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ESSPreliminaryDesignReview
May20,2015
Year One Communications Plan (Feel free to add some school spirit to the title page)
Team:
Date:
1
Year 3: Progress Report 3
April 10th, 2014
I
TABLEOFCONTENTSTableofContents........................................................................................................................................I
TableofFigures..........................................................................................................................................II
ListofTables...............................................................................................................................................II
TableofAcronyms......................................................................................................................................II
ProjectPlan................................................................................................................................................8
ESSTimingPlan......................................................................................................................................8
ESSDesignManagementProcess...........................................................................................................8
RisksandRiskMitigationPlans...............................................................................................................8
VehicleArchitectureOverview...................................................................................................................9
PowerflowDiagram................................................................................................................................9
Vehicle-LevelRequirements...................................................................................................................9
Enclosure/MechanicalPackaging.............................................................................................................9
PackagingofBatteryHardware..............................................................................................................9
SealingandVenting..............................................................................................................................11
LVandHVWireRouting.......................................................................................................................13
CoolantLineRouting............................................................................................................................14
ComponentMounting..........................................................................................................................14
ESSAssembly........................................................................................................................................16
ElectricalDesign.......................................................................................................................................22
HVSchematic........................................................................................................................................22
HVInterlockLoop.................................................................................................................................23
ElectricalIsolation.................................................................................................................................24
Safety.......................................................................................................................................................24
PreliminaryFailureMode.....................................................................................................................24
MSDPlacement....................................................................................................................................25
FingerProofingandSecondaryCover..................................................................................................26
ThermalSystem........................................................................................................................................27
RequirementsforBatteryThermalPerformance.................................................................................27
CoolingMethod....................................................................................................................................28
InitialThermalSystemAnalysis............................................................................................................28
Charger.....................................................................................................................................................30
CompatibilitywithBatteryHardware...................................................................................................30
II
EMI...........................................................................................................................................................31
DesignFeaturestoMitigateEMIImpacts.............................................................................................31
Appendix..................................................................................................................................................32
SupplementaryESSDesignCADImages...............................................................................................32
SupplementarySchematics..................................................................................................................43
TABLEOFFIGURESFigure1ESSGANTTchart...........................................................................................................................8Figure2:FMEATable.................................................................................................................................8Figure3:PowerFlowDiagram...................................................................................................................9Figure4:CompleteESSassembledinvehicle..........................................................................................10Figure5:Structuralsupportrailsattachedtovehicleframe....................................................................11Figure6:Detailviewofsealinginterfaceandlatches..............................................................................12Figure7:Pressurereliefvalvelocation....................................................................................................12Figure8:Lidinterfaceatcenterofthebatterypack,clampandlidsealvisible......................................13Figure9:LocationofHVpacksideconnectorallowingsimplewireroutingtojunctionbox..................14Figure10:BatteryModulemountingwithindexingstructurevisibleinyellow......................................15Figure11:Removablecontrolhardwareshelfwithcomponentsattached.............................................16Figure12:Viewofcontrolhardwareshelfinstalledinpack....................................................................16Figure13:ESSHVSchematic....................................................................................................................23Figure14:HVILSchematic........................................................................................................................24Figure15:ESSDFMEAChart.....................................................................................................................25Figure16:Interlockingtwoliddesign......................................................................................................26Figure17:MSDlocationfrontview..........................................................................................................26Figure18:Tempriseat50%SOC.............................................................................................................29Figure19:TempRiseat10%SOC.............................................................................................................29Figure20:SimscapemodelofESS............................................................................................................30
LISTOFTABLESTable1Acronyms.......................................................................................................................................IITable2:ChargeCurrentLimits.................................................................................................................27Table3:DischargeCurrentLimits............................................................................................................28
TABLEOFACRONYMSTable1Acronyms
Acronym MeaningBEV BatteryElectricVehicleBCM BatteryControlModuleCSM CurrentSenseModuleCAD Computer-aidedDesign
III
CD ChargeDepletingCS ChargeSustainingDC DirectCurrentEDS EmergencyDisconnectSwitchEDM ElectronicDistributionModuleEMI ElectromagneticInterferenceESS EnergyStorageSystemEREV ExtendedRangeElectricVehicleEV ElectricVehicleFt FeetFMEA FailureMode&EffectsAnalysisG GravitationalConstantHV HighVoltageHVAC Heating,ventilation,andairconditioningHVIL HighVoltageInterlockLoopICE InternalCombustionEngineIVM InitialVehicleMovementKm KilometerL Liter
MSD ManualServiceDisconnectMVEC MultiplexedVehicleElectricCenterNYSR Non-YearSpecificRulesPHEV Plug-inHybridElectricVehicleSec SecondRPN RiskPriorityNumberSOC StateofChargeVTS VehicleTechnicalSpecificationsUW UniversityofWashingtonWh Watt-hour
8
PROJECTPLANESSTimingPlanError!Referencesourcenotfound.showstheEnergyStorageSystem(ESS)GANTTchart,whichdisplaysatimescheduleofkeyactivities
andtasksintegraltotheESSdesignandintegrationprocessfromyear1throughyear2.Thelegendatthetopofeachchartshowscolor-markedsquaresdefiningplanning,actual,andcompletestagesoftheproject.Theplanningstageofaprojectdefinessettingupaprocedureanddeadline,whichtypicallyonlytakesaweekdependingontheactivity.Theactualstageoftheprojectiswhentheteamstartsfulfillingtheplanandimplementingtasks.Andthecompletestageoftheprojectmarkstheexpectedprojectdeadline.ThedesignprocessbeginsinAprilofyear1andfinishesthebatterypackintegrationprocessneartheendofAprilofYear2.Keybatterypackdesignactivitiessuchastheenclosuredesign,modulearrangement,component-shelfdesign,andpowerrequirementsarestaggeredacrossAprilallbeforePreliminaryDesignReview(PDR)SubmissionbeginsinearlyMay.OncePDRandFDRSubmissionarecomplete,weplantoorderthesekeycomponentsthroughA123andvariousothersourcesinmid-July.AtthebeginningofYear2FallQuarter,theelectricalteamwillassemble,test,andadjusttheBatteryPackuntilwereceivetheChevrolet2016CamaroinlateNovemberorearlyDecember.Finally,theBatteryPackInstallationisplannedtobegininJanuaryandstretchthroughtheendofAprilbeforeYear2Competition.
Figure1ESSGANTTchart
LEGEND: Plan Actual CompleteEach year starts in September (Quarter System)
Year 1 2
MONTHS Apr. May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr.
ACTIVITY %COMPLETE WEEKS 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52Enclosure Design 100%Module Arrangement 100%Component Shelf Design 100%Power Requirements 100%PDRSubmission 100%Cooling Plan & Simulation 50%Connector Placement & Wire Routing 25%PartSourcing 25%FDRSubmission 0%ReceiveA123Parts 0%ReceiveSourcedParts 0%Outsourcingmanufacturing 0%AssembleBatteryPack 0%ReceiveCamaro 0%BenchTest&BalanceBatteryPack 0%BatteryPackInstallation 0%
ESS Time Schedule
8
ESSDesignManagementProcessTheelectricallead,JakeGarrison,isprimarilyresponsibleforoverseeingthebatterypackdesignandintegrationintheChevrolet2016CamarothattheUWEcoCARwillreceiveattheendofthisyear.TheaboveGANTTchartbroadlyoutlinesthetimingplanfortheESSbatterypackdesignandintegrationoverthecourseofthisyearandnextyear’sEcoCAR3competition.Theworkonthedesignandintegrationofthebatterypackissplitintotwosub-teams:mechanicalandelectrical.MatthewPalmerisinchargeofthemechanicalteamworkingonthisproject,anddirectlyreportshisprogresstoJakeGarrison.Matthewhasfullpowerovermakingdecisionsonmaterialdesign.Alldecisions,however,mustbeapprovedbyJakeGarrison.WhileJakeGarrisonhasexecutivepowerandauthorityoverthisproject,hisworkonthedesignandintegrationwillbereviewedbytheengineeringteamleadsandourfacultyadviserProfessorBrianFabien.Openissuessuchascomponentsourcingwillbehandledwithaweeklymeetingofelectricalteammemberswhoarepresentforthesummer.TheelectricalteammembersinthelabwillalsosendaweeklyreporttoJakeGarrisontoupdatehimonkeyactivities/tasksaswellastoaskanyquestionsinlightofuncertainty.Intimesofuncertainty,JakeGarrisonwillreachouttooneoftheorganizeradvisers,JesseAlley,foradviceandguidance.RisksandRiskMitigationPlansUWEcoCARusesFailureModeandEffectsAnalysis(FMEA)toconduct,organize,andassessriskanalysis.TheFMEAtableshowninFigure2calculatesaRiskPriorityNumber(RPN)bymultiplyingtherisks’severitybyitschanceofoccurrencebyitsdifficultyofdetection.Eachoftheabovecategoriesarequantifiablyrankedfromascaleof0-10,meaningthehighertheRPNthehigherrisk-levelitrepresents.Belowisalistofbatterypackdesignriskswiththeireffectsandrootcausesaswellasrespectivecontingencyplansintheeventoftherisks’occurrence.Thehighest-levelriskwiththebatterypackdesignisthepotentialissuewithaninadequatecoolingsystem,whichcanresultintheoverheatingofthebatterypack.Thisrepresentsasignificantriskinitsseverityanddifficultyofdetection.Throughcarefulplanninganddesignefforts,theteamhasmanagedtoreduceallriskschanceofoccurrencetoarelativelylownumber(1-3range),thusproactivelylesseningRPNsofESSrisks.
