The battery has now been on charge for about 20 hours at the charger's
12A setting, but most of the time the ammeter on the charger has shown
only about 5A. The cells are all still gassing.

Is this battery likely to come back to life again, or is it toast? Any
remedial actions to take?


It sounds to me that it is likely to survive, but I hope you
are not over charging?! I assume you are also monitoring the voltage? To
be sure how it turns out, you really ought to get a guage to measure the
specific gravity of the electrolyte in each cell and check. Should be
available cheap at auto supply stores.


Ed K7AAT