Fix a puffed LiPo?

I checked through my LiPos recently, I should have done it a long time ago, might have been able to save them if I had. Now I have to dispose of something like twelve batteries, varying from 6S 5000mAh to 3S 1300mAh. They were all left at storage charge, but that was a long time ago. When my eyes had stopped watering at the cost of replacing this little lot, I sat and trawled the Internet for info on what the rest of the World does with puffed LiPos. I found to my surprise that in places where the climate is hot and humid, the cure for a puffed LiPo is a sharp pin and a strip of sticky tape. There was even a video by an Australian as he de-puffed a largish LiuPo, slit the plastic with a scalpel, released the gas then sealed the cut with Cyano. I assume that these life threatening antics are to be taken seriously, or are they?
I decided to try the technique on a 3S 1300mAh Zippy Compact LiPo, it looked about ready to burst, it was brand new and still had its safety label attached. Suitably kitted out with safety glasses and surgical gloves, I laid the battery on a wooden board, held it with a short length of batten, just to apply some pressure to the battery case. I made a tiny slit in the case using a new scalpel blade. It was almost a non-event, there was a slight "click" as the tip of the blade went through. The side of the pack gently collapsed and the merest hint of electolyte oozed from the cut. I cleaned this off with a tissued damped with alcohol, then sealed the cut with clear sealant/adhesive backed up with a wrapping of masking tape. I repeated the process on the opposite side of the battery. Once again, a non-event.
I charged the battery at 1A, can't remember how long it took, but the battery checker read 94% charge.
Today I'll give the battery something serious to get on with, driving the fan in my old MIG 15 at full throttle should warm it up and drain it quite quickly.
I am not suggesting that anyone else should try this de-puffing routine, but it does make me wonder if it is a valid method of rescuing a battery. If it works on this fairly small battery, I'll try it on a big 6S, if that works then I would assume that anything in between would work too.
In the meantime, I'm going to dabble with some strangely labelled "18650" batteries, they seem to pack a lot of power for their size. I might be wrong, but I thought it was worth a try, especially as they seem to cost a fair bitt less than the LiPo equivalent.
Looking at a puffed LiPo, it would appear that the puffing is confined to the two outer cells. I wonder if the answer is to enclose the battery in a hard case?
The cynical view might be that it wouldn't be in the battery manufacturer's interest to produce longer lasting batteries. In the meantime I'll try to figure out a way of convincing MissusLadyWoman that a 6S LiPo really is worth two months of my pension!
 

Personally I would not recommend it.  I have got a few puffed lipos too  and at storage level and they are big-uns. I checked their cell internal resistance and quite good.  So, they still have life in them for use.  Of course some being a bit wider means they won't necessarily fit in the models they were bought for. 

I hope you were wearing leather gloves, leather apron and safety glasses during your experiment...

Today the Zippy Compact 3S 1300mAh LiPo went through seven three minute "flights" in the MIG 15. Several bursts of full throttle to simulate take off, loops etc. but mostly stooging at between half and three quarter throttle. The elevators and ailerons were moved continuously, in fact a lot more than in real flight. .. At the end of each three minute session, the battery was barely warm, and was promptly recharged at 1A. So far there has been no puffing.. I'm recording each run,  there have been no measurable changes in capacity or performance.
I feel that releasing the gas from a puffed battery can only be a temporary fix, whatever caused the puffing in the first place hasn't gone away, and whatever the puffing did to the state of the electrolyte must have some effect somewhere along the line. I wouldn't be surprised if, during the crude tests I'm doing, the battery suddenly degrades very rapidly and turns back into the plump yellow shape that tempted me to try the gas releasing trick.
I had considered doing the same exercise on another battery, but I think that if something unfortunate happened causing damage to either a third party or their property,then the fact that the battery had been tampered with would have a significant effect. on any claim made through the BMFA insurance.
In any case, I'd not consider using a de-gassed battery in a model, it might be safe on the ground, but with a casing weakened by being opened (however slightly) it just wouldn't be worth the risk of using it in flight.
 

There is still life in "old puffers".  Yes, I did mean to use P rather than D.  I have some puffy 3000 mah 3 cells packs and use them to power Christmas LED lights and fairy strip lights in the garden.

Brian - Interesting to read your test results after " depuffing"
Wise decision not to use any of them in a model,  also they could possibly decide to let go in your car , ejection seats not fitted to
Mini Countrymen yet.
Why did they puff ?
Possibly high summer temp in your shed ?
Catch up soon.
Regards
Colin

The depuffing biz has been a big disappointment. I was hoping for at least one exciting incident, perhaps a puff of smoke, or a slight "pop" followed by a hiss and a jet of flame that just missed the back fence. Instead I have a dull looking battery with straight sides and holding a charge that claims to be 94%.I must admit that I started this project with a view to resuscitating  LiPos and putting them in models. However, after considering the dreadful consequences of LiPo accidents, I decided that de-puffing a 1300mAh Zippy Compact was as far as I want to go.
I didn't spend two months pension on a couple of 3S 2200mAh LiPos, I went to the Bank and arranged a small mortgage, fortunately the kind Lady Manager has a soft spot for doddery old gents with no money.
Anyway, with a view to re-equipping my few electric powered models as cheaply (and safely) as possible, I'm now going to get all the gen I can on the remarkable LIIon batteries that go under the name of "18650". The cells are metal cased, they probably won't "puff" but I wonder if they might detonate?