Item: Battery Pack Design
Involved Teams:
WrongDimensionsUnabletomount,setbackincostandtime,andrequiresredesign
7IncorrectprocessingofCADtodesign
3 2 42MoreintensiveCADprocessingandredesign
Unabletoimplementduetosizeconstraint
NotMeetForceConstraints
Packdesigndoesnotpasstheefficientdesignreview,setbackintime
5Lackoftrainingandforesightinchoosingmaterials
2 1 10 RedesignmaterialselectionIdentifiedeitherbydesignreviewpaneloroursimulations
CoolingSystemInadequateCoolingSytem
Overheat 7Lackofairflowfrompoordesign
3 8 168 Addfansandventsinternally Testingonthevehicle
HighVoltage SafetyShockandteammemberinjury
10Poortraininganddesignisasafetyrisk
1 1 10Trainingtutorialsandmandatorytestingonrulesoutlinedinsafetybinder
Quarterlytrainingfornewmembers
NotfitsizeconstraintNotservicableandnotsafe
4Poordesignandforesight
5 1 20Explorealternativeoptionsforconsumeracceptability
Notbeingabletoofitsuitcasesincar,andnotbeingabletoservicepackasneeded
ConflictwithrulesSetbackfromgettingpackcertifiedbycompetition
6Miscommunicationsbetweenorganizersandteam
2 1 12Thoroughcommunicationswithorganizerstoconfirmcompliancewithrules
Periodicemailsandcallstoorganizers
Packaging
EnclosureDesign
ProcessFunction PotentialFailureMode PotentialEffect(s)ofFailure
Sev
PotentialCause(s)/Mechanism(s)of
FailureContingencyPlan ContingencyPlanTriggers
FAILURE MODE AND EFFECTS ANALYSIS
All engineering teams
Occur
Detec
RPN
Figure2:FMEATable
9
VEHICLEARCHITECTUREOVERVIEWPowerflowDiagram
Figure3:PowerFlowDiagram
Vehicle-LevelRequirementsInordertoachievetheperformancedesired,UWEcoCARhaschosentouseanA123batterypackwith7x15s3pconfiguration.Thispackgivesthehighestpoweroutputanditisalsothemostpackageablesetupavailablefortheteam’sapplication.Thispackisratedat58.8Ahincapacityand18.9kWhinenergy,whichprovidesaround50milesofEV-range.Inaddition,thissetupprovidesapeakpackvoltageof375Vandpeakcurrentof612Afor10seconds,whichisdesiredforanaccelerationof5.3secondsfromIVM-60mph,2.9secondsfrom50-70mphandatopspeedof85mph.
ENCLOSURE/MECHANICALPACKAGINGPackagingofBatteryHardwareAtthebeginningofthisproject,theteamestablishedspecificgoalstooptimizetheintegrationwiththeexistingstructure,thepracticalityofassembly,andtheeaseofserviceability.ThesethreethemesgovernedthedecisionmakingforallsectionsoftheESSpack.
