POWER SUPPLY SYSTEM AND RELAY STATE DETERMINING METHOD

A power supply system includes a power storage device; a power control device with a capacitor configured to be pre-charged with electric power from a power source other than the power storage device; a contact relay configured to electrically connect the power storage device and the power control device and disconnect a connection between the power storage device and the power control device, and a controller that sets a target voltage for a pre-charge of the capacitor in response to a system startup request and outputs a closing command for the contact relay in response to a completion of the pre-charge. The controller sets the target voltage to a value different from a voltage of the power storage device before or after an output of the closing command and determines a state of the contact relay based on a voltage of the capacitor after the output of the closing command.