Battery ParameterEstimation
Battery Parameter Estimation
ImportanceofBatteryparameterEstimationThe model parameters changes with operatingconditions and battery aging. If they are notupdated, the model is no longer accurate. ThenSoc estimation will lose accuracy.The capacity Q reduces due to battery agingEstimation of Q is the main task for SOHestimationThe parameters reflect battery conditions andare critical indicators for battery diagnosis
Importance of Battery parameter Estimation • The model parameters changes with operating conditions and battery aging. If they are not updated, the model is no longer accurate. Then SOC estimation will lose accuracy. • The capacity Q reduces due to battery aging. Estimation of Q is the main task for SOH estimation. • The parameters reflect battery conditions and are critical indicators for battery diagnosis
Parameter Estimation of RC-BranchBatteryModelsRpOCIState equation is linearROutput equation is nonlinearv(t) = vocv + Ri(t)+v,(t) = f(s(t)+v,(t)+ Ri(t)Theparametersto beestimated:Q,R, Rp,Cp,VocvThe nonlinearfunction f(s)
State equation is linear 1 1 Q s(t) = 1 i(t) vp (t) =− v p (t) + i(t) RpCp Cp Rp R v i vocv vp + - + - Cp v(t) = vocv + Ri(t) + vp (t) = f (s(t)) + vp (t) + Ri(t) Output equation is nonlinear The parameters to be estimated: Q, R, Rp, Cp, Vocv The nonlinear function f(s) Parameter Estimation of RC-Branch Battery Models
APractical Method forObtaining R,Vp,Rp,VocvinRC-BranchModels byOff-line Experimental MethodRVocv
Rp R v i vocv vp + - + - Cp A Practical Method for Obtaining R, Vp, Rp, Vocv in RC-Branch Models by Off-line Experimental Method
Switchoffatt=oBatteryDigital storageoscilloscopeMeasureboththeterminal voltage(V)andcurrent (l)atatime ofdischarge
Battery Measure both the terminal voltage (V) and current (I) at a time of discharge Switch off at t = 0