batty_professor

I'm leaning toward a corroded battery connector somewhere. We are afterall dealing with lead-acid batteries here. And though they may be sealed, they still may have "gassed" at some time. That's corrosive. Do the batteries all connect to one central pair of terminals on the mainboard? I'd pay close attention to that area too. Do you have an analog meter available to you? and can you use such to watch the voltage at that point when attempting startup/selftest? I would say "careful", but you sound confident inside this thing.