(ET) NiCD battery maintenance

[Chris Zach <cz alembic crystel com>]

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)