US Patent 9523740 Method for determining remaining lifetime

A method includes discharging an assembled battery (10) formed of a plurality of batteries until a state of charge (SOC) of the assembled battery becomes smaller or equal to a lower limit of a predetermined normal use range used in charge and discharge control of the assembled battery, measuring the discharge capacity of each of a plurality of battery blocks in the discharge of the assembled battery, the plurality of batteries being divided into the plurality of battery blocks, calculating the capacity difference in the discharge capacity among the plurality of battery blocks, and determining the remaining life of the battery block or the assembled battery based on the calculated capacity difference.