CHEVROLET VOLT BATTERY • PAGE 1 Chevrolet Volt Battery: An Introduction Chevrolet Volt Battery: BATTERY 101 Advanced Batteries and the Chevrolet Volt Why Lithium-ion is the Right Battery Astheautomotiveindustrytransitionsfromcarsandtruckspowered Whilethemajorityofhybrid-electricvehicles(HEVs)ontheroadtoday primarilybypetroleumtovehiclespoweredbyelectricity,theheartofthis usenickelmetalhydride(NiMH)baerytechnology,theChevroletVolt transformationwillbethe rapidadvancementofbaerytechnology. extended-rangeelectric vehicle(E-REV)will bepowered by a16kWh When theChevroletVoltgoesintoproduction, targetedforlate2010, lithium-ionbaerypack manufacturedbyGMandcomprising more itwillbepoweredbyabaerypackthatdeliversupto40milesof than200lithium-ioncells.Lithium-ion baeriesprovide nearlytwo gasoline-andemissions-freedriving. tothreetimesthepowerof aNiMHbaery inamuchsmallerpackage. Contrarytopopularthinking,all lithium-ionchemistriesare notalike. Infact,lithium-ionisafamilyof dozensof chemistries withdifferent capabilitiesandperformancecharacteristics.Thecharacteristics requiredforautomotiveapplicationsdiffergreatlyfrom consumer electronics,such aslaptopcomputers. Lithium-ionbaery chemistry isthefastest-growingand most promisingbaerychemistryforseveralreasons,including: •Superior specificenergyandpower •Longlife •Highefficiency •Durability •Lowerinitialmaterialcostandfewerreplacements •Highcell voltagemeansfewercellsareneededto give desired After extensivetestingofdifferentlithium-ion baerysolutions, voltagerange GeneralMotorshasamuchgreaterunderstanding oflithium-ioncells, •Higherenergy-to-weightratio, animportantconsiderationin controlhardwareandthemanufacturabilityofthebaerycomponents automotiveapplicationssinceexcessmassaffectsefficiency neededfor theChevyVolt’s baerypack.Liketoday’s conventional •Configurableintoawidevarietyof shapesandsizesso asto powertrains,GMbelievesthedevelopmentandassemblyofadvanced efficiently fillavailablespacein thedevicesthey power baeriesisacorecompetency.GMisrapidlybuildingcapability and resources tosupportthisstrategicdecision,includingassemblyof •Sufferslileornomemory(lazybaery)effect,whichcanoccur theVolt’sbaerypacksatafacilityintheUnitedStates.Thebaery whenbaeriesgraduallylosetheirmaximumenergy capacity if packwillincludecells,majorelectronic componentsandhardware theyarerepeatedlyrechargedafterbeingonlypartiallydischarged suppliedbyLGChem. •Encounterslowlossof charge(alsoknownasself-discharge) whennotin use GM’sexperienceasamanufacturer–combinedwiththebaery integrationskillsandthe technicalexpertiseofits suppliers–will resultinbaerypacksthatmeettheVolt’squality,safety,performance andtimingrequirements. CHEVROLET VOLT BATTERY • PAGE 2 Fast Facts •TheChevroletVoltfeaturesa16kWhlithium-ionbaery pack •Foruptothefirst40milesof driving,theChevroletVolt’sfully thatweighslessthan400pounds(181.4kg). chargedlithium-ionbaerypack powersanelectric motor. •Thebaerypackismadeup ofmultiplelinkedbaerymodules. Additional energy captured during vehicle braking (theVolt Alltogetherthemodulescontainmorethan200baery cells. isequippedwithRegenerativeBrakes)isconverted into electricityandstoredinthebaery pack. •ThebaerypackisT-shaped,allowing designerstocreate uniquevehicledesignsacrossmultiplebrands.Thebaery’s •Controlsystemswithin thebaery packpreventitfrom floor,or“pan”,isactuallypartofthevehicle’s structure. dischargingbelowitsminimalstateof charge. •Thebaerymodulesandpacks willbeassembledbyGMat •ThevehicleseamlesslyswitchestoExtended-Range modeonce afacilityinMichigan. thebaeryhasreacheditsminimalstateof charge. Inthis secondarymode,asmall flex-fuelpoweredengine-generator operates at one of several optimized speeds, turning the generatorandproducingtheelectricity neededtopowerthe Volt’selectricmotorundermostdrivingconditions. •Thebaerywillcontinuetostoreenergyfromregenerativebraking andany unusedelectricity createdduringextended-range mode operation. Thisenergywillbeusedtosupplementthe engine- generatortoprovidepeakperformancewhenitis required. •Theenginegeneratordoesnotfullyrechargethe baery because theobjectiveof theVoltistominimizeoreliminatetheuse petroleum. Theonly waytofullyrechargethebaery istoplug thevehicleintoanelectricaloutlet. Thecostof energy from electricityisabout1/6thecostof gasolinesoplugging inthe vehicletochargethebaeryprovidesthelowest operating cost. How the Battery Propels the Volt •TheVolt’slithium-ionbaeryiscontrolledsothatitoperates Recharging the Battery withinastate-of-chargewindow atanygiventime. Controlling •TheChevroletVoltbaeryisrechargedbypluggingthevehicleinto thebaeryinthiswayavoidsfullychargingor dischargingthe ahousehold-typeelectricaloutlet.Rechargingtakesabouteight baerywhichcanshortenthelifeofthebaery. hoursusinga120V outletandlessthanthreehourson240V. CHEVROLET VOLT BATTERY • PAGE 3 