學位論文--汽車專業(yè)翻譯battery-electric-vehicle

Formorepapersgoto

/paperclub

youcanalsosubmityourpaperstothisE-Mail:

paperclub@

withyourname,college&department:soyourpaperwillbepublished.

BATTERYELECTRICVEHICLE

ABSTRACT

BATTERYELECTRICVEHICLE

Petroleumamazesuseveryday–itspricessimplykeeprisingandrising.Itisalmostimpossibletopredictifyouwillbeabletokeepdrivingyourcarasyouusedto,inthefuture.Mostpeoplearealreadyshorteningtheirvacationsandholidaytripstosavealittlemoregasandpollsreportthatmanypeoplearealreadycuttingbackontheireverydayexpensesinordertopayfortheirgas.

Adheringtogassavingtipshasbeenusefulupuntilnowforsome,butjustaspeopleadjusttothenewprices,thepricesriseagain!Luckily,thereisasolutionthatcanhelpyoucutdownyourgasexpensesandsavemoneynomatterhowhighgaspricesrise.Theinterestinthesetypesofvehicleshasrisenwithinthepastfewyears,notonlybecausetheydonotneedalotofgas,butalsobecausetheyareenvironment-friendly–abigconcernnowthatglobalwarminghasbecomesuchanimmediatethreat.Afterall,whowouldn’twantacarthatischeaptotravelwithandkeepstheenvironmentgreenandtheairclear?Mostpeoplewould–aslongastheycanaffordtheinitialinvestment:electriccars!

Batteryelectricvehicle

Thebatteryelectricvehicle,orBEV,isatypeofall-electricvehiclethatuseschemicalenergystoredinrechargeablebatterypacks.Aselectricvehicle,itemployselectricmotorsandmotorcontrollersinsteadofinternalcombustionengines(ICE’s).SomeconfusionarisesbecausetheindustryoftenreferstoBEV’swhenitmeanselectriccars.("Batteryelectricvehicles"includingcommercialvehiclesinadditiontopassengercars.)

PRINCIPLEOFOPERATION

Howdoelectriccarswork?

First,anelectriccarispoweredbyanelectricmotor,comparedtoold-fashionedcarsthatcontainagasolineengine.Fromtheoutside,itisalmostimpossibletotellwhetheracariselectricorpoweredongasoline.However,whenyouaredrivingthecar,youwillgetafewhints–forexample,theengineisverysilent.Themaindifferenceappearswhenyouopenthehoodandgetaglimpseoftheelectricengine,whichispoweredbyacontroller,andtherechargeablebatteries,thatareusedtopowerthecontroller.

Atypicalelectriccar,thisonehassomeparticularlysnazzydecals.ThisvehicleisownedbyJonMauney.

Thiselectricvehiclebeganitslifeasanormal,gasoline-powered1994GeoPrism!.

Herearethemodificationsthatturneditintoanelectriccar:

Thegasolineengine,alongwiththe

muffler

,

catalyticconverter

,tailpipeandgastank,wereallremoved.

The

clutchassembly

wasremoved.Theexisting

manualtransmission

wasleftinplace,anditwaspinnedinsecondgear.

AnewACelectricmotorwasboltedtothetransmissionwithanadapterplate.

AnelectriccontrollerwasaddedtocontroltheACmotor.

The50-kWcontrollertakesin300voltsDCandproduces

240voltsAC,three-phase.Theboxthatsays"U.S.Electricar"isthecontroller.

Abatterytraywasinstalledinthefloorofthecar.

Fifty12-voltlead-acidbatterieswereplacedinthebatterytray(twosetsof25tocreate300voltsDC).

Electricmotorswereaddedtopowerthingsthatusedtogettheirpowerfromtheengine:thewaterpump,

powersteering

pump,airconditioner.

Avacuumpumpwasaddedforthe

powerbrakes

(whichusedenginevacuumwhenthecarhadanengine).

Thevacuumpumpisleftofcenter.