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Figure4:CompleteESSassembledinvehicle
Thepackwillfitwithinthevehiclestructurebyutilizingatiereddesigntoconformtotheshapeofthevehicle’stieredtrunk(SeeFigure4).Itwillconsistoffrontandrearhalvesthatwillberigidlyconnectedtoformtheenclosure.Thepackwillbesealedandcoveredwithatwo-piecelid.Thepackitselfwillbeattachedtofoursupportrails,stretchingbetweentheframerailsoneachsideofthevehicle(SeeFigure5).Tabswillbeweldedtotheexistingvehicleframethatwillallowthesupportrailstobeattachedtothevehicle.Theseweldedtabsandrailswillbedesignedandanalyzedtoensuretheymeetthestructuralrequirementsofthe8Gverticaland20GlateralstaticloadconditionswhentheESSpackisfullyinstalled.
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Figure5:Structuralsupportrailsattachedtovehicleframe
TheenclosurewillbeconstructedfromaluminumsheetandthetwolidswillbeconstructedfromBoltaron™.Aluminumischosenforitsstrengthandeaseofmanufacturing,andBoltaron™ischosenforitsabilitytobeformedintocomplexsurfacesanditslowelectricalandthermalconductivity.Insidethepack,thebatterymoduleswillbeorientedintworows.Theupperhalfofthepackwillhousearowof4moduleswhilethelowerhalfwillhousearowofthreemodules.Eachofthesetworowswillbemountedtoasecondarystructureinsidetheenclosuredesignedtofixthemodulestothestructuralsupportrailsandprovideevenspacingbetweenthemodules.SeetheComponentMountingsectionforfurtherdetailsonthissubsystem.TheotherESScomponentsincludingtheBSM,CSM,EDM,andMSDreceptaclewillbemountedonaremovableshelfwithintheenclosure.Thisshelfwillmountdirectlyabovethebatterymodulesinthelowerenclosure(SeeFigure11).Itwillallowforeasyassembly,effectiveuseofspace,andsimpleservicing.Serviceandinstallationofthebatterymodulesintheenclosurecanbeperformedfromeitherthetrunkorthroughtherearpassengerseatopening(seeAppendix:SupplementaryESSDesignCADImages).Thetwo-piecelidsecuredbydrawlatcheswillallowforeasyaccesstotheinsideoftheenclosure.Clearancesbetweentheenclosureandthesurroundingtrunkstructurearerelativelysmall,buttheenclosureiscapableoffittingwithintheacceptablelocationsdefinedbytheNYSRandnoportionoftheESScomponentsarelocatedinthedesignatedcrushzones(seeimagesinAppendix:SupplementaryESSDesignCADImages).SealingandVentingThebatterypackwillbesealedtopreventboththeingressandexitofvapors,moisture,andcontaminants.Theinterfacebetweentheenclosureandthelidwillbesealedbysiliconrubberedgetrim.Thelidwillbeclampeddownwithspringdrawlatchesthatwillmaintainclampingforceonthelidandthusguaranteethatthelidremainssealedeveninthecaseofpositivepressureinsidethepack(seeFigure6).Allholesthroughtheenclosurewillhavegasketsorothersealants.
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Figure6:Detailviewofsealinginterfaceandlatches
TheESSdesignalsoutilizesaninlinepressurereliefvalvelocatedadjacenttothepackside-HVconnector(seeFigure7),thatwillmaintainthepacksealbutallowinternalpressureandoff-gassingtoberoutedoutsideofthepassengercompartment.
Figure7:Pressurereliefvalvelocation
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Figure8:Lidinterfaceatcenterofthebatterypack,clampandlidsealvisible
LVandHVWireRoutingThewireroutingwithintheESSistobeimplementedwithsafety,serviceability,andprotectionofcomponentsinmind.Specifically,thephysicaldesignofspansofcable,connectionsandterminals,andwireintersectionsshalladheretotherelevantsectionsoftheNYSR,whilealsoservingtheteam’spurposeandmodularESSdesign.ThefollowingguidelinesandideasareinfluencedbytherelevantsectionswithintheNYSR(I-3DesignRulesforHighVoltageSystems,I-4DesignRulesforEnergyStorageSystems),andareadaptedtotheteam’sspecificpackconstruction.AswireroutingwithintheESSisstillintheconceptualstageandnodesignshavebeenmadeconcrete,manyoftheseguidelineswillrequirefurtheranalysisandperhapsrevision.Theteam'snexttaskistoincludewireroutinginCADmodeltosolidifythefinalstrategy.HVExteriorConnection:ThemodulardesignoftheESSallowsforoptimalpositioningoftheHVterminal.Theterminalisplacedsuchthattheinternalpositiveandnegativecablesareunderlowbendstresswhenaccommodatingtheconnection.Theexteriorterminalfacestowardthefrontofthevehicleandiscenteredalongthevehicle,whichallowsforoptimalconnectingtotherearjunctionbox.Thecableshieldingisalsofedthroughthisconnector(SeeFigure9).
