BATTERY MANAGEMENT SYSTEM AND BATTERY MANAGEMENT METHOD

The battery cellar (2) includes a storage cabinet (21) that stores a plurality of used batteries, a power converter (an AC/DC converter (22) and a DC/DC converter (23)) electrically connected between the plurality of used batteries stored in the storage cabinet (21) and a power system (5), and a server (20) that controls the power converter to charge or discharge the plurality of batteries in response to a demand response request from the power system (5). The server (20) selects, from the plurality of used batteries, a first battery, the degradation degree of which has reached a reference value, and a second battery, the degradation degree of which does not reach the reference value but is predicted to reach the reference value within a predetermined period, as replacement target batteries.