Cell puncture leaks

ajw22

ajw22

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Joined
Nov 16, 2018
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About one in 200 cells develops a leak on the negative side when I pull off the spot welded tabs. Sometimes the electolyte oozes out slowly, sometimes drips out forming bubbles.

So far, I've put duct tape on before throwing on the "might be dangerous" pile outside. Yesterday I wiped and sealed the leak with some glue before quarantining the cell.

Do you have similar experiences? Is it just my bad technique? What do you do with leakers?
 
ajw22 said:
About one in 200 cells develops a leak on the negative side when I pull off the spot welded tabs. Sometimes the electolyte oozes out slowly, sometimes drips out forming bubbles.

So far, I've put duct tape on before throwing on the "might be dangerous" pile outside. Yesterday I wiped and sealed the leak with some glue before quarantining the cell.

Do you have similar experiences? Is it just my bad technique? What do you do with leakers?
Click to expand...

Um, you should really biff them. They will slowly degrade and end up taking your pack down....

I just chuck mine in the pile to go back to the recyclers.

The only time I have had a hole in a cell was when I was a bit too over-enthusiastic with the spot welder amperage settings....
 
ajw22 said:
So far, I've put duct tape on before throwing on the "might be dangerous" pile outside.
Click to expand...
Wise attitude! I'm not sure how long the tape will close the hole but it will make the cell much safer, that's for sure!

About 3 months ago i received 3 Lipos from Aliexpress for one of my drones. All 3 were puffed though capacity was ok and they were working well in my drone. I gently cut the transparent heat shrink tube, punctured the pack using a very thin needle, let the air go, then put a piece of an ordinary transparent tape on the hole. I did it with all 3 packs and they are ok till now.
 
thunderheart said:
ajw22 said:
So far, I've put duct tape on before throwing on the "might be dangerous" pile outside.
Click to expand...
Wise attitude! I'm not sure how long the tape will close the hole but it will make the cell much safer, that's for sure!

About 3 months ago i received 3 Lipos from Aliexpress for one of my drones. All 3 were puffed though capacity was ok and they were working well in my drone. I gently cut the transparent heat shrink tube, punctured the pack using a very thin needle, let the air go, then put a piece of an ordinary transparent tape on the hole. I did it with all 3 packs and they are ok till now.
Click to expand...

Jeez, that just doesn't sound safe...lol...
 
in a metal bin of salted water outside is perhaps a good way doing it?
 
thunderheart said:
ajw22 said:
So far, I've put duct tape on before throwing on the "might be dangerous" pile outside.
Click to expand...
Wise attitude! I'm not sure how long the tape will close the hole but it will make the cell much safer, that's for sure!

About 3 months ago i received 3 Lipos from Aliexpress for one of my drones. All 3 were puffed though capacity was ok and they were working well in my drone. I gently cut the transparent heat shrink tube, punctured the pack using a very thin needle, let the air go, then put a piece of an ordinary transparent tape on the hole. I did it with all 3 packs and they are ok till now.
Click to expand...

I knew someone who did this to LiPo cells. Never had a problem with them. But for me NO WAY! Its not worth risking.

Same goes for holes in 18650s I imagine. You could probably plug them with solder. But again, I wouldn't do it. Perhaps for the sake of an experiment, but I would still treat them as dangerous.

Best trick with spot welds, if they prove stubborn at all, I just cut the nickel off as close as possible to avoid puncturing the cell.
 
That's just it. The tabs are max 0.25mm thin and not stubborn at all to remove - they come off quite easily. But about 1 in 300 (not 200, upon second look at my harvest data), the cell wall gives instead of the tab sheet, and I end up with a leaking cell. Nobody else having this problem?
 
ajw22 said:
That's just it. The tabs are max 0.25mm thin and not stubborn at all to remove - they come off quite easily. But about 1 in 300 (not 200, upon second look at my harvest data), the cell wall gives instead of the tab sheet, and I end up with a leaking cell. Nobody else having this problem?
Click to expand...

Yes. It does happen. Batteries that are designed for high current applications are most prone to it (ebike and power tool batteries). Spot welding hardens the metal making it brittle, and therefore more likely to crack. I have never had the issue, as I use a sharp pair of side cutters, which cut the nickel - leaving little pieces on the spot welds. Makes cells a bit nasty to handle, as they can cut, but saves damaging them.
 