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Figure9:LocationofHVpacksideconnectorallowingsimplewireroutingtojunctionbox
LVExteriorConnection(NotyetinCADmodel):DesignconsiderationsforthisconnectionincludemitigationofEMIonLVcommunicationssignals,andexternalroutingoptimization.TheLVconnectorislikelytobeplacedontherearportionoftheenclosure,oneithertheleftorrightside.Internally,thisallowsLVcommunicationlinestohaveoptimaldistancefromHVcablestomitigateEMI(SeeEMISection).Externally,theconnectorroutestheLVthroughthepassengercompartmenttowardsthesupervisorycontrollerinthefrontofthevehicle.PossibleShelfConfigurations:InordertoreducetheamountandcomplexityofHVlinesaroundtheshelfareaoftheESS(wheretheCSM,MSD,BCM,andEDMarelocated),theteamisconsideringafewdifferentoptionsintermsofinterfacingshelfcomponentswithconnectionsfromthebatterymodules.Inordertoconnecttheshelftothemodules,thedesignwilleitherhaveconnectionsaroundtheedgeoftheshelfupfromthemodules,orcomingthroughtheshelf.Witheitheroftheseoptions,theteamstillhastheissueofconnectingeachshelfcomponent.Powerdistribution(busbars)thatsitsontheshelfmaybeonesolution.Thiswouldinvolvehavingcustomlaminated/insulatedbusbarsinsteadofcableroutingthatcouldbecustom-builtbyMersenfortheteam’sapplication.Othersolutionsmayincludesimplykeepingseparatecables,orre-arrangingshelfcomponentstooptimizespaceusageandensuretheteamisnotcompromisingonminimumbendradiusof1/0cable.Forreference,theChamplainEXRAD1/0hasaminimum-bendingradiusof105mm,orapproximately4inches.CoolantLineRoutingUWESSwillutilizepassivecooling.RefertoThermalSystemsectionforadditionaldescription.ComponentMountingInsidethepack,thebatterymoduleswillbemountedtoaninternalstructurethatwillallowforevenspacingandsturdyattachmentofthemodules(SeeFigure10).Thisstructurewillbeconstructedfromaluminumandwillbemountedthroughtheenclosuredirectlytothesupportrails.Themountingstructurewillalsoutilizeapolycarbonateindexingstructurethatwillaidinaligningthemodulesduring
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assemblyandmaintainingmodulespacing.Eachmodulewillbespacedaminimumof10mmfromadjacentmodulesorenclosurewallsoneitherside,allowingforthermalexpansionandcoolingofthemodules.ThissecondarybatterymodulemountingstructureandconnectionswillalsobedesignedandanalyzedtoensurestructuralrequirementsspecifiedbytheNYSRaremet.Additionally,allthehardwareusedtoattachtherails,enclosure,andmoduleswillbeclass12.9andlockinghardwarewillbeusedwhereapplicable.
Figure10:BatteryModulemountingwithindexingstructurevisibleinyellow
TheBCM,CSM,EDM,andMSDreceptaclewillbefixedtoaremovablepolycarbonateshelf(SeeFigure11:Removablecontrolhardwareshelfwithcomponentsattached)andwillbeassembledoutsideoftheenclosureforconvenient,safeassembly.Aftereachcomponentisattached,theshelfismountedintheenclosureabovethelowerrowofbatteriesandissupportedatthecornersbyfourmountingbrackets.FurtherdiscussionoftheMSDmountingcanbefoundintheSafetysection.
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Figure11:Removablecontrolhardwareshelfwithcomponentsattached
Figure12:Viewofcontrolhardwareshelfinstalledinpack
Theplacementoftheshelfwillbeabovethelowerassemblyofbatteriesforeaseofservicing(SeeFigure12).Additionally,alllowerbatteriescanbeaccessedbysimplydisconnectingandremovingtheshelffromtheenclosure.Thisassemblygivesthebestbalanceofspaceconservationandaccessibility.ESSAssembly1. Weldstructuralattachmenttabsontopofvehicleframerails.InstallsupportrailsinCamaro,twoin
thefrontofthetrunkrightbehindtherearseatandtwointhesparetirewell.Bolttherailstothetabs.
