BATTERY POWER CIRCUIT

The present invention aims at obtaining a power circuit for a battery which is capable of, even when an idle-stop operation is continuously performed, preventing reduction of an electric power supplied to a motor at start-up to obtain a predetermined engine rpm. The power circuit for a battery of the invention includes a series-connected power supply in which a battery 1 having a load (not shown) as an object of electric power supply connected thereto and a capacitor group 2 are connected in series with each other, a DC/DC converter 3 for shifting an electric power between the battery 1 and the capacitor group 2, and between the battery 1 and the load, and a controller 5 for controlling the DC/DC converter 3. The controller 5 detects a voltage of the capacitor group 2, and when the detected voltage is lower than a first threshold voltage (e. g. , 4.0 V), controls the DC/DC converter 3 so that the capacitor group 2 is charged with electricity.