POWER SUPPLY SYSTEM FOR ELECTRIC VEHICLE, AND CONTROL METHOD THEREOF

An electric powered vehicle (100) is equipped with a main battery (10) for storing electric power input to and output from a motor (30), and an auxiliary battery (70) as a power source for an auxiliary system including a control system. A DC/DC converter (60) converts an output voltage of the main battery (10) to a level of an output voltage of the auxiliary battery (70). During operation, a BAT-ECU (85) monitors states of charge of the main battery (10) and the auxiliary battery (70) and controls operation/stop of the DC/DC converter (60). When the electric powered vehicle is in a key-off state (running stop state), the BAT-ECU (85) is intermittently operated, while an external charging system and a vehicle running system are stopped.