Well, you learn something new every day. I think I might have fixed the
"irreparable" battery.

Optima battery terminals are made of a core that carries the current from
the innards, and an outside cap that connects it to the lug terminals. When
you cut the posts off, you sever this connection.

The battery place I bought this from welded it back together. However, given
the difficulty of heating the metal up without risking explosion or even
melting the plastic, the welds didn't hold for long. That seems to have been
the problem with my battery. Fingers are crossed.

I tried soldering it, but the heat problem made that questionable--it's hard
to get a serious bond when you can't heat up both surfaces. So I drilled a
small hole right between the inner and outer cores and screwed in a sheet
metal screw to provide contact. Result: battery charged to 100% in about
five minutes.

Still, though,  even if it works--don't cut them posts!

Just my $165 worth.

Like Dennis's suggestion: buy cheapie batteries and consider them
expendables.  Better than screwing around with Optimas.