Patent ID: 7009401

Claim:
A method for evaluating characteristic of a secondary battery passing power to/from one or more electric devices mounted on a vehicle, the method comprising steps of: measuring the current and voltage of the secondary battery according to a plurality of frequencies generated by the one or more electric devices; calculating impedance of the secondary battery from the measurement results; and evaluating the battery characteristic of the secondary battery from the impedance calculated; wherein the electric device is a motor/generator for driving the vehicle and generating electricity by receiving drive force from the vehicle, and the method further comprises steps of: controlling the motor/generator during a non-power running period of the motor/generator; measuring the current and voltage of the secondary battery while changing the frequency of the state detection current applied to the secondary battery; calculating the impedance from the measurement results; calculating the remaining amount of the secondary battery from the impedance and the battery characteristics; calculating a parasitic capacity of the secondary battery from the remaining amount and the impedance; performing deterioration calculation to obtain a service life; calculating a correction value of the change of the remaining amount or the service life according to the integration current of the secondary battery successively measured during the impedance calculation; maintaining an error of the calculation result of remaining amount or the service life up to the preceding time; calculating an error of the calculation result this time after correcting the change from the preceding calculation result; and calculating a weighted mean according to the preceding error and the current error.