A driver controls a switch inserted in a current path between a secondary battery and an inverter that drives a motor. A first abnormality detector instructs the driver to turn off the switch when an abnormality of the secondary battery is detected. A second abnormality detector is disposed in parallel with the first abnormality detector, and instructs the driver to turn off the switch when the abnormality of the secondary battery is detected. The first abnormality detector suspends an instruction to turn off the switch to the driver, even when the abnormality of the secondary battery is detected, in cases where an ECU instructs discharge-stop prohibition of the secondary battery. The second abnormality detector instructs the driver to turn off the switch after a lapse of a certain time from when the abnormality of the secondary battery is detected, regardless of an instruction from the ECU.