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elec03 battery.pdf

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ELEC03 BATTERY
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Electrical Circuit Diagnosis - Course 623 3-1 ThebatteryisthemainsourceofelectricalenergyonToyotavehicles. Thebatterypowersthesemajorelectricalsystems: w Starting w Ignition w Charging w Lighting w Accessories The Battery The battery is the main source of electrical energy in the vehicle. Fig. 3-01 TL623f301 Section 3 The Battery The BatterySection 3 3-2 TOYOTA Technical Training Engineoff- Thebatteryprovidesenergytooperatelightingand accessories. Enginestarting- Thebatteryprovidesenergytooperatethestarter motorandignitionsystemduringstarting. Enginerunning- Thechargingsystemprovidesmostoftheenergy requiredwiththeenginerunning;thebatteryactsasavoltagestabilizer toprotectvoltagesensitivecircuits,particularlydigitalcircuits. Battery Functions The battery provides energy to operate lights and accessories and to start the engine. It also serves as a voltage stabilizer. Fig. 3-02 TL623f302 Battery FunctionsThe Battery Electrical Circuit Diagnosis - Course 623 3-3 Lead-Acid- Virtuallyallautomotivebatteriesarelead-acidbatteries. Twodifferentmetals,bothleadcompounds,areimmersedinanacid electrolyte.Thechemicalreactionproducedprovideselectricalenergy. LowMaintenance/NoMaintenance- Somemanufacturersusethis terminology.Lowmaintenance“meansthatelectrolytecanbeadded. Nomaintenance“meansthatthebatteryissealed. Vented- Mostbatterieshaveremovableventedcapsthatareusedto checkelectrolytelevelandadddistilledwaterasnecessarytorestore thelevel.Thecapsalsoallowhydrogengas,abyproductofbattery charging,toescapeduringcharging. Sealed- Somelead-acidbatteriesaresealed,thatis,thereareno removablecapstocheckelectrolyteorreplenishit.Someofthese batterieshaveasmalleye“toindicatechargelevel.Stillothersare sealed,butincludeconnectionstoexternalventtubes. Foralltypesofbatteries,alwaysfollowthemanufacturers’ recommendationsforchargingandtesting. Lead-Acid Battery Lead-acid batteries are called by different names: vented, sealed, low maintenance, and no maintenance. Fig. 3-03 TL623f300 Battery Type NOTESection 3 3-4 TOYOTA Technical Training Battery Case The battery case holds and protects all of the internal components and contains the electrolyte. Fig. 3-04 TL623f300 Thebatterycaseandcover... w Formasealedcontainer. w Protecttheinternalparts. w Keeptheinternalpartsinproperalignment. w Preventelectrolyteleakage. Battery Construction Battery CaseThe Battery Electrical Circuit Diagnosis - Course 623 3-5 Twotypesofplatesareusedinabattery:positiveandnegative. Positive- Positiveplatesaremadeofantimonycoveredwithanactive layerofleaddioxide(PbO2). Negative- Negativeplatesaremadeofleadcoveredwithanactive layerofspongelead(Pb). Onlythesurfacelayersonbothplatestakepartinthechemicalreaction. Platesurfacearea- Asthesurfaceareaoftheplatesincreases,sodoes thecurrentcapacityofthebattery.Surfaceareaisdeterminedbythesize ofeachplate,aswellasthetotalnumberofplatesinabattery.Generally speaking,thelargerthebattery,thehigherisitscurrentcapacity. Surfaceareahasnoeffectonbatteryvoltage. Positive and Negative Plates Positive plates are covered with lead dioxide (PbO2); negative plates are made of lead (Pb). Fig. 3-05 TL623f305c PlatesSection 3 3-6 TOYOTA Technical Training Theplatesareseparatedbythinporousinsulators.Theseallow