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
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