Theshifterforthemanualtransmissionwasreplacedwithaswitch,disguisedasan

automatictransmission

shifter,tocontrolforwardandreverse.

Anautomatictransmissionshifterisusedtoselectforward

andreverse.Itcontainsasmallswitch,whichsendsasignaltothecontroller.

Asmall

electricwaterheater

wasaddedtoprovideheat.

Thewaterheater

Achargerwasaddedsothatthe

batteries

couldberecharged.Thisparticularcaractuallyhastwochargingsystems--onefromanormal120-voltor240-voltwalloutlet,andtheotherfromamagna-chargeinductivechargingpaddle.

The120/240-voltchargingsystem

TheMagna-Chargeinductivepaddlechargingsystem

The

gasgauge

wasreplacedwithavoltmeter.

The"gasgauge"inanelectriccariseitherasimplevoltmeteroramoresophisticatedcomputerthattrackstheflowofampstoandfromthebatterypack.

Everythingelseaboutthecarisstock.Whenyougetintodrivethecar,youputthekeyintheignitionandturnittothe"on"positiontoturnthecaron.Youshiftinto"Drive"withtheshifter,pushontheacceleratorpedalandgo.Itperformslikeanormalgasolinecar.

Herearesomeinterestingstatistics:

Therangeofthiscarisabout50miles(80km).

The0-to-60mphtimeisabout15seconds.

Ittakesabout12kilowatt-hoursofelectricitytochargethecaraftera50-miletrip.

Thebatteriesweighabout1,100pounds(500kg).

Thebatterieslastthreetofouryears.

Tocomparethecostpermileofgasolinecarstothiselectriccar,here'sanexample.ElectricityinNorthCarolinaisabout8centsperkilowatt-hourrightnow(4centsifyouusetime-of-usebillingandrechargeatnight).Thatmeansthatforafullrecharge,itcosts$1(or50centswithtime-of-usebilling).Thecostpermileistherefore2centspermile,or1centwithtime-of-use.Ifgasolinecosts$1.20pergallonandacargets30milestothegallon,thenthecostpermileis4centspermileforgasoline.

Clearly,the"fuel"forelectricvehiclescostsalotlesspermilethanitdoesfor

gasoline

vehicles.Andformany,the50-milerangeisnotalimitation--theaveragepersonlivinginacityorsuburbseldomdrivesmorethan30or40milesperday.

Tobecompletelyfair,however,weshouldalsoincludethecostofbatteryreplacement.Batteriesaretheweaklinkinelectriccarsatthemoment.Batteryreplacementforthiscarrunsabout$2,000.Thebatterieswilllast20,000milesorso,forabout10centspermile.

Comparisonwithinternalcombustionvehicles

Purchasecost

Batteriesareusuallythemostexpensivecomponentofelectriccars,thoughthepriceperkilowatt-hourofenergycapacityhasfalleninrecentyearsforthemorerecentlyintroducedtechnologiessuchaslithium-ionandlithium-polymer,aswouldbeexpectedforanynewtechnology.Oldertechnologiessuchaslead-acidhavebecomemoreexpensiveduetoincreaseinmaterialscost,particularlylead,drivenbydemandforuseinpoweredbicycles(particularlyinChinaandIndia)andinuninterruptiblepowersuppliestosupportsmallcomputersystems.Sincethelate1990s,advancesinbatterytechnologieshavebeendrivenbyskyrocketingdemandforlaptopcomputersandmobilephones,withconsumerdemandformorefeatures,larger,brighterdisplays,andlongerbatterytimedrivingresearchanddevelopmentinthefield.Theelectricvehiclemarketplacehasreapedthebenefitsoftheseadvances,butthecostperunitofenergycapacitystillfavorsolder,heavier,lessefficienttechnologies.

Somebatteriescanbeleasedorrentedinsteadofbought(seeThinkNordic).In1947,inNissan'sfirstelectriccar,thebatterieswereremovablesothattheycouldbereplacedatfillingstationswithfullychargedones.

