Seite - 150 - in Emerging Technologies for Electric and Hybrid Vehicles

Energies 2017,10, 1503 2.3.3.Open-WireFaultDiagnosis In themulti-cellLIBpack, thevoltageofeachcellneeds tobemonitored inreal-time. Inaddition, battery-cell balancing is required for thecells that areunbalanced, that is,when theSOCofoneor more cells areunequal. Therefore, there aren+1 (n is the cell number in thebatterypack)wires from the cells to the balancing board. It is often difficult to ensure that all thewires are always connectedproperlyduringtheactualoperation. Someof thewiresmaybe looseordisconnecteddue to frequency impactorvibration fromthemechanical structure thatencloses thecells. Thefloating voltageof theLTC6804 inputpinswillbearound0,orhigher than5Vwhentheopen-wirecondition occurs. Basedonthefloating-voltagesensor, the fault-diagnosis strategy isproposedtodiagnose the open-wire fault. The failurewillbedisplayedvia thegraphical-user-interface (GUI) toalert theuserof the fault that requiresattention. In thiscase, it isnotpossible toautomaticallyconnect thewire,as it will requirehumaninvolvement. Theflowchartof thediagnosis strategycanbeseen inFigure7. Figure7.Flowchartofopen-wire faultdiagnosis strategy. Adual-entrance interface isdesigned fordifferentusers toconfigure thesystemfor the initial use. Severaldefaultparameters forvariousbatterieshavebeenstored in thesystemmemoryforease ofoperation. Theordinaryusersdonothavetoworryabout theexactvalues. Instead, theyneedto select the typesofbatteries, thebattery-packgrouping information, thebattery-cell rated capacity andthemaximumdischargingcurrent. Thesystemwill automatically initialize thecorresponding parameters according to the informationprovided. Currently, four lithiumbattery types, such as LiFePO4,Li-ion,LiCoO2andlithiumpolymers,aresupported in theproposedsystem. Inaddition, the systemhas anoption to customize theparameter values such asprotection-voltage level and charging- or discharging-current limitation for further analysis. The entrance design for system parameterconfiguration isdescribed inFigure8. Figure8.Entrancedesignforsystemparameterconfiguration. 150