v Overhead cost

Optimum design v Comparison with the best or target batteries v Grid, AM, Top lead optimizations v Life in use / Life cycle performance v Suitability with respect to use.

Labour - Any Labour which helps to change materials towards making the product is Direct Labour eg. Casting, Pasting operator. - Any labour which does not add value to the product is Indirect Labour eg. Stores, Material handling, Maintenance, Clerical staff, Security. Conversion of Indirect labour to direct labour, is cost reduction. Productivity increase -

Selective Automation. The focus be replacement of man and taking care of fatigue.

Combination of work. Many work can be combined also multiskilling

Men to machine match, a person can run more than one machine. Also look for

Continuous Production.

Training and having right man for right job.

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Bench mark and incentives

Avoidance of re-work.

Lead related -

Waste reduction target at each stage.

Reuse of Sump paste fully and acid discharged

Consistency of Weight and Dimensions

Maintain right Alloy level

Strict process control

Invest on measuring equipment

Manufacture on Throughput basis -

Reduces cost of holding and interest cost.

Eliminates piling up defective products

Clean and Organized shop floor-reduce wastages. Improves morale

Convert all waste to money terms.

LOOK for problems and deviation

Daily discussion in shop floor in Morning Market

Cost reduction targets and achievements must be discussed periodically and new initiatives be planned every time. COST is often compared in cost/kg or cost/Ah. Basic profit and loss statement. Dispatch as per factory realization, with net of GST MINUS following costs. - Material cost’ - Direct Labour cost - Indirect labour cost - Consumables and spares cost - Repair and Maintenance cost - Packing cost - Overhead costs - rent, fees - Any outsourcing cost - Freight and other sales and distribution cost- Marketing costs Manufacturing Concepts of Lead Acid Batteries

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After all these deductions one gets Profit before depreciation and interest If we exclude depreciation and Interest. We get profit before tax PAT. That is What The Business is About.

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Material Handling and Storage Storage Process Materials: Battery making is a batch process. And material needs to be moved from one area to next area. It starts from Lead and Alloy storage and ends up into battery. Distance moved needs to be as short as possible. A machine handling few types of inputs, and as such not needed have to wait as machine is using one. Most manufacturers, continue to make WIP (Work in Progress), in spite of required amount has been made. So if the same is not utilized, it becomes an excess stock. Other than aging, which needs to be stored for 3 days, in rest of the process there is no waiting time. If something is waiting, it is inefficiency. Curing ovens are sometimes large, and 12/18 skids loaded with plates comes out at a time. That also makes some skids to wait. If the ovens are smaller, not only curing is better, one has low inventory also. Every storage needs SPACE. How the same is kept needs careful evaluation. Empty skids released from plate cutting areas to be kept too. It has been seen that storing more than required causes damage, deposition of dusts and sometimes can get out of mind. If the product type is discontinued then it waits for days/weeks. Grid storage be on floor or in racks, 4 high, one above other. The grids be marked with type,date,shift, inspector/operator signature. Although batteries from Assembly line can straightway go to Jar formation conveyors, by trolley, but some storage space be kept for Dry batteries on floor or on racks. Keeping on racks with forklift is better, for retrieval as and when needed. Proper planning of machine operation is key to reduce unnecessary storage. It is always better to stop midway most of the times than produce extra. Most Chinese factories are efficient, as they do not produce any extra. So people are very conscious that no in process grid, plate, groups, battery is wasted. Input Materials Generally people keep lead and alloys separately in a yard. Better managed / designed plants offload the material at the point of use. Saves

Manufacturing Concepts of Lead Acid Batteries

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money from double handling. Only some special types occasionally needed be kept in a separate location. Alloys be color coded. One should also think of, the journey the materials undertook to reach the plant. How many times loaded/unloaded and moved. This is applicable for all materials. The best way to improve is by Toyota Way. There is tremendous focus on inventory. They themselves get materials needed for the day. So the manufacturing plant does not become an extended store of suppliers! Further some such loaded items at factory can become obsolete. Other than lead most materials are light. But one has to see their packing sizes to decide about racking space in height, width. Needless to say all items should move by FIFO (first IN first OUT). The material which does not go to shop floor has to be supplied manually. Even excess material has to come back (with paperwork) or stay at use point indefinitely. Keeping in Racks and manual loading unloading, can have low aisles. But for High Reach Truck it is 2.5 m and FLT it is 3.6 m aisle. If kept on pallet, it should be flush. Generally 1mx1,2 m pallets are common if it is plastic, wooden pallets can be 1.1mx1.2 m. Some items are in bags and can be piled up one over other. Container, Thermocole are voluminous. So also lids. Proper marking with dates are very important, with quantity, color. If stores are in mezzanine, the container, lids can come at location from top directly. There should be one inspection zone for input materials and also for rejection/rework zone. Needless to say storage be all via computer. Evenit’s ordering. The aisles be clearly marked. A dirty looking work place, leads to poor quality of product. People can make dirty place dirtier, but do not try this in clean places. Periodically inventory should be physically verified and matched with recorded inventory. Some input material have lead time for making / also for transport, so its inventory be managed in such a way that when new consignment comes, the existing stock is almost zero. Some items have shelf life and storage temperature. eg AGM separators, cork powder etc. Acid storage areas should have containment area, in case accidental damage of tank. Acid supply lines be protected from leakages. Manufacturing Concepts of Lead Acid Batteries

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Output items Output items are the ones which customer will buy finally. Naturally it should look neat and have enough items printed which will make the customer happy to select. While everything may not get loaded immediately after packing line/s so again question comes how to store them. It is better to store them in racks on pallets. One can opt for G + 4 racks. Since battery is heavy, the Storage vehicle eg High Reach or Fork Lift loading limit decreases with height. While Automotive batteries can be stored 4 high on pallet. Tall tubular be two high. For seasonal batteries needing long storage, it is better to keep without packing, so that if need be a freshening charge be given before dispatch. Cartons will not get wasted. There is another system for storing for long period and without aisles. It is called moving pallet method. Where the pallet moves the pallets with battery to the end of rack. One can store 8 high too. The moving pallet can be shifted by Fork Lift Truck to any row at any height and be used on the other side two. The pallet is battery powered. Since space is saved, it can be a good option, for seasonal storage. The loading of batteries in vehicles can be via dock leveler, scissor lift or sloped ramp. Some time it can be done by putting a pallet truck first and the pallets are moved by it to location. Finally the Pallet truck is taken out. This is mainly for export container loading. For floor storage, one can store keeping aisles. Normally 25% area be considered for aisles in such storage. Here the batteries for cars can be stored 5 high. Transport costs can be reduced if one uses bigger vehicles of higher tonnage. Batteries can be packed multi high in pallets and well secured. This transport is suitable for Factory to Depot, if they have unloading arrangement. Other than these, there are items which goes out. - Scrap to smelting for recovery. - ETP Sludge for disposal at safe site - Waste packing materials, reusable etc - Acid supply for DC battery. v v v

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25) Quality Control Concepts of Quality Control Quality of a product is not just its dimensional features, life, performance, but it should be to the satisfaction to the customer with commercial satisfying to the maker. Data Collection The first step on any improvement project is data collection. A fact can be known objectively is by information or data. Correct data and right data are very important to solve any problem. If data is wrong - corrective action will also be wrong. Purpose of data collection : a) Identification of present status b) Problem solving c) Control of Process d) Work adjustment e) Judgment of acceptance or rejection Data can be variable or attributable a) Continuous data - length, weight, time, temperature etc. b) Discrete values - numbers of production, defectives, wrong entries, no. of units rejected etc. Before starting data collection : a) Identify the purpose of data collection b) Stratify the data according to the purpose The Stratification be based on t Time of day, week, month, season etc. t Working group, skill, gender etc. t Machine model, equipment t Method-like

temperature, pressure, speed and other working

conditions t Material - composition, specification, supplier etc. t Measurement

- test equipment, measuring instrument, person measuring etc.

t Others - ambient conditions, usage condition, location etc.

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Data should be collected in a sheet, in tabular form, graphically, in sequence, measuring equipment, who is collecting etc. Correct data collection is very important. Data Analysis Statistics play a big role in analyzing the data. Sampling can be at random or 100% depending on data requirement/class of data e.g. homogeneous or heterogeneous. Tools of Quality Control a) Stratification Example : No. of defective by unit of machine Battery type

No. of defective

The chart gives an idea as to where the problem lies and investigates for further details. Some can be reworked and some needs to be disposed off. Pare to Diagram helps to see what area or item needs most attention or work. It is an excellent tool to prioritize. Know the factors that are causing a problem. Find the vital problem to be solved tirst. b) Cause and effect diagram (Ishikawa diagram) In this all possible causes of a problem can be analyzed in terms of man, machine, method, materials, and measurement. Like while analyzing defective plates, the reasons can be charted in this diagram. Cause-and-effect Diagram (Example : Quality) Machine

Man

Skill level

Quality Operating practices

Method

Material

Fig.12 Manufacturing Concepts of Lead Acid Batteries

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c) Histogram This can give the distribution or dispersion of data. Say if grid weight is measured every 10 minutes and then they are presented by numbers of time each weight is recorded, then it can be give a general distribution of data.

Weogjt (Ibs)

1. Histogram (Example : Weight)

Length (inches)

Fig.13 Analysis of Histograms Shape of Histogram : When the shape is almost symmetrical, the distribution is normal and process is under control. When some part has separated value, there could be a mix of defectives or a measurement error. The reason needs to be investigated. When it shows two peaks/crests it could be due to some mistake in recording. Histograms should be compared with standard values and limits. If the distribution is within limits and the peak occurrence is at the center, the process is presumed to be in control. But if the width of dispersion is such that the center is located closer to either of the limits, then it needs a closer look. If some occurrence is beyond the limit it shows some defects have been produced. Efforts be made to bring it within limits. If the dispersion is spread across the two limits, it calls for stricter supervision. If the dispersion crosses the limits on both ends, the cause needs to be identified and corrected. d) Cp / Cpk Histogram data can be used for cp/cpk analysis and also control chart. Manufacturing Concepts of Lead Acid Batteries

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One needs to put USL upper specification limit and LSL, lower specification limit in X & Y axis of histogram or upper and lower line in control chart, as shown. Cp and Cpk which are mathematically calculated are indication of quality of process. Cp is process quality index =(URL-LSL) / 6 sigma. Sigma is standard deviation ie. Specification width / process width. Cpk= ability of process to produce output within specifications. Cpk

Sigma level

Process Yield

Ppm

0.33

68.27%

317311

0.67

95.45%

45500

1.00

99.73%

2700

1.33

99.99%

1.67

99.999%

0.0002

99.99999

This can help identifying relation between working condition and failure location types. e) Scatter diagram This is made to see relationship between two factors. Say for studying robust parameters of ICW, KA and cycles can be X &Y axis. Good weld and poor weld are marked in the chart at various conditions.

% Defects

Scatter Diagram (Example : Defects - Temperature)

Temperature

Fig.14 Manufacturing Concepts of Lead Acid Batteries

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The place where there is maximum width of graph is there, with good welds, a middle point can be selected, so that even with some variations in other operating parameters, there is provision to get a good welds. f) Check Sheet This is a tabulated sheet on which basically data can be noted giving the working conditions and failure quantity. This can be given an indication of working conditions and failures, to give an idea if working conditions have an effect on the failures. The amount of defective and non-conformity can be recorded. Check Sheet (Example : Defects) Type

Number of occurrences

Total

Cracks

Discoloring

Bends

Scars

Others

Fig.15 Brain Storming Post data collection, brain storming is to be done amongst the group members. Basically while doing it:-

Criticism be avoided

Free and open ideas are encouraged

Take advantage of other members opinions

The number of ideas are more important, than quality of ideas

g) Control Chart Control charts are based on time series with upper and lower control limits (UCL & LCL). Any deviation beyond the limits ¯ shows abnormality.

