Storageandtransport
Transport
Loadunits:dimensionsandweights
Observethetransportsheetsforthebatteries.Theycontaininformationon:
■ dimensions,
■ weight,
■ liftingpoints,etc.
Additionalinformationonthedimensionsandweightscanbefoundon thebatterycase.
WARNING!
Useonlyloadhandlingdevicescomplyingwiththetechnicaland legalregulationsforthetransportofloads. Youcouldbeseriouslyinjuredorevenkilledbyfallingloads. Useonlysuitableloadhandlingdevices.
Shipment
Depotsorusingorganizationsmaymakeshipmentsofmotivepower batteriesinachargedandwetconditionifintendedforusewithinaperiodof90days.Thebatteryserviceweightisusuallystampedintothe steeltraynearoneoftheliftingholes.
Beforecratingawetbatteryforshipment,itshouldbegivenafresheningchargeasdescribedinChapter5ofthismanual.Atagshouldbe attachedtoboththebatteryandthecrateshowingthedateofthelast chargeandthespecificgravityoftheelectrolyteatthecompletionofthe charge.
Makecertainthatthebatteryisproperlyprotectedwhencrated.
Thereceivingorganizationshouldbealertedtotheneedforafresheningchargebeforethebatteryisputintoservice.
Depotswillnormallymakedomesticandexportshipmentsofnewbatterieswhichusuallywillbeinachargedanddrycondition.Batteries, andtheaccompanyingelectrolyteinseparatecarboys,whichareintendedforexportshipmentmustbepackagedinaccordancewithapprovedmethods.
NOTICE!
Wheneverbatteriesareshippedbycommoncarrier,ICCregulationsapply.
Unpackinguponreceipt
Uponreceiptofaminepowerstoragebattery,performthefollowing:
Itisimportantfirsttoexaminetheexteriorofthepackingforwet spotsonbottomorsideswhichmayindicateleakingjars.Inspect alsoforphysicaldamagetobatterypackagebecausethebattery couldbeaffectedaswell.Reportanydamagetoyoursupervisor.
Makecertainthatthepackageisrightsideup,withskidmounts restingfirmlyonfloor.
Useaforklifttruckorcraneofsufficientcapacitytoremovethe packagedbatteryfromthetruckorfreightcar.Ifacraneisemployed,besuretheslingissecuredagainstthebottomoftheskid andnotaroundtheskidmounts.
WARNING!
Liftingdevicesusedtomovebatteriesmustbecapableofcarryingtheweightstampedonthebatterycase.Keepallpersonsand bodypartsfromunderthebatterieswhentheyarelifted.
Movethecratedbatterytotheuncratingareaandremovepackaging,includinganywrappingorotherprotectionprovidedtothebatteryterminalcableconnectors.
Inspectbatteryandreportanydamagetoyoursupervisor.
Useaproperlyinsulatedliftingbeamofadequatecapacitytoliftthe battery,bymeansofanoverheadhoist,fromthebatteryskid.
Whenliftingbatteries,alwaysuseadevicewhichexertsaverticalpull ontheliftingeyeortab.Ifachainmustbeused,itshouldbeincombinationwithaliftingbeamwithprovisionforadjustingliftinghookcenterstotheexactlengthofthetray.Anymethodofliftingwhichtendsto squeezeorstretchthebatterytraymaydistortitandcoulddamagejars ordisturbcellseals.
Apieceofrubbersheetorotherinsulatingmaterial,temporarilylaidon thebatterywhilelifting,willpreventanypossibleshortcircuitsfrom chainsorhooks.Asanadditionalprecautionagainstaccidentalshorting,theliftingbeamhooksshouldbeelectricallyinsulatedfromeach other.
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Installation
Installation
Pointstoobservepriortoinstallation
Whoisallowedtocarryoutinstallation?
Installationisonlyallowedtobecarriedoutbypersonnelhavingreceivedadequatetrainingtoperformthistask.
WorkonthebatteryshouldonlybecarriedoutbyBucyrusAmerica, Inc.serviceengineersorbyspeciallytrainedpersonnel.
Whichtoolsarerequiredforinstallation?
Nospecialtoolsarerequiredtoputthebatteryintoservice
Variousitemsofauxiliaryequipmentandmachinesmayberequiredat thepointofinstallation.
Theseinclude:
■ hoistswithadequateliftingcapacity
■ meansofattachmentwithadequateliftingcapacity
■ unloadingdock
■ jackswithadequateliftingcapacity
■ batteryplugandreceptaclewrench
Notesoninstallation
CAUTION!
Seriousdamagecanbecausedtothebatteryasaresultofincorrectinstallation.Thebatteryshouldthereforeonlybeinstalled undertheinstructionofspecialistsfromBucyrusAmerica,Inc.
toolbox
Pre-installationchecklist
NOTICE!
Thebatterywasinspectedpriortoshipmentfromthefactoryto ensureproperfunctioningandinstallationofallcomponents.