Runningcosts

Electriccaroperatingcostscanbedirectlycomparedtotheequivalentoperatingcostsofagasoline-poweredvehicle.Aliterofgasolinecontainsabout8.9

kW·hofenergy.Tocalculatethecostoftheelectricalequivalentofaliterofgasoline,multiplytheutilitycostperkW·hby8.9.Becauseautomotiveinternalcombustionenginesareonlyabout20%efficient,thenatmost20%ofthetotalenergyinthatliterofgasolineiseverputtouse.

Acarpoweredbyaninternalcombustionengineat20%efficiency,getting8

L/100

km(30

mpg),willrequire(8.9*8)*0.20=14.2

kW·h/100

km.Atacostof$1/L,8

L/100

kmis$8per100

km.Abatteryelectricversionofthatsamecarwithacharge/dischargeefficiencyof81%,andchargedatacostof$0.10forkW·hwouldcost(14.2/0.81)*0.10=$1.75per100

km,orwouldbepayingtheequivalentof$0.22/L.TheTeslausesabout13

kW·h/100

km,theEV1usedabout11

kW·h/100

km.

Servicingcostsshouldbelowerforanelectriccar.Themovie“WhoKilledtheElectricCar“showsacomparisonbetweenthepartsthatrequirereplacementinagasolinepoweredcarandtheEV1(none),statingthattheybringthecarsinevery5,000miles,rotatethetires,fillthewindshieldwasherfluidandsendthembackoutagain.Evenbrakesrequirelessmaintenancebecauseoftheregenerativebraking,thesameaswithahybrid.

Electriccarsusinglead-acidbatteriesrequirereplacementofthebatterypackonaregularbasis,whileinternalcombustionenginescanlastthelifeofthevehicle,withroutinerepairs.Lithium-ionandNiMHbatteriestypicallylastthelifeofthevehicle.NoToyotaPriushaseverneededtheirNiMHbatteryreplacedfromwearandtear.

Energyefficiency

Anelectriccar'sefficiencyisaffectedbyitscharginganddischargingefficiencies.Atypicalchargingcycleisabout85%efficient,andthedischargecycleconvertingelectricityintomechanicalpowerisabout95%efficient,resultingin81%ofeachkW·hisputtouse.TheelectricitygeneratingsystemintheUSAloses9.5%ofthepowertransmittedbetweenthepowerstationandthesocket,andthepowerstationsare33%efficientinturningthecalorificvalueoffuelatthepowerstationtoelectricalpower.Overallthisresultsinanefficiencyof0.81*0.3=24.2%fromfuelintothepowerstation,topowerintothemotoroftheEV.

Productionandconversionelectriccarstypicallyuse10to23kW·h/100

km(0.17to0.37

kW·h/mi).Approximately20%ofthispowerconsumptionisduetoinefficienciesinchargingthebatteries.TeslaMotorsindicatesthatthewelltowheelsenergyconsumptionoftheirli-ionpoweredvehicleis10.9

kW·h/100

km(0.176kW·h/mi).TheUSfleetaverageof10

L/100

km(23

mpg

US)ofgasolineisequivalentto96

kW·h/100

km(1.58

kW·h/mi)andthe3.4

L/100

km(70

mpgUS)HondaInsightuses32

kW·h/100

km(0.52

kW·h/mi)(assuming9.6

kW·hperliterofgasoline),sohybridelectricvehiclesarerelativelyenergyefficient,andbatteryelectricvehiclesaremuchmoreenergyefficient.

A2001DOEestimatecalculatesabatterypoweredEVat7￠/kW·hcanbedriven69

kilometers(43

mi)foradollarandat$0.33/L($1.25/USG)agasolinevehiclewillgo29

kilometers(18

mi).At$3.75/USGthatislessthan10

kilometers(6.2

mi).

