BACK-UP POWER SUPPLY SYSTEM AND BACK-UP BATTERY RACK FOR DATA CENTER

A data center includes a server rack and a back-up battery rack. The back-up battery rack includes a plurality of battery modules, each of which has completed a primary usage as an emergency power source for the server rack. A monitoring device determines a system configuration of the plurality of battery modules in the back-up battery rack, based on a specification required for the back-up battery rack and a history characteristic of each of the battery modules that has completed the primary usage in the server rack.