STORAGE BATTERY SYSTEM, METHOD, AND COMPUTER PROGRAM PRODUCT

A storage battery system includes a cell module including storage battery cells, a battery management unit configured to maintain a contactor having a normally open contact in a closed state, while being supplied with power, and a power supply control circuit that DC to DC converts the power of the cell module for supply to the battery management unit. The power supply control circuit includes an SOC estimator that determines from a voltage of the cell module whether or not the cell module is in an overdischarge state, and after determining that the cell module is not in the overdischarge state, outputs a status signal to the power supply control circuit. In response to no receipt of the status signal from the SOC estimator, the power supply control circuit interrupts the power supply to the battery management unit from the cell module.