Equalization device, battery system and electric vehicle including the same, equalization processing program, and equalization processing method

An SOC of each battery cell is periodically detected, and an SOCmin and an SOCmax are determined. Battery cells having the SOCs larger than SOCmin+± are selectively discharged. After an elapse of a preset equalization processing time period, discharge of all the battery cells is stopped. The equalization processing time period is set based on a rate of change in the SOC of the battery cell subjected to discharge and a rate of change in the SOC of the battery cell not subjected to discharge such that a magnitude relationship between the SOC of the battery cell having the SOCmin and the SOC of another battery cell is not reversed.