METHOD AND DEVICE FOR ESTIMATING REMAINING CAPACITY OF SECONDARY CELL, BATTERY PACK SYSTEM, AND ELECTRIC VEHICLE

There is provided a battery pack system with estimation accuracy of a remaining capacity of a secondary batter enhanced. A current accumulation coefficient correction section 109 calculates a correction amount α with respect to a current accumulation coefficient kin accordance with a battery electromotive force Veq from an electromotive force calculation section 105. A remaining capacity calculation section 112 estimates a remaining capacity SOC by current accumulation, based on the current accumulation coefficient kcalculated from a correction amount α, and a charging efficiency η based on a currently estimated remaining capacity calculated by a charging efficiency calculation section 110.