Page - 134 - in Emerging Technologies for Electric and Hybrid Vehicles

Energies 2016,9, 563 squarederrorbetweenthemeasuredvoltageandthesimulatedvoltagebymodel1 is less than1%. However, itperformedtheworst in thesecondtest. Thegoodperformanceofmodel1 in thefirst test ascribedto the fact that the test conditionswerenearlymatchingthestandardconditionfordefining theconstantvoltage (E0).E0 isequal to thenominalvoltageat20˝C,which isequal to3.21Vandthe initialvoltageof thesinglebatterycell isestimatedas3.25V.Whenthetest seconddrivingtestwas performedatdifferentcircumstances, theoutcomewasnotasgoodas it in thefirstcase. Figure10a revealsarelatively largeoffseterror in theresponseofbatterymodel1withameansquareerror (MSE) ofabout2.24%.Model2performedmoderatelywithpercentageerrorsbetween1%and2%.Theoffset errorsbetweenthereferencesignalandinitialvoltagevalueofbothbatterymodels2and3wereminor, whereasEquation(3) isemployedinbothmodels for theestimationofVOC. Thesimulationresultsof model3 indicate lessdynamicresponse thantheother twomodels. It couldnotconduct thedrastic changes in thebatterycurrent inputsignal. 0 20 40 60 80 1002 2.5 3 3.5 4 4.5 SOC[%] Discharge measured at T=20°C Charge measured at T=20°C Voc of battery model 2 Voc of battery model 3 Figure7.ComparingtheVocmodelwithmeasuredexperimental results. Table4.Accuracyof theproposedVOCmodel. Temperature˝C MSEinDischargeModel% MSEinChargeModel% 10 0.5232 0.8914 20 0.5320 0.5719 40 0.5751 0.4522 ȱ (a)ȱ ȱ (b) ȱ (c)ȱ Figure8.ThenewVocmodelandmeasuredexperimentaldata: (a)T=10˝C;(b)T=20˝C;(c)T=40˝C. 134