Gens Ace lipo swelling after sitting?

[Thirdgen89GTA]

Today I had a bash session with some guys and I ran both my 3S twin packs, and my 2S twin packs down. The 3S packs were run in parallel, but I run the 2S packs in series for 4S.

Jammin X1 Truggy
RCM X1 CRT mount (18/62 spur)
MMM 2200kv
(2) 2S1P Gens Ace 40c 5000mah Hard Case lipos in series.
(LVC set stock @ 3.2v)

Since this was the first bash session I kept an eye on the temps. On 3S the ESC, batts, and motor never exceeded 110* (3S batts were 91*. on 4S after some wide open throttle runs when I brought it in the ESC was 130* and the motor 120*. The batts reported 108* and 110*.

However when I pulled out the twin 2S batts one of them was very slightly swollen! I left it on a curb with nothing but concrete around it till I was ready to go home. The swelling has gone down some and most people wouldn't even notice the swelling unless they placed the battery on a flat surface or compared it with another of the same batteries.

So i'm torn right now. A large part of me is rather upset, I've been monitoring the temps and its been nothing but happy to take whatever I throw at it. I really haven't bothered to throw many speed runs at it on 6S. At the tracks its been perfectly happy with temps on 4S and 3S staying below 110* for everything. I thought for sure I was using safe gearing for its main purpose which is bashing and track day practice.

The truck never flipped, or took a hard hit of any kind. It was all pretty much straight line runs and wide ovals.

Most of me is ready to trash this pack right now. I bought the packs to use in series, so if I trash one then I have to buy another 7.4V 5000mah pack of the same brand or I may run into issues.

Below are pics of the two batteries. Left is always on left, right is always on right.

http://home.comcast.net/~thirdgen89g...l/IMG_1725.JPG

[Thirdgen89GTA]

First (non swollen 2S battery) has finished charging now. Pack never got warm to the touch while charging and took 4730mah in charge.

Balanced charged it at 1C, its definitely swollen like the other one. :(

At this point I may consider both of these packs a waste, thats $65 down the drain. :( I was going to buy another set of batteries so I had another 4S set to play around with. 3 sets of batts would let me run through an entire 5hr open practice session at the local track with marshalling and breaks between runs. Now it looks like I'm gonna have to trash these packs and use the $$$ I had for a 3rd set, to be my 2nd set. :( :(

I'll call hobbypartz on monday and see if they can do anything for me. I don't think I over-discharged the pack, I had the LVC still set at the default MMM setting of 3.2v and I heard the 4 beeps when I plugged the batts in.

[bruce750i]

I would use a little higher cutoff like 3.4v if you have a c-link.

Check each cells voltage in that pack for abnormalities.

Did the puff reduce after charging?

[Thirdgen89GTA]

Originally Posted by bruce750i

I would use a little higher cutoff like 3.4v if you have a c-link.

Check each cells voltage in that pack for abnormalities.

Did the puff reduce after charging?

I've already increased the cut-off to 3.3v vs the stock 3.2v.

I did read that charging a pack can reduce the swelling sometimes. Its currently balance charging at .5C right now. And that sometimes it can take several cycles.

I don't have a volt-meter right now. I suppose I should get one of those nifty little testers that report back on each cell so I don't have to probe each one.

___________________

However, I first charged the non-swollen pack, and after balance charging it at 1C its swollen NOW. It wasn't when I started charging it. So I'm thinking I may have to junk both packs unless I want to risk running them and having my truck go up in flames. I've heard that some people continue to run a slightly swollen pack without issue. I'm not sure if I want to take that risk.

I will see what the vendor will do for me. I ran the 3S lipo's in parallel with the same voltage cut-off setting as the 2S and those are fine. But the twin 2S packs are exhibiting problems.

[j.f.s]

You should measure the internal resistance of both packs. I've got a Turnigy 3s pack that puffs slightly after each run but IR is still around 1-3 mOhms after charging. A high IR will cause the pack to run hotter and cause more swelling.

[Thirdgen89GTA]

Still don't have a VOM to test the cells. Will probably pick one up this week. Broke my last one. :(

I discharged them using the charger to 3.1v/C and then charged them backup. The swelling is visibly gone, I can't see it at all anymore. If I place it on a flat surface (computer desk) I can very slightly rock them back and forth.

I'll cycle them a few more times at low charge rates using the charger and see if that goes away. At least then I can do it in the steel sink with a charge bag.

[jhautz]

I had a gens ace pack slightly puff like that Bill. Happened when I ran it all the way down trying to finish a 10 minute race with a heavy Losi SCTE 4x4. 5000mah wasnt quite enough. I made it the practice pack but in reality it ran just as well as the other packs that didn't swell and Im still using it. Not recommending that you do the same but I haven't had any issues with it. Im sure it wont last as long as it should and I pay attention with that pack and dont run it all the way down any more either.

I also agree with the previous poster. Bump up the LVC setting. That seems to be the fastest way to ruin a good pack is to run it down to the cut off. Most damage is done to your lipos in the last minute you are running them. Especially if you are running them hard in the last minute. Just not worth the cost for an extra 30-sec to minute of run time IMO.


Where were ya bashing at in February in Chicago????

[Thirdgen89GTA]

Originally Posted by jhautz

I had a gens ace pack slightly puff like that Bill. Happened when I ran it all the way down trying to finish a 10 minute race with a heavy Losi SCTE 4x4. 5000mah wasnt quite enough. I made it the practice pack but in reality it ran just as well as the other packs that didn't swell and Im still using it. Not recommending that you do the same but I haven't had any issues with it. Im sure it wont last as long as it should and I pay attention with that pack and dont run it all the way down any more either.

I also agree with the previous poster. Bump up the LVC setting. That seems to be the fastest way to ruin a good pack is to run it down to the cut off. Most damage is done to your lipos in the last minute you are running them. Especially if you are running them hard in the last minute. Just not worth the cost for an extra 30-sec to minute of run time IMO.


Where were ya bashing at in February in Chicago????

Berwyn forrest preserve. It wasn't much of a bash. Showed up, one other guy did. I was the only one with a running truck.

Both packs took ~4750mah for a full balance charge at 1/2C so I could keep an eye on them. I've cycled them twice so far and the swelling has all but disappeared. I can't physically see it, or feel it with my fingers.

But if I place it on a level surface like a desk I can rock the pack back and forth slightly.

Lately though its been trips to Leisure Hours raceway with the Jammin, and the Streamwood track with the Mini 8ight.

I don't remember breaking Wing Mounts and rear chassis braces as much as I have lately on the Jammin truggy. I wonder if the plastic has gotten crappier being that the truggy is out of production and they switched to a cheaper supplier.

It also bent my rear shock tower. :( Never did that before, ever. Got it straightened out, but it'll never be 100% right. Can't decide if I want to replace it, or simply continue to use it.