CHARGED STATE ESTIMATING DEVICE AND CHARGED STATE ESTIMATING METHOD OF SECONDARY BATTERY

A method of estimating charged state of a secondary battery (10) provided with a detector (30, 32, 34) capable of detecting input/output current (Ib), an output voltage (Vb) and battery temperature (Tb),characterized in that it comprises: a first estimating step (S200) of estimating the remaining capacity (SOC) of said secondary battery by calculating an amount of change in said remaining capacity based on an integrated value of said input/output current; a second estimating step (S220) of estimating the remaining capacity of said secondary battery based on a battery model using said input/output current, said output voltage and said battery temperature as input variables; a time measuring step (S 120, S210, S230) of measuring duration (Tcnt) of continuous execution of the estimation of remaining capacity by said first estimating step; and a selecting step (S 160, S 170) of selecting one of said first and second estimating steps of estimating said remaining capacity, based on determination as to whether said input/output current is within a prescribed range (125) that allows use of the battery model or not and on said duration of continuous execution obtained by said time measuring step.