Are you sure it is an internal cell failure and not just a loose or dirty connection within the bussbar? The heat on that image looks only on one area from the whole cell. Keep in mind that those ‘prismatic’ cells comes on tens or hundreds of thin rectangular layers with the same shape of the plastic enclosure. And a high internal resistance developed in cell chemistry would probably show up an evenly hot across the enclusure. (Please correct me of wrong).
Why don’t you try first to check for a poor electrical contact at that spot, clean it, re-tighten it and repeat your test? Marco Gaxiola Sent from my iPhone > On Sep 30, 2019, at 8:57 PM, Mr. Sharkey via EV <[email protected]> wrote: > > 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? > > _______________________________________________ > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > ARCHIVE: http://www.evdl.org/archive/index.html > INFO: http://lists.evdl.org/listinfo.cgi/ev-evdl.org > Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA) > _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub ARCHIVE: http://www.evdl.org/archive/index.html INFO: http://lists.evdl.org/listinfo.cgi/ev-evdl.org Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