17
2. InstalltheHVconnectorandpressurereliefvalveonthefrontoftheloweraluminumenclosure.Lineinteriorofbothenclosureswithelectricallyinsulatingmaterial.(SeesectiononElectricalIsolation)
3. Installbothaluminumenclosuresinthevehicletrunkontopofthesupportrails.Bolthalves
together.
18
4. Insertbatterysecondarystructureintoenclosures.Attachstructuretosupportrailsbyinstalling
boltsthroughenclosuretounderlyingrails.
5. Mountthebatterymodulestothesecondarystructurewithinslotsdesignatedbytheindex.Install
fourmodulesinthefrontenclosureandthreeintherearenclosure.Oncethemodulesareinplace,
19
installboltsthroughmodulesintothesecondarystructure.Installwiringbetweenmodulesaccordingtoschematic.
6. Installshelfmountsflushagainstthesidewallsofthelowerenclosure.
20
7. AttachtheCSM,BCM,EDM,andMSDreceptacletothecontrolhardwareshelf.Installwiring
accordingtoschematic.
8. Installtheassembledcontrolhardwareshelfintherearenclosureandbolttothefoursupport
brackets.Completeallnecessaryelectricalwiringandconnections.
21
9. Installthelidonthefrontenclosure,ensureproperfitandsealandsecureittotheenclosureusing
thedrawlatches.
10. Installthelidontherearenclosure,ensureproperfitandsecureittotheenclosureusingthedraw
latches.
22
11. InstalltheMSDplugontherearlid.
ELECTRICALDESIGNHVSchematicHVschematicofESS(SeeFigure13)showshighvoltageconnectionsbetweenthecomponentsandsomeofthelowvoltageBCMandHVILwiring.Thegenerallayoutofthecomponentsinthefigureissimilartothephysicalmodel.NoticetheMSDsplitsthepack.ForaschematicofourHVsystem,seetherespectivesectionintheAppendix.
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Figure13:ESSHVSchematicHVInterlockLoopThepurposeofHVIListodisconnectthehigh-voltageDCbatteryfromtheelectricsystemtoavoiddamageanddangertothedriver.Thebatterywillbedisconnectedinthefollowingsituations:
• Inertiasensoristriggeredwhenthecarhasaccelerationgreaterthan8G’s,whichistypicalinacrash
• EmergencyDisconnectSwitches(EDS)inthefrontandbackofthecararepressed• LVconnector,HVconnectororMSDisdisconnected• 12Vbatteryfailsorisdisconnected
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Figure14:HVILSchematic
ElectricalIsolationToensurethattheexteriorofthebatterypackiselectricallyisolated,theteamhaschosentousealidconstructedfromBoltaron™withproperlidsealingdescribedintheSealingandVentingsection.Inaddition,theinteriorofthealuminumenclosurewillbecoveredupwithNomex®electricalisolationfoamwhichpreventstheenclosurefromhavingcontactwiththecomponentswithin.Inaddition,thehighvoltageconnectorandtheMSDaredesignedtobefingerproofandacrylicinsertsnearthebatteryterminalswillbeusedtobetterprotectthemaswell(SeethesectiononFingerProofingandSecondaryCoversectionformoreinformation).Finally,allthewiresandbusbarsusedinESSarecoveredwithhighdielectricinsulatingmaterial.
SAFETY
PreliminaryFailureModeTheESSstatusiscontinuouslymonitoredbythesupervisorycontrolsystemtodetectonsetofanyfailuremodessuchasoverheating,groundfault,communicationfailure,faultcurrentetc.TheDFMEApreparedfortheESS(SeeFigure15)describingfailuremodesandsubsequentresponseactionrequiredforavoidinganyfurtherdamagetothesystemservesasthebasisforthefailurediagnosticsignalsfromthesupervisorycontroltothecomponentsandthedriver.
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Figure15:ESSDFMEAChart
MSDPlacementToensurethattheESSissafetoservice,aMSDwillbeincorporatedintothedesign.GreatcareistakenintheconsiderationoftheplacementoftheMSD,asitneedstobeeasilyaccessibleforservicingandmustalsopreventaccesstotheESSwithoutbeingdisconnected.Forthisreason,theMSDplugislocatedontopofthelidoftheenclosureandiseasilyaccessiblefromtheopeningofthevehicletrunk.Thepackisdesignedtohavetwosections,takingadvantageoftheCamaro’stieredtrunkdesign.Tofitintothisspace,thebatteryenclosurewillhaveatwo-piecelid.Thebacklidwillinterlockintothefrontlid,makingitsremovalimpossiblewithoutfirstremovingthefrontlidandtheMSD.
