PURPOSE: To surely prevent the over discharge of a storage battery by allowing an operating means to change the reference voltage one after another in response to the condition of the battery, and consequently opening a switching means when battery voltage becomes lower than the reference voltage.
CONSTITUTION: When driving a load 3 is started by a battery unit 1, the energizing current and battery temperature of the battery unit 1 are detected by a current detecting means 4, a voltage detecting means 5 and a temperature detecting means 6 so as to be outputted to an operating means 7. Meanwhile, the output of the voltage detecting means 5 is compared with the reference voltage by a comparison section provided for the operating means 7. And a battery condition detecting section provided for the operating means 7 operates the output of the current detecting means 4 and the temperature detecting means 6, so that the reference voltage is changed based on the result of the operation. In addition, the timer section of the operating means 7 outputs a signal to open a switching means 2 when a condition that the output of the voltage detecting means 5 is lower than the reference voltage, is continued for the specified period of time. In this case, the battery unit 1 is disconnected from the load 3, so that the over discharge of the unit 1 is thereby prevented.
FURUSE TERUHIRO
TAKEI FUMINORI
ITO TSUKANE
