SOS! Battery died while hooked to shore power.

Mini breakthrough. I flipped the breaker labeled "converter" and heard what sounded like a fan come on. It stayed on for about three seconds then went off. I flipped the breaker, waiter thirty seconds, flipped the breaker back on and, again, a fan or hum for three seconds and it went off. So it sounds like it wants to start but can't for some reason. The problem is I can't find the dumb converter to take a look at it.