Patent ID: 7593823

Claim:
A method for determining state of a battery by estimating response voltage when a predetermined discharge current pattern is applied, to determine SOF (State Of Function) or SOH (State Of Health) of a battery, comprising the steps of: preparing in advance a prescribed correlative equation, a plurality of coefficients of which are given by functions of the temperature and the SOC (State Of Charge) of the battery, which calculates the response voltage when the predetermined discharge current pattern is applied, by using the measured value of either the internal impedance or the internal resistance of the battery; determining the values of the coefficients by measuring the temperature and the SOC of the battery; substituting the measured value of either the internal impedance or the internal resistance in the correlative equation with the values of the coefficients incorporated to calculate the response voltage when the predetermined discharge current pattern is applied; and determining the SOF and the SOH of the battery based on the response voltage thus calculated.