PURPOSE: To supply the power to a starter momentarily without restrictions on the battery voltage, external air temp. or the like by furnishing a battery, a converter to convert its voltage, and a capacitor to charge and discharge the converted power, and by using them as a power supply to the starter.

CONSTITUTION: The voltage of a battery 1 is converted by a booster chopper 2, and the converted power is charged in and discharged from a capacitor 3, and these 1-3 are connected with a starter 4 through respective relays 5. From the battery 1 to a reactor 21, energy is stored by turning on a semiconductor switch 20 of the chopper 2. On the other hand, the energy is transferred from the reactor 21 to a capacitor 22 by turning off the semiconductor switch 20, and energy is supplied from the battery 1 to the capacitor 22. That is, the output voltage is controlled by varying the switching intervals etc. Then the relays 5 are turned on so that current is fed to the starter 4 from the capacitor 3, and thus the engine is started.