Safety •TheLGChemcellusesamanganese-basedcathodechemistry Differentelectrodematerialshavedifferentcurrent-carryingcapacities, withadditivestoimprovebaerylifeunderhigh-temperature andthisaffectsthestoragecapacitiesof thecells. conditions. Each of theVolt’smorethan200 cellsisa“buildingblock”withinthe •Numerous measures havetakentohelppreventthesafety largerbaerymoduleandpack. An individualcellisabout thesize of issues–namelyshortcircuitingandoverheating–thathave a5-inchby7-inch(12.7-cmby17.7-cm)photoframe,islessthana occurredinlithium-ionbaeriesusedinconsumerelectronics. quarter-inchthickandweighsnearlyapound. LGChem’sexclusiveSafetyReinforcedSeparator consistsof semi-permeablemembranesseparatingtheelectrodesinthe cells,whicharemechanicallyandthermallysuperiortocommonly usedseparators. •Primary,aswellasbackup baerypackcontrols, regulate voltage,currentstateofchargeandtemperature. •Rigoroustestingoflithium-ionbaerypacksinGM’sbaery labsandon-roadinearlyengineeringdevelopmentcarshasnot revealedanysafetyorperformanceissues. Durability •Automotivebaeriesoperateinaruggedandhostileenvironment withtheexpectationtheywilllastthelifeofthevehicle:GMis currentlytestingbaerypacksinthelabandengineering developmentvehicles. ThistestingwillhelpGMbeerunderstand howthesepackswilloperateinreal-worlddriving conditions, includingextremehotandcoldweatherclimatesandroad. •TheChevroletVoltbaerycellisencasedina polymer-coated EachVolt’sbaerycellcontainsacarbonanode(thenegativeelectrode), aluminumpackage.This thermallyefficientandsafepackageis a manganese-based cathode (the positive electrode) and a safety- designedtobemoreforgiving underharshconditionsandhelp re inforcedseparator, which providesthemediumforthe transferof reducethecostand complexityofthebaerycooling system. electricalchargeionsbetweentheanodeandthecathode inside the baerycell. The Battery Cell Theprotectivepolymer-coatedaluminumcoverencasesthe cell, helps Abaerycelldeliverselectriccurrentastheresultofanelectrochemical preventgaspermeation andimprovesbaery coolingefficiency. reaction.Electricalcurrentiscarriedbylithiumions,fromthepositive Tabsatthetopof thecell areusedtolinkthecellswithinthe module. electrode(cathode) tothenegativeelectrode (anode)duringcharging, andfromnegative topositiveduring discharging.Theionsaresmall andresidewithinthecrystalstructureoftheelectrodematerials. CHEVROLET VOLT BATTERY • PAGE 4 The Battery Module Numerous designsarepossibleforassembling cells intoabaery pack •Temperaturesensors foranelectricorhybridvehicle.Amodulardesignisusedinmostcases, allowforinlet/outlet with anumberofcellspackagedtogether intoaunitcalleda“module.” coolantmeasurement Controlsareusedtomonitorthevoltageandcurrentofa cell to •Manifoldsandcoolant determinewhentochargeordischarge.Multiplemodulesarecombined linesallowforheat intoabaerypacksizedto match therequirements ofthevehicle. exchangewiththe Thesamemodulescouldbeusedina varietyofdifferentbaery packs. cell surfaces •Connectorsallowfor singlepointentry/exit of highvoltageloads •Baerycover/enclosure protects andinsulates the pack from the ambientenvironment Design •Currentlayoutisintheshapeof aT •Steeltray,plasticcover Integration •Pack ispartof thevehiclestructure The Battery Pack •Pack isanunderbody-mountedcomponent Abaerypackisthefinalassemblyusedtostoreanddischarge electricalenergyfor ahybridor electricvehicle.TheVoltbaery pack Looking Ahead consistsofmultiplemodules, configuredinseries, retainedwithinan Futuregenerationswillproducebaerieswith: enclosurefor underbodyinstallation.Componentsforthecontroland •Lesscostduetobeeruseof partscommonality(lessparts) monitoringofdischargeorchargeenergyarealsohousedwithinthepack. •Higherenergydensity,moreefficientuseof packaging •Modulesareclampedto abaerytrayandjoinedby •Beercold-weatherperformance flexibleinterconnects •Moreefficientinsulation/energyconservation •Relaysandmechanicalassembliesallowforautomatedor manual controlofsubassemblyoutputvoltage •Lowermass •Increasedpowerperformance CHEVROLET VOLT BATTERY • PAGE 5 Battery 101: Commonly Used Terms (Source: International Energy Agency) Advanced Technology Partial Zero Emission Vehicle (AT-PZEV): Baery state of charge: Theavailablecapacityinabaeryexpressed AsdefinedbytheCalifornia Air ResourcesBoard(CARB), avehicle asapercentageof ratednominalcapacity. that uses electricdrivecomponents to helptheindustryintroduce Capacitance: Theratioof thechargeononeof theconductorsofa ZeroEmissionVehicles(ZEVs) suchasElectricVehicles(EV)orFuel capacitor tothepotentialdifferencebetweentheconductors. Cell Vehicles(FCVs). Capacitor: Adevicethatconsistsof twoconductorsinsulated from Baery cell: Thesmallest,mostdiscreetrepeatingunitof abaery. each otherbyadielectricandwhichintroducescapacitance intoa Acellcontainsananode, cathodeandelectrolyteto deliverelectric