VEHICLE-MOUNTED BATTERY SYSTEM

An in-vehicle battery system comprises: a battery; a relay for establishing or cutting off an electrical connection between the battery and an inverter; a plurality of switches respectively provided in a current path for switching the relay; and a battery control apparatus that supervises a status of the battery. The plurality of switches include a first switch provided in the battery control apparatus and a second switch provided in a vehicle control apparatus which controls traveling of the vehicle; the first switch and the second switch are serially connected to each other in the current path; the battery control apparatus controls a status of switching the first switch; and the vehicle control apparatus controls a status of switching the second switch.