Manufacturing Concepts of Lead Acid Batteries

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Control Chart (Example : Dinension)

Dimension |+

UCL

LCL

Tme

Fig.16 Abnormality types a) When a point falls outside control limit b) When seven points appear continuously on either side of center line c) When 7 points rise or fall continuously d) When points are aligned with periodicity e) When points appear close to the control limits f)

When 10 out of 11 or 12 out of 14 or 14 out of 17 or 16 out of 20 continuous points appear on same side of the center line, it is also an abnormality

From control charts cp & cpk analysis be done also Cp> 1.33 - Sufficient > 1.0 Cp < 1.33 - Present insufficient 0.67 < Cp< 1.0 - lacking consistency 0.67 > Cp - considerably lacking cp & cpk calculation has been given.

Manufacturing Concepts of Lead Acid Batteries

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h) Analysis of Scatter diagram

% Defects

Scatter Diagram (Example : Defects - Temperature)

Temperature

Fig.17 If X increases, so does Y

Strong positive correlation

If X increase, by Y in general

weak positive correlation

If no relationship

Non correlation

If X increases, Y decreases generally -

weak negative correlation

If X increase, Y decrease

strong negative correlation

Such a statistical presentation enables one to identify relationship. i) Analysis of Graphs Histograms, Pareto, control chart, scatter diagram is difficult when a large amount of values are to be handled. In that case a graph is an useful tool. There are several forms of graphs. a) Bargraph - by length of each bar with the value it represent, one can compare. If the difference is small - we make a comparison of difference in heights, if they are large then we compare proportion. Graph (Example : Production Record)

Produollon Unill8

Goal

Actual

9/1

9/15 Date

9/30

Fig.18 Manufacturing Concepts of Lead Acid Batteries

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b) Polygonal line graph - This helps us to check charge of values with respect to time. This can show a predictive value of future condition. c) Pie-chart - This is a circular chart, to show proportional ratio of various items, for the sake of comparison visually. The circle represents total data in which each item is shown as a proportion Pie Chart (Example : Small Group Improvement Activities by Industry in Japan) Mining and Heat Generation

Serivce 10 Manufacturing 39

Finance and Insurance 11 11 Transportation and Communications

Retall and Distribution 18

Fig.19 d) Radar chart - It has radiating line from center of a circle, with the same member as that of the items, in which the size of valve is indicated on each time. This enables us to check the balance among the items, the degree of goal accomplishment or time series change of proportional ratios. Radar Chart (Example : Level of Shop Floor Management) Core Values 10 Management Support System 10

Customer Orientation 10

5 5

5 10 5

Leadrship

Involvement of Everybody

10 ProblemSolving

Fig.20 Manufacturing Concepts of Lead Acid Batteries

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Other statistical techniques a) Testing/comparing of two methods to reduce defectives / problems. In this case samples are compared in order to compare their population. b) Estimation - this is basically estimation, with certain degree of confidence, as to the changes happening for a value as a result of work. This is by taking a mean value with certain range above and below the mean. Experiments : by changing the parameter at a time e.g. temperature pressure etc and see the result for comparison. Complicated problems can be analyzed by evaluating the results of changing one parameter at a time. v v v

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26) Battery Sizes Battery sizes in use in India SLI BATTERIES (Nomenclature) Japanese Sizes (JIS Sizes) L&R denote Left hand Right layout of Terminals Numerals A, B, D, E, F, G, H denotes types of container. First ten digits are near to capacity at 20 hr rate The two digits before L & R are approx. Container length in Cm. 5 hr 20 hr CCA

Wt.With Acid

28A19 R or L

260

197 129 163

187

7.8

28B17 R or L

246

167 127 203

227

8.5

34B17 R or L

279

“

8.5

38B19 R or L

290

“

9.8

“

187 127

40B19 R or L

300

“

9.8

42B19 R or L

340

“

10.2

36B20 R or L

310

“

38B20 R or L

332

“

10.2

42B20 R or L

340

“

10.2

46B24 R or L

325

238

“

12.4

50B24 R or L

390

“

12.6

55B24 R or L

433

“

12.6

50D20 * R or L 40

350

208 173 185

207

12.4

55D23 * R or L 44

430

231

“

14.4

65D23* R or L

525

231

“

14.9

70D23* R or L

525

“

14.9

75D23 * R or L 44

550

“

15.2

48D26 R or L

350

260

“

204

225

15.6

55D26 R or L

475

“

16.4

65D26 R or L

550

“

17.7

75D26 R or L

550

“

18.7

197 129

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80D26 R or L

600

“

19.5

90D26 R or L

680

“

19.9

65D31 R or L

530

306

“

20.1

75D31 R or L

630

“

20.7

95D31 R or L

650

“

21.6

105D31 R or L 64

700

“

21.6

95E41 R (L)

80 100

625

332

“

220

240

26.4

95E41 R or L

80 100

700

408

“

213

234

28.3

105E41 R or L 83 100

750

“

28.3

115E41 R or L 88 100

760

“

29.2

120E41 R or L 88 100

780

“

29.2

130E41 R or L 92

110

800

“

29.2

115F51

96 120

750

505 182

“

35.4

130F51

96 120

800

505 182 213

234

35.4

145F51

112 135

850

“

39.2

150F51

108 135

916

“

39.2

160F51

112 135 1005

“

39.2

145G51

120 150

930

234

41.3

160G51

120 150

950

“

180G51

128 160 1090

“

190H52

160 200

241

58.5

210H52

160 200 10001"

“

225H52

176 200 1313

“

925

508 215 213

512 277 220

8 “

59.9

* These some additional varieties with taller batteries, say 204 mm in place of 186 mm with higher weights. v v v

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27) Maintenance Management Good maintenance practice ensures good quality of product and also longer life of machines with high efficiency. While TPM is a major tool for improving efficiency of machine, but some basic points in general are mentioned below. Basically Maintenance is subdivided into, maintenance of: -

Production Plant & Equipment

Utilities/Service Equipment

Civil maintenance

Production Plant & Equipment 1) Must specify correct utility availability with range, during procurement. Efficiency, spares consumption, running cost etc. must be known before one should procure a machine 2) Installation as per manufacturers’ recommendation and key thing is ‘level’ of machine. 3) Accessibility for maintenance work. 4) Consumable and insurance spares stock and availability. Initial Spares with machine be seen in detail for its usefulness during ordering. 5) READING in depth of the manual of the machine. Most problems and solution are already listed. 6) NEVER, ‘by-pass’ any feature. There is reason for every part being there and that is to be respected. 7) Preventive maintenance schedule and follow up. Visible display of Schedule on a Board is best, with jobs ticked when done and crossed if not done. 8) Cleaning and lubrication is extremely important. Lot of dust accumulation can be detrimental for sensitive control and fail safe devices. Cleaning every shift with vacuum/cloth etc. has to be ensured. 9) While replacement of wear parts/oil etc. are periodic, but any failure needs to be investigated in depth with PDCA cycle. 10) Machine makers are generally not battery maker, as such, the machines. Manufacturing Concepts of Lead Acid Batteries

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working can be continuously improved with Kaizens. 11) Display boards in shop floor can be placed in key locations, where any problem in production be written by Supervisors, this can be viewed by higher ups and follow up. 12) When there is standby item, use the weaker one, so that when this fails the good one come into use, giving time to repair. 13) It is good practice to have a vibration meter and record vibration of bearings. Any rise in vibration indicates bearing is reaching its end. So before it fails, the bearing can be replaced. 14) Display in board with pictures all lubrication points and frequency. Lubrication points be marked also with suitable numbers. 15) The earthing be measured of its status once a year. Power capacitors are also measured every 6 months. 16) On off days look for sound for air leakages and take actions. Utilities For a new plant budget be made for following. It will vary as per size and capacity of plant. Also process followed eg. Formation facility will need different facilities, compared to Jar Formation. Utilities Include : (a) Electrical HT/LT/distribution/lighting etc. (b) Standby Power generation. UPS requirement. (c) LPG, Diesel, Furnace oil, Oxygen, Acetylene/ Hydrogen storage for use. (d) Material handling equipment, lifting tackle, monorail, EOT, lifts, vehicles etc. (e) Environment related equipment e.g. ETP, STP, Bag filters, scrubbers, Precipitates, monitoring equipment, Fresh Air ventilation. (f) Firefighting equipment, hydrant system, warning system, protective appliances, and wearables depending on the size of plant be provided. (g) Water related items - storage, distribution, soft water, RO, DM water, cooling towers, pumps, valves, tube wells, water meters, Acid recovery plant, DM water recovery plant. (h) Compressed air system, compressor, air driers, lubricators, boosters, storage. Manufacturing Concepts of Lead Acid Batteries

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(I) Hydraulic equipment, dock leveler, lift tables. (j) Boiler and its related equipment, condensate recovery. (k) Furniture fittings - Communication equipment, computer, server, office furniture, UPS, display boards etc. (l) Storage racks including high level storage bins. (m) Weigh bridge, weighing scales. (n) Various meters and measuring gauges as required. (o) Acid related. Storage, Dilution, pumps, acid lines, Acid proof linings. All these should get focus with periodic inspection, maintenance plan, periodic service, replacement. Fire is a key area where besides trained manpower, regular drill is a must. Civil Buildings in one floor is better, with high roof areas for Mill, Mixer and Silos. Many have multiple floors. While foundations are mainly needed in Oxide Plant, Silo, Mixer, rest of the plant is floor mounted. Maintenance of Buildings, structures, drains, pits, rain water conservation, solid waste management, plantation, gardens, Road, pathways etc. are part of civil maintenance. Yearly checks, white wash of internal walls are necessary. This cleans of any lead dust accumulated / sticking to walls. Guards beside drains and pits be provided. Path ways of material handling / movements be marked both inside and outside of shop floor. Acid proof linings need maintenance for leakages / damages. Outside building foundations, earth pits be checked yearly. Disaster Management A disaster management plan must be in place and all concerned be aware of it, including booklets available. Assembly point for people in case of fire must be marked and people be aware of same. The plan should include all contact details of Hospital, Administrative people, Police as specified in sample plan available in net. The names and phone numbers of important persons must be displayed near gate. Use of siren for warning be there. Selection of Equipments -

This should always be a team effort and do analysis of comparative equipment

Decide beforehand, what is the need now and in future.

Find the performance from other users. Visit them if possible.

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Costliest offer may not be the best one.

Give detail specifications. Electronic electrical, pneumatic, hydraulic , space be specified

Inspect and do trial run before dispatch. Send items for trial run to machine maker.

Installation - Installation be as per manufacturers drawing and specification. For complex machine take help from supplier. In many cases warranty in not valid, if not installed by maker’s people. All service connection be ready, so that machine is ready for use in shortest time. -

During installation operators be Involved.

The output of machine be checked thoroughly on physical and chemical terms.

Read the manual thoroughly and share its copies. Keep one handy near machine.

Keep Preventive Maintenance schedule, Lubrication chart on display.

