PURPOSE: To make a battery to stop its discharge when its potential drops to the discharge stop voltage by providing a circuit to obtain the first reference voltage, the partial pressure circuit to obtain the second reference voltage, the comparison circuit and the gate circuit etc.

CONSTITUTION: A voltage comparison circuit 6 operates so as to generate voltage at output only when reference voltage VR2 is higher than the reference voltage VR1 while no voltage is generated at output when the reference voltage VR2 is lower than the reference voltage VR1. The output gate circuit 7 is controlled by said voltage comparison circuit 6 and operates to supply load 8 with power only when some output voltage is existing in the voltage comparison circuit 6. As the reference voltage VR2 is the voltage in proportion to the voltage of a battery 1, no voltage appears at output of the output gate 7 thus to stop to supply load 8 with power, when the voltage of the battery 1 becomes lower than the voltage fixed by said circuit. Accordingly, when the voltage of the battery 1 reaches the discharge stop voltage through said circuit, the power supply to load 8 stops automatically thus to prevent the battery 1 from overdischarge.