This battery disconnect switch or cut-off (breaker circuit) is designed to automatically turn off any battery operated device when its user has forgotten to switch it off within a preset period of time and so it will preserve the battery’s life.


How does the the battery cut-off switch work? When the device connected to this circuit is turned on (S1), the capacitor C1 gets a voltage of +9 volts through the diode D1. The connected device is now turned on as in a normal case. C1 slowly charges via R2. After two, three minutes, the gate voltage of T3 is much reduced to a level that T3 turns off. At this time, T2 turns off the power output to the connected device.

Battery Switch Circuit Diagram

battery disconnect switch circuit diagram
Using this battery disconnect switch circuit is simple. To build it in the device, the positive line of the power (battery) to the device must be cut and the circuit (S1 and output) connected in series to this positive line. The ground line of the circuit must be connected to the minus line.

This battery cut-off switch circuit can handle current consumptions up to 150 miliampers. Originally, it was used to control a multimeter.