The Air Pollution requirement be done, before the machine is put in regular use.

Safety features be checked for its effectiveness. Awareness to operators be taught.

Manufacturing Plant and Equipment A manufacturing plant essentially is based on 1) Products to make now and in future with time line. 2) Capacity of plant for various products. Plant and equipment varies a lot with capacity requirement. -

1. Grid casting options Hand / Grid casting machine / continuous grid making. Also related tooling and Molds

2. Oxide plant are of various capacities and different types

- 3. Pasting options from hand/machine pasting / continuous plate making. -

4. Curing from small 2 skid ovens to large 18 skid ovens

5. Formation of single row/3 row tanks. Tack or tackless

6. Plate cutting from hand / sawing / slitting machines

7. Plate stacking making with manual or machine stacking

8. Group making in jig boxes or in cast-on-strap(COS)

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9. Assembly lines from semi-automatic to fully automatic

10. Jar formation with air cooling to water cooling or even chilled acid circulation system.

11. Finishing and packing from manual to automatic lines.

Every facility again as various options with degree of mechanization. Higher the capacity plan, the degree enhances. Options available changes with capacity and when one shifts to higher capacity in future some investments made earlier needs to be replaced. Say one can have floor level paste mixers from 100 to 500 kgs per mix, but beyond that it will be mixer at high level above pasting machine, with cone feeding arrangement. Such mixers needed conveyors for transfer of oxide from silos, which in turn are fed from oxide plant. For tubular it can be hand filling to machine filling with conveyors for dry filling or wet filling options. Every such decision has impact on utilities needed. Power, water, DM plant, Softener, ETP, Compressor, Boiler, Acid dilution plant, Cooling towers, Chargers, recovery and recirculation, various pumps, weighing, Material handling facilities, skids, racks, hoists, cleaning equipment, waste area, drinking water area, bore wells etc. Then there are people based facilities. Toilet, Ablution, canteen, medical facilities, parking etc. Finally one needs laboratory for in house quality control and also to check bought out items. A test house is needed for physical and electrical testing of batteries made and also compare with competitors’ products. Selection of Equipments -

This should always be a team effort and do analysis of comparative equipment

Decide beforehand, what is the need now and in future.

Find the performance from other users. Visit them if possible.

Costliest offer may not be the best one.

Give detail specifications. Electronic electrical, pneumatic, hydraulic , space be specified

Inspect and do trial run before dispatch. Send items for trial run to machine maker. v v v

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28) Manufacturing Plant The manufacturing plant makes something on its own and some are outsourced. So it involves very detailed planning to operate efficiently. Inventory plays a big role in manufacturing efficiency. The requirement of various products within a given time, generally monthly, is the basic document on which the planning starts. Before deciding the plan, one has to look at -Various capacities available in each process/equipment to achieve the volume. A chart of each process and mapping its utilization level is important. - Products/materials in stock, - Material needed to achieve the plan. Raw Materials, BOP (Bought out Parts), ORM (Other Raw Materials). Stores and Spares, Consumables. - Manpower constraints, plan to mitigate them. - Delivery dates of particular products, if specified - Working days available. For some constraints holiday work may be needed. - Utility constraints if any. - Any additional need of outsourcing, where constraints are seen needs actions - New or modified product, trial manufacture. It is TEAM who works out the details, in their respective areas. Based on above a tentative week wise, date wise plan needs to be charted out. This plan can be a revolving plan too based on inputs and changes in dispatch plan. Material Plan Materials specific to the products needs to be ordered based on Manufacturing plan. Ideally the material should be available ‘Just In Time’. And most completion of run there should be ZERO stock, specific to the Product. Some imported products and some items coming from long distance

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involves careful planning to reduce freight costs. But it is quite possible to get smaller required lots with logistic/supply chain plan. For nearby items, it is better to collect them as per requirement only. Not making the factory as storage space for such material. Vendors to store and plan as plan given by factory. The plan is to have tentative monthly plan, from weekly plan, even rolling plan. Vendors must know the plan in advance. 1) Effluent quantity, chemicals used, 2) Inventory - this is best measured in amount per days of production, for items as BOP, ORM, Spares, Consumables, WIP, FG or Finished Goods. Anything excess is adding upto cost of product in some way. 3) There are two more items to evaluate, Cost savings In material cost and cost saving in conversion cost. One can include transport cost if it is part of plant cost. Since Lead and Alloy consists of major cost of product. A metal variance analysis is a must for every month. The difference between standard consumption and net consumption and its variance needs evaluation and study for improvement, Recycled scrap from outside to be taken into consideration. There is also a loss of around 0.5% considered for evaporation and sweeping loss, not collected for recovery. ‘KANBAN, this is a plan, based on requirements of dispatch upto the first process by series of boards with cards, in each specific department. Say Dispatch puts cards stating requirements from earlier process in a future date, to Charging giving the date products needed. Charging puts cards to Assembly and likewise goes Parting, Pasting, Casting, Oxide Making etc. The cards are of different color and put in identified slots. This automatic system once followed regularly, it makes production on thru-put basis automatically. With present day computerized planning of each activity, it may not be needed, but it teaches one thing, that make products only to the requirement of next stage. People easily understands what they are supposed to do on each date. One common happening is that people keeps on producing the items to utilize manpower up to end of shift or next tool / mold change. This is very wrong and slowly builds up stocks which are not needed immediately. Shop Manufacturing Concepts of Lead Acid Batteries

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floor of most companies are full of items which are not needed immediately. Everything has a cost. Such accumulation leads to high inventory, and puts pressure on profitability. Same holds good for all BOP items. The car companies get things just in time, so a battery company can also work on JIT. One way to control BOP is to collect from vendor as needed and as informed earlier.’ Some Summary Points Cork spray - causes surface roughness on cast grid, for adhesion of AM. Cork powder has good adhesion to hot mold surface. Neither it is too fine nor too coarse to facilitate entrapped air to escape. Acts as an insulator to see that Alloy fills up the entire cavity, being good insulator. A touch up is needed when weight reaches upper control level. Fibre - It should be added, dispersed in water. Homogenous mixing is very important. In positive it prevents shedding- slow down its rate. 3 or 5mm are common length. Curing Test - Uniform color, no yellow/no red and pass the drop test. Expander- The expander quantities varies for cold/tropical climate. It is lower in tropical climate. Alloy - Iron and Copper cause self-discharge, Gel : Electrolyte formed/set with Silica and Sulfuric acid. So it becomes immobile. It develop fissures and cracks with initial charge discharge cycles Recombination of gasses also takes place. During overcharge period, Oxygen is evolved at the positive plate, which upon reaching the negative plate oxidizes spongy lead to lead oxide and then combines with Sulfuric acid to form water. No hydrogen is evolved out in negative plate. But during idling period, Hydrogen evolved due to chemical attack of acid with negative plate lead. Batteries fail due to escape of this. No fissures, small fissures, large fissures exist. So Oxygen travel through Gel is not uniform. During deep discharge this effect is more and gasses escape with eventual failure. AGM- Almost 85% of AGM separator is with acid and 15% is empty. Separator is starved. These empty spaces provide passageway for the gases to travel and combine. Oxygen evolved in positive plate is absorbed at negative plate. The total acid quantity in battery is less, so acid is used of much higher gravity. Between 1290-1330 gravity to supply required sulfate Manufacturing Concepts of Lead Acid Batteries

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ions. The safety valve is very important. While it should release high pressure generated but also does not allow gases to escape as it is with loss of electrolyte. Making battery dry. Antimony Leaching - Antimony is attacked by electrolyte at grid surface and dissolves as Antimony Sulfate in electrolyte. It finally reaches negative plate forming minute cells, leading to loss of capacity. The corrosion of positive grid leads to failure. It is best if positive grid surface is fully covered with paste to reduce leaching drastically. Charge Levels - At about 70% charge level oxygen starts evolving at positive plates and at about 90% charge level Hydrogen starts evolving at negative plate. Hydrogen is lighter and voluminous. Its escape is water loss. So Ah capacity of negative plate has to be more than required. So in MF application design is always positive limited. Capacity Levels - A 100 Ah C20 rated battery will be 88 Ah at C10 and 75Ah at C5 level. Progressively 50Ah at C1, Water Loss due to float current- car battery gets charged only during the car is in operation. When the battery is fully charged, it gets small overcharge during the period. Inverter batteries can remain in float charging after fully charged. Some inverter can take care of this overcharging by switching off. One Ah of current electrolyzes 0.336 ml of water ie, 0.0056 ml/minute. A battery with 2 hrs /Day float is about 600 hrs per year. Considering a float current of 0.25A, Total Ah per year = 150 Ah. So water loss 150x 0.336= 50.4 ml/year ANS40 battery with 30 mA float current after full charge 600x 0.03 = 18 Ah = 7.048 ml/year v v v

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29) Edifice Science (Vastu) Vastu is an ancient science which act as a precaution against unforeseen negative consequences. Source of Energy (on which the science is based) - Sunrays falling on earth’s surface and atmosphere - Gravitational pull of earth - Magnetic field of earth - Effect of heavenly bodles Sun rays have all 7 visible lights, ultraviolet rays in the eveing and infrared light in the morning. Some of the advises below are on location of entrance to factory. - North side of NE, South side of SE, West side of NW, East side of NE. Generally it should not be in a corner. Also road must not hit the factory entrance. East: ‘East side to keep open with space for morning sunrays, consisting of infrared. Input materials must enter from east door of factory building. No door be there on opposite wall. Avoid toilet in east. WTP / ETP can be on West. South - East : It is energy sector. Keep electrical Sub-station, Transformer, DB, here. Keep DG, Acetylene and Diesel storage here. South - SW : Location of tallest structure, shed, chimneys, trees, wall be in this zone. Heavy machines like Oxide Plant Mixer, Casting machines be located here. West - NW : Factory output storage be on west wall. Dispatch W-NW. Chargers be on west. Toilet can be on west or away on east. No pit be on west. North & North East : Space outside building on north is good. Building floor and land to slope down to north-NE. Rainwater harvesting can be on east. Underground storage in NE. In existing factories, if not running well, Vastu consultants can study and recommend corrections. Process flow movement from South to North. Movements of goods be clockwise. Central area of building be open / clear. People in office be facing NE, with solid wall at back. For new location, square or rectangular plot better, extended corners can be spaced out with wall. Many failed units have wrong Vastu. v v v Manufacturing Concepts of Lead Acid Batteries

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30) Basics and Key to Achieve That Battery Design : 1 Faraday (F)= 96484.56 Coulomb (C). Again 1 C is 1 Ampere/Sec. So 1F = 96484.56/60x60 = 26.80 Ah Molecular weight of PAM (PbO2) is 239.21 gm. This quantity can deliver 2F of electricity. That is 2x26.80 = 53.6 Ah So amount of PAM required for 1Ah= 239.21/53.60 = 4.463 gm/Ah Specific capacity of PAM = 1/ 4.463 = 0.2241 Ah/gm Similar way For Neg AM it is 3.866 gm/Ah and specific density of 0.2587 Ah/gm Sulpfuric acid it is 3.66 gm/Ah and Specific density of 0.2732 Ah/gm Actual Ah of battery is based on utilization level of AM. Say for a 60 Ah ( 20hr rate) cell with 50% utilization of PAM, 60% of NAM and 70 % of Acid Weight of PAM required = 60 x 4.463/0.50 = 535.60 gms Weight of NAM required = 60 x 3.866/0.60 = 386.60 gms Weight of Sulfuric acid = 60 x 3.66/0.70 = 313.70 gm of pure acid This will be equal to 825.5 gm of 1.283 gravity sp. gravity = 645 cc of 1.280 gravity acid. In actual practice these figures can become different eg, actual percentage of PbO2, Pb, Charging quality due to process deviations, affecting utilization of AM. Where as in each stage, there is a range for UCL/LCL, but you need to produce all batteries perfect! Manufacturing has a major role to achieve designed performance of the Battery. To achieve that. Paste weight control, the loading level of Paste in hopper is very important in pasting machines. Keeping consisting level in hopper ensures proper design weight. Again this gets affected with return of fallen paste. So keeping proper weight of plates within the bands is very important. Plate thickness control, the main area to control is at Grid Casting Machine and then at Pasting. Pasted plate can have higher thickness at some places. Particularly in the middle. This needs periodic measurements of thicknesses. Pasting machine hopper internals may need adjustments. Manufacturing Concepts of Lead Acid Batteries