26
Figure16:Interlockingtwoliddesign
Inturn,theMSDwillpreventthefrontlidfrombeingremoved.ThisistoensurethatnopartoftheESScanbeaccessedwhilefullyenergized.Toaccomplishthis,thereceptacleportionoftheMSDwillbemountedtotheshelfdirectlybelowthefrontlid.TheplugportionoftheMSDwillpinthefrontlidtotheinternalshelfpreventingthefrontlid'sremovalwithoutdisconnectingtheMSDplug.
Figure17:MSDlocationfrontview
FingerProofingandSecondaryCoverExteriorfingerproofingissatisfiedthroughthetwoBoltaron™lidsandthetwobaseenclosures.Theywillbesealedtogethertightlywithspringlatchestopreventaccess(inpurple,Figure17).AllHV
27
exteriorreceptacles(MSD,HVconnectorandTestConnector)aredesignedtobefingerproofaswell.Withintheenclosure,allbatterymoduleterminalsandcomponentterminalswillbecoveredbyinsulatingacryliccoverssecuredbyVelcro.Allwireswillalsobecoveredbyinsulatingmaterial.Finally,asstatedintheElectricalIsolationsection,thepackwillbelinedinhighdielectricNomex®materialtopreventelectricalshortsthroughthealuminumenclosure.
THERMALSYSTEMRequirementsforBatteryThermalPerformanceAccordingtodocumentationsuppliedbyA123,theoptimalperformanceofthe7module15s3ppackoccursatcelltemperaturesfrom20to50°C.ThiscanbevalidatedthroughtheinformationonTable2andTable3.
Table2:ChargeCurrentLimits
Forchargingcurrent,themaximumcontinuouscurrent(60A)canoccurfortemperaturesrangingfrom10to50°CatallSOCanddropsatapproximately2A/degreeCoutsidethatrange.Alsothemaximum10-secchargecurrent(300A)occursfortemperaturesbetween20and50°CforallSOCwithanalmostimmediatedropoutsidethatrange.
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Table3:DischargeCurrentLimits
Fordischargecurrents,themaximumcontinuouscurrent(180A)occursfortemperaturesbetween0and50°CatallSOCanddropsalmostimmediatelyoutsidethatrange.Alsothemaximum10-secdischargecurrent(612A)occursfortemperaturesbetween20and50°Candhaslessofatemperatureeffectasstateofchargeisincreased.Inallcasescellshaveamaximumoperabletemperatureof50°C.Basedontheseresultsitcanbeshownthatthebatterypackperformsclosetoidealattemperaturesbetween20and50°C,withlesseffectsfromSOCwhenattemperaturesabove30°C.CoolingMethodTheUWESSwillutilizepassivecooling.TheteamlearnedthroughEcoCAR2,theprovidedA123docs,andsimulationsoutlinedinthissectionthatthebatteriesoperatemosteffectivelybetween20and50°C,withslightlybetterperformancesabove30°Candthroughpassiveaircoolingtheapproximatemaximumtemperatureriseislessthan20°C.InitialThermalSystemAnalysisTheteambegantheanalysiswithdatafromA123,whichwasderivedfromtestinglogswithoutactivecoolingrelyingonheattransferthroughthepacktoambient.Thefirsttesthadanambienttemperatureof25°C,withcurrentofapproximately48Aand51.5%capacityused.Basedontheseconditionsonlya5°Cincreaseofcelltemperaturewasseenoveraperiodof44minutes.
29
Figure18:Tempriseat50%SOC
Thesecondtesthadanambienttemperatureof25°C,withcurrentofapproximately165Aand90%capacityused.Basedontheseconditions15.5°Cincreaseofcelltemperaturewasseenoveraperiodof17.7minutes.
