Although everybody says you shouldn't do it - I've successfully recovered a couple of 12v gel batteries from a disability scooter that read less than one volt each before I started - well, it was either do that or buy new, at over £100 each, and I am notoriously stingy :)
All it cost me was a gallon of distilled battery water (and one cheapo, old fashioned, basic car battery charger ..) and it took just over a week to accomplish. As I had nothing to lose, I opened the batteries up and slowly added water to the cells (the gel had dried badly and looked more like a died up tropical lake bed than 'jelly' .. LOL..) whilst they were put on a low charge. To give some idea of how dry they were, I ended up adding just over 1.5L of distilled water to each 12v battery. It was not particularly successful to start with, and I was about to give up when it was suggested to me that I 'reverse charged' them for 12 hours at a high rate, (about 5 amps was the best I could manage) and this brought the volts up to almost 10v - which was just enough to encourage me to go further :) They were then discharged back down to 'flat' and recharged properly - starting with a high charge for 4 hours then reducing it to 2 amps for a day which gave me another volt before they were discharged flat again. Also on 'advice', whilst they were being charged for the first time, they were sequentially 'rolled' (i.e. laid on each side / end) for a quarter of an hour or so in each position so that the 'free' liquid had a chance to work its way around all of the 'non-gel' gel. After a second reverse/forward charge cycle they came back to just over 12.5 volts so I again discharged them completely and recharged at 5 amps until they reached 11v - at which point they were able to be charged again by the electronic charger that came with the scooter (it wouldn't touch them under 10.5v). They were then given a final 'top up' with battery water - and they have worked ever since (I did it during August last year), although they probably only provide 85% of their original capacity; this last bit is a little bit of a guess as I haven't owned the scooter from 'new' (it was actually on offer in my local 'Freecycle' group!). In terms of 'range' and 'speed', I have never been disappointed in its subsequent performance - although how long they will continue to give 'acceptable' service is quite another factor, and one which I naturally cannot answer right now. Looking inside the batteries recently showed that most of the gel seems to have taken up some water and there isn't any 'free water swimming around on top either); there are still a few small dried up lumps of dead gel remaining on the top of the plates which have not changed back, but 99% of it appears to have 'recovered :) _/*'Elf 'n Safety' Notice!*/_ Obviously I can't recommend this form of treatment for gel batteries as I had absolutely no idea of any potential risks involved - or the chemistry involved for that matter (which might be interesting to find out one day) as I could just as easily have been turning them into b*mbs! All I can really say is that *I* managed to do it, on a couple of older, and effectively totally dead, 12v gel batteries, and that I was happy that I'd *beaten* the b*ggers - and now had a perfectly usable mobility scooter which continues to take a reasonably useful charge :)) Trevor Iain Street wrote: The gel won't leak, but they may produce gas if charged at too high a rate, or over charged. Any gas produced is a loss of electrolyte, which cannot be replaced. [Non-text portions of this message have been removed]