electrolytetopassfreelybetweentheplates,butpreventtheplates fromtouchingeachotherandshortingout. Insulators Insulator plates keep positive and negative plates from touching each other and shorting out. Fig. 3-06 TL623f306c SeparatorsThe Battery Electrical Circuit Diagnosis - Course 623 3-7 Atypicalleadacidbatteryisorganizedintocells. Eachcell... w Consistsofmultiplepositiveandnegativeplatesimmersedintheir ownelectrolytereservoir. w Producesabout2.1volts,regardlessofbatterysize. Automotivebatteriesareratedat12volts.Tomakeupthisvoltage,six cells,eachproducing2.1volts,areconnectedinseries. 6x2.1volts=12.6volts Asaresult,actualbatteryvoltageistypicallycloserto12.6volts. Cellsareconnectedinserieswithheavyinternalstraps. Apositiveandanegativeterminalpostprovideconnectionpointsfor thevehicle’sbatterycables. Battery Cells A typical automotive battery contains six cells connected in series. Each cell produces 2.1 volts. Fig. 3-07 TL623f307 CellsSection 3 3-8 TOYOTA Technical Training Onsomebatteries,ventcapsallowacontrolledreleaseofhydrogen gas.Thisgasformsnaturallyduringbatteryrecharging,whetherby thevehicle’salternatororbyanexternalcharger. Battery Vent Caps Vent caps allow the controlled release of hydrogen gas as the battery charges. Fig. 3-08 TL623f308c Venting SystemThe Battery Electrical Circuit Diagnosis - Course 623 3-9 Theelectrolyteisamixtureofsulfuricacid(H 2SO4)andwater(H 2O). Theelectrolytereactschemicallywiththeactivematerialontheplates toproduceavoltage(electricalpressure). Battery Electrolyte Acid in the electrolyte reacts chemically with the positive plate’s lead oxide (PbO2) and the negative plate’s sponge lead (Pb) to produce a voltage. Fig. 3-09 TL623f309c ElectrolyteSection 3 3-10 TOYOTA Technical Training Thefunctionofaleadacidcellisbasedonasimplechemicalreaction. Whentwodissimilarmetalsareimmersedinanacidsolution,a chemicalreactionproducesavoltage.Usingthisreaction,alead-acid batterycanbedischargedandchargedmanytimes. Therearefourstagesinthedischarging-chargingcycle: w Positiveplatecoveredwithleadoxide(PbO 2 ). w Negativeplatecoveredwithspongelead(Pb). w Electrolytecontainswater(H 2 O)andsulfuricacid(H 2 SO 4 ). w Currentflowsinthecellfromthenegativetothepositiveplates. w Electrolyteseparatesintohydrogen(H 2 )andsulfate(SO 4 ). w Thefreesulfatecombineswiththelead(bothleadoxideandsponge lead)andbecomesleadsulfate(PbSO 4 ). w Thefreehydrogenandoxygencombinetoformmorewater,diluting theelectrolyte. w Bothplatesarefullysulfated. w Electrolyteisdilutedtomostlywater. w Reversesthechemicalreactionthattookplaceduringdischarging. w Sulfate(SO 4 )leavesthepositiveandnegativeplatesandcombines withhydrogen(H 2 )tobecomesulfuricacid(H 2 SO 4 ). w Hydrogenbubblesformatthenegativeplates;oxygenappearsat thepositiveplates. w Freeoxygen(O 2 )combineswithlead(Pb)atthepositiveplateto becomeleadoxide(PbO 2 ). How Batteries Work Fully Charged Discharging Fully Discharged ChargingThe Battery Electrical Circuit Diagnosis - Course 623 3-11 Lead Acid Chemical Reaction The charging-discharging cycle has four distinct stages, all based on a reversible chemical reaction with lead and sulfuric acid. Fig. 3-10 TL623f310cSection 3 3-12 TOYOTA Technical Training Anautomotivebatterymustbeabletocranktheengineforstarting andstillhaveenoughreservecapacitytooperatethevehiclesystems oncetheenginestarts. Batterycapacityis: w