BATTERY MODULE AND POWER SUPPLY SYSTEM

A battery module includes a battery, a bidirectional DC-DC converter, and a controller. The bidirectional DC-DC converter may convert a direct-current voltage output from the battery and thereafter output the direct-current voltage to a load. The controller is configured or programmed to perform constant voltage control of the bidirectional DC-DC converter and receive a stop warning signal providing advance notice that output of a power supply is to stop. The controller is configured or programmed to, before receiving the stop warning signal, perform control such that an output voltage of the bidirectional DC-DC converter is lower than a first target voltage, and, after receiving the stop warning signal and before the output of the power supply stops, increase the output voltage of the bidirectional DC-DC converter to the first target voltage or higher.