Another thing to try is to roll the tabs, instead of pulling/yanking on them. This applies a different force and usually makes the tabbing tear and let go. Then snip off the remaining.
If you do any kind of sanding, make sure that it is as small as possible of a patch to not take off the layer nickel that's on the cells. Otherwise you'll get rust/corrosion later on
 
Korishan said:
Another thing to try is to roll the tabs, instead of pulling/yanking on them. This applies a different force and usually makes the tabbing tear and let go. Then snip off the remaining.
If you do any kind of sanding, make sure that it is as small as possible of a patch to not take off the layer nickel that's on the cells. Otherwise you'll get rust/corrosion later on
Click to expand...

Irollthe tabs on the majority of my cells. I've only had one cell where the negative terminal was so thin rolling the tab pulled it to the point of creating a puncture. I put that cell off to the side in my quarantine pile about 4 months ago and slowly over time it has created a small black deposit sealing the hole. In my experiences Samsung cells tend to have relatively thin terminal walls compared to LG cells or Sanyo cells.
 
I have better luck twisting rather then rolling.

Rolling works most of the time, but when it doesn't it to late and you already did the damage.
 
Chablis_m said:
I have better luck twisting rather then rolling.

Rolling works most of the time, but when it doesn't it to late and you already did the damage.
Click to expand...

i rework them a little bit with the dremel , the spot is then weakend and if you pull then the nickel strip , it snaps around the welds
then i grind the last bits and peaches off
 
Leipi35 said:
Chablis_m said:
I have better luck twisting rather then rolling.

Rolling works most of the time, but when it doesn't it to late and you already did the damage.
Click to expand...

i rework them a little bit with the dremel , the spot is then weakend and if you pull then the nickel strip , it snaps around the welds
then i grind the last bits and peaches off
Click to expand...

Would never have thought to do that. Seems to be the surest way to ensure that the nickel strip gives, instead of the cell bottom. Though I supposethere's the danger of accidentally grinding off too much.
It'dbe a lot of work dremel'ing all the spot welds... but thenickel stripswould come off with much lesseffort...

I'll try it when I get my next set of powertool batteries.
 
Never grind into the cell. It will corrode over time. Its ok to grind on the nickel strip though

Note that the time above takes you can pop 5 other cells ready so unless you are very short on cells i never do above. Perhaps 1 cell out of 300 here gets punctured but the time i save is alot :)
 
Ya I had a cell leak on me when i took off the nickel strip, It smelled very sweet so thats when you know its leaking.

I threw it outside lol.
 
thunderheart said:
About 3 months ago i received 3 Lipos from Aliexpress for one of my drones. All 3 were puffed though capacity was ok and they were working well in my drone. I gently cut the transparent heat shrink tube, punctured the pack using a very thin needle, let the air go, then put a piece of an ordinary transparent tape on the hole. I did it with all 3 packs and they are ok till now.
Click to expand...

Apparently you don't realise but the danger of doing that is pretty high!
Just to elaborate: for work related matter I visited a lipo factory in Shenzhen earlier this year. The last part to activate the cell is to fill it up with liquid electrolyte before it is sealed off. This is done in a chemical chamber and in a vacuum. This is because the electrolyte will react and oxidate with the oxygen from the air.
If you puncture a puffed cell (already indicating problems) you will expose the electrolyte to oxygen and will increase the likelihood of a battery failure.
There's enough proof on the internet that messing with lithium packs is a very, very bad idea!
 
daromer said:
Never grind into the cell. It will corrode over time. Its ok to grind on the nickel strip though

Note that the time above takes you can pop 5 other cells ready so unless you are very short on cells i never do above. Perhaps 1 cell out of 300 here gets punctured but the time i save is alot :)
Click to expand...

That maybe a fact but the nickel strips on the ebike accu's are a pain in the ass.
With Laptop accu's , i never had problems
 
Leipi35 said:
daromer said:
Never grind into the cell. It will corrode over time. Its ok to grind on the nickel strip though

Note that the time above takes you can pop 5 other cells ready so unless you are very short on cells i never do above. Perhaps 1 cell out of 300 here gets punctured but the time i save is alot :)
Click to expand...

That maybe a fact but the nickel strips on the ebike accu's are a pain in the ass.
With Laptop accu's , i never had problems
Click to expand...

I really start to dislike the ebike accu's, just punctured 5 out of 7 cells... let's order the dremel and try by weakening the nicle strip.
 
Cut Them instead of ripping Them. Leave the tab on
 
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