This is an odd one for me, 2 of my brand new SMC lipos i bought last year and ran 2 times before the snow flew have been in storage all winter, I check all my batteries every couple weeks (with a cell voltage indicator) and put them on the charger to double check.
These 2 both puffed up at the exact same time, and they are both still at 3.8v/cell.
What could have caused this and is there a way to reverse the puff?

http://www.begoracing.com/shop/index...&product_id=75

2 of these with maybe 20 minutes of run time on them, i sure hope they can be recovered.

I have had luck putting them in the freezer over night to get the puffing to go away.

SMC states that they use low profile cases, and that a puffed battery is normal for theirs because there is very little room inside the case to allow the batteries to expand.

As you can tell by the pics, the majority of the puff is on the bottom of both cells.
Which again is just too friggin weird.
One of the cases actually cracked on the bottom. I have seen lipo puff before but never 2 at the exact same time while NOT being used.

I'll put em in a lipo bag overnight in the freezer and see if that helps at all.
I would hate to write these 2 off so early in their life span. Last year was an expensive year as i finally laid about 8 SPC to rest.

I've had good results doing this as well. I had 2 4s Turnigy packs (wouldn't buy any turnigy again mind you!) that puffed and the freezer treatment worked well to reduce the puff.

well 18 odd hours in the freezer in a lipo bag certainly took the majority of the puff out of them. I'll let them thaw in the lipo bag in my Plano box and see how they react.

I'll try putting mine in the freezer to see.
So how long does it have to be there?
If after the freezer treatment, will the swelling come back again when used?

Put them in for a good 24hr period. Once out bring them slowly up to room temperature prior to cycling them at 1C a couple of times and then leave at storage voltage for a couple days and see what happens.

After coming back up to room temperature overnight after a night in the freezer they swelled right back up again.
Not particularly impressed.
9 other batteries here the have the same treatment over the winter months and not one with an issue.
But both of these new $75ea batteries are as far as im concerned NFG.

I may try cycling them, i may not. More inclined to go back to SPC which have never led to issues with me before. The 8 i got rid of last year were an average of 4-5 years old IIRC.

I've got a couple of the same SMC batts, and there are swollen some, but not quite as much as your appear. I've ran them like this last year, and have been in storage for the Winter, and are still OK. Another user posted about how these cells are really rammed in there in order to get that capacity, and the case ballons somewhat. All cells do this, just some have more room in the case, so you don't see the effect.

My son's SMC did the very same thing. I store my batteries in my garage at a stable 75° and his SMC pack and my Reedy Saddles swelled back up.

Contacted both companies and Reedy just sent me a replacement pack free of charge and SMC's best solution was for my to dull out another $35 for a replacement pack. Still not terrible but with the SMC being a few months newer, I would've expected them to offer to send me a new one before Reedy did.

Either way, it goes to show that it doesn't matter if its a $40 Lipo or a $150 Lipo… They're all susceptible to swelling and failure at random, and as such, you might want to rethink spending wads of cash on "brand name" batteries.

The only brands I can truly vouch for as being superb are Venom and TrakPower. The ESC shelf on my 4.2 even caught fire and it melted one of my Venom shorties and I thought it was toast, but after thorough testing and cycling, it proved to be just as good as new. It's been that way for 1.5 years without skipping a beat. Venom's CS is also excellent. Very friendly and knowledgeable people.

Oh yeah absolutely, there is no real guarantee that an expensive one will last any longer than a cheapo from china. I as a personal choice, choose to stick with the local-ish suppliers and those with warranty to deal with issues like this.

The biggest thing about this is how they both did this.

I have a couple Terra Nova 4s packs and am in love with them. i may replace these SMC with a couple 2s Terra Novas since SPC seems to be out of everything right now.

(or on the back of a DEX408t kit and a 2nd XO-1 purchase, wait it out a bit and give the bank account a rest lol)

Of the two modern SMC packs I have bought, one lasted about 15 cycles in 4wd SC before a cell crapped out. The other one is still going.

IP packs from ProMatch for me.