POWER SUPPLY SYSTEM AND CONTROL METHOD THEREOF

A power supply system includes a power storage device, a positive electrode-side relay, a negative electrode-side relay, a power control unit that includes a capacitor configured to be pre-charged in response to a system start request and that is connected with the power storage device via the positive electrode-side relay and the negative electrode-side relay, and a control device programmed to close the positive electrode-side relay and the negative electrode-side relay at different timings always or under a predetermined condition in response to the system start request and programmed to change a sequence of closing the positive electrode-side relay and the negative electrode-side relay in accordance with a predetermined restriction. This configuration effectively extends the lives of the positive electrode-side relay and the negative electrode-side relay.