Patent ID: 8108161

Claim:
A state estimating device of a secondary battery, comprising: a detecting unit for detecting a voltage, a current and a temperature of said secondary battery; a battery state estimating unit successively estimating a state quantity of said secondary battery according to a battery model equation based on at least one of the battery temperature and the battery voltage, and the battery current detected by said detecting unit; a storing unit prestoring data relating to change characteristics of an initial state parameter value of said secondary battery with respect to changes in battery state in connection with a predetermined parameter of parameters used in said battery model equation; and a change rate estimating unit estimating a parameter change rate being a ratio of a present parameter value with respect to said initial state parameter value in connection with said predetermined parameter, wherein said change rate estimating unit performs parameter identification based on said battery model equation using said battery temperature, said battery voltage and said battery current detected by said detecting unit as well as said initial state parameter value corresponding to the present battery state based on the data read from said storing unit, and thereby estimates said parameter change rate.