The longer any lead-acid battery sits at lower SoCs, the more it sulphates. Level of discharge X time, and it's cumulative. This is also why it's super important to have the absorption phase to fully charge it, otherwise it's "not quite charged" and it will still slowly sulphate.
Only way to know is to do a capacity test. On Tue, Dec 7, 2021 at 6:01 PM Ken Olum via EV <[email protected]> wrote: > Hi, all. In my Electric Ox I have 4 12V 135Ah AGM batteries from > Universal Battery. I got this set in April 2019, so they've been > through 3 summers of mowing and two winters of snowblowing (which puts a > lot more stress on them). My previous set lasted 10 years, though they > were showing their age after 7. When I got the current set, I also > installed individual very high quality 12V chargers from CTEK, and I was > hoping for even longer life than the previous set. > > However, this fall when I was jacking up the tractor to improve the > wiring I mistakenly left on the "push" switch that retracts the parking > brakes. (There should have a been a warning beeper, but it broke and I > foolishly did not replace it.) This draws about 0.7A, but I left it on > for a long time. A week? Two? Then I disconnected the batteries > completely without noticing the problem and they sat for a week or two > like that. Today I went to reconnect everything and discovered the > problem. Only two batteries are affected, because these electric > retract brakes take 24V. The affected batteries each read 5V. I > connected my charging system and these batteries are charging up now. > > The question is what to do now. How badly do you think they have been > damaged? If they now have significantly less capacity than the > unaffected two, I'm going to have to be very careful that I don't > overdischarge the bad ones when I'm snowblowing at 130A or so. There > also could be a problem caused by the very high inrush current when I > start my snowblower. There's no controller, just a contactor to connect > the batteries to the permanent magnet motor. > > I could replace the two damaged batteries, but then they would be out of > sync the opposite way, at least to some degree. > > I have a meter on my dashboard that indicates charge level. It seems to > work by measuring the lowest voltage that is seen for some short (but > nonzero) amount of time. Maybe this will warn me, if I extrapolate > properly, that the bad two are getting discharged. > > There won't be a problem with charging, at least, because they are > independent for that. > > I'd appreciate any advice. Thanks. > > Ken > _______________________________________________ > Address messages to [email protected] > No other addresses in TO and CC fields > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > ARCHIVE: http://www.evdl.org/archive/ > LIST INFO: http://lists.evdl.org/listinfo.cgi/ev-evdl.org > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20211207/7d9e6173/attachment.html> _______________________________________________ Address messages to [email protected] No other addresses in TO and CC fields UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub ARCHIVE: http://www.evdl.org/archive/ LIST INFO: http://lists.evdl.org/listinfo.cgi/ev-evdl.org
