Anyone else vented A123's?

I gotta admit, I really didn't know this was possible, but happened to me about a week ago and I finally got around to doing something about it. In my crawlers I run 3s1p A123 packs and thought I'd cycle my packs with some runs behind my house. I charged up the first pack at 4a fine with a Lipo Dapter between it and the charger, but the second pack (the one I didn't use as much) had the charger peak and then I heard a POP. Sure enough, that one ran like crap, and I checked the voltage yesterday to see it was only at around 7v while charging. Figuring it was a dead cell, I did trial and error, and found one of the three had only .004v.......yup, dead cell. I pulled the pack apart and rebuilt it as just a 2s, so now I have a 3s and a random 2s........this sucks.

[BrianG]

Could have been a defective cell. What charge rate and profile are you using? And, what kind of discharge currents are you pulling?

[cart213]

I had an A123 Racing 2s2p pack crap out on me last month. Half of the pack died so that it was running like a 1s2p. I sent the pack back to A123 Racing, and they replaced it free of charge!

Well, I built these from DeWalt packs, so I could have messed them up a little in the assembly process......but I do think this particular cell was defective or something.

Before charging, I discharged with my Deans 20a light bulb discharger and then set it to charge at Nimh 4a on my Pro Peak Prodigy 2........I don't remember how much it took, but the charger began to beep that the pack was peaked, and I heard the infamous pop.

[MetalMan]

Of all of my custom assembled A123 packs using 30 cells total, I still have yet to have any problems. Looks like you got unlucky, David!

[jhautz]

I have an a123 2s2p pack built by a123 that has a bad cell in it. I was using it in series with a 3s2p pack that I built from a dewalt pack, for 5s2p total in my Savage. I ran it and all looked good, but when i went to charge it It wouldnt take a proper charge. I checked the volttages and it apears that one cell is virutally at 0. But I never heard a pop or anything. I havent done it yet, but I am planning to replace the bad cell with one that I have left over from a dewalt pack. So I guess it does happen. Ive gotten bad NIMH cells before too. What are ya gonna do.

Well, I guess it could have been the fact that they sat for a few months.....but I was hoping the discharging first would wake them up and prevent anything like this from happening. Oh well, at least it was with one of the crawler packs and not the main other ones I have.

Crap, had another one fizzle out this week, just without the cool "pop" the last one had. It was in the other crawler pack (the one I thought was still good), and voltage just started dropping from 8.5v during a fairly gentle 3.5a charge. Sure enough, I checked the different cells and one was at .2v and refused to do anything but drop more under charge.

Here's the odd thing, both of the cells that died were in the same location, as far as the pack was built. I had 2 cells taped/shrink wrapped together on the front axle, with a lead running to the back axle and a third cell. The two front cells were connected on the back end with copper braid soldered to the ends, with one having a 4mm gold plug soldered straight to it and the other with one end of the long 3rd cell's lead. Here's the thing, both times, it was the cell with the plug soldered to the end.....could they have been overheated and weakened somehow? I didn't think I heated them up too much when soldering, but I guess it's possible. From now on, I'll try to use a wire lead to the plug instead, just to be sure.

Wow, yet another pooped out, so this brings the total to 3 so far now. I rebuilt the two packs into one 4s though, and it worked great last Saturday, and still took a good charge the next day when I wanted to goof around in my back yard.....don't know what was up with those other ones.

[jhautz]

when you soldered them did you solder to the tabs or directly t the cell? The a123 is more sensitive to heat than MiMH cells and I read that if you overheat them by soldering direct to the seal in the cell will be damaged and they will vent. Could this possibly be your problem? You could probably overheat a cell by keeping the heat on the tab too long as well if your not carefull.

[highflier]

They tend to pop if you overcharge the A123's. You must not use NMHI logic for charging. If you are using lipo mode you are on over spec. The other issue is you can get a wrong cell count on start of charge so watch carefully. It surly is not the amp charge rate, I start my charging at 20 AMP. and sustain 10+ amps for a good portion of the charge.
Highflier