Patent attributes
Provided is a secondary battery system capable of suppressing degradation of a battery capacity. When it is determined that a battery pack is brought into a non-use state, a battery state detection unit in a battery controller compares an SOC of the battery pack calculated by a battery state operation unit and a standard SOC. When the SOC of the battery pack is higher than the standard SOC, the battery state detection unit in the battery controller calculates a capacity value in which the SOC of the battery pack becomes lower than the standard SOC, from a difference of the SOC of the battery pack and the standard SOC, and transmits the calculated capacity value to a cell controller. The cell controller discharges the battery pack, on the basis of the capacity value transmitted from the battery state detection unit.