I have a sailboat with a combo starting/deep cycle battery and a solar panel to keep the battery from going flat when the boat isn't used for long periods.
Unfortunately, the regulator doesn't keep the panel from putting enough voltage into the battery to electrolyze the electrolyte away. The battery is in a horribly inconvenient place to check the level, and over the several years since I last replaced it the battery has, on two occasions, been electrolyzed down to below the level where it will start the engine.
Attempting to start the engine in this condition apparently causes the formation of bubbles on the remaining wetted surface which suddenly "disconnect" the battery under the heavy load, then bubble away a few seconds after the load is removed. Lower level loads (like lights) shut down during cranking, come back when cranking is stopped, then suddenly brighten up a couple seconds later. (No, there's no circuit breakers or other electronics to explain this, and the delay varies.)
On both occasions I've refilled the battery with distilled water. When first done the behavior is the same, but after an hour or so (I'm guessing: once the plates are well wetted and the acid and water are mixed better) it is able to crank the engine nicely, even if this is after dark and no charging has been done. When I went back after a week or so the battery seemed fine, capable of many minutes of cranking (in half-minute bursts, of course).
My question is: What happens to such batteries when they are electrolyzed down to such a low level? What sort of damage, if any, should I expect? Is the battery likely to be OK at this point, have resuced capacity, or perhaps be prone to some sort of sudden failure?
