The circuit board measures only 0.5” x 1.5 ... They are both inexpensive and BRIGHT! The 12v battery level indicator unit in the photo has no reverse polarity diode and R2 is the calibration ...

There’s a circuit right out of the textbooks ... found himself in with this custom LED battery level indicator. As the video below unfolds we learn that he didn’t start exactly from scratch ...

It is an ideal solution to protect rechargeable batteries from deep discharge. It gives an LED indication when the voltage level in the battery drops below 5.1 volt. CA 3140 Op Amp is used as a ...