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Cells touched a little water
I have to be concerned about used cells they seems to touch water in the past? Not tested them yet.

Funny coincidence, I just posted something about NOS (new old stock) cells, some with rust. And I don't think mine were touched by water. But, in storage that is not climate controlled, all bets are off. Here in S.E. Texas, with often high humidity and hot temps, things rot fast, even if protected from direct exposure to water.

You might start by cutting the wrapper off and seeing how much and how far the rust has spread. I think you might be surprised and answer your own question based upon visual inspection. As for electrical worthiness, that is a good question. Could the cells be cleaned up and rewrapped with no difference from a regular cell I guess is the question. I would assume the cells are made water tight and without vents. But I have also heard that water and lithium don't mix well. Not quite "boom goes the dynamite", more like vigorous reaction and sometimes red flame (according to wiki). FYI: one of the advantages of Lifo4 is suppose to handle environmental issues better, not that I would take a bath with one Smile

So, strip those cells and let's see what they are like without their clothes on. You know how clothes can hide an ugly body.
Keep humidity below 50% and they still ~ could ~ be fine.
Go with Scott, take the rapper of and see how bad it is, but rust over there, i would bin them.
Rust will keep on going.
I bin cells looking like that. I dont use any cells that have any signs of degradation that can hurt Them. Corrosion is horrible to deal with Smile

With that Said you work with what you have and got in hands
thunderheart likes this post
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There is no way to be sure the CID is still in good condition, so ... bin them , better safe than sorry.
Nemo and thunderheart like this post
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My setup:
1) I wouldn’t even consider using cells that looked like that
2) I would be curious to see what it looks like with the wrapper removed
3) Trash em for saftey
thunderheart likes this post
On the same subject I had a cell with a damaged wrap so I took it off to replace it. Once the wrap and insulation ring was off the was clear corrosion that had been pretty well hidden before.

Obviously I plan to discard this cell but it's made me a bit paranoid about how many other cells are corroded like this and flying under the radar by having an intact wrap. Should I be unwrapping every one?

thunderheart likes this post
Bin them.

Corrosion can come from 2 things:
1. Water. Bin them.
2. The acid from the electrolye from the battery is out. Bin them harder.
Korishan and thunderheart like this post
The power of lithium ion is in our hands!
We'll show them what we're made of!
What acid ?
I think BlueSwordM meant electrolyte.
Check out my long-term capacity test of 18650s:

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