Low Voltage Battery Warning Circuit

Thread Starter


Joined Feb 7, 2008
Hi there,

I need help with a project.
I would like to make a simple Low Voltage Battery Warning Circuit for my 12 volt forklift battery (1800 AmpH). It should be a warning device that alert me the battery is below the level that I have adjust it. So I can adjust it between 3 and 15 volt with a screw driver or something.
This circuit should monitors the battery voltage between 3-15 volts once set.
Whenever the voltage falls below a predetermined value a LED indicator lamp lights up.
I know there is a circuit schema somewhere out there but cant get it.
Somebody knows how I can get one?? Or any other idea?


Joined May 16, 2005
ONE THREAD PER QUESTION ONLY, if you please. Other copies of this have been deleted, including the one which hijacked another thread.


Joined Aug 8, 2005
You can try something as in the attached.

When the battery on comparator (+) drops below the (-), which is set at a nominal 3V, then the LED will light. By adjusting the pot, you can set it for different failure points (I suggest using a 10-turn or similar pot).

BTW -- with the values given the unit will draw ~10mA through the 3V zener, this may be a bit high to keep connected to your battery all the time. You could try increasing R2 to 4.7K - 10K.