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Cell puncture leaks
#1
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?
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https://secondlifestorage.com/showthread.php?tid=6458
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#2
(11-26-2018, 04:03 AM)ajw22 Wrote: 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?

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....
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#3
No, I'm definitely not using them again. I'm just worried they might start some chemical reaction, so I quarantine them for a few weeks before sending them to the recyclers.
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#4
(11-26-2018, 04:03 AM)ajw22 Wrote: So far, I've put duct tape on before throwing on the "might be dangerous" pile outside.
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.
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#5
(11-26-2018, 04:48 AM)thunderheart Wrote:
(11-26-2018, 04:03 AM)ajw22 Wrote: So far, I've put duct tape on before throwing on the "might be dangerous" pile outside.
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.

Jeez, that just doesn't sound safe...lol...
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#6
in a metal bin of salted water outside is perhaps a good way doing it?
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#7
(11-26-2018, 04:48 AM)thunderheart Wrote:
(11-26-2018, 04:03 AM)ajw22 Wrote: So far, I've put duct tape on before throwing on the "might be dangerous" pile outside.
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.

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.
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#8
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?
Modular PowerShelf using 3D printed packs.  60kWh and growing.
https://secondlifestorage.com/showthread.php?tid=6458
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#9
(11-27-2018, 04:13 AM)ajw22 Wrote: 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?

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.
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#10
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
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