a solar cell power system includes a device which determines the occurrence of solar array bus lockup by detecting the voltage of the power bus , the discharge current of the storage battery , and the solar array current and performing a calculation using these items of data in addition to the regulated bus voltage to emit a lockup signal , by which the magnitude of the load is reduced , thereby cancelling the lockup state . alternatively , a solar cell system may include a lockup cancelling drive device , which accumulates in a coil cancelling - drive , energy supplied from the storage battery and then discharges this energy to the power bus , thereby cancelling the lockup stage without reducing the magnitude of the load .