\o"SourcesofelectricityintheU.S.2006[2]"

Carbondioxideemissions

Whileelectriccarsareconsideredzero-emission-at-tailpipe-vehicles,theycauseanincreaseinelectricalgenerationneeds.Generatingelectricityandprovidingliquidfuelsforvehiclesaredifferentcategoriesoftheenergyeconomy,withdifferentinefficienciesandenvironmentalharms.A55%to99.9%improvementinCO2emissionstakesplacewhendrivinganEVoveraninternalcombustion(gasoline,diesel)vehicledependingonthesourceofelectricity.accordingtotheElectricVehicleAssociationofCanada,(whosellelectricvehicles)CO2andothergreenhousegasemissionsareminimalforelectriccarspoweredfromsustainableelectricitysources(forexample,bysolarenergy)orforinternalcombustionenginecarsthatarerunonrenewablefuelssuchasbiodiesel.

IftheobjectoftheexerciseinlookingatalternativestoconventionalvehiclesistoreduceCO2emissions,thenthathastomeanusingthemostcarbon-efficientvehicleyoucanbuy.Thisdependsonthesourceofyourgridelectricity;averyhighpercentageofCaliforniaelectricityisfromhydropower,whilealmostallTexaselectricityisfromcoal].Forthe"average"USgrid,currentlyadieselisbetterthananEV.MostelectricitygenerationintheUnitedStatesisfromfossilsources,andalotofthatisfromcoal,accordingtotheU.S.DepartmentofEnergy.Coalismorecarbon-intensivethanoil.-TheUSnationalgridisunderinvestedandishavingtroublemeetingevencurrentlevelsofdemandaccordingtotheUSDOE.

OverallaverageefficiencyfromUSpowerplants(33%efficient)topointofuse(transmissionloss9.5%),(USDOEfigures)is29.87%.Accepting90%efficiencyfortheelectricvehiclegivesusafigureofonly26.88%overallefficiency.Thatislowerthantheefficiencyofaninternalcombustionengine(Petrol/Gasoline30%efficient,Dieselengines45%efficient-Volvofigures).Soadieselwouldbebetterifyourgridpowerwascomingfromanearlydiesel-burningpowerplant.Theactualresultdependsondifferentrefiningandtransportationcostsgettingfueltoacarversusapowerplant.Dieselenginescanalsoeasilyrunonrenewablefuels,biodiesel,vegetableoilfuel,withnolossofefficiency.Usingfossilbasedgridelectricityentirelynegatestheinvehicleefficiencyadvantagesofelectriccars.Themajorpotentialbenefitofelectriccarsisallowingdiverserenewableelectricitysources,includingnuclearpower,tofuelcars.

AmodernTDIPDorcommonrailtypedieselenginevehicleisalmosttwiceefficientwhenusingfossildieselthananEVrunningongridelectricitywhichismostlyfromfossilfuel.Itcanalsorunonrenewablewastevegetableoilfuel,whichisviewedascarbonneutral,orlowcarbonimpactifprocessedintobiodiesel,butcontroversialifnewoilisused,becausebiofuelshavebeenblamedforhigherworldfoodprices,(particularlyUSbio-ethanol)andincreasedrainforestdepletiontogrowpalmoil.Aswellaswasteoil,newvegetableoilfuelsfromalgae,andforestrywastebeingpilotedinFinlandwithNokiaventurecapital,arenewrenewabledieselenginefuelsourcesthatarecomingonstream.

ElectricvehiclesdidnotwintheUS'TourdeSol'competitionforgreenestcar,aVWTDIrunningonWasteVegetableOildid.

Smog

TheOntarioMedicalAssociationannouncedthatsmogisresponsibleforanestimated9,500prematuredeathsintheprovinceeachyear.Electriccarsorplug-inhybrids,especiallyinemission-freeelectricmode,couldvastlyreducethisnumber.

Rangevscruisingspeed

ThetradeoffforrangeagainstcruisingspeediswellknownforICvehicles;typicallyacruisingspeedofaround50mphisnear-optimal,althoughforspecificcarsitcouldfallaslowas25mph,orashighas60mph.Forelectricvehiclestheequationislesscomplex,andmaximumrangeisachievedatcomparativelylowspeeds.

