low voltage sensor ckt.

I have a different thing that I am trying.  I have been installing 12v power inverters in service trucks.  I have installed remote starts for manual battery maintenance after a heavy load.  I am pulling my hair out trying to find a relay or ckt to sense a low battery voltage to switch a 12v relay to trigger remote start automatically.  does anyone have any ideas? thanks charlie

I like this idea . Lets see what we can come up with.

with a Opto isolator where the led goes.

You could also use a voltage divider with a 5vdc reference.

If you set up the voltage divider with a 1:3 ratio it will divide your car voltage by 3.  You can then use a seperate trimpot to to set your scaled low voltage limit.j

Run both of these values in to a comparator and transistorize the output and you're done.

No pretty pictures from me though!  :)