After 4 years and 3 batteries, I finally got around to installing a $28 battery disconnect.
It's odd that a battery is 12 volts but when it gets close to 12 volts on a meter it is almost dead. I tried charging mine but when it gets down into the 11 volt mark, they are DOA.
I could be wrong, but I have been told by several on FRF that:
You have to have battery power to activate the controls to the AC, fridge, furnace, etc. When you turn the AC on with a low to dead battery, it's saying NAW!