A charging control system for charging a secondary battery from a solar battery, including a first path for transmitting power from the solar battery to the secondary battery, a second path for sensing the voltage of the secondary battery, and a comparison unit for comparing the solar battery voltage with the sensed voltage of the secondary battery. The first path includes a first interrupter, controlled by the comparison unit, which interrupts the first path to prevent discharge of the secondary battery through the solar battery when the solar battery voltage falls below the secondary battery voltage. The second path includes a second interrupter that interrupts the second path after the first path is interrupted, to prevent the secondary battery from discharging through the second path when not being charged through the first path.