Accelerationperformance

Althoughsomeelectricvehicleshaveverysmallmotors,15

kW(20

hp)orlessandthereforehavemodestacceleration,therelativelyconstanttorqueofanelectricmotorevenatverylowspeedstendstoincreasetheaccelerationperformanceofanelectricvehicleforthesameratedmotorpower.AnotherearlysolutionwasAmericanMotors’experimentalAmitronpiggybacksystemofbatterieswithonetypedesignedforsustainedspeedswhileadifferentsetboostedaccelerationwhenneeded.

Electricvehiclescanalsoutilizeadirectmotor-to-wheelconfigurationwhichincreasestheamountofavailablepower.Havingmultiplemotorsconnecteddirectlytothewheelsallowsforeachofthewheelstobeusedforbothpropulsionandasbrakingsystems,therebyincreasingtraction.Insomecases,themotorcanbehouseddirectlyinthewheel,suchasintheWhisperingWheeldesign,whichlowersthevehicle'scenterofgravityandreducesthenumberofmovingparts.Whennotfittedwithanaxle,differential,ortransmission,electricvehicleshavelessdrivetrainrotationalinertia.

AgearlessorsinglegeardesigninsomeEVseliminatestheneedforgearshifting,givingsuchvehiclesbothsmootheraccelerationandsmootherbraking.Becausethetorqueofanelectricmotorisafunctionofcurrent,notrotationalspeed,electricvehicleshaveahightorqueoveralargerrangeofspeedsduringacceleration,ascomparedtoaninternalcombustionengine.AsthereisnodelayindevelopingtorqueinanEV,EVdriversreportgenerallyhighsatisfactionwithacceleration.

Forexample,theVenturiFetishdeliverssupercaraccelerationdespitearelativelymodest220

kilowatts(300

hp),andatopspeedofaround160

km/h.SomeDCmotor-equippeddragracerEVs,havesimpletwo-speedtransmissionstoimprovetopspeed.TheTeslaRoadsterprototypecanreach100

km/h(62

mph)in4secondswithamotorratedat185

kW(248

hp).

Reliability

Safety

Thekeytoattainingacceptablerangewithanelectriccaristoreducethepowerrequiredtodrivethecar,sofarasispractical.Thispushesthedesigntowardslowweight.Inacollisiontheoccupantsofaheavyvehiclewill,onaverage,sufferfewerandlessseriousinjuriesthantheoccupantsofalightervehicle.Anaccidentina2000lb(900kg)vehiclewillonaveragecauseabout50%moreinjuriestoitsoccupantsthana3000lb(1350kg)vehicleElectriccarsuselowrollingresistancetires,whichtypicallyofferlessgripthannormaltires.Theweight(andprice)ofsafetysystemssuchasairbags,ABSandESCmayencouragemanufacturersnottoincludethem.

VARIOUSSOURCESOFENERGY

ELECTRICITYORGASOLINE?

Althoughelectricvehicleshavefewdirectemissions,allrelyonenergycreatedthroughelectricitygenerationwhichwillemitpollutionandgeneratewaste,unlessitisgeneratedbyrenewablesourcepowerplants.EvenwithpowerplantsemittingCO2,theoveralllevelswouldbereducedbecausetheentireprocessofmovingacarismoreefficientusingelectricitythanproducinggasolineandburningitinacar'sengine.Sinceelectricvehiclesusewhateverelectricityisdeliveredbytheirelectricalutility/gridoperator,itiseffortlesstomakevastamountsofelectricvehiclesmoreefficientorreduce/eliminatepollutionbymodifytheirgenerationstationsthataretheelectricalsourceforthem.Thiswouldbedonebyanelectricalutilityorbythegovernmentunderanenergypolicy.