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Curing of Plates, The curing starts from mixing stage itself and both RL and Moisture goes down progressively. So the use of the Mix, be as quick as possible till it reaches the Curing Oven. Higher the moisture level of AM in plates, it is better for curing operation. Further the plates to have some gap in between for movement of air. The movement is such, that it picks up the moisture reaching the surface from inside the AM, so that further moisture in vapour form can come up to surface. But the airflow has to be controlled too, so that the process of removal is slow or just enough. If one sees colour of plates light orange, it means the operation needs improvement. One indication of attention be dissimilar color on plate surfaces. Physical size and shape of plates. Plates have to be of proper thickness and shape. If the plates have some deviation, then it starts from casting, proper aging and then pasting. Particularly the thickness of plates are very important for VRLA, be it MC or other types. Non uniform thickness, leads to abnormal compression of AGM, affecting the recombination of gases. If physical size has some deformation it will get stuck in plate stackers. So also presence of any lump. Strap casting, can be manual and automatic. In automatic, basic fusion takes place at the freshly cut lug surface. So time gap between plate cutting and COS has to be short. Further the lug faces have to be clean and without grooves, so that fluxes do not remain to form bubbles. Good fusion is needed for the performance and life of battery. For manual operation straps have to be used within hours of casting and so that it goes to ICW immediately for proper welding. If one uses later, then it should be after 3 days and with higher settings of ICW. Pole heights, this is where mistakes happen. Manual pole burning needs short pole height for metal addition. If COS strap is used for manual pole burning it makes the pole heights more. With manual strap, automatic burning should not be used. Formation. All plates should have uniform and required PbO and Pb levels. Otherwise one can see faster OCV drops in batteries. 2

Jar Formation, Watch out for proper cooling and Ampere hour input. Measuring gravities and temperature in pilot cell is essential for control. Post acid filling, batteries should be put on charge within 70 minutes. With chilled acid temperature of electrolyte should be below 55 degree C.

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Key Concepts - It is possible to have zero scrap of grid and plate. - It is possible to have zero rejection in assembly line - It is possible to operate with about 8 days WIP for most batteries from lead to battery. The BOP arrives or collected for Assembly. Just in time. So almost 40% turn round of money per year. No extra WIP be there in shopfloor. - Comparisons with best in business is a continuous process. If we follow right process, formulation and right equipment it is possible to better that, - Daily waste autopsy in morning market is key to do continuous improvement. - Charging of battery has undergone changes and one can reduce charging time and energy with pulse charging, two shot charging, Acid recirculation charging. - Study of feedback and cut open results gives insight about the product. It should be strong focus area. - Every machine has many variables some are controlled automatically and some manually. Always try to eliminate manual variables or train to improve skills. - Again at every stage of manufacturing, there are set of control limits. Inspite of all above Manufacturing has to produce a perfect product! That is a challenge! The Book is for Manufacturing people and hopes to provide some knowledge & apprise of concepts. Understanding the product makes things happen. v v v

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31) Some Key Conversion Items, Needed Frequently In Battery Industry

Conversions Metric to British units (some are near approximation) Volume : 1cu.in= 16.39 cu.cm. 1 cft = 28.32 litre . 1 lt. = 0.035 cft. 1 cu.m = 35.3147 cft Flow

: 100 CMH = 58.85 CFM or 100CFM = 170 CMH approx.

Linear : 1 feet = 30.48 cm: 1 meter = 3.281 feet = 39.37 inches. I mil = 0.001 inch Weight : 1 ounce = 28.35 gm : 1 lb = 453.65 gms. : 1kg = 2.205 lbs Temperature : 25"C = 77' F. ( Chilled air in Mixer ) 11"C = 51.8' F (Chilled acid for filling) 55’C = Max Mix temp, Max Charging Temp, Max Formation temp. 27' C = 80.6' F General Test temp. Distance travelled : @ 10 m/min = 0.547 feet/ sec. Conveyor speed.= 16.67 cm/sec A 515cm battery takes = 16.67x0.515 = 8.58 sec. to clear its footprint @10m/min Duct Diameter: 200mm dia. = 314.16 sq.cm. 500 mm dia. = 1963.5 sq.cm Discharge rate of Battery : Gravity C20 at 80’F 20 hrs 100% of capacity

1.290

100%

5 hrs 85.6 % of capacity

1.310

102.2%

3 hrs 77.2 % of capacity

1.260

94.4 %

1 hr 59 % of capacity

1.220

83.5 %

AH required

Cubic weight conversion (Mix Density)

Reduction to Pb - Oxidation to PbO2

gm/cc

gms/cu.in

PbO Pb3O

PbSO

109

65.6

142

4.2

68.8

4.4

72.1

233

1.0

16.4

Energy : 1 KwH = 859.85 Kcal = 3412.14 Btu Manufacturing Concepts of Lead Acid Batteries

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Density of Lead and its compounds Lead. Pb

11.341

Tet.PbO

9.500

Ortho. PbO

9.500

PbSO

6.30

PbO.PbSO

6.92

3PbO.PbSO .H20

6.50

4PbO.PbSO

8.15

Alpha PbO

9.873

Beta PbO

9.696

These figures are important to understand how the volume of Active Material changes due to conversion of one compound to other. The pore size and number of pores are key to consider pastes for Cranking or deepcycle, motive power or UPS applications. The active material is different for different application. The variability is achieved -

by varying oxide quality e.g. oxidation, AD, process of manufacture.

by varying Additives.

by varying acid content.

by varying use of temperature & humidity.

by use of special additives.

by varying paste density & penetration. v v v

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ACKNOWLEDGEMENTS l Machinery

& Product Makers - Wirtz, TBS, Lih Shan, Sovema, Penoraya, Hadi, Tiegel, Farmer, Rosenthal, Tekmax, Om Impianetti, Rozario, New Battery Engg., Tekmax, Bitrode, Digatron, Firing Circutis, CEMT, Shan Huan, Jinfan, CSIC, Zibo Xinxu, DSC, Gang Ii, Jih Sing, Kae li, Hammond, Daramic, Superior Graphite, Black Diamond, Ador, Powercon, Assad Consulting, Singhania, Mehendra Udyog, Devaki, Hydrochem, Hygrotech, Rane Ovens, A.S.Enterprise, Manika Moulds, Aquatherm, Fulid-O-Matic, Vega, Koshyma, Kamal Kor, Shin Kobe, Furukawa. l Battery Units - Exide, Luminous, Livgurad, Sukam, Minda, Gold Star, Sparco, Auto Bat, Genus, Supreme, Panna, Hamko, Spiker, Padmavati, Okaya, Microtek. l Friends Related to Battery Industry - K.Raghunandan, Vijayrajan, Pratap Rane, Avijit Swant, Rakesh Mittal, Vikas Kapre, Kushal Bhatia, Arvind Tuli, Ramesh Natarajan, BD. Sharma, VK Agarwal, Chandramohan ji, Arvind Mohan, PK. Mukherjee, D. Chatterji, Rajiv Dutta, A. Gaffoor, Gaurav Agarwal, HR. Suman, Rakesh Singh, Manish Chaube, MM. Parsana, A. Thurasinhgham, ATM Mustafa, Lokman Hussain, Nitin Gupta, Raman Gupta, Subodh Gupta, S. Jakkli, Jaspal Saini, Jitendra Gupta, Rakesh Agarwal, Subhash Kankaria, Yashpal Kanotra, Ajoy Roychaudhuri, Sanjeev Sahaya, Mohan Sundar, Rakesh Malhotra, Navneet Kapoor, Many in Shinkobe, Many in Furukawa.

l Ex - Exide and Colleagues - Mr. SB Ganguly, Dr. SK Mittal, Dr. Anshuman Roy, Dr. Sugumaran, Dr. Shivkumar, Dr. Nilotpal Bhattacharjee, AB. Oke, K. Ganesan, Alakesh Ray, Ashish Ghosh, Pulak Pramanik, Rupak Dutta, Alman Das, AK Jena, Satish Chauhan, Shared Naik, NB Sarwate, SK Nag, Subhro Sen, Arnab Mitra, Anil Verma, PN Ghosh, Sumit Ghsoh Sourav Ghosh, Sunil Das, Sanjay Chittal, Akshy Rout, Nabeyndu Chatterji, Brajesh Kumar, Achal Sarna, Ravinder Singh, Dinesh Rana and Laxmi Iyer. l Exide - There are many and working. So not naming them.

From Every one I have learned and want to Thank You all. I might have missed few important nemes. Please excuse me for that. - Ranbir Chakrabory Manufacturing Concepts of Lead Acid Batteries

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32 ) Lead Acid Battery’s Use In Environment Friendly Vehicles With focus on environment, Vehicles needs to be environment friendly. This is great focus area all over the world. The progress have been 1) Use of Hydrogen, LPG, CNG in vehicles. LPG and CNG are being extensively used in cities in commercial vehicles. The exhaust is nonpolluting. Hydrogen is still not commercially successful. Expensive to produce and store at high pressure.. It’s cheaper production and handling is a big research subject in various parts of world. Hydrogen as it is explosive. So utmost care and safety precautions are needed. This is the best alternative energy to drive a vehicle All these vehicles use Lead Acid battery to start the engine. 2) Start Stop Vehicle. I SS. Emission levels are higher when a vehicle stops anywhere/signals with engine running. In Start Stop system engine stops and battery takes over all items needing power. This period is about 30-40 seconds and thereafter engine starts automatically. Or if the accelerator is pressed to move, the engine starts again. So during the period when engine is not running, the pollution is halted. This feature is standard feature in most vehicles now a days. The size of battery used is 80D26 or basically N50 size. For ISS, formulations are different. Same has been mentioned earlier in the book in Chapter 6 end. This is also Lead Acid Battery 3) Hybrid Electric vehicle. Here the vehicle can be run by Battery/Engine or Both. In city drive, battery be used. Regenerative braking is also there, to get battery charged during braking. When battery charge level drops to a pre-set level, Engine comes into operation and vehicle runs on Engine also battery gets charged. For boosting/high acceleration both Engine and Battery runs together. There has been great research of using Lead Acid battery. Cylindrical cells, with both end connections have been tried. Vehicle manufacturers have tried Nickel- Cadmium batteries too. Off late Lithium ion Batteries have been used. There are various other batteries too. For starting a hybrid vehicle engine, a Lead acid battery is needed. Manufacturing Concepts of Lead Acid Batteries

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4. Electric Vehicles.Here the vehicle runs only on battery. Various battery types have been tried out. The vehicles are currently using Lithium ion polymer batteries. The two wheelers of China, which used VRLA batteries only, are changing to Lithium batteries. Cars from Tesla, have been leading the field by using Lithium based batteries. Many other manufacturers are also using the same aggressively. Basic issues are range per charge and recharging. It needs infrastructure. Need to have charging facility at home. High rise houses to have the facility at ground level or at parking place in basement.. Other option is to quickly change the battery pack, at dealers on way or getting it charged in less than half hour at various locations. Some countries are planning charging from road below, non-contact type at intersections or in charging lane. Here the vehicles do not need Lead Acid Battery as there is no engine. The cost of Lithium ion based batteries is high and major problem is in disposal or economic recovery of expensive metals being used. Unless this problem is solved, large scale use of such batteries will get halted. Lead Acid Battery in Electric Vehicles. Till early 20th century the cars used to run with Lead Acid Batteries. With Ford coming out of IC engine vehicles, the battery vehicles lost out, slowly. While large use of Lead acid battery is in Motive Power, that is in Fork Lift and similar applications.Both Tubular and VRLA batteries are in use. The use of VRLA batteries would continue in 2 wheelers.

