12VDC Battery Question

Thread Starter


Joined Aug 26, 2010
Hi All,

I am using 12VDC battery for my circuit. How do I know when I need to recharge the battery? Do you have any circuit to tell that the battery need to recharge by display LED?



Joined Mar 14, 2008
Then you just use a comparator set to trip at about 12V (12.6V is full charge). That will indicate a discharge of the battery to about the 50% point. Going lower than that will tend to shorten the life of the battery.


Joined Mar 3, 2011
If this is an automotive lead acid battery, then you may be able to use the technique that is used there. The alternator voltage is regulated at about 14.2V or so that the terminal voltage at the battery is about 13.5V. This is to account for the voltage drops along cables. So I think if you can have the terminal voltage at about 13.5V, you can push current into the battery to charge it. The open-circuit voltage of the automotive lead-acid battery is about 12.6-12.8V (2.1-2.15V per lead acid cell, 6 cells per battery pack).


Joined Aug 7, 2008
Kevin, I think you have a low battery warning ckt mixed in with weight dpop ckt. composed of a LM 393 comp, V divider, precision ref Lm 385Z- 1.233 V, & red LED.