I'm processing these medical packs from Battery Hookup - and I'm running into a number of cells like this:
/Cut Image/
where the corrosion is around the top ring but doesn't extend into the positive top area.
That's kind of interesting about medical