To prolong the service life of a secondary battery by making effective use of regenerative energy and eliminating damages to the secondary battery and a capacitor, attain control capable of high speed operation even at a low voltage at low cost, without the risk of electrical shocks, and achieve reduction in a charging period of the secondary battery.

There are provided a regenerative load device B, and a combined secondary battery circuit A of charging electrical energy from the load device B. The combined secondary battery circuit A, in which a secondary battery 1 and a capacitor 2 are connected in parallel and a bidirectional switching device 3 connects the secondary battery 1 with the capacitor 2, comprises a charging and discharging control circuit 10 for driving the switching device 3 and a detecting control circuit 20. The detection control circuit 20 detects the condition of the secondary battery 1 and the capacitor 2, outputs the detected signal, corresponding to the condition as a current command Ic to the charging and discharging control circuit 10, and controls the switching device 3. A bidirectional step-up/down chopper is provided between the combined secondary battery and the load device.