||OK so the next step is to disconect the batteries completly, charge them properly (slow charge three days) then see what happens.
The bad part of this is that repeated stone cold dead batteries will ruin the batteries.
So we need to find out if the batteries will hold a charge at all
Then we need to find the draw that caused the problem.
When we have proved we have a battery that will hod a charge you need to use a amp-meter that will deal with 100 amps and start hooking things up.
I have a fancy inductive one that will do from 0.5 amps to 600 amps, but you will find one of your neighbors or freinds probably has a battery load tester that will be acurate enough to do what you want.