Fossilfuelvehicleefficiencyandpollutionstandardstakeyearsordecadestotakeeffectoveramajoritynation'svehiclefleet,sincethosenewefficiencyandpollutionstandardscanpropagatethroughretirement,scrapping,andtotalingofvehiclesalreadyontheroad.Toupgradeorchangetheenergysourceofallonly-fossilfuelvehiclesalreadyontheroadorapplynewpollutionorefficiencystandardstothematonce,wouldbeimpossibleinmostsocieties,becauseofunaffordabilitybythevehicles'ownersorupgradecostsexceedvehiclecosts,ownerpossessivenessandsocialupheaval.Indemocracies,thepopulaceand/orelectedofficialswouldterminatesuchaplan,innon-democraticnations,amilitaryresponsewouldberequiredtoenforcesuchupgraderegulationsleadingtoinstabilitywhichcouldresultinalossofpoweragainstthecurrentregime.InnationswithfixedcutoffsofretirementofoldvehiclessuchasJapanorSingaporeamandatoryupgradeofallvehiclesalreadyontheroad,orinnationswithoutalowerormiddleclassowningvehiclesorthenationswheresuchwouldbeillegal(whichleavesonlylargebusinessand/orgovernmentand/ortheupperclassowningfossilfuelvehicles),wouldbemorefeasibletomassupgradesoffossilfuelvehiclesalreadyontheroad.

Naturally,electricvehicleswilltakeadvantageofwhateverenvironmentalgainshappenwhenarenewableenergygenerationstationcomesonline;afossilfuelstationisdecommissionedorupgraded.Thereisaconditiontothis,ifagovernmentoreconomicconditionsoranelectricalutilitydecidestorunaregion'selectricalgridoffmorepollutingfossilfuels,ormoreinefficiently,thereversecanhappen.Eveninsuchasituation,electricalvehiclesarestillmoreefficientthanacomparableamountoffossilfuelvehicles.Inareaswithaderegulatedelectricalenergymarket,anelectricalvehicleownercanchoosewhethertorunhiselectricalvehicleoffconventionalelectricalenergysources,orstrictlyfromrenewableelectricalenergysources(presumablyatanadditionalcost),andswitchatanytimebetweenthetwo.

Ifalargeproportionofprivatevehiclesweretoconverttogridelectricity,theexistingpowerplantandtransmissioninfrastructurewouldbenearlysufficient,assumingmostchargingoccurredovernightusingthemostefficientoff-peakbaseloadsources.Buttherewouldbeasignificantneedforadditionalresources(andemissions)ingeneration.However,theoverallenergyconsumptionwoulddiminishbecauseofthehigherefficiencyofelectricvehiclesovertheentirecycle.

Electromagneticradiationfromhighperformanceelectricalmotorshasbeenclaimedtobeassociatedwithsomehumanailments,butsuchclaimsarelargelyunsubstantiatedexceptforextremelyhighexposures.ElectricmotorscanbeshieldedwithinametallicFaraday'scage,butthisaddsweighttothevehicleanditisnotconclusivethatallelectromagneticradiationcanbecontained.

Issueswithbatteries

Old:Banksofconventionallead-acidcarbatteriesarestillcommonlyusedforEVpropulsion

\o"75

watt-hour/kilogramlithiumionpolymerbatteryprototypes.NewerLi-polycellsprovideupto130Wh/kgandlastthroughthousandsofchargingcycles."

.NewerLi-polycellsprovideupto130Wh/kgandlastthroughthousandsofchargingcycles.

Onanenergybasis,thepriceofelectricitytorunanEVisasmallfractionofthecostofliquidfuelneededtoproduceanequivalentsamountofenergy.Issuesrelatedtobatteries,however,canaddtotheoperatingcosts.

Lead-acid

Traditionally,mostEVshaveusedlead-acidbatteriesduetotheirmaturetechnology,highavailability,andlowcost(exception:someearlyEVs,suchastheDetroitElectric,usednickel-iron.)Likeallbatteries,thesehaveanenvironmentalimpactthroughtheirconstruction,use,disposalorrecycling.Ontheupside,vehiclebatteryrecyclingratestop95%intheUnitedStates.Deep-cycleleadbatteriesareexpensiveandhaveashorterlifethanthevehicleitself,typicallyneedingreplacementevery3years.

