SF Man wrote:
The lawn mower chewed up the 18 volt AC wire going to the driveway
gate about a year ago and I just got around to fixing it.

Both batteries inside were new a year ago but both are dead as a
doorknob.

I've had a 6amp 14-volt battery charger on them for two days and
still, less than a volt (and no current on the gauge).

What does it take to resurrect sealed lead acid batteries?
(Model RB500 & UT1270)

All it takes is replaceing them. These batteries don't respond well to abuse,
and you've abused them to the limit.