Bipolar

batteries can play a role here, which is also of Lead Acid battery family. E- Rickshaw. The three wheelers are all using Lead Acid battery. South Asian countries have large fleets of E- Rickshaws and are used commercially for transporting people and even goods, municipal wastes. It is not being used as personal vehicle, but soon we may see that too, to compete with Lithium based batteries. In India, there is large scale use of such vehicles in city and suburbs, for pooling and transporting people. The major issue is life of batteries. It is deep cycle application and PSOC ( Partial State of Charge) operation too. The driver of vehicles has to regularly take care of batteries with respect to electrolyte level and giving full charge overnight. Manufacturing Concepts of Lead Acid Batteries

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So India is already “IN” Electric Vehicle use with E- Rickshaws and these exclusively use Lead Acid Batteries. The growth is fantastic and growing further, As an electric vehicle India is leading users of Electric Vehicle in the world. And the most important thing is that they all use lead acid batteries. Lead being recyclable compared to Lithium based batteries, it has an advantage. BATTERIES FOR E-RICKSHAW.Currently N100 size container is being used for both flat and tubular types. Later is costlier but gives longer life and range. Tubular battery can face PSOC better. Manufacturers of these batteries are continuously developing newer designs, Grids with newer alloys. The failures/end of life situations of batteries are being closely monitored. Since it is evolving continuously, so the book is not giving any particular design details. But likely development pointers are i) Going for taller flat plates than normal sizes. ii) Considering taller containers in vehicles where it can be fitted. iii) Using higher Antimony alloys for positive. Motive power batteries gives long life are with higher Antimony alloy. One leading maker of golf cart batteries in the world uses - Positive grid Alloy of Sb- 4.33,Sn-0.44, As- 0.135, Se-0.0212 - Negative grid Alloy of Sb-2.70, Sn-0.192, As- 0.165, Se- 0.0112 Additives - The Active material also needs various improvements. More porus active material for positive. Negatives with Carbon/Graphite up to 2% with Expander or instead Carbon additives of various grades, which are available from reputed makers. The same be tried out. (we have to wait for Carbon based negative in future).2% TBLS be used in positive flat plates. Use of Poly- Aspartic Acid of about 0.5litre per 100 Kg be tried out along with expander. It can be used replacing that amount of water in mix. It has benefits of - Suppression of accumulation of lead sulphate in negative plates - Reduction of internal resistance - Higher back up and increased cycle life The same can be added in Electrolyte too.

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Only physical Test results after trial be considered for implementation. Additive for Tubular Positives could be with following TBLS 1.15%, Graphite 0.9%, and Calcium Sulphate Dehydrate 0.85%. Over last decade huge research activity has been done on deep-cycle as well as PSOC applications. Additives as mentioned above are products of such research. These are recommendations of vendors and be used only after trial and getting claimed benefits. The E- RICKSHAWS use have sky rocketed, being a cheap and environment friendly vehicle. The product development has lagged. The early failures by 6 months are things of past and makers of batteries are trying with various options. Only increased life can sustain Lead Acid Battery against competition of Lithium based batteries. There are few important things on this application. - Topping up of of water in time. It has been seen this care has increased the life of batteries. Further E- Rickshaw makers must design vehicles with easy access to battery for top up. -

As Antimony percentage is likely to go up in positives, use of

appropriate Separator to arrest Antimony migration is needed. There are Separators claiming these features and are available. - Charger quality is another area of concern. The features needs to be standardised, so that it can do proper charging. Change from Tubular to flat and vice versa would need change of settings. Battery makers be proactive on proper charger use to get more life out of their batteries. The buyer of ERickshaw is an important customer for Lead acid battery. His lively hood depends on battery. Production process, including Pasting, Curing and Charging have been explained earlier in the book, be seen. E- Rickshaws are not only personnel carrier, but being used for waste collection and dumping, Carrier of goods to the last mile is another application. These vehicles are boon to Lead- Acid battery makers. v v v

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33) Layout of Battery Plant The Layout is something all have views, be it new plant or existing plant. Battery making is a batch process. Between each process and next process there is movement and likely storage. In most cases due to operation mismatch there needs to be some storage. Starting from Casting.( Automotive/Flat Inverter/E- Rickshaw) Lead and Alloy : Stored for feeding Casting and Oxide Plant. Storage of Oxide for Aging Casting : Stacking in flat or vertical skids for Aging. Aging : Antimonial grids needs 3 days aging. Calcium Grid can be aged in a shift in oven. So storage at ground level or multilevel racks needed. Storage Pasting : Aged grids to Paste and collect at the end of Process / FDO. Collected in Skids which now need to move to next operation quickly to empty oven. Curing And Drying : Combined operation and can be between 36 to 40 hrs. Loading and unloading time to consider, with about an hour for conditioning the Oven. Skids move out and stored for next operation. Storage Plate Cutting And Brushing : Make the plates part,clean the lugs/cut and move to storage before Assembly. Storage Assembly - Involving, enveloping/ stacking/group making and to Assembly line. Battery stored and waits charging. Storage Charging - Filling acid and charging in water cooled tanks Finshing - Battery electrolyte is levelled, washed and then tested for HRD. Stored for packing if finishing line is not on line. Storage Packing this operation Battery is made Ready to despatch. Again Storage involved. So we can see there are 7 Storage areas in above. For formed plate there are two additional operations with Storage. In above, except storage of Grids for aging which is an operation, rest is storage of Work in Process (WIP). Each also needs a movement. These6 Manufacturing Concepts of Lead Acid Batteries

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storage areas mentioned above, are not adding any value to the product and may involve extra men to move. Ideally keeping to storage isthe job of the one making the same and taking for operation for next operation be job of next operators. This reduces indirect manpower for movements. So LAYOUT be such that it can be easily be with nearness of succeeding and preceding operations. If storage of or placements are multi high then obviously one needs a Fork Lift Truck.( FLT) and its manning and cost adds to overall cost. But doing such you save some ground level space. Layout has to take care of 1. Placement of Machine/Equipment 2. Storage space for WIP. 3. Passage/Aisles for material movement. 4. Any imbalance or strategic storage. Tubular, VRLA be very similar. New Plant :a. Basic issues. 1. Plant and machinery for immediate plan based on capacity/output level. 2. Requirement of utility and their location. Gas, Air, Water, Effluent handling, Toilet STP etc 3. Clubbing of power hungry equipment nearest to MDB and also Ventilation areas with their stacks. 3. Passage of movement and intermediate storages 4. Plant and machinery for future expansion in same Product or start a new Product line. 5. Land available and permitted use of Covered area. 6. Cardinal directions of Land. (Inputs in Edifice science be seen) 7. Access to Land. Vehicle and people access. Their movement. 8. Availability of Power, Water, Drainage, External parking availability. 9. Adjacent area surrounding and nearby factory proposed. 10. Year round weather conditions. 11. Daily movement of vehicles. IN,OUT, PARKING. Manufacturing Concepts of Lead Acid Batteries

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12. Shed with height requirement, Space for drain, utilities outside. 13. Loading and Unloading of goods coming in going out. 14. Security needs. 15. Welfare needs. Toilet, Ablution, Canteen etc. Each has an impact while doing the layout. Each should be evaluated. - Straight linelayout can be first operation to despatch. Rectangular plot - “U” type layout. With Formation at the turning. - “CI” type layout with “Assembly, Charging, Despatch” in “I” portion. Advantage of this layout is that each operation can be extended sideways. Also suited, for more square type plots. Existing Plant : 1. Further addition/subtraction of plant/equipment, sheds, and buildings. 2. Change in Utility requirement. Water/ Air/Electricity/ETP/STP 3. Level of Automation to reduce fatigue of people and increase productivity. 4. Reduce travel distance. 5. Use of Vertical space to create space at ground level. Some Basic Concepts : 1.

Keep Power hungry equipment, like Mill, Grid Casting, Melting pots, Mixing/Pasting close by to Main DB. So that cable cost and voltage drop loss is less.

Ventilation/Extraction from various pots, hoods is preferably in straight line, for ducting straightness.

Stacks be close by and be in same foundation with enclosed structures, to avoid many foundations and self-supporting chimneys.

It is better to use Vinyl lining in most acidic areas. Passages be with vertical acid proof bricks or steel plates. Any other lining does not work.

Straight line movement is best suited to move heavy weights. Least movement be focus area.

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Drainage of effluents be planned to take them to pit straight line for recovery.

Utilities like independent Bag filters, Scrubbers with fan and stacks all areto be outside shed. Between Road edge and building be around 4/6m (depending on plant size) to accommodate utilities. Self-supporting stacks are expensive.

Maximum amount of recirculation’s of water be considered and with preferable pressure and temperature control.

Welfare facilities should satisfy the requirements of people.

10. Lab, shop office, stores, Maintenance areas be located for easy access. 11. Seasonal products need some extra storage. 12. Suitable location of Office. Ground or higher level. 13. Use of natural lights to the maximum with shed design 14. Unless fresh air is supplied, the ventilation/extraction systems do not work well. 15. No roof extraction in battery plant. Lead in air increases for inhaling. Supply of fresh air above people working is good. A poor layout can lead to excess movement, damage due to mishandling, over storage of WIP (if space is there it fills up), lowers morale, outlook of workmen. A clean and neat place with straight aisles, leads to better quality v v v

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34) Manufacturing Plant With 100 / 200 / 500 / 1000 Batteries Per Day Assumptions : 1. N100 Battery with 7Positive and 8 Negative Flat plates. 42/48 plates per battery 2. Lead Antimony Grids 3. Factory charged. Charged with green plates. Charging all 30days 4. 25 working days. 8 hrs shift. 5. Paste weight 285/230 gms. Oxide 250/207 gms for Positive/Negative Panels. 6. Grid casting 12000 per day. Mixing time, 50 minutes. Curing cycle time, 48hrs 7. Assembly 400/shift with stacking, group burning, boxing. Charging, cycle time 48 hrs. 8. Skids 2100/2500 PANELS of Positives/Negatives.5 high skid. 1mx0.9m x 1m.size. 9. FDO can be Electric. For without FDO speed below 60/min for Manual collection 10. For any other type, one can work out similarly Manufacturing Facilities Sl.No Items

100/day

200/day

500/day

1000/day

Positive plates

4200

8400

21000

42000

Positive Grids

2100

4200

10500

21000

Negative plates

4800

9600

24000

48000

Negative Grids

2400

4800

12000

24000

Total Grid Panels

4500

9000

22500

45000

Casting

Hand

2GCM

4GCM

Positive Paste. Kgs.

