Successfully depuffed a lipo cell

[zombiess]

This isn't something you should do if you aren't comfortable working with LiPo

Just wanted to post a success story. By following AussieJesters directions I depuffed a cell in one of my packs. Now it's going to be monitored. My first charge was done outside (just in case) at 5A into a Turnigy 6S 5Ah pack to see if it would get warm, it didn't heat up at all. I normally parallel charge 8 packs at a time in a 40Ah configuration 6s8p. This cell has always been the weakest out of all my packs, but doesn't go out of balance if I don't discharge below 3.7V resting. I charger reports a resistance of 2mOhm which seems normal for my packs which vary between 0-2mOhm for each cell and an average of 4-6mOhm per pack. I do notice that when measuring the packs each one needs to be done several times as the cell values keep changing but almost always average out to 4-6mOhm total for a pack of 6S 20C.

All 8 of my packs have gotten a little soft from over discharging to 2.8-3.1V one time (my fault) to LVC set at 3.0 per cell. This one cell did puff up a little more than I liked and has been in that state for about 4 months. I used a small metal pin (tooth pick would have created too big of a hole) to very carefully create a very tiny hole in the crease and release the gas and then sealed the entire edge with hot glue quickly. If this cell puffs even a little, it's going to be replaced.

The over discharge was intentional. I should have stopped but didn't and rode it until the cutoff kicked in and the packs got pretty warm. I won't be doing that again, next time I'll walk it home. Based on other stories I've read this repair should be successful, but only time will tell. I know many on here are afraid of LiPo cells, but after watching all the videos of people physically abusing them and knowing how hard hard RC guys use them I'm not afraid of them, but I do respect them.

 

[mvly]

I heard that you can apply pressure while discharging the cell to get it to shrink. have you tried that before poking holes in you lipo?

 

[zombiess]

I heard that you can apply pressure while discharging the cell to get it to shrink. have you tried that before poking holes in you lipo?

No I haven't. Never heard that, have you ever tried it before? Poking a hole does work from what I've read.

 

[dogman dan]

After a year of use, occasionally abused by discharging all the way to 3.5v, pretty much all my turnigy is slightly puffed. Not puffed like some bad 4s packs I once got, but definitely no hard like they were when new. In a case like that, I see no particular need to de puff.

Really puffed, I chuck the puffed cell. When I get enough spare cells, I might make some 7s packs for my 24v mower.

 

[Bazaki]

I had a brand new Turnigy 5000mah 6s 20c with a puffed cell, I store it in a metal closet and the puffing was getting worse and worse, the voltage was still nice 3,85v just like the rest of the cells.
About 2 weeks ago I did check the 6s pack again and now this puffed cell wasn't puffed anymore. The whole pack charge and discharge fine, but there is some imbalance with the cell that was puffed.
So I won't use it anymore, maybe as a spare part.

 

[liveforphysics]

I heard that you can apply pressure while discharging the cell to get it to shrink. have you tried that before poking holes in you lipo?

This is absolutely 100% not true. If you apply enough pressure that it shrinks, you just broke the seal of the pouch in some seam that you don't even know where it has a hole to patch.

 

[dogman dan]

Yeah, Bazaki's puffy cell just popped. slowly discharge that cell and dispose. Or dispose of in a fun way if you choose.

 

[zombiess]

Yeah, Bazaki's puffy cell just popped. slowly discharge that cell and dispose. Or dispose of in a fun way if you choose.

That's exactly what I did with a brand new pack that came puffed. Figured it had impurities so I seperated and discharged the bad cell which went in the garbage. Kept the other 5 cells.

The pack with the cell I degassed is wrapped in duct tape so it's obvious which one has the hole. If it starts to puff or cause problems I'll replace the cell. The cell wasn't puffed a whole lot but enough that I wanted to try this method.

 

[liveforphysics]

If you puffed them from a user-error, and you de-puff the cell, you are likely going to be good to go, and get a bunch more happy life out of that cell.


If they puffed on arrival, they are defective, and those cells should be destroyed. (Overcharging them is my favorite method. ) A bucket of salt water is a tame and safe method.