On Oct 20, 2021, at 6:31 PM, Chris Zach via Elec-trak <elec-trak cosmos phy
tufts edu> wrote:
So it's fall and I need to get the tractor ready for snow season. A few
weeks ago I topped off the batteries (120 BB600 30ah cells in 4 strings)
and this past weekend I noticed that the tractor had a high
self-discharge. So I did a check of the battery cells.
First step was to charge then let it sit overnight. Then for each pack I
checked banks of 7 cells in the front (plus the last 2) for voltage to see
if they were different. Front cells were all good, read about 1.2 volts
under an idle motor load.
Rear cells were different. Bank 1 (doing 5 cells at a time) looked
balanced but bank 2 was off by a volt between 1/2 of the pack and the
other. Checking strings of five I isolated it down to a single cell that
was reading .8v when the others were at 1.2 or so. In the back box (one
string of 30) I found another cell reading 0 volts.
Pulled those two cells, replaced with a spare pair at 1.1 volts and am
letting the pack charge overnight. Hopefully that will fix the imbalance
problem and boost the range. As for these cells I need to troubleshoot
them, they look fine, no melting or other damage. Maybe I just need to
wash them out completely and refill them with a 30% KOH solution to
restore them to functional. Will try that over the winter.
The E15 was towed out of the weeds and I'm looking at it now. Have a new
pack of 30 cells in it, but it does nothing. The fuse is good, and there
is voltage on the tractor side of the disconnect so that's working. Might
be a problem with the positive side, or the huge amount of mouse crap on
Card 1 has shorted everything. Card 1 is out, I'll look it over.
C
(I replaced the edge connector with a nice big molex+soldered wires to the
board. That edge connector is completely for the birds)
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