To provide a battery which can supplement a weak point of a secondary battery or a normal temperature type fuel battery and can meet output requirements over a wide range from a low load to a high load as a battery for an electric car.

A DC power supply comprises a power battery 2 composed of a secondary battery and connected to a motor, and an energy battery 1 composed of a fuel battery and connected in parallel to the power battery via an energy battery control switch. A battery voltage/current control means which controls a step-up circuit 7 in accordance with the current or voltage of one of the power battery, the energy battery and the motor 14 to keep the voltage of the DC power supply within a predetermined range; and a charge control means which charges the power battery 2 by the energy battery 1 if the charge value of the power battery 2 is not larger than a predetermined value, when a key switch 15 is opened and stops the charging if the charge value is larger than the predetermined value; are provided.