Time to turn up the dial on the technical channel.
After converting my car to a lightly-used set of Thundersky 160's,
I've finally gotten around to having some thermal images taken of the
cells after running the car up to temperature. My purpose was to make
sure that none of my cell interconnect wiring (copper strap stock)
was heating up. What I found was somewhat unexpected. One of the 38
cells was showing an elevated temperature from the rest.
First, the IR image of the right-hand half of the pack, taken from
behind the car. the suspect cell is at the center cross-hairs:
http://www.westlanetv.org/~sharkey/evgfx/IR_0677.jpg
A close-up of the cell, looking from the front of the pack. It's been
photoshopped to blend the IR image with the visible image to provide
some perspective of the actual appearance:
http://www.westlanetv.org/~sharkey/evgfx/Hot_Cell_2.jpg
The car ran a 15 mile trip at about 55 MPH, pulling 100 - 125 amperes
most of the way. A couple of 275 - 300 amp sprints pulling out into
traffic, etc. Photos were taken immediately thereafter.
All of the cells had been carefully (manually) balanced a few days
before the photos were taken. During balancing, this cell was about
15 ampere-hours lower than most of the rest of the pack, but not the
lowest of the 8 cells that needed attention. It came right up with a
balancing charge. None of the other cells showed any variance in
temperature in this series of photos.
Questions for the list:
The cell isn't actually "hot" but it's obviously warmer than the
rest. What's everyone's take on this one cell warming up? Can I just
assume that it may have higher internal resistance, and therefore
more heating under load? Is the heating indicative of a coming
(perhaps spectacular) failure?
I've got about 1,600 miles on this new pack, and it seems to be
performing well. I'd like to keep using it in this configuration, but
if it seems risky to continue loading this one cell, it ~could~ be
jumpered out of the pack (not my first choice).
Opinions or advice?
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