600

1200

3000

6000

Negative Paste. Kgs

550

1100

2750

5500

Oxide Kgs Total

1035

2070

5175

10350

Oxide Plant/mill

BOP

6T/DAY

12T/DAY

MIXER capacity in Kgs

200

300

500

1000

No.of Shifts

1.25

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Pasting

Hand

1m/c

Curing 2skid

4 6

Assembly

1 1

1m/c+fdo

Charging Circuits

Plate Parting saw/slit

Manual

Machine

Enveloping

Bop

Machine

Assembly Line

Semi

Auto

Charging Circuits

Water Cooled Tanks

Floor

PVCTanks

Acid Filler/leveller

Semi

Machine

Hrd Testing

Manual

Machine

Compressor Cfm

100

250

500

Dm Water Plant Lit/hr

100

Acid Dilution

Bop

Plant

Cooling Tower

1 2

Effluent Treatment

Pit

Etp

Pallet Truck

2 3

Fork Lift

Scrubber With Stack

Bag Filter With Stack

1 2

Power In Kva

100

200

600

Etp

1 1350

These Are Just Guidelines. One Can Debate Building Just Adequate Or Future As Per Choice Mostly Local Machineries Considered

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35) Lean Management For Production Shop Floor and Support Service Lean Philosophy : The traditional and Lean comparison below, gives basic concepts. In a battery unit, after meeting a planned target, if there is no component lying in shop floor, it is a good example of Lean Management. Elements

Traditional

Lean

Company Goals

Beat the competition

Acquire customers

Management Culture

Solve Problems

Avoid Problems

Priorities

Results

Results & Process

Procedure

Static

Dynamic

Employees

Cost & Nuisance

Source of Ideas

Machinery / Equipment Expensive& Dedicated

Small & Flexible’

Handling Problems

What’s the Solution?

Who to Blame?

Need to understand what is adding to value and what is not adding value. Say Grid Casting is adding Value but, Handling Skids to a location of storage is not adding value. The focus should be to eliminate, if not possible, reduce. Wastes : The SEVEN areas of Waste l Over Production l Inventory l Over Processing l Rework l Transport l Movement l Waiting

Waste is anything the customer should not pay for Some Examples – Waste exists every where l Keeping l Zig zag

Buffer Stock, producing more than needed.

transportation

l Inventory

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Machine l l Double l Untidy

Down time

Handling

Workplace.

Indirect Areas This is often overlooked l Redundant

activities - Look for the same, to eliminate.

l Work Back

log- keeping decision pending

l Excessive l Process

control and Approval process.

error – Mostly due to wrong specifications

l Transmission l Information

and Waiting times.

failures - Information delayed/wrong information

“lean” Focus On Non Value Added Activities Is Very Important. Financial Impact needs to be evaluated in every stage. Make the Process deficiencies transparent for everybody. Define improvement projects. Involve team work. Reduce Number Of Steps To Market - That Is Reduce The Time From Input Of Materials To Product Reaching The Customer. v v v

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36) Application Related Inputs Application needs can help Manufacturing decision making. Technical Particulars of 12V Monobloc Flooded Tubular Batteries Equalising Charge : Equalising Charge is carried out in lead acid batteries to reverse the negative effects of electrolyte stratifications in fully charged condition. It also helps to remove any sulphating of plates due to storage in discharged condition or partial state of charge for long periods. Equalising charge may be carried out once in six month interval, However if the specific gravity variations are not much in the batteries (± 0.005) then equalising charge can be performed at once a year interval. The maximum charging current shall be kept between 15 % ~ 20 % 0f the rated capacity of batteries

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Design Life of 12V Monobloc PP Batteries

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Temperature correction factor for Capacity calculation:

Cap @ 27°C = Ct + Ct * R ( 27 – t ) / 100 }

: Observed capacity at t°C

: Variation factor chosen from above table

: Average electrolyte temperature measured in pilot cell at regular

intervals during discharge

Battery Capacity Selection Tubular Batteries : UPS Rating

7.5 KVA

Efficiency

90%

Power Factor

0.8

Cut Off Voltage

210 Volts (1.75 volts per cell)

Load pattern

Full load for 60 minutes & 120 minutes

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Discharge Current : 7.5 x 1000 x 0.8 210 x 0.9 31.75 amps x 1 = 32Ah Recommended battery size is 20 No’s of 12V - 60Ah PP battery for 1 hr back-up

For 2 hr Back-up period : 31.75 x 2 = 63.5 Ah Capacity at 2 hr as percentage of 10 hr Capacity 63.3% 63.5 / 0.633 = 100.32 Ah Recommended battery size is 20 No’s of 12V - 100Ah PP battery for 2 hr back-up Table 1.

Tubular batteries UPS Rating Efficiency Power Factor Cut Off Voltage Load pattern Discharge Current :

: : : : :

11.2 KVA 90% 0.8 315 Volts (1.75 volts per cell) Full load for 60 mins & 120 mins

11.2 x 1000 x 0.8 315 x 0.9 31.60 amps x 1 = 32Ah Recommended battery size is 30 No’s of 12V - 60Ah PP battery for 1 hr back-up For 2 hr Back-up period : 31.75 x 2 = 63.5 Ah Capacity at 2 hr as percentage of 10 hr Capacity 63.3% 63.5 / 0.633 = 100.32 Ah Manufacturing Concepts of Lead Acid Batteries

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Recommended battery size is 30 No’s of 12V - 100Ah PP battery for 2 hr back-up Tubular batteries UPS Rating Efficiency Power Factor Cut Off Voltage Load pattern

: 16.8 KVA : 90% : 0.8 : 315 Volts (1.75 volts per cell) : Full load for 60 minutes

Discharge Current: 16.8 x 1000 x 0.8 315 x 0.9 = 47.41 Amps x 1 Hrs = 47.41 Ah Recommended battery size is 30 no’s of 12V- 100 Ah PP Battery for 60 minutes back-up

Battery Care and Maintenance: Battery is a protective safety device against power cuts and poor quality of mains supply, all care must be taken to ensure the batteries are properly maintained to get the maximum desired life. w Adjust Float Voltages correctly w Top-up with distilled or de-ionised water at periodic intervals before electrolyte reaches minimum level, While adding water do not exceed maximum level. w Do not add sulphuric acid during maintenance w Keep the battery clean and dry w Keep the connectors clean and use lead plated lugs and fasteners for interconnections. w Equalise Charge the batteries periodically to maintain proper state of charge and no electrolyte stratification. Manufacturing Concepts of Lead Acid Batteries

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Maintenance : w Keep containers, lids and battery rooms clean w Wipe out salt and acid stains on terminals, connections and lids with wet sponge. w Do not clean the battery components with solvents, detergents, oils or similar products. w Once in three months Check, the battery terminal voltage and it should be equal to applied float voltage per cell multiplied by number of cells. w Measure voltage, specific gravity and temperature of a few reference cells w Check electrolyte levels in all the cells w Check the ambient operating temperature and record w Apply equalising charge if the gravity measured are different in cells to normalise the electrolyte w Use good quality hydrometer, Thermometer, Filling device and Voltmeter for measurements. w Tighten all wiring connections to proper specification and ensure that the contact with terminal is intact & good w Check all battery cables and their connections. Replace cable that are defective and suspiciouss.

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37 ) Making Quality Products Existing or New plant can follow following guidelines area wise. Oxide : While using Oxide, one must consider whether it is Mill or Pot. For Mill AD is important. While for Automotive application the AD can be around 1.2 and for deepcyce application around 1.4. Pot oxide is preferred for Tubular plates. For VRLA small one can have AD lower to 1.1, by pulverizing. AD of oxide can help in getting micro or macro pores as desired in active material. If one can choose AD, above guidelines be considered. 72 hrs of aging of Mill Oxide is needed, For Pot Oxide no aging period. Alloy : This has important bearing in product plan. Low Antimony positive and Calcium negative is for Hybrid MF. For Deep cycle application it is higher Antimony alloy. Small parts/group burning can beat 3.2 % Antimony alloy. Most important point is depletion of alloying elements. Products with designed alloying products have very devastating effect on battery. Corrosion is one. Poles can melt or corrode. The Alloy temperature below 490 degree C, Selenium/Tin/ Calcium float out first to get lost in dross. So it is better to keep pots insulated and kept at higher temperature. Top can be covered too. Pots started from cold temperature be stirred as soon as the alloy melts. Depletion of alloying elements are to be be made up by using Master Alloys. With OES ( Optical Emission Spectrophotometer) , one can know alloy quality in use faster, but not affordable for most units. Given below analytical way to find out the same, so that timely adjustments are possible,Various alloys of antimonial lead are used in the works for making grids for all types of batteries and for various ancillaries. Key elements are Antimony, Selenium, Tin, Arsenic. It is very important for battery quality and life, the alloying elements are within the limits. (Analytical Test method supplied by a technologist) Antimony( Sb) : .Required equipment :A.) Analytical Balance B.) Spatula and Glass Stirring Rod Manufacturing Concepts of Lead Acid Batteries

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C.)Conical Flask – 500 ml. D.)Graduated Cylinder -100 ml. E.) Burette Stand with Burette – 25 ml. .Solution :1.

0.1 N Potassium Bromate

Methyl Orange Solution

.Method Transfer 1 gm. Of a coarsely filed sample to a 500 ml. flat – bottomed flask. Add 30 ml. of con. Sulphuric Acid and heat. Gently at first until the atmosphere, until the initial vigorous reaction has subsided, then strongly until the atmosphere inside the flask is clear, and white fumes appear only from the neck of the flask. Alloy to cool, carefully add 100 ml. of distilled water followed by 30 ml. of concentrated hydrochloric acid. While still hot, titrate with 0.1 N Potassium bromate solution using methyl orange solution as indicator. The end point is indicated by a rapid bleaching of the color. CALCULATION 1 ml. 0.1N KBrO3

= 0.00609 ml Sb

Sb % =Titrate x 0.00609 x 100 Wt. of Sample TIN (Sn) : .Required Equipment:A.) Analytical Balance B.) Spatula and Glass Stirring Rod C.) Conical Flask – 500 ml. D.) Graduated Cylinder -100 ml. E.) Burette Stand with Burette – 25 ml. F.) Beaker 500 ml. . SOLUTION :a. 1.N Iodine Solution b. Starch Solution c. Eached Nickel Foil d.10 % SODIUM CARBONATE SOLUTION PROCEDURE :Transfer 5 gm. Of a coarsely filed sample to a 750 ml. Conical flask, and Manufacturing Concepts of Lead Acid Batteries

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add 60 ml. Concentrated Sulphuric acid .Heat gently at first , until the initial vigorous reaction is completed, and then strongly until the atmosphere inside the flask is clear, and copious fumes are distilling from the neck of the flask. Cool, add 100 ml. of water, and 50 ml. concentrated HCL Assembly the reduction apparatus as shown fig 2 with the end of the tubing dipping in to Na2CO3 solution remains strongly alkaline. At the end of the reduction period cool the flask, first in the air, then under running water, ensuring that the end of the tubing remains under the surface of Na2CO3 Solution. When cold, add a few ml. of a starch solution, and titrate quickly with standard Iodine solution, until the appearance of a permanent blue end point. Calculation:1 ml.Iodine solution =0.005935 ml Sn %=

