AC impedance behaviour of the high capacity Ni-MH battery at different SOC

The AC impedance behavior of the high capacity Ni-MH battery at several state-of-charge(SOC) values was studied.The impedance spectra comprise of a semicircle at high frequency and a line at low frequency.The test results showed that,the ohm resistance and the frequency corresponding to it,the electrochemical reaction resistance and the frequency corresponding to the maximum value of imaginary impedance of semicircle were useful for analyzing and predicting SOC of Ni-MH batteries.