After a fairly long phone call from a friend who does many solar
installations with LiFePO4 batteries, then seeing (-Phil-)'s
response, I got a very uncomfortable feeling and went straight to the
garage, put the battery pack on a hand truck and rolled it out to the
middle of the driveway about 75' from the house. It didn't help that
I found that the two modules I had been slowly discharging all day
were noticeably warm to the touch, this accelerated my concern to anxiety.
Assembled tools, protective gear, a bucket of water and the metal
wheelbarrow in case I needed a bigger reservoir. I tore into the pack
with the goal to separate the rapidly swelling modules from the
remaining good modules. It had become evident that in the previous
hour or so, the swelling had increased rapidly and was really
straining the through bolts and bar clamps.
Set to work pulling the through bolts first. One of the bar clamps
that I had put on before lunch as now so tight I couldn't loosen it
and had to place a second clamp alongside it to lessen the pressure.
It took a couple of fetches to let the clamps out until I ran out of
threads on the handle, placing another clamp beside it and taking up
the pressure, then taking that clamp off, etc. Probably 4-5" of
additional travel over what the through bolts would have allowed.
Always watchful for heat or smoke while doing this work.
In the end, it all came apart and I separated the bad from the good.
None of the rest of the modules in the pack exhibit any signs of
swelling. I'll be leaving the whole mess out in the driveway all
night and probably all of tomorrow, checking the cell voltages on the
now re-compressed partial pack of "good" modules to see if the big
squeeze damaged anything internally. If the checks out for a few
days, In go the replacement modules and then I'll dig in the top
dresser drawer for my lucky rabbit's foot and try a bit of mowing in
the front yard, and a charge afterwards.
BIG LESSONS HERE: If you think your pack has problems, don't wait a
year or two to check it out like I did. Apparently, just allowing
your cell(s) to reach a very low state of charge initiates the
swelling, which at a minimum is destructive to the cells, if not the
rest of the pack. The only cells in my pack to reach this state were
the two half-modules that had a high self-discharge rate.
Photos:
http://www.housetrucks.org/evgfx/swollen_1.jpg
First two (good) modules removed. Cases a little bent, but otherwise intact.
http://www.housetrucks.org/evgfx/swollen_2.jpg
I didn't mangle these taking them off, they were splayed out like
popcorn in the kettle as the pressure let off. Wish me luck trying to
get the recycle kiosk at the dump to take them now...
I always did want to see what the inside of a Leaf module looked like.
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