The method of separation secondary battery

A method for disassembling a battery pack to separate a secondary battery which can be reused, without impairing the performance of a secondary battery, having remaining life which, constitutes the battery pack. A pair of holding plates is brought into contact with binding plates on both ends of a battery pack to compress the battery pack in the stacking direction. The open circuit voltage before and after the compression is measured, and based on an amount of change of the open circuit voltage before and after compression, a battery pack which can be reused is separated.