12.2V is a good point. It represents about 50% discharge. Discharging below
50% starts to shorten the life of the battery.

Doug

"varnish" wrote in message
. uk...
I've got a 300AH domestic battery bank and monitor the voltage across it
while cruising. It's usually around 12.8 when charged. What does it
have to drop to before I run the engine to recharge it?