VEHICLE ELECTRIC POWER SYSTEM

There is provided a vehicle electric power system comprising: a battery; a first DC-DC converter configured to step down a voltage of electric power; a second DC-DC converter configured to step down the voltage of the electric power; an electric power storage unit configured to accumulate energy of the electric power whose voltage is stepped down to a first voltage by the second DC-DC converter; an electric power receiving unit configured to receive an electric power from an external device, a voltage of the received electric power being less than the first voltage; and a control circuit configured to control the first DC-DC converter and the second DC-DC converter; wherein the control circuit is started with the electric power received by the electric power receiving unit and operated with electric power, whose voltage is a second voltage less than the first voltage.