Titrate x 0.005935 x 100

.Wt. Of Sample Copper (Cu) Required equipment: A.) Analytical Balance B.) Spatula and Glass Stirring Rod C.)Conical Flask – 500 ml. D.)Graduated Cylinder -100 ml. E.) Burette Stand with Burette – 25 ml. F.)Beaker 500 ml. .SOLUTION :1. Dilute Nitric acid (1 : 1 ) 2.Dilute Sulphuric acid ( 1: 1 ) 3.Standard copper solution (1 ml. = 0.0001 g Cu ) .Method:Transfer 5 gm . of a coarsely filed sample to a 250 ml. beaker , and dissolve in 50ml Dilute Nitric acid by heating gently. Dilute to about 100 ml. heat almost to boiling and precipitate the lead by adding 25 ml. Sulphuric acid. Cool thoroughly filter of the PbSO4 on a filter paper, and a few glass beads to the filtrate. Cover the beaker with a watch glass, and evaporate the contents to copious fuming. Cool continually wash down the watch glass and walls of the beaker with about 20 ml of water, Mix and cool again. Filter through a whatman filter Manufacturing Concepts of Lead Acid Batteries

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paper to a 100 ml. Graduated flask, washing three times with small portions of water. Dilute the solution in the flask to about 60 ml. add. NH4OH Until the solution is just ammonia sol. Prepare a blank in a second flask by adding NH4OH. Mix Thoroughly with out contamination add Std. Cu Solution drop by drop and match the turbidity. And finish the test as quickly as possible. Calculation:Cu% = Titrate x 0.0001 x 100 Sam. Vol. x Wt. sample Arsenic Test Required Equipment :A.) Analytical Balance B.) Spatula and Glass Stirring Rod C.) Conical Flask – 500 ml. D.) Graduated Cylinder -100 ml. E.) Burette Stand with Burette – 25 ml. F.) Beaker 500 ml. SOLUTION 1. Methyl orange indicator solution 2.0.1 N KBrO3 3.Dilute sulphuric acid (1 : 1) Procedure :Transfer 5 g of a coarsely filed sample to a 500 ml. flask, and add 25 ml of Sulphuric acid and 5 gm potassium bisulphate. Heat over a low flame until the first vigorous reaction is complete, and then heat strongly until the atmosphere inside the flask is clear. Cool, add 60 ml of water and about 0.5 gm H2N.NH2.H2SO4 and 200 ml HCL add several glass beads. To the flask and contact to the distillation apparatus to a lubing condenser. At the collection end fit a suitable adapter with long tail dipped in 100 ml. D.M Water Start heating and heat strongly to boiling from the commencement of boiling to the appearance of fine crystals of PbCl2 the time should be approximately 25 min. Wash the condenser with little volume of D.M water and titrate with KBrO3 at 80 -90 °C using few drops of methyl orange indicator bleaching of red color marks the end of titration. Calculation:Manufacturing Concepts of Lead Acid Batteries

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As % = Titrate x 0.00188 x 100 Sample wt. - Selenium test Required Equipment :A.) Analytical Balance B.) Spatula and Glass Stirring Rod C.) Conical Flask – 500 ml. D.) Graduated Cylinder -100 ml. E.) Burette Stand with Burette – 25 ml. F.) Beaker 500 ml. Solution :1. Hydrobromic Acid Bromine Mixture : Dissolve 5 ml. Bromine in 100 ml. hydro Bromic Acid

. (Sp.Gr. 1.46 – 1.49)

2.0.01 N Sodium Thiosulphate (1 ml. of 0.01N Sodium Thiosulphate =0.0001974 g Selenium) 3. Sodium Hypophosphite Solid Procedure :Dissolve 5 Gm. Sample in a 30 ml. Of hydrobromic Acid Bromine mixture at temperature below 50° C. When Solution is complete add 30 ml. of Water, Heat to 80°C and just sufficient Sodium Hypophosphate to precipitate the Selenium from solution. Filter of the precipitated selenium. Using suction, on a Pulp pad in a bucher funnel. Wash wellwith boiling water. Dissolve the selenium from the pad into the original beaker using two small portions of hydrobromic acid bromine mixture. Allowing the solution to drain after each addition .Wash the filtrate to remove the excess bromine. Leave the solution over night to remove. Add 5ml.Concentrated HCL followed by 0.25 gm KI. And immediately titrate the solution against 0.01N sodium thiosulphate solution, Using Starch solution as the end point indicator. When the blue color of the starch disappears and the color of the precipitated selenium appears. Calculation % Se = Titer x 0.0001974 x 100 Wt. of sample The Analytical test is possible, if having a Laboratory and Chemist. In a Manufacturing Concepts of Lead Acid Batteries

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steady running plant, the alloy percentage adjustments are much easier. Grids : The grid design be different for hand casting and machine casting. One can have offset lug in machine casting, which can reduce internal resistance and also weight of top lead. The internal wires can be 0.1mm below frame level on both side. The wire cross section is more as it approaches top frame. Grids can have radial, tree radial etc shape. One must compare grid weights and thickness of reputed makers and match the grids accordingly to optimise the weights. Grid thickness reduction of positives, often reduces life Mixing : Key items of Mixing for quality assessment are paste density, penetration, moisture, residual lead and Sulphate content. Paste density is not same for various applications. The acid and water contents for various application are different. Sulphate content has bearing on porosity of active material. For Automotive application sulphate content of positive active material is almost 16%.. For Inverter application high density is needed for positives, as such sulphate content is low. Then additions of additives vary with applications. TBLS are now in paste Mix to get better size crystals in active material. Mixing with Sigma/Z blade mixers are good and temperature limitation be 55 degree with cooling arrangement. Pasting : Hand pasting gives good wire coverage over grid wires. Plates post pasting are pressed with rough cloth for surface impression. The advantage is placement of plates with uniform gaps, giving better curing conditions. Also moisture level is high. For machine pasting, one can avoid FDO if pasting is below 60 per minute. FDO consumes lot of energy. It is more needed for productivity. The important thing is that the grooved rollers inside hoppers must maintain its sharp edges so that paste flows properly to grids. The Roller be replaced periodically. Finishing roller after pasting plays an important role to give a better bottom finish and helps in wire coverage. Acid wash needed is basically to retain moisture in plates for better starting moisture in Curing. One must have around 9.5% and 8% moisture in positive and negative plates respectively. If it is not there, one must work to reach or exceed this level. Manufacturing Concepts of Lead Acid Batteries

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Curing : This is heart of Battery making is curing operation. Any new curing oven be initiated with adequate Relative Humidity( RH) close to 95% and temperature of oven to start with at 40degree C. Every two hours Residual Lead and Moisture be measured and plotted. They should get lower progressively together. If one of them falls faster than others, the oven conditions is to be modified. Try achieving moisture level of 3/4 percent after 9 hrs from start and not earlier. Later is better.. Some times to get that RH one may set the RH higher. If the Temperature moves up, RH setting can be reduced. Basically there are 3 parameters RH, Temperature of Oven and Airflow are to be controlled to get the best Curing. Once set, same can be followed with periodic check. The humidity be created by steam produced electrically or by steam boiler. Never try with spraying with mist sprayers. The need is gas and not fine moisture particles of water. Once the curing activity peaks temperature of plates will go up and be as hish as 60 degree C. Oven temperature be maintained 40 degree in the PLC See that there is provision of fresh air entry in oven. Plates need Oxygen. It is always better to have single row oven and airflow be lamellar or very slow during curing operation. Just enough to pick up moisture from plate surface. As the moisture is removed from surface fresh vapour is generated inside active material exothermically and comes to surface, creating a pore passage. Some people in tropical condition use wet gunny bag cover over skids. Gap maintained at bottom for air entry. Small holes can be at top so that air flow is there from bottom to top. But where ambient temperature is low, this will not work. Minimum 30 degree C is needed to start curing. In cold conditions this is not the way to cure. Use Ovens. Drying : After effective curing with moisture and lead below 1.5 % for positive and <3% lead of negative, one needs to dry the plates. Almost 24/28 hrs is needed to achieve these figures. The same oven be designed for drying, but Drying stage of about 80 degree be reached slowly (around 3 hrs). This is to prevent crack and separation of active material from Grid wires. The absorption of temperature and the expansion of grid is faster than active material. Grid is metal. If one does Formation of plates they can keep plates on skids for two Manufacturing Concepts of Lead Acid Batteries

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days. With <0.8% moisture plates be used in Formation. For green plate Assembly, it should be <0.5%. So for later one may need oven drying. Drop tests by dropping from a height and measuring weight loss are to done periodically. Colour of plates be uniform. Orange colours indicate high temperature faced by plates and most likely plates were too close to each other. The battery performance is very mush dependent on good Curing and Drying. Assembly : The operation involves stacking with enveloping, group burning and boxing in container. Small Parts : Depletion of alloy often happens at this stage as it is on and off daily. This can cause premature failure of poles and straps by corrosion. Be very particular on alloy level in pot. Antimonial Alloy gets hardened slowly after 4 hrs of casting. The hardness reaches maximum after 8hrs and continues for 72 hrs and drops to a lower level (but more than initial hardness). So if inter cell welding (ICW) is not within 4 hrs, then it should be after 72 hrs. but with higher setting of pressure in ICW. If the practice is to do within 4 hrs, then any excess small parts must go back to melting pot. Small parts half flat bottom so that they sit upright on combs. Group Burning : The jig box quality and combs be of good quality material and machining. It is better to invest money for better combs and jigs. The burner be very experienced and skilled. Boxing : This operation be such that, with packings the groups go in easy on its own weight up to 50% of cell and then it should be pushed in. Next important thing is alignment of straps. The flags on both face of container partition be flat. So that they are not dragged to do the welding. The reason is that, if a taper gap exists between metal and plastic, the acid can go up by capillary action to weld joints and corrode it. It is better to keep a pen mark on partition to show the hole position for proper alignment. The flashes sticking to small parts be cleaned out by knife/ pincers. This is an area where suction ventilation is desired from bottom of stacking, enveloping area and from side top of group burning area. Assembly Line : The machines used by, many are with manual placement of battery to individual machines. Machines for 500/1000 battery a day level be with automatic feeding to machines and placement. During the Welding and Heat sealing operation the conveyors be off or must not Manufacturing Concepts of Lead Acid Batteries

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move battery. Welding parameters are by robust weld parameter study, as explained earlier. The hand shear tester can be used to test strength of weld. Dummy welding of straps can be done once a shift, preferably at starting of shift. Visual inspection and manual short circuit tests be done be fore fitting in the lid. Many use partly recycled plastic in lids and as such heat seal parameters be set accordingly. The mirror surfaces be cleaned and lubricated with silicone oil. Periodically platen and mirrors be checked for flatness with scale. More details have given earlier in the book. Charging : Mostly is now with green plates. The chargers have undergone change, When earlier only constant current chargers, to chargers which can be programmed. Batteries while being charged, have a period when Top Of Charge (TOC) voltage is low. This is almost half of the total period and then the voltage shoots up to take care of back emf. This initial period is a period with high charge acceptance. One can pump in much higher current keeping electrolyte temperature below 55 degree C. One can have steps of high and low current looking at temperature of electrolyte. In the next period when TOC moves up, one needs to give a rest period to clear the blockages of gases, before charging again but at reduced current. The end of charge is when consecutive 3 gravity readings are same and not achieving a TOC of say 16Volt. Overcharge causes harm to the joints of grid and active material and life of battery gets reduced. In another method pulse charging can be done with 5 minutes charge and then 10 seconds rest and cycle continuously. One can have 3 charge regimes. Initially almost at 40 C10 A current and finally at 20 C10A current. Generally 85/86% PbO2 level of positive active material is good enough. In another method one can charge at low gravity to almost 90% level and change the acid with higher gravity acid. A period of charge be done to make the acid uniform. All these methods save electricity much more than just constant current method. Almost 30% of energy is consumed in charging while making battery. An investment in charger pays off fast. While Charging, please also note batteries cycling needs periodic equalizing charge. Even in car battery if dischrage takes place below by 30%, due to some abnormal operation, car fails to charge the battery full Manufacturing Concepts of Lead Acid Batteries