Theamountofelectricalenergythebatterycandeliverwhenfully charged. w Determinedbythesizeandtotalnumberofplatesandthevolume andstrengthoftheelectrolyte. Refertothemanufacturer’sspecificationforinformationspecifictoa particularToyotavehicle. Whileitisoperatingthestarter,thebatteryexperiencesalarge dischargecurrent. Themeasureofabattery’sabilitytoprovidethiscurrentisexpressed asCold-CrankingAmperes,orCCARating. TheCCARatingspecifies(inamperes)thedischargecurrentafully chargedbatterycandeliver... w at0 5F(-18 5C), w for30seconds, w whilemaintainingatleast1.2voltspercell(or7.2voltstotalfora six-cell,12-voltbattery). BatteriesinToyotavehiclestypicallyhaveaCCAratingbetween350 to560amperes,dependingonvehiclemodel.RefertoTIStoobtain informationforspecificToyotavehicles. Thebatterymustprovidereserveenergyfortheignitionsystemand forlightsandaccessoriesifthechargingsystemfails. TheReserveCapacityratingmeasures(inminutes)theamountoftime afullychargedbatterycan... w dischargeat25amperes,whilemaintainingavoltageofatleast 1.75voltspercell(totalof10.5voltsfora6-cell,12-voltbattery). BatteriesinToyotavehiclestypicallyhaveanRCratingbetween55 and115minutes,dependingonvehiclemodel.RefertoTIStoobtain informationforspecificToyotavehicles. Capacity Ratings Cold-Cranking Amperes Reserve Capacity (RC)The Battery Electrical Circuit Diagnosis - Course 623 3-13 TheAmpere-Hours,orAHrating,isanotherimportantmeasureofa battery’sdesignperformance. TheAHratingexpressesthedischargecurrentafullychargedbattery candeliverfor20hours... w at80 5F(27 5C), w whilemaintainingavoltageofatleast1.75voltspercell(totalof 10.5voltsfora6-cell,12-voltbattery). Abatterythatcandeliver4ampsfor20hoursisratedat80amp-hours. BatteriesinToyotavehiclestypicallyhaveanAHratingbetween40 and80amp-hours,dependingonvehiclemodel.RefertoTIStoobtain informationforspecificToyotavehicles. Ampere-Hours (AH) EXAMPLESection 3 3-14 TOYOTA Technical Training Batteryserviceshouldalwaysbeginwithathoroughvisualinspection. Suchaninspectionmayrevealsimple,easilycorrectedproblemsor problemsthatrequirebatteryreplacementwithoutfurthertesting. Includethesestepsinavisualinspection: 1. Checkforcracksinthebatterycase.Checkparticularlyaround batteryterminals.Thesearesometimesoverstressedwhen removingandinstallingbatterycables.Replacethebatteryifthere isanyevidenceofcracking. 2. Checkforcrackedorbrokencablesorconnections.Replacecables orconnectorsasnecessary. 3. Checkforcorrosiononterminalsanddirtoracidonthecasetop. Cleantheterminalsandcasetopwithamixtureofwaterand bakingsoda.Wirebrushheavycorrosionontheterminals. 4. Checkforaloosebatteryhold-downandloosecableconnections. Tightenasneeded. 5. Onbatterieswithremovableventcaps,removethecapsandcheck theelectrolytelevel.Adddistilledwatertoeachcelltorestorethe levelifnecessary.Avoidoverfillingandneveraddadditionalacid. Tapwateraddscontaminants,andwillreducebatteryefficiency. Visual Inspection A visual inspection can reveal easy-to-correct problems with the battery and conditions that will require battery replacement. Fig. 3-11 TL623f311c Visual InspectionThe Battery Electrical Circuit Diagnosis - Course 623 3-15 Battery Indicator Eye The battery indicator eye can give a quick indication of battery condition. Fig. 3-12 TL623f312c 6. Checktheindicatoreye.Aredeyeindicatesthebatteryisseverely dischargedortheelectrolyteislow.Theelectrolytelevelis sufficientandthebatteryisatleast25%chargedifatleastsome blueisshowing. 