Lipo Question - Puffed Cell

[Duster_360]

I went out of the country on business for what turned out to be just short of 3mos. Right before I left I charged all my batts including my 5 different 2S lipos. I then discharged the lipos to about half capacity (750-850mah). Getting home, I found 4 of the 5 lipos now have a puffed cell - always the cell that was on top. The oldest and most used one was the only one that did not puff and even has a slightly puffed cell.

The ones with the puffed cell have nearly identical voltage of 7.8v - suspect that doesn't tell much though. I've read that these should now be condsidered bad, having failed in some way to cause this puffed condition. Anyone know whats going on internally when a cell puffs?

I assume they are unsafe to use now and I'm replacing them. What happens if you put a load on these - try to run them in something? Thought with discharging I'd be good for more than just 3 months - this is going to wind up being an costly experience, lol!!

[guver]

I'm not sure what happens inside, the best you might do is to salvage all the good cells and make packs if they happen to be identical cell. The puffed ones are goners.

[Duster_360]

Thanks, I was headed in that direction, if I can figure how to get rid of the white stuff they used to cap/seal the cells, I may be able to salvage one since only two are the same. May be just too much trouble for a $30 lipo.

I found some detail about them - no one knows what happens inside when they puff (or is willing to share the info) - these just self discharged since they were just sitting on my bench while I was gone. Two had over 100 cycles on them, one about 30 and one was new, never used.

Been told they may run for a few cycles, but sooner or later they will go up and vent/smoke, definitely not safe to use, so they are headed to a bucket of salt water after salvaging my deans connections and maybe a little silicone wire.

[guver]

Make sure you discharge them before disposal. I like to hook a wire between the + and - on a single cell and leave it i the fire pit for days. No need to use saltwater.

[rccardude04]

If you put the +/- together, you're going to have an explosion. That's kind of unsafe. Salt water is the safe way to do it. But only after it's been discharged as low as possible on a discharger.
As far as storage goes, I've never discharged mine any before storing them. I leave them at 100%. I figure they're not going to gain voltage from sitting. They'll lose some but not gain any. I've never had a cell puff other than one I got that did it on the first charge.
-Eric

[Duster_360]

When I knew I was going to be gone for a while and all the advice for storage is to charge then discharge them for 1/2 rated capacity.

I thought I'd be gone 30 days and was gone nearer to 90days. I guess the advice is for a shorter time period. I do the same thing you do if I don't get to run, I charge them and put them away.

I discharged them on my Ice charger, salvaged the wiring and conns and then they went to a bucket of salt water.

[guver]

Make sure you discharge them before disposal. I like to hook a wire between the + and - on a single cell and leave it i the fire pit for days. No need to use saltwater.

Do this only after dischargeing cell down low. Salt water is a no-no on a charged cell.

[stanmondz]

whats the salt water do?

[guver]

the saltwater eats the tabs away and doesn't get rid of the energy.

[rccardude04]

Actually, correct me if I'm wrong, but salt ionizes the water and allows a low electric current to pass through it, discharging the cells to zero volts. After a few days they will be COMPLETELY dead and safe to dispose of in the trash.
-Eric

[guver]

The tabs may be eaten before the energy is drained. I think a saltwater may be good for a puctured pack.

[SS Pede]

So we never figured out why multiple LiPo packs all got puffed cells after being properly stored for a few months? This to me is the overriding issue in this thread. It is unacceptable for a battery pack of any type to just die in a few months if it has been properly stored. What went wrong?

[guver]

You're right, Maybe Duster can tell us how and where they wer stored.

Strange it was the top cell. Maybe they were a bit over the recommended storage voltage, but that shouldn't ve done it.

I'd be real curious as to the exact voltage of all cells (good and bad)

ps I'm going to go flip all my "stored" batteries over. I did once store a new on in a sealed bag in fridge for a year, it is fine and I use it today.