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again. With not fully charged battery running, the life of battery goes down very fast. Such batteries if charge periodically with an equalising charge, the life is extended by good margin. For Tubular batteries with proper acid pickling, the charging is not much of a problem, but with plates just ammonia dipped, one needs to charge at pickling current for 6 hrs. Some makers gives two discharges of two hours instead with Ammonia dipping of 5 to 10 minutes. But former is better. Particularly for cycling batteries like E- Rickshaw. The bonding of active material with grids is very sensitive and fragile. This is called corrosion layer and developed during curing operation. It bonds active material with grids at grain boundaries. So it is always better to have low starting current for an hour before stepping up. During winter, one needs to charge at higher current and still keeping the limit of 55 degree. Charging at low temperature is inferior to charging at higher temperature. Cut Open Analysis : Cut open analysisof own and competitors battery can reveal the weak and strong points of each. One can take corrective actions. Learning from major battery makers about their design can help improve own batteries. Battery test results and its comparison is another way to improve one’s battery. Hope above inputs specially written for MSME sectors help them to improve. Without good improvement it is difficult to sustain in the competitive environment. v v v

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38) Battery Application Related Question And Answers (Reproduced From Exide Product Literature.) FAQs ( Frequently Asked Questions) What is a Battery& How it works? A lead-acid battery is composed of a series of plates immerse in a solution of sulfuric acid. Each plate consists of a grid upon which is attached the active material (lead dioxide on the negative plates, pure lead on the positive plates.) All of the negative plates are connected together, as are all of the positive plates. When the battery is discharged (when it is subjected to an electrical load), acid from the electrolyte combines with the active plate material. This releases energy and converts the plate material to lead sulfate. The chemical reaction between constituent parts of the electrolyte and the spongy lead of the negative plates and The lead dioxide at the positive plates turns the surface of both plates into lead sulphate. As this process occurs the hydrogen within the acid reacts with the oxygen within the lead dioxide to form water. The net result of all this reaction is that the positive plate gives up electrons and the negative plate gains them in equal numbers, thereby creating a potential difference between the two plates. The duration of the reactions producing the cell voltage is limited if there is no connection between the two plates and the voltage will remain constant. Different Types of Batteries: Basically there are two types of batteries, starting (cranking), and deep cycle (marine/golf cart/Fork-lift trucks). The starting battery (SLI starting lights ignition) is designed to deliver quick bursts of energy (such as starting engines) and have a greater plate count. The plates will also be thinner. The deep cycle battery has less instant energy but greater long-term energy delivery. Deep cycle batteries have thicker plates and can survive a number of discharge cycles. What are volts? It is the units of force or pressure of electric current. The voltage of a battery depends on the number of cells. Each lead acid cell has 2 volts. What is meant by “specific gravity” of battery electrolyte? It is the weight of the sulfuric acid-water mixture compared to an equal volume of water. Pure water has a specific gravity of 1. Are lead acid batteries recyclable? Lead acid batteries are 100% recyclable. The plastic containers and covers of old batteries are neutralized, reground and used in the manufacture of new battery cases. The electrolyte can be processed for recycled wastewater uses. In some cases, the electrolyte is cleaned and reprocessed and sold as battery grade electrolyte. In other instances, the sulfate content is removed as Ammonia Sulfate and used in fertilizers. The separators are often Manufacturing Concepts of Lead Acid Batteries

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used as a fuel source for the recycling process. What is the difference between a Cell and a Battery? Strictly, an electrical “battery” is an interconnected array of one or more similar “cells”. A car battery is a “battery” because it uses multiple cells. Multiple batteries or cells may also be referred to as a battery pack as a set of multi-cell 12 V batteries in an electric vehicle. A 12 Volt monoblock battery consists of 6 cells, but a plante’ or 2 Volt tubular battery is a battery though it consists of a single cell. What is Battery capacity? The capacity of a battery to store charge is often expressed in ampere hours (1 Ah = 3600 coulombs). If a battery can provide one ampere (1 A) of current (flow) for one hour, it has a real-world capacity of 1 Ah. If it can provide 1 A for 100 hours, its capacity is 100 Ah.Battery manufacturers use a standard method to determine how to rate their batteries. The battery is discharged at a constant rate of current over a fixed period of time, such as 10 hours or 20 hours, down to a set terminal voltage per cell. So a 100 ampere-hour battery is rated to provide 5 A for 20 hours at room temperature. The efficiency of a battery is different at different discharge rates. What is Battery lifetime & how it varies? Rechargeable batteries can be re-charged after they have been drained. This is done by applying externally supplied electrical current, which causes the chemical changes that occur in use to be reversed. Devices to supply the appropriate current are called chargers or rechargers.Temperature Effects on BatteriesBattery capacity (how many amp-hours it can hold) is reduced as temperature goes down, and increased as temperature goes up. The standard rating for batteries is at room temperature 25 degrees C. Battery charging voltage also changes with temperature.Plate ThicknessPlate thickness (of the Positive plate) matters because of a factor called “positive grid corrosion”. The positive (+) plate is what gets eaten away gradually over time, so eventually there is nothing left - it all falls to the bottom as sediment. Thicker plates are directly related to longer life. Most industrial deep-cycle batteries use Lead-Antimony plates rather than the Lead-Calcium used in AGM or gelled deep-cycle batteries. The Antimony increases plate life and strength, but increases gassing and water loss.Cycles vs. LifeA battery “cycle” is one complete discharge and recharge cycle. It is usually considered to be discharging from 100% to 20%, and then back to 100%. Battery life is directly related to how deep the battery is cycled each time. If a battery is discharged to 50% every day, it will last about twice as long as if it is cycled to 80% DOD. If cycled only 10% DOD, it will last about 5 times as long as one cycled to 50%. Does lead acid batteries discharge when not in use? Yes. All batteries, regardless of their chemistry, will self-discharge even Manufacturing Concepts of Lead Acid Batteries

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when no load is present. At a temperature of 27 degrees C, a lead acid battery will self-discharge at a rate of approximately 4% a week. A battery with a 125 amp-hour rating would self-discharge at a rate of approximately five amps per week. For MF batteries it is much less.A rule of thumb is to ALWAYS keep your batteries fully charged while not in use! Charging Lead-Acid Batteries A multi-stage charger first applies a constant current charge, raising the cell voltage to a preset voltage, takes about 5 hours and the battery is charged to 70%. During the topping charge, the charge current is gradually reduced as the cell is being saturated. The topping charge takes another 5 hours and is essential for the well-being of the battery. If omitted, the battery would eventually lose the ability to accept a full charge. Full charge is attained after the voltage has reached the threshold and the current has dropped to 3% of the rated current or has leveled off. The final is the float charge, which compensates for the self-discharge. What is an Equalization Charge& Why it is Necessary? In any cyclic application, a series of batteries will always need to be equalized from time to time in order to ensure that the battery cells remain at the same voltage throughout the pack. During the charge cycle the voltages of the different batteries will very. In order to bring them all to the same level it is necessary to give some a slight overcharge in order to bring the other up to full charge. Equalization is done by allowing the voltage to rise while allowing a small constant current to the batteries. The voltage is allowed to rise above the normal finish voltage in order to allow the weaker batteries/cells to draw more current. Calculating the battery runtime? A battery can either be discharged at a low current over a long time or at a high current for only a short duration. At 1C, a 10Ah battery discharges at the nominal rating of 10A in less than one hour. At 0.1C, the same battery discharges at 1A for roughly 10 hours. While the discharge voltage of lead acid decreases in a rounded profile towards the end-of-discharge cut-off. The relationship between the discharge time (in amperes drawn) is reasonably linear on low loads. As the load increases, the discharge time suffers because some battery energy is lost due to internal losses. This results in the battery heating up. What is battery Sulphation and when does it occur? Sulphation (or Lead Sulfate) is the formation of hard crystals on the plates of your battery. Initially, the lead sulfate coating is soft, thin and easily reconverted into lead and sulfuric acid when battery is recharged. It is important to remember, the longer your battery remains discharged, the more it will begin to form hard crystals of lead sulfate…recharge Your Battery As Soon As Possible! Manufacturing Concepts of Lead Acid Batteries

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Can I hook different batteries in parallel? No, when hooking batteries together in parallel, they should be of identical make and model and similar age. When should I add water to my batteries? How often use and recharge your batteries will determine the frequency of watering. It is best to check your battery water level frequently and add distilled water when needed. Never add tap water to your battery. Tap water contains minerals that will reduce battery capacity and increase their selfdischarge rate. And never add acid. Only distilled or de-ionized water should be added to achieve the recommended electrolyte levels. What are the reasons for failure of batteries? Self discharge of plates and premature capacity loss; excessive float charge current and improper polarization of plates; shorts through separator, mossing or dendrite growth; overcharging of battery from high current and subsequent excessive gassing; excessive heat and loss of water; antimony transfer; low cold cranking performance; poor charge acceptance; inadequate high rate discharge performance. Battery Maintenance Procedure Maintenance is an important issue. The battery should be cleaned using a baking soda and water mix; a couple of table spoons to a pint of water. Cable connection needs to be clean and tightened. Many battery problems are caused by dirty and loose connections. A serviceable battery needs to have the fluid level checked. Use only mineral free water. Distilled water is best. Don’t overfill battery cells especially in warmer weather. The natural fluid expansion in hot weather will push excess electrolytes from the battery. To prevent corrosion of cables on top post batteries use a small bead of silicon sealer at the base of the post and place a felt battery washer over it. Coat the washer with high temperature grease or petroleum jelly (Vaseline), then place cable on the post and tighten. Coat the exposed cable end with the grease. Most folks don’t know that just the gases from the battery condensing on metal parts cause most corrosion. Battery Do’s Think Safety First. Do read entire tutorial Do regular inspection and maintenance especially in hot weather. Do recharge batteries immediately after discharge. Do buy the highest RC reserve capacity or AH amp hour battery that will fit your configuration. Battery Don’ts Don’t add new electrolyte (acid). Don’t use unregulated high output battery chargers to charge batteries. Don’t disconnect battery cables while the engine is running (your battery acts as a filter). Don’t put off recharging batteries. Don’t add tap water as it may contain minerals that will contaminate the electrolyte. Don’t discharge a battery any deeper than you possibly have to. Don’t let a battery get hot to the touch and boil violently when charging. Don’t mix size and types of batteries. v v v Manufacturing Concepts of Lead Acid Batteries

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39) Process Failure Mode & Effects Analysis (PFMEA)

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Manufacturing Concepts of Lead Acid Batteries