18 February 2010

Low-battery indicator circuit

I designed this little circuit to show a battery’s status.

It lights an led to show the battery is OK, and will change to show another colour when the battery’s low.

The transistors can be any npn-type, and the leds can be any colour (in the diagram, green=ok, red=low)

The operating voltage range is ~3v-12v, and by adjusting the resistor values it will work beyond that.

The voltage the low led comes on at, is set by the potentiometer.


  1. Hi Daftmike !!!

    Many many thanks for sharing this simple circuit for everyone!!!

    I have since made 4 stripboard circuits AND 4 PCB's of this Low Battery Indicator !!!!

    As i have only started learning electronics i had found your instructions from your post on ModRetro extremely easy to follow because you used pictures and made it idiot-proof, lol !!!

    Truly AWESOME !!!

    Thank you so much!!!


  2. great!
    for my modded power bank!

  3. Is there a way to modify this circuit such that at particular low level of the battery, say 11volts, a buzzer alarm would sound, and also when the battery gets further lower, say 10.5volts, a connected relay would disconnect the battery from a given load?. Thanks