I'm reasonably sure I cooked a battery, interested in knowing what went south

[Slyp Dawg]

I've got a duratrax branded, probably IB1400 cell sideXside pack that I soldered my own deans connector onto about a year or so ago, ran in my RC18T with no issues, ran in my scorpion for a few comps/tough truck challenges with no issues, and now I've been running it a very little bit in my scorpion-converted-to-a-SCX-10, and I think I managed to kill it today. I was running aruond my house, ran through some cat puckey (what can I say, shit happens ), put the tire with said cat poo on a boot cleaner, pushed down a bit, and buried the trigger, then did the same, jsut in reverse, and in the process probably put quite a bit of load on te battery. a bit later in the run, I picked up the rig, body off (haven't painted the bushwacker I got for it just yet, still need to get the wheelbase on the chassis sorted), and put my thumb on the tail end of the pack, and it was all I could do to not drop the rig from the heat. I went inside, unplugged the battery to break the circuit, set the rig down, and noticed a distinctive burning smell, looked at the cell that was blazing hot, and the shrink wrap on the cell was starting to shrink a bit more and the sticker was peeling up a bit. I took it outside, put it on my driveway, took a temperature probe to it, and that cell was sitting at a balmy 214*F. measured the cell at the opposite end of the pack, and it was a much more reasonable 92.something*F. also, the two cells beside the hot one (cells 4 and 5 from the plug end) were around 190*F, according to my thermometer. I understand that my method of removing the cat puckey wasn't the best for the battery, but logic would say that it would roast all 6 cells instead of just the back 3, and even then, I've got quite a bit of reduction in the rig (43/13 R&P in the axles, 87/14 gearing I believe, Losi 1.9s, powered by a Park 400 outrunner), so one would think that load like that wouldn't do a whole awful lot to the pack. after all, scalers often weigh a lot more than my rig does, and you don't often hear about people burning up packs in porky 1.9 scalers or even 2.2s. I plan to drop the pack by HTU's little battery disposal thing today, but just for future reference, any clue what could have caused this? I did notice a TINY (and I mean TINY) dent in the side of the very end cell that got so hot, but the next 2 in line weren't far behind as far as heat goes

[jrkilburn]

I think what you are seeing is age, slight damage and load results on a battery. I use the 1500 version of these and from time to time one cell will go south on me. I spent the money for a cell conditioner a long time ago when I was racing. These will tell you the condition of the individual cells.

Best practice is to break down the pack and test each cell if you can. Find the bad one and replace it instead of chucking the whole pack.

You will most likely find that if you take the obviously bad cell out of the pack and recharge it, discharge it with a constant load like a string of 12V bulbs with a volt meter in line (unplug it when you get to 1.1V per cell), let it rest and cool and finally recharge it you will be able to tell by the no load voltage drop off if it can be salvaged.

When you replace the bad cells repeat the process after rebuilding the pack to "balance" it. Try not to mix in different cell types though. For a trail pack you should be just fine.

I would buy a box of loose cells and replace them as needed or build your own replacement packs to your liking.

Hope it helped.

[floogldood]

I would guess the cells were out of balance and the hot one was the worst. It either was the smallest/weakest or it just got that way. It may still be ok, and the adjacent cells picked up a lot of increase from the hot one so they may have been much cooler if it had not been for the hot one.