7. Checkforcloudyordiscoloredelectrolyte.Thiscanbecausedby overchargingorexcessivevibration.Correcttheproblemand replacethebattery.Section 3 3-16 TOYOTA Technical Training Safetyshouldbeyourfirstconsiderationwheneveryouinspect,test,or replacealeadacidbattery.Theelectrolytecontainssulfuricacid.This acidcanburnyourskin,injureyoureyes,anddamagethevehicle,your tools,oryourclothing. Ifyousplashelectrolyteontoyourskinorintoyoureyes,immediately rinseitawaywithlargeamountsofcleanwater.Contactadoctor immediately. Ifyouspillelectrolyteontoanypartofthevehicle,neutralizetheacid withasolutionofbakingsodaandwater,thenrinseliberallytoremove anyresidue. Whenabatteryischarging,theelectrolytemayreleasegasses (hydrogenandoxygen).Hydrogengasisexplosive,andoxygen supportscombustion.Aflameorsparknearachargingbatterycan causeanexplosion. Takethefollowingprecautionswhenworkingwithautomotivebatteries: w Wearglovesandsafetyglasses. w Neverusespark-producingtoolsnearthebattery. w Neverlayanytoolsonthebattery. w Ifitisnecessarytoremovethebatterycables,alwaysremovethe groundfirst. w Whenconnectingbatterycables,alwaysconnectthegroundcable last. w Donotusethebatterygroundterminalwhencheckingforignition spark. w Takecarenottospillelectrolyteintoyoureyes,ontoyourskin,and ontoanypartofthevehicle. w Ifyoumixelectrolyte,pourtheacidintothewater(notthewater intotheacid). w Alwaysfollowtherecommendedproceduresforbatterytesting, charging,andforconnectingjumpercablesbetweentwobatteries. Safety First PrecautionsThe Battery Electrical Circuit Diagnosis - Course 623 3-17 Therearetwotestsforbatterydrain: 1. Parasiticload 2. Surfacedischarge Aparasiticloadiscreatedbyadevicethatdrawscurrentevenwhen theignitionswitchisturnedtoOff.“Evenasmallcurrentcan dischargethebattery,ifthevehicleisnotusedforanextendedtime. Checkforaparasiticloadasfollows: 1. Connectanammeterinseriesbetweenthebatterynegative terminalandthegroundcableconnector. 2. Selecttheappropriatescaleandreadthecurrentdraw. 3. Toyotavehiclestypicallydrawbetween20and75milliamps(thisis currentusedtomaintainelectronicmemories). 4. Anyreadinghigherthan100milliampsisunacceptable.Locateand correctthecauseoftheexcessparasiticdrain. 5. Makesurethatyouwaitafewminutesbeforecheckingforparasitic load.Afterthevehicleisshutdownoradoorisopened,parasiticload maybe50-75milliamps,dependingonmodel,forafewminutes. Battery Drain TestsSection 3 3-18 TOYOTA Technical Training Surfacedischargeisasmallcurrentthatrunsbetweenthetwobattery terminals,acrossthesurfaceofthebattery.Thiscanoccuronlywhen thatsurfaceisdirty. Checkforsurfacedischargeasfollows: 1. Connectavoltmeter,blacktestlead(negative)tothebattery’s negativeterminal;redtestlead(positive)tothetopofthebattery case. 2. Selectanappropriatescaleandreadthevoltage. 3. Ifthemeterreadingishigherthan0.5volts,cleanthecasetopwith asolutionofbakingsodaandwater. Two Tests for Battery Drain Parasitic load current and battery surface discharge can cause batteries to discharge over time. Fig. 3-13 TL623f313cThe Battery Electrical Circuit Diagnosis - Course 623 3-19 Youcanuseabatteryanalyzertoobtainanindicationofbattery conditionthatismoreaccuratethanjustitsstateofcharge.The MidtronicsMicropro815BatteryAnalyzerusesconductancetestingto evaluatetheconditionoftheplatesinsidethebattery. Thereareseveraladvantagesofusingthisbatteryanalyzer: w Batter
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