Automotive Electrical & Electronic Systems Classroom Manual

Page 147

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11:26 AM

Page 135

Automotive Battery Operation

135

WARNING: When lifting a battery, excessive pressure on the end walls could cause acid spill through the vent caps, resulting in personal injury. Lift with a battery carrier or with your hands at opposite corners. For more information, see the “Battery Safety” section in Chapter 7 of the Shop Manual.

Specific gravity is the weight of a given volume of liquid divided by the weight of an equal volume of water. Since the acid is heavier than water, and water has a specific gravity of 1.000, the specific gravity of a fully charged battery is greater than 1.000 (approximately 1.260 when weighed in a hydrometer). As the battery discharges, the specific gravity of the electrolyte decreases because the acid is changed into water. The specific gravity of the electrolyte can tell you approximately how discharged the battery has become: • • • • •

1.265 specific gravity: 100% charged 1.225 specific gravity: 75% charged 1.190 specific gravity: 50% charged 1.155 specific gravity: 25% charged 1.120 specific gravity or lower: discharged

These values may vary slightly, according to the design factors of a particular battery. Specific gravity measurements are based on a standard temperature of 80°F (26.7°C). At higher temperatures, specific gravity is lower. At lower temperatures, specific gravity is higher. For every change of 10°F, specific gravity changes by four points (0.004). That is, you should compensate for temperature differences as follows:

fallen below a minimum level, and it also functions as a go/no-go hydrometer. The indicator shown in Figure 7-8 is a plastic rod inserted in the top of the battery and extending into the electrolyte. In the design used by Delco (now Delphi), a green plastic ball is suspended in a cage from the bottom of the rod. Depending upon the specific gravity of the electrolyte, the ball will float or sink in the cage, changing the appearance of the indicator “eye” from green to dark. When the eye is dark, the battery should be recharged. Other manufacturers use either the “Delco Eye” under license, or one of several variations of the design. One variation contains a red ball and a blue ball side by side in the cage. When the specific gravity is high, only the blue ball can be seen in the “eye”. As the specific gravity falls, the blue ball sinks in the cage, allowing the red ball to take its place. When the battery is recharged, the increasing specific gravity causes the blue ball to move upward, forcing the red ball back into the side of the cage. Another variation is the use of a small red ball on top of a larger blue ball. When the specific gravity is high, the small ball is seen as a red spot surrounded by blue. As the specific gravity falls, the blue ball sinks, leaving the small ball to be

• For every 10°F above 80°F, add 0.004 to the

specific gravity reading. • For every 10°F below 80°F, subtract 0.004

from the specific gravity reading When you study battery service in Chapter 7 of the Shop Manual, you will learn to measure specific gravity of a vent-cap battery with a hydrometer. See the section on “Inspection, Cleaning and Replacement” for more information.

STATE-OF-CHARGE INDICATORS Many low-maintenance and maintenance-free batteries have a visual state-of-charge indicator or built-in hydrometer installed in the battery top. The indicator shows whether the electrolyte has

Figure 7-8. Delco (Delphi) “Freedom” batteries have this integral hydrometer built into their tops. (Delphi Corporation)


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Summary

4min
page 363

Cruise Control Systems

3min
pages 357-358

Review Questions

3min
pages 364-366

Radios and Entertainment Systems

6min
pages 337-339

Theft Deterrent Systems

7min
pages 353-356

Heated Seats

6min
pages 343-345

Power Seats

2min
pages 341-342

Power Door Locks, Trunk Latches, and Seat- Back Releases

2min
page 346

Heating and Air-Conditioning Systems

12min
pages 328-334

Class 2 IPM-Controlled HVAC Systems

2min
pages 335-336

Review Questions

1min
page 326

Summary

1min
page 325

Windshield Wipers and Washers

10min
pages 319-324

Summary

1min
page 314

Review Questions

2min
pages 315-316

Head-Up Display (HUD

5min
pages 311-313

Electromagnetic Instrument Circuits

11min
pages 296-300

Review Questions

2min
pages 293-294

Malfunction Indicator Lamp (MIL

5min
pages 301-303

Summary

1min
page 292

Instrument Panel and Interior Lamp Circuits

4min
pages 289-291

Circuits

1min
page 288

Backup Lamp Circuits Side Marker and Clearance Lamp

1min
page 287

Circuits

2min
page 286

Stop Lamp and Turn Signal Circuits Hazard Warning Lamp (Emergency Flasher)

