PURPOSE: To effectively use excess power of a solar cell circuit and to weaker the influence to the cell characteristics by selectively connecting a constant- current controller for outputting a constant current from a main bus to supply it to a battery bus, in parallel with a charging array in response to the requested power of a load.

CONSTITUTION: A constant-current controller 11 connected in parallel with a charging array 7 operates in the same way as the array 7, and a constant current output is supplied from a solar cell circuit 1 to a battery bus 10. A plurality of the controllers 11 are connected in parallel, and connection/ disconnection is controlled by a relay switch 12. A heavy load might be connected in a satellite. In this case, the surplus power is used through the controller 11. When a heavy load is not applied, the controller 11 is opened, and the power is consumed in a shunt unit 2. Thus, the surplus power of the circuit 1 can be effectively used. Thus, battery discharge power at the time of sunshine is reduced to weaker the influence to the cell characteristics.