I just picked up another 701a, this one has a battery reading about 7 volts. Do you think it is too far gone? I have a friend who says he can de-sulfate it with his arc welder. These batteries seem hard to come by. Any thoughts?
He's not really going to 'de-sulfate' it, what he's going to do is blast so much current through the short between the plates (which may or may not be sulfate) that it explodes/vaporizes the short and allows the cell to work normally again. In so doing, you can end up with a lot of little pieces of battery and battery acid all over the landscape. It does often work, and given the stupid amount of money these batteries cost, it's probably worth a try. But I'd make sure I was wearing lots of PPE and the battery was well away from anything that I cared about, ideally in a steel box that would catch the shrapnel.
I got a battery exactly like this with my MEP-701A and I haven't done the shock treatment to it yet. If I can't get it to come back to life, I figure a pair of motorcycle batteries should fit in the stock footprint (I don't like cutting up the ASK if I can avoid it), and given how puny the one-lung Onan is, I don't anticipate a pair of 14 AH motorcycle batteries having any trouble spinning the thing over.