Figure19:TempRiseat10%SOC
Thesetestsshowthatinbothnormalcontinuousoperationandmaximumdischargethatthepackremainsbelowthesafemaximumcelltemperatureincreaselimitof20°Casstatedonthe15s3pmodulespecificationsheetprovidedbyA123.AccordingtothespecificationsprovidedbyA123thepackscellsmustremainwithin8°Cofeachotherforproperoperationandtopreventdamage.Theproposedpackdesignhasauniformdistributionofmodelswhichallowsforevenheatconvectionbetweenthem.Thenextstepofanalysisisthroughmodelingofthesystem.ThemodelconsistsofadualparallelRCcombinationalrepresentationofalithiumioncellwithvaluesderivedfromchargeanddischargecharacteristicsprovidedbyA123.Heatgenerationisdirectlyderivedfrompowerdissipatedthrough
30
internalresistanceineachcell.Thesecellsareconnectedina15s3pmodularorientationwiththermalconvectionbetweeneachdirectlyproportionaltosurfaceareaandconvectionheattransfercoefficientforeachcell.Sevenofthesemodulesareconnectedinserieswiththermalconvectionbetweeneachproportionaltosurfaceareaandconvectionheattransfercoefficientforeachmodule.
Figure20:SimscapemodelofESS
Currentlythismodelismissingthenecessarycoefficientsforthermalconvectionbetweencellsandmodulesbasedonaircooling.TheteamisintheprocessofobtainingvaluesfromA123andestimatingparametersbasedontheUWdesign.Currentlythemodelselectricalcharacteristicsandpowergenerationisveryaccurateandmatchesreallogsquiteclose.ThismodelwillbeusedtotestconditionsnotsuppliedbyA123andaddrealisticfactorsrelatedtopackconditions.
CHARGERCompatibilitywithBatteryHardwareTheUWdesignusesawatercooledBrusaNLG5133.7kWonboardcharger.Thechargerhasaninputvoltagerangeof100-264V(48-62Hz)whichisperfectforpracticallyanystandardhomeplugin.The7module15s3pbatterypackhasavoltagerangeof263-378Vandthechargerhasanoutputrangeof200-520Vthusthevoltagesarecompatible.Additionally,thepackhasamaximumchargecurrentof60AandtheBrusachargerhasanoutputchargingcurrentof12.5Awhichmeetscurrentrequirements.BrusaalsohastheoptionofpreprogrammingthechargerfortheA1237module15s3pbattery
31
managementsystemandcommunicatesviaCAN,whichmakesitanidealintegration.Thechargerisalsolightweightatonly6.2kgand93%efficientanddirectlydesignedforautomotiveapplications.
EMIDesignFeaturestoMitigateEMIImpactsIndesigningtheESS,appropriatestepswillbetakentoensurethatthefollowingcompetitionrulesareadheredtoinordertoreduceunwantedEMIbothwithinandoutsideofthepack.Oncepreliminarydesignsareaccepted,wewillbeabletosimulateoursystemandconductananalysisoftheEMIeffectsonoursystem.NYSRI-3.6:ExposedHighVoltageandHighVoltageConnections
• ExposingHVsystemsmustnotbeaprerequisiteforaccessingnon-HVsystems• Allshieldedconnectorsmustfollowpropergroundingpracticesandmustbecheckedforlossof
isolationthroughtheshielding.Note:Theteamhaschosentouse1/0ShieldedEXRADHVcableintheinterioroftheESS.ESSEnclosureFortheESSenclosure,theteamhaschosentousealuminumcasingandBoltaron™lid.Inaddition,alayerofNomex®electricalinsulationfoamwillbeusedintheinteriorofthealuminumcasing(asoutlinedinourElectricalIsolationsection).Withthissetup,wecanmitigatetheEMIfromESStotheothercomponentsoutsidetheESS.WireroutingStrategyTheteamisfollowingtherulesoutlinedbelowforwirerouting.Whencircuitscannotbeappropriatelysegregated,theywillbecrossedperpendicularlyinordertominimizeinter-circuitnoisetransmission.NYSRI-3.10:SegregationofHVandLVCircuits
• IfHVlineis<100V,spacingmustbe1cm(0.4in.)• IfHVlineis≥100and≤200V,spacingmustbe2cm(0.75in.)• IfHVlineis>200V,spacingmustbe3cm(1.2in.)
ShieldTerminationStrategyToavoidterminatingcableshieldsinalocationaninconvenientlocation,thecableshieldingwillallbegroundedwithinthejunctionboxoftheESS.
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APPENDIXSupplementaryESSDesignCADImages
Linkback:PackagingofBatteryHardware
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SupplementarySchematics
Linkback:HVSchematic
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