load has small impedance the overcurrent can be reliably released fig4 is a circuit diagram of a battery device according to a third embodiment of the present invention a battery state monitoring circuit 3 of the battery device according to the third embodiment includes a control circuit 22 a pull down circuit 24 a comparator circuit 25 a comparator circuit 27 a reference voltage circuit 26 a reference voltage circuit 28 a positive power supply terminal 11 a negative power supply terminal 12 a resistor 41 a current source 42 a charge discharge control signal output terminal 13 and an overcurrent detection terminal 14 the resistor 41 has one end connected to the overcurrent detection terminal 14 and the other end connected to a first input terminal of the comparator circuit 25 the current source 42 is connected between the resistor 41 and the positive power supply terminal 11 the comparator circuit 27 has an output terminal connected to a control terminal of the current source 42 the current source 42 switches its output current depending on a signal input to the control terminal other circuits and connection relationships are the same as those in the battery device according to the first embodiment.