6min
pages 282-285

Taillamp, License Plate Lamp, and Parking Lamp Circuits

1min
page 281

Common Automotive Bulbs

1min
page 280

Headlamp Circuits

16min
pages 270-279

Summary

1min
page 267

Review Questions

1min
page 268

Spark Plug Construction

4min
pages 264-266

Distributor Cap and Rotor

3min
pages 259-261

Primary and Secondary Circuits

1min
page 248

Voltages

4min
pages 246-247

Basic Circuits and Current

1min
page 241

Silicon-Controlled Rectifiers (SCRs

1min
page 233

Review Questions

2min
pages 236-238

Summary

1min
page 235

Transistors

9min
pages 229-232

Rectifier Circuits

2min
page 228

Semiconductors

7min
pages 222-224

Photonic Semiconductors

2min
page 227

Review Questions

3min
pages 218-220

Starter Motor and Drive Types

8min
pages 210-214

DC Starter Motor Operation

5min
pages 206-208

Summary

2min
pages 216-217

Overrunning Clutch

1min
page 215

Specific Starting Systems

6min
pages 200-203

Summary

2min
pages 191-192

Differences

13min
pages 183-190

Review Questions

3min
pages 193-194

Charge/Voltage/Current Indicators

3min
pages 180-181

Solid-state Regulators

9min
pages 175-179

Electromagnetic Regulators

1min
page 174

Voltage Regulation

2min
page 173

Current Production in an AC Generator

9min
pages 168-172

Diode Rectification

3min
pages 162-163

AC Generator (Alternator) Components

7min
pages 164-167

Review Questions

4min
pages 157-158

Battery Installations

4min
pages 150-151

Battery Installation Components

2min
pages 152-153

Summary

2min
page 156

Battery Life and Performance Factors

5min
pages 154-155

State-of-Charge Indicators Wet-Charged and Dry-Charged

2min
page 147

Battery Electrolyte

2min
page 146

Electrochemical Action

8min
pages 142-145

Review Questions

3min
pages 138-140

Wire Color Coding

2min
pages 121-122

Multiplex Circuits

8min
pages 112-114

Ground Paths

2min
page 111

Connectors and Terminals

5min
pages 108-110

Wire Size

6min
pages 105-107

Wire Types and Materials

2min
page 104

Wiring and Harnesses

2min
pages 102-103

Review Questions

4min
pages 97-100

Parallel Circuit Voltage Drops Calculating Series Circuit Total

1min
page 87

Series and Parallel Circuit Faults

3min
pages 94-95

Series-Parallel Circuits

4min
pages 91-93

Review Questions

2min
page 82

Summary

3min
pages 80-81

Electromagnetism

9min
pages 67-71

Electromagnetic Induction

11min
pages 72-76

Magnetism

2min
page 66

Power

2min
page 56

Capacitance

8min
pages 57-60

Review Questions

2min
pages 62-64

Summary

1min
page 61

Complete Electrical Circuit

3min
pages 52-53

Summary

2min
page 43

Historical Figures in Electricity

2min
page 42

Fire Extinguishers

1min
page 31

Safety Tips for Technicians

2min
pages 25-26

Nuts

1min
page 15

Review Questions

2min
pages 44-46

Electrical Cord Safety

1min
pages 29-30

Safety in Lifting (Hoisting) a Vehicle

2min
pages 27-28
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