Abstract: Detecting a defect in a rechargeable battery includes measuring an output signal by applying an input signal to the battery while modulating frequency, calculating an AC impedance according to the frequency and the output signal, Nyquist plotting the AC impedance and building an equivalent circuit model based on the plot, calculating a product of a charge transfer resistance and an electric double layer capacitance in the model as a time constant or calculating a slope of a straight line appearing in a low-frequency region in the plot, comparing the time constant with a predetermined time constant or comparing an absolute value of the calculated slope of the straight line with a predetermined slope absolute value, and determining the battery is defective when the time constant is less than the predetermined time constant or when the absolute value of the calculated slope is smaller than the predetermined slope absolute value.

Abstract: Detecting a defect in a rechargeable battery includes measuring an output signal by applying an input signal to the battery while modulating frequency, calculating an AC impedance according to the frequency and the output signal, Nyquist plotting the AC impedance and building an equivalent circuit model based on the plot, calculating a product of a charge transfer resistance and an electric double layer capacitance in the model as a time constant or calculating a slope of a straight line appearing in a low-frequency region in the plot, comparing the time constant with a predetermined time constant or comparing an absolute value of the calculated slope of the straight line with a predetermined slope absolute value, and determining the battery is defective when the time constant is less than the predetermined time constant or when the absolute value of the calculated slope is smaller than the predetermined slope absolute value.