Lead-acidbatteriesinEVapplicationsendupbeingasignificant(25%-50%)portionofthefinalvehiclemass.Likeallbatteries,theyhavesignificantlylowerenergydensitythanpetroleumfuels--inthiscase,30-40Wh/kg.Whilethedifferenceisn'tasextremeasitfirstappearsduetothelighterdrive-traininanEV,eventhebestbatteriestendtoleadtohighermasseswhenappliedtovehicleswithanormalrange.Theefficiencyandstoragecapacityofthecurrentgenerationofcommondeepcycleleadacidbatteriesdecreaseswithlowertemperatures,anddivertingpowertorunaheatingcoilreducesefficiencyandrangebyupto40%.Recentadvancesinbatteryefficiency,capacity,materials,safety,toxicityanddurabilityarelikelytoallowthesesuperiorcharacteristicstobeappliedincar-sizedEVs.

Chargingandoperationofbatteriestypicallyresultsintheemissionofhydrogen,oxygenandsulfur,whicharenaturallyoccurringandnormallyharmlessifproperlyvented.EarlyCriticalownersdiscoveredthat,ifnotventedproperly,unpleasantsulfursmellswouldleakintothecabinimmediatelyaftercharging.

Lead-acidbatterieshavebeenre-engineeredbyFireflyEnergy,increasinglongevity,slightlyincreasingenergydensity,andsignificantlyincreasingpowerdensity.Fireflyisexpectedmarketlightweightvehiclebatteries,eitherdirectlyorthroughmanufacturingpartnersin2008.

Lead-acidbatteriespoweredsuchearly-modernEVsastheoriginalversionsoftheEV1andtheRAV4EV.

Nickelmetalhydride

Nickel-metalhydridebatteriesarenowconsideredarelativelymaturetechnology.Whilelessefficientincharginganddischargingthanevenlead-acid,theyboastanenergydensityof30-80Wh/kg,farhigherthanlead-acid.Whenusedproperly,nickel-metalhydridebatteriescanhaveexceptionallylonglives,ashasbeendemonstratedintheiruseinhybridcarsandsurvivingNiMHRAV4EVsthatstilloperatewellafter100,000milesandoveradecadeofservice.Downsidesincludethepoorefficiency,highself-discharge,veryfinickychargecycles,andpoorperformanceincoldweather.GMOvonicproducedtheNiMHbatteryusedinthesecondgenerationEV-1,andCobasysmakesanearlyidenticalbattery(ten1.2V85AhNiMHcellsinseriesincontrastwithelevencellsforovonicbattery).ThisworkedverywellintheSaturnEV-1.Itremainsaviableandpracticalsolutiontoday,asfarasasuperioralternativetotheleadacidbattery.

However,fornon-technicalreasonsneithercompanywillprovidetheirNiMHbatteryforautomotiveapplications-apolicystrictlyenforced.Moreover,GMnowownspatent(s)onsomeproprietarytechnologyandprocessesusedtomanufacturethistypeofbattery.Thereforenoothercompanycanproduceasimilarbattery(withcapacitieslargeenoughforelectricvehiclepropulsion)withoutinfringingGM'spatents.So,despiteitstechnicalsuccess,unlessGMwillchangetheirpositionontheissueNiMHtractionbatterytechnology,itisconsideredadeadend.InlightofthelatestdevelopmentsinlithiumbasedbatterytechnologyandpatentissuesofNiMH,lithiumwillmostlikelyrepresentthefutureEVbatterytype.

Zebra

Thesodiumor"zebra"batteryusesamoltenchloroaluminate(NaAlCl4)saltastheelectrolyte.Alsoarelativelymaturetechnology,theZebrabatteryboastsagoodenergydensityof90Wh/kgandnearlosslesscharge/dischargecycles.Sincethebatterymustbeheatedforuse,coldweatherdoesn'tstronglyaffectitsoperationexceptforinincreasingheatingcosts.IthasbeenusedinseveralEVs.ThedownsidestotheZebrabatteryincludepoorpowerdensityandtherequirementofhavingtoheatth