Toensurethatnotransitdamagehasoccurred,thefollowingprestartupchecksshouldbeperformed:
■ performdailymaintenance
■ checkthatallcoversandguardsareinplaceandsecure
■ checkthatalltagsandinstructionlabelsareinplaceandsecure
batteryidentificationanddata
Operation
Thischaptercontainsimportantinformationontheoperationandmaintenanceofthebattery.Readthischaptercarefullyandthoroughly.In particular,observethesafetyinstructionsinchapter2,“Yoursafety”.
Definitions
Thedefinitionsreferencedthroughoutthismanualgenerallyagreewith acceptedindustrystandards.Foramorecompletelistingof "DefinitionsforLead-AcidIndustrialStorageBatteries",seeNEMA StandardspublicationNo.1B1-1971.
CopiesofNEMAstandardsmaybeobtainedatnominalcostbywriting to:NationalElectricalManufacturersAssociation,DepartmentofEngineeringandSafetyRegulations,2101LStreet,N.W.Washington,D.C. 20037.
Descriptionandconstruction
Battery
Minepowerlead-acidbatteriesforelectricvehiclestypicallyconsistofa steeltrayintowhichthecellsareassembled,abatteryterminalconnector,andvariousothercomponentsnecessarytosecureandprotect thecellsandprovidethenecessaryelectricalinterconnections.
Theessentialinformationnecessaryforpropercareofanindustrial motivepowerbatteryappearsonthebattery,eitherstampedintoone oftheintercellconnectorsoronanameplateaffixedtothetray.This informationusuallyincludesthemanufacturer'snameandmodel,numberofplatespercell,batterycapacity,batteryvoltage,serialnumber, suggestedchargingrate,andfullychargedspecificgravityofelectrolyte.
Ifvitalinformationismissingorisnolongerlegible,theinformationcan beobtainedbycontactingyournearestBucyrusAmerica,Inc.representative.
Somemanufacturerslist,asapartofthemodelortypedesignation, theratedampere-hourcapacityofasinglepositiveplate,suchas "SS75".Asanalternatemeansofdeterminingratedbatterycapacity, thisnumbershouldbemultipliedbythetotalnumberofpositiveplates inonecell.Tofindthenumberofpositiveplatesinacell,subtractone fromthetotalnumberofplatesanddividebytwo.Tofindthecapacity ofabatterydesignated"SS75-19,"therefore:19 - 1=18;18dividedby 2=9;9x75=675Ahbatterycapacity.
cellarrangement
connectorarrangement
Theindividualcells,whichcontaintheenergygeneratingcomponents ofthebattery,maybearrangedslightlydifferentlyforvarioustypesof equipment.Thecellsofallmotivepowerbatteriesare,however,alwaysconnectedinseriestoproducetherequiredvoltage.Celland batterycapacity,whichistheavailableampere-hoursorwatt-hours,isa functionofthetotalnumberandsizeofplateswithineachcell.Voltage, though,isthesameforallcellsregardlessofsize.Eachlead-acidcell yieldsanominal2volts.
Connectionsbetweencellsaremadebyintercellconnectorswhichmay belead-coatedcopperstrapsorbecastofsolidlead.Theseconnectionsarealwayswelded,inpropersequence,bytheapplicationofheat totheterminalsofthecells.Energyfromthebatteryisdrawnoffby terminalcableswhichextendbeyondthesteeltraywallandareinturn permanentlyjoinedtothebatteryterminalconnector.
Cell
Thecell(Fig.1)isthebasicunitofanybattery.Itisagalvaniccell whichproduceselectricalenergywhenconnectedtoanelectricalload and,afterbeingdischarged,mayberestoredtoitsoriginalfullycharged condition.Ithasanominalvoltageof2voltsandconsistsofanelementfromwhichtheenergyisderivedandanelectrolyte.Boththeelementandtheelectrolytearecontainedbyanimpactresistant,molded plasticjar.
Theelementispreventedfromcontactingthebottomofthejarby meansofahighimpactbridge,whichconsistsofaseriesofsupport ribs.Theseribsprovidesedimentspacebelowthebottomoftheelementtoaccommodateparticlesofactivematerialshedbythepositive platesduringnormaloperationofthebattery.
Thetopofeachcellisfittedwithamoldedrubberplasticcoversealed tothejarattheedges.Aventorfillercapislocatedinthecenterofthe cover.Thisventpermitstheescapeofhydrogenandoxygenwhilethe cellsaregassingand,whenremoved,providesanopeningthrough whichwatermaybeaddedtothecell.Thepositiveandnegativeterminalposts,whicharepartoftheelement,fitthroughopeningsinthe cover.Priortobeingconnectedtogether,cellsareplacedsothatthe positiveterminalofonecellisadjacenttothenegativeterminalofthe next.Thisarrangementpermitsaconvenientlymadeseriesconnection.
Fig.1:Cell
Cover:withleadinsert bushing,preventsleakage andvoltagetoground.
Post:specialalloyforincreasedstrengthandconductivity.
Postplatestrap:extraheavytoinsure apermanentconnectionbetweenpost andplates
Positivegrid:non-porousleadalloy casting,designedformaximumcurrentcarryingcapacity,capableof manyyearsofservice.
Activematerial:speciallyformulated anduniformlyappliedunderrigidlaboratorycontroltoinsuremaximumefficiencythroughoutlongbatterylife.
Jar:Moldedofhighimpact materialtoremainleakfree underroughtreatment.
Bridge:providesfirmelementsupportandample sedimentspace.
Ventcap:quarterturnbayonettypesimplifieswatering andinspection.
Separatorguard:Whitein colortoincreasevisibilityfor fastelectrolytecheck.
Negativeplate:designedto complimentpositiveplate performance.
Verticalmat:Laminatedconstruction comprisedofuniformlyspacedfine glasstapethatimbedsintotheactive materialandaninterwovenglassfiber matwrappedverticallyaroundthepositiveplateinsuringoptimumactivematerialretention.
Horizontalmat:Madeofglassfibers withaninsolublebinder,breaksupgas bubblesandincreasespositiveplate insulation.
Retainerandbottomshield:Highporosity,perforatedenvelopthatencases positiveplateandglassmatstoprevent shortsandinsuremaximumperformanceandlife.
Separator:Deepchanneled,microporous,impervioustoheat,acidandcorrosion;providesinsulationbetweenpositiveandnegativeplateswhileallowing thefreeflowofelectrolytethroughout thecell.
BucyrusAmerica,Inc.minebatteriesincorporateeveryfeaturerequiredby today’smines.Theyaredesignedbyengineeringtechnologyandbuiltby masterbatterycraftsmenaccordingtostrictqualitycontrolguidelines. BucyrusAmericaInc.batteriesarethefinestavailabletomeettoday’sminingrequirements,andourprecisionconstructionprovidesnewequipment performancethroughoutalonglife.
Theelementofthecellconsistsofonegroupeachofpositiveand negativeplatesmeshedtogether.Theplatesareinsulatedfromeach otherbyseparatorswhichareinsertedbetweenallplates.Aplastic elementprotectorispositionedontopoftheseparators.Thisprevents mechanicaldamagetotheelementandaidsinpreventingelectrical shortswhichoccurwhenparticlesofactivematerialbridgethespace betweenplates.Terminalpostsareweldedtoeachgroupandare usedtoelectricallyconnectonecelltoanother.
Thisisanassemblyofplatesoflikepolarityconnectedinparallelby weldingtoacommonstraporbusbar.Acellmustcontainonepositive andonenegativegroup.Thenegativegroupalwayshasonemore platethanthepositivegroup.Oneormoreterminalpostsarewelded toeach.
Theplates(alsocalled"electrodes")areeitherpositiveornegativeand consistofacastleadalloygridandactivematerial.Thegridprovides supporttotheactivematerialandbecomestheprimaryelectricalconductor.Theactivematerialsresultfromtheadditionofchemicalsto leadoxideswhichareconverted,byelectrochemicalprocessing,to leaddioxideinthepositiveandtospongeleadinthenegative.
Thegridofthepastedplateconsistsofhorizontalandverticalordiagonalcastleadconductingmemberswithinarectangularcastframe.A slurryofactivematerialispastedorsqueezedintothevoids,andthe surfacesarethencoveredbyporousglassandplasticretainerstopreventthelossofactivematerial.
Theelementwithinthejarisimmersedinanelectrolyte,whichisasolutionofsulfuricacidand"pure"water.Thispermitsthenecessary chemicalreactiontooccurandprovidesaconductingmediuminwhich theflowofelectriccurrenttakesplace.Theelectrolyteinafully chargedcellnormallyhasaspecificgravityofbetween1.280and 1.295at77°F.Asacelldischarges,thespecificgravitydecreases. Measurementofthisspecificgravity,bymeansofahydrometer,indicatesthestateofchargeofacell.Tosavetimeindetermining- this stateofchargeforthebattery,apilotcellorcellsmaybechosen;.A pilotcellisaselectedcell(s)whoseconditionisassumedtoberepresentativeoftheconditionoftheentirebattery.
Separatorsaremadefrommicroporousplastic,whichisresistantto heatandacid.Separatorsprovidemechanicalandelectricalinsulation betweenpositiveandnegativeplates,butareporousenoughtopermit passageofelectrolyte.Thegroovedorribbedsideoftheseparatoris placedtowardthepositiveplatetoallowafreeflowofelectrolytetothe activematerial.Theflatsidefacesthenegativeplatetocontainthe spongelead.
Pastedtypeplateretainersareadded,afterpasting,typicallybywrappingtheplatefirstwithfibrous-typeglasstapeormatsandthenbya perforatedplasticenvelopecompletewithbottombootorbyothersuitablefilteringsystems.Alltypesofretainersacttopreventtheescape ofpositiveactivematerialduringnormaluse.Retainersarenotneeded onnegativeplates.
Charging
Whenchargingabattery,observethefollowingprecautions:
■ Whenconnectingthebatterytothecharger,alwaysconnect positive(+)topositive(+)andnegative(-)tonegative(-).
■ Alwaysrechargethebatteryassoonaspossibleafterdischarge.
■ Keepventcapstightlyinplacewhilethebatteryisbeing charged,exceptwhenservicingthecellorwhenmeasuring specificgravityortemperature.
■ Makesurethatthebatteryandchargervoltagesandamperehourratingsmatchwhenpreparingtochargeabattery.
■ Prohibitsmokingandopenflamesinchargingarea.
■ Makecertainthatchargingareaiswellventilated.
■ Donotallowtoolsorothermetalobjectstocontactintercell connectors.
■ Wearproperpersonalprotectiveequipment.
■ Knowthelocationoffreshwaterforemergencypurposes.
■ Useproperequipmenttoliftandmovebatteries.
■ Provideacceptablefireextinguishingequipment.
■ Followallsafetyguidelinesandhealthpracticeslistedinthis manual.
General
Economicalanddependableperformancefromastoragebatterydepends,toagreatextent,uponpropercharging.Faultycharging causesadecreaseinbatteryservicelifeanddissatisfactionwithits performance.Theselectionofsuitablechargingequipmentandmethodsisasimportantastheapplicationofthecorrectbattery.Amine batteryinstallationiscompletelysatisfactoryonlywhentheunit,battery,andchargeroperateasasmoothlyfunctioningteam. Thistext onchargersisforgeneralinformationandguidanceonly. Ifspecificdataisrequiredonaparticulartypeofcharger,contactthenearest BucyrusAmerica,Inc.salesrepresentative.
Whenpreparingabatterytobecharged,makecertainthatallpointsof contactbetweenthechargerandthebatteryarecleantoassuregood conductivity.Alsomakecertainthatthepositiveterminalofthebattery isconnectedtothepositiveterminalofthechargerandthatthenegativeterminalofthebatteryisconnectedtothenegativeterminalofthe charger.
CAUTION!
Makecertainthatthepositiveterminalofthebatteryisconnected tothepositiveterminalofthechargerandthatthenegative terminalofthebatteryisconnectedtothenegativeterminalofthe charger.Permanentdamagetothebatteryorchargermayresultif thebatteryisconnectedincorrectly.
ChargingPrinciples
Charging,asappliedtoastoragebattery,istheconversionofelectrical energyintochemicalenergywithinthecellorbattery.Thisrestoresthe activematerialsandisaccomplishedbymaintainingaunidirectional currenttothebatteryintheoppositedirectiontothatduringdischarge. Whenacellorbatteryissaidtobecharged,itisunderstoodtomean fullycharged.Thetypeofbattery,servicecondition,timeavailablefor charging,andthevariationinbatteryvoltageswillstronglyinfluence whichchargingmethodisbestforaparticularsituation.Normallyleadacidbatteriesarerechargedin8hoursfollowingafulldischarge.However,theycanberechargedwithinothertimeperiodswhendesirable. Adeeplydischargedbatterywillabsorbhighcurrentrateswhenthe voltageislow.Asthechargeprogresses,thevoltagesteadilyincreasesuntilitreachesgassingvoltage,approximately2.37voltsper cellat77°F.Atthispoint,batterychargersnormallyreducecharging ratesautomaticallyandtapertofinishingrates,whichareusedtocompletethecharge.Thebatteryisfullychargedwhennearlyalloftheactivematerialhasbeenconvertedandwhenthespecificgravityofthe electrolyteandcellvoltagehavereachedtheirmaximumorconstant values(correctedfortemperature),asindicatedbysimilarreadings overatwoorthreehourperiod.
Batteriesusedinminepowerapplicationsarecycled:theyareeither beingchargedordischarged.Inmostcircumstances,batteriesare chargedaftereachshiftofuse,sotheyarecycledmanytimesduring theirlifetime.Incorrectchargingforonlyafewcycleswilldolittleharm, butifrepeateddayafterday,thebattery'sservicelifewillbeseriously shortened.
Chargingrates
Properchargingmeanschargingthebatterysufficientlywithoutovercharging,overheating,orexcessivegassing.Thechargeisusually startedathighamperage,whichisknownasthestartingrate.Later duringthecharge,therateofcurrentflowisreducedtowhatiscalled thefinishingrate.Itissuggestedthatthefinishingrateshouldnotexceed5amperesper100ampere-hoursofratedbatterycapacity.The startingratemaybeasmuchasfourtofivetimeshigherthanthefinishingrate.
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Lead-acidbatteriesshouldbechargedforasufficientlengthoftime andataratewhichwillputbackintothebatterythesamenumberof ampere-hoursremovedondischarge,plusapproximately10%additionalwhichisanacceptable,andinfactdesirable,overcharge.The specificamountofoverchargedependsuponthetemperature,age, andhistoryofthebattery.Ingeneral,itismoreharmfultoexcessively overchargeanolderbattery,oronewhichisoperatingathightemperature,thananewbatteryoroneoperatingconsistentlyatroomtemperature.Anychargerateispermissiblewhichdoesnotproduceexcessive gassingorcelltemperaturesgreaterthan110°F.
Controlofgassing
Gassingistheevolutionofgasesfromoneormoreoftheelectrodes duringelectrolysis.Itisanaturalphenomenonwhichtakesplacewhen abatteryonchargecannolongeracceptallofthecurrentbeingappliedtoit.Gassingisevidencedbybubblingoftheelectrolyte.The gasesliberatedareoxygen(evolvedatthepositiveplates)andhydrogen(evolvedatthenegativeplates).
Thepointatwhichsignificantgassingbeginsisdeterminedbyvoltage, buttheamountofgasdependsupontheportionofthechargingcurrent thatisnotbeingabsorbedbythebattery.Normally,noticeablegassing willbeginwhenthevoltageexceeds2.30voltspercell.At2.40volts percell,gassingwillbenormal;at2.50,itwillberapid.Theamperage atwhichgassingbecomesexcessivedependsprimarilyuponthestate ofchargeandelectrolytetemperatures.Asthebatteryapproachesfull charge,itisnecessarytoreducethechargingratetoapointatwhich excessivegassingisprevented.Thissaferateisthefinishingrateor below.Whenproperchargingequipmentisused,thetaperingofthe chargingcurrenttothefinishingrateisachievedautomatically.
Methodsandequipment
Themodernstoragebattery,usedwithaproperlydesigned,modern, automaticcharger,needsonlynormalwateradditions,occasional cleaning,andregularcheckingofbothchargeradjustmentandbattery conditiontoprovidelong,dependableservice.
Therearetworecommendedmethodsforthenormalchargingofmotivepowerbatteries:
Themodifiedconstantvoltagemethod,inwhichthetaperingofthe chargingrateisaccomplishedgradually,requiresasourceofdirect currentwithaconstantbusvoltageofapproximately2.63voltsforeach cell.Thisisforan8-hourcharge.Properseriesresistanceintheoutputcircuitinherentlyprovidesthecorrectstartingrateandassuresthat theratewillautomaticallybereduced,asthechargeprogresses,tothe recommendedfinishrate.Theconstantvoltagesourcemaybeeithera motor-drivengeneratororrectifier.
Thetapermethodcanbeusedwitheithergeneratororrectifiertype equipment.Thechargerisdesignedtoprovidethecorrectchargerate duringaconstantlytaperingcharge.Thisisaccomplishedbycoordinatingtherisingbatteryvoltagewiththedesigncharacteristicsofthe charger.Theshapeofthecurrent-tapercurvewillvarywithdifferent typesofequipment,buttheresultisessentiallythesame.Solidstate chargersareavailablewhichdeliverasmuchcurrentasthebatterycan accept,uptomaximumchargeroutput,andthentapertheinput sharply,whencellsbegintogas,tokeepfinishrateslow.Thesechargersdonotrequireadjustment.
Typeofcharge
Thetwogenerallyrecommendedtypesofnormalorroutinecharges, followingadeepdischarge,aremodifiedconstantvoltagechargeand tapercharge.
Aboostchargeofastoragebatteryisapartialcharge,usuallyatahigh rateforashortperiod.Suchachargeisgiveninanemergencywhenit isbelievedthattheamperehourcapacityofthebatterymaybeless thannormalandinsufficienttocompleteaplannedperiodofwork.A boostchargemayalsobeusedwhenitisnotpossibletogiveabattery oneoftherecommendedtypesofnormalcharge.
Anequalizingchargeofastoragebatteryisaprolongedcharge,usually atthefinishingrateorless,tocorrectanyinequalitiesofvoltageorspecificgravitywhichmayhavedevelopedbetweencellsduringservice.It consistsoffollowinganormalchargewithanextendedchargeof4 hoursataratenohigherthanthefinishingrate. In minepowerapplications,abatteryshouldreceiveanequalizingchargeweekly.
Afresheningchargeofastoragebatteryisachargegiventobatteries instorageorduringinactiveperiodstoreplacelossesduetoselfdischargeandtoassurethateverycellisperiodicallybroughttoafully chargedstate.
Principlesofoperation
Fundamentalsofcycling
Acycleisadischargefollowedbyacharge.Duringthecharge,the electricalenergysuppliedbythechargercausesanelectromechanical reactionwithinthebattery.Thisrestorestheactivematerialstoafully chargedcondition.
Thepositiveandnegativeplates(electrodes)areseparatedfromeach otherandimmersedinelectrolyte.Inthefullychargedcondition,the activematerialofthepositiveplateisleaddioxideandthatofthenegativeplateisspongelead.Theelectrolyteisasolutionofsulfuricacid andwaterthatnormallyvariesinaspecificgravityfrom1.280to1.295. Thecombinationproducesavoltageofapproximately2voltsonopen circuit.Thisvoltagepotentialresultsfromthefundamentalcharacteristicofastoragebatterywhichdictatesthatwhentwoelectrodesofdissimilarmetalsareimmersedinsuitableelectrolyte,andacircuitis closedbetweenthetwo,electronsbegintoflow.Afullychargedcell shouldnormallyhaveanon-chargevoltageoffrom2.45to2.70volts whenchargingatthefinishrate.
Whileabatteryisbeingdischargedorused,leaddioxideandsponge leadcombinewithsulfuricacidtoformleadsulfatewithinbothplates. Thisactioncausesthespecificgravityoftheelectrolytetodecrease. Asthedischargeprogresses,individualcellandbatteryvoltagesdecline,generallyindirectproportiontotherateofdischarge.
Asthedepthofdischargeincreases,moresulfuricacidisremoved fromtheelectrolyte,causingthespecificgravitytodecrease,possibly below1.100asitapproachesthespecificgravityofwater.Almostallof theactivematerialofbothpositiveandnegativeplatesisconvertedto leadsulfate,andaneffectiveelectromechanicalreactionisnolonger possible.Atthispoint,thebatteryhasreacheditsdischargelimit.
Thechargingactionbeginswhentheterminalsofthebatteryareconnectedtoanexternalsourceofdirectcurrent.Theelectromechanical reactionisreversedandthepositiveplates,negativeplates,andelectrolytestartreturningtotheiroriginalchargedcondition.Charging causesthebatteryvoltagetoriseasactivematerialsarerestored.A cellbeingchargedmayhaveavoltageoffrom2.12to2.70voltsdependinguponchargingrateandtime.
Storagebatteriesdonotactuallystoreelectricalenergy;instead,they accepttheelectricalenergydeliveredtothemduringchargingandconvertitintochemicalenergy.Duringdischarging,thischemicalenergy isreconvertedintoelectricalenergytobeusedasneeded.
Toobtainthebestperformanceandlifefromaminepowerstoragebattery,thebatteryshouldusuallybechargedaftereachshiftofuseor wheneverthespecificgravityoftheelectrolytefallsbelow1.240.Itis veryimportantthatproperventilationbeprovidedduringchargingto makecertainthatthehydrogengas,givenofftowardtheendofthe chargingprocessisdissipatedandthatindividualcellelectrolytetemperatures,duringnormaloperations,donotexceed110°F.
Ampere-hourcapacity
Theelectricalcapabilityofastoragebatteryisusuallyexpressedinampere-hours.Theampere-hourcapacityisthenumberofampere-hours whichcanbedeliveredunderspecifiedconditionsoftemperature,rate ofdischarge,andfinalvoltage.Basically,ampere-hoursaredeterminedbymultiplyingthenumberofampereswhichthebatterywilldeliverbythenumberofhoursduringwhichthecurrentisflowing.Total cellorbatterycapacitythenisdeterminedbythesizeandnumberof plateswhichmakeuptheelement.Duetothevarietyofjobrequirements,batteriesareproducedwithmanydifferentsizesofcells.
Voltage
Withreferencespecificallytostoragebatteries,many"voltage"conditionshavebeenrecognized.Themostimportantoftheseare:
Thisisthevoltageofacellorbatteryattheterminals,whennocurrent isflowing.Thenominalopencircuitvoltageofanindividualfully chargedcellis2volts.Thisistrueregardlessofcellsize.Thevoltage ofa64celllead-acidbatteryisstated,therefore,as128volts.
Theinitialvoltageofacellorbatteryistheclosedcircuitvoltageatthe beginningofadischarge.Itisusuallytakenaftercurrenthasbeen flowingforasufficientperiodoftimefortherateofchangeofthevoltagetobecomepracticallyconstant,usuallyamatterofminutes.
Theaveragevoltageofthecellorbatteryistheaveragevalueofthe voltageduringtheperiodofchargeordischarge.
Thefinalorcut-offvoltageofacellorbatteryistheprescribedvoltage atwhichthedischargeisconsideredcomplete.Itisusuallychosenso thattheusefulcapacityofthebatteryisrealizedwithoutsubjectingitto harmfuloverdischarging.Finalvoltagewillvarywiththerateofdischarge,celltemperature,andthetypeofservice,butforminepower applicationsitisconsideredtobe1.70voltspercell.
Initialvoltage,averagevoltage,andfinalvoltagearemonitoredwhen conductingtestdischarges.
Ratedcapacity
Theratedcapacityofastoragebatteryisthenumberofampere-hours orwatt-hourswhichthebatteryiscapableofdeliveringwhenfully chargedandunderspecifiedconditionsoftemperature,rateofdischarge,finalvoltage,andspecificgravity.UnitedStatesindustrystandardsforminepowerbatteriesalwaysspecifythistobeatthe6hour rateofdischarge.Thetotalcapacityavailablefromabatteryisgreatest atlowratesofdischargeoveralongperiodoftime.Dischargingathigh currentratesreducesthetotalampere-hoursavailable.
Sulfation
Sulfationoccurswhenconditionswithinthecellcausesufficientaccumulationofabnormalleadsulfateatboththepositiveandnegative plates,permanentlyaffectingthenormalchemicalreactions.Habitual overdischargingbelowfinalvoltage,prolongedoperationinanunderchargedcondition,andextendedstandperiodswhileinadischarged statearemajorcausesofsulfation.Aservicingscheduleshouldbe followedtoprovidefrequentmonitoringandadequatecharging.See themaintenancesectioninthischapterformethodsofrestoringasulfatedbattery.
Operatingcycle
Anoperatingcycleofastoragebatteryisthedischargeduringuseand subsequentchargetorestoreitsinitialcondition.
Servicelife
Theservicelifeofastoragebatteryistheperiodduringwhichitprovidesusefulpowerwhilebeingdischarged.Itisusuallyexpressedas thetimeperiod,ornumberofcycles,whichelapsesbeforetheamperehourcapacityfallsbelow80%ofitsratedvalue.Toobtainmaximum servicelife,itisrecommendedthatabatteryberestrictedtoonefull cycleper24hourdayorfewerthan300cyclesperyear.Otherfactors whichmostoftenadverselyinfluenceservicelifeare:
■ Abnormallyhighorlowelectrolytetemperatures.
■ Frequentoverdischarging.
■ Failuretoaddwaterregularly.
■ Frequentovercharging.
■ Poor,orhigh,resistance,connectionsorcontacts.
■ Addingtoomuchwater.
Temperature
Thenormaloperatingcharacteristicsofastoragebatteryaremodified byunusuallyloworhighcelltemperatures.
Availablebatterypowerisreducedbylowtemperaturebecauseelectrolyteviscosityandresistanceisincreasedanddiffusionthroughout theporesoftheactivematerialisretarded.Forexample,afully chargedbattery(1.280to1.295specificgravityat77°F.),whenits electrolytetemperatureisabout32°F,willdeliveronly75%ofthecapacitywhichwouldbeavailableatnormalroomtemperature.This dropsto40%at0°F.Theelectrolytecouldfreezeifadischargedbatterywereexposedtoverycoldtemperaturesforseveralhours.(See Table1forfreezingpointsofvariouselectrolyteconcentrations.)
lowtemperature
hightemperatures
Inadditiontothedischarge-relatedproblems,thechargeacceptanceof alead-acidbatteryisimpairedwhenelectrolytetemperaturesdropbelow60°F.Asaresult,batteriesshouldalwaysbekeptfullycharged, especiallyincoldweather.Theyshouldbeheated,evenduringoperationorstorage,ifexposureissevereenoughtocausethetemperature oftheelectrolytetoapproach32°F.
Althoughhightemperatures(upto110°F)donotcauseareductionin availablecapacity,batteryoperationisadverselyaffected.Because mostchemicalreactionsareacceleratedathightemperatures,therate ofcorrosionofthepositivegridisincreasedandtheactivematerialis shedmorerapidly.Evenelectrolytetemperaturesabove90°Fwill causesomereductioninservicelifeandshouldbeavoidedwhenever possible.Celltemperaturesshouldneverbeallowedtoexceed110°F.
Table1:Freezingpointsofvariouselectrolyteconcentrations
PreparationforUse
Establishingbatteryrequirements
Thenumberofbatteriesrequiredforservicedependsprimarilyupon thenumberof8-hourshiftsineffect.Normally,foroperationonasingle-shiftbasis,theminimumnumberofbatteriesrequiredwillbethe sameasthenumberofoperatingmachinesandthebatteriesneednot beremovedfromtheunitforcharging.Foroperationona2- or3-shift basis,theminimumnumberofbatteriesrequiredwillbetwicethenumberofoperatingmachinesanditwill,therefore,benecessarytoexchangedischargedbatteriesforchargedbatteriesattheendofeach workshift.Wheneverpossible,itisrecommendedthatmorethanthe minimumnumberofbatteriesbeavailableformultiple-shiftoperation, providingatleastan8-hourcoolingperiodaftercharging.Inanemergency,anyonebatterycanbeusedfortwo8-hourshiftsduringa24hourperiod,butthisprocedure,repeatedregularly,willprobablycause highelectrolytetemperaturesandcouldseriouslyaffectservicelife. Therefore,where3-shiftoperationisnormal,3batterieswillberequired permachine.
Acidtowaterproportions
Sulfuricacidtowaterproportionsrequiredtomakeelectrolytearegiven inTable2.
Chargedandwetbatteries
Chargedandwetbatteriesareshippedwithcellsfilledandfully charged.Preparethesebatteriesforuseasfollows:
WARNING!
Propereyeandbodyprotectionmustbewornatalltimeswhen servicingbatteriestopreventelectricalshockandcontactwith batteryacid.Cleanandneutralizeanyacidspillimmediately.
Examinebatterytoseeifelectrolytehasbeenaccidentallyspilled.If so,cleanandneutralizeanyspillagewithacloththathasbeen dippedinabicarbonateofsodasolution.Rinseareawithclearwater.
Removeventcapsandchecktheelectrolytelevelineachcell. Measureandrecordthespecificgravity,electrolytetemperature, andindividualopencircuitvoltageofeachcell.Noteanyirregularities.
Checktomakesurethatallcellsareproperlyconnectedandthat terminalconnectionsaretight.Ifthereareirregularitiesintheelectrolytelevelsorspecificgravityreadings,orifthebatteryhasbeen instorageformorethan30days,itshouldbegivenafreshening chargetoassurethateverycellisatafullychargedstate.
Recheckelectrolytelevelsafterchargingandaftergassinghas stopped.Again,measureandrecordspecificgravityandelectrolyte temperatures.Ifirregularitiesinelectrolytespecificgravityreadings stillexist,theyshouldbeadjustedasdescribedintheMaintenance
Table2:Sulfuricacidtowaterproportions
Instructionsonthemaintenance
Maintenanceatregularintervalsincreasestheoperationalsafetyof andprolongstheservicelifeofthebattery.
Inparticular,observethesafetyinstructionsinchapter2“Yoursafety”.
Importantnotes
WARNING!
Batteriesmustberestingsecurelyinamachine,onabatterytable,orplatformcapableofsupportingtheweightofthebattery whileperformingmaintenanceorserviceonthebattery.Mineservicebatteriescanweighseveralthousandpoundsandcould causesevereinjuryordeathshouldthebatteryfallonapersonor onabodypart.
WARNING!
Thebatteryproduceslethalamountsofcurrentwhetherconnectedtothemachineornot.Batteriesshouldbemaintainedand servicedbyqualifiedpersonnel.Thebatteryshouldbedisconnectedbeforeservicing.Electricalshockcancausedeathorseriousinjury.
WARNING!
Batteriesproduceexplosivegasesthatcouldignite,causing burnsorexplosions.Batteriesshouldbewellventedbeforeservicing,particularlyifweldingorburningonthebattery.Batteries shouldbemaintainedbyqualifiedpersonnel.
WARNING!
Batteriescontainstrongacidthatcouldcausesevereburnsif spilledorsplashedonbodypartsorintheeyes.protectiveclothing,gloves,andeyewearmustbewornwhenworkingonbatteries.Batteriesshouldbemaintainedbyqualifiedpersonnel.
WARNING!
Batterycoversmustbesecuredwiththecoversupportedwhen workingunderthecovers.Batterycoverscouldfall,crushing hands,arms,orfingers.
General
Themodernindustrialbatteryisdesignedandbuilttogiveanaverage of1500cyclesofchargeanddischargeduringitslife,dependingupon theapplicationandtheoperatingenvironment.Theexactlengthofthe servicelifewilldepend,toagreatextent,uponthecarethebatteryreceives.Thefollowingmaintenanceprocedures,carriedoutatthe propertime,willdomuchtoprolongthelifeofthebatteryandprovide efficient,satisfactoryservice.
WARNING!
Batteries,chargers,andrelatedelectricalequipmentshouldonly beservicedbyqualified,properlytrainedpersonnel.
Specificmaintenanceprocedures
Everyshift
chargeradjustment
hydrometerreading
Makesurethatthechargeradjustment,usedforcontrolofcharging ratesandcut-off,iscorrect.Thiswillensurethatthebatteriesareproperlychargedwithnoexcessiveovercharge.Batteriesthatareoverchargedregularlywillneedwatermoreoften,andcelltemperatures usuallywillbehigherthannormal.Ifeitherconditionisevident,adjust thechargeratedownward,inthosechargerswhichhaveprovisionfor adjustment,soitisbetweenanormalfinishrateandone-halfnormal finishrate.
Measureandrecordthespecificgravity:
Withthetipofthehydrometerimmersedintheelectrolyte,squeeze thesyringebulbandthenslowlyreleaseit,drawingintothecylinder orbarreljustenoughelectrolytetopermitthehydrometerfloatto ridefree.Thefloatstemmustnottouchthesideofthecylindernor thetopofthesyringe.Ifthefloatstemtouchestheupperareaof thesyringe,toomuchelectrolytehasbeendrawnup;ifthefloatstill restsonthebottom,toolittleelectrolytehasbeendrawnup.(See Fig.2.)
Readthehydrometerfloatscalewithyoureyeatthesamelevelas theelectrolyte.Thereadingshouldbetakenatthesurfaceofthe liquid,disregardinganyslightcurvature.Thisreadingwillbethe specificgravityuncorrectedfortemperature.(SeeTable4forcorrectionfactors.)
Returnallelectrolytetocell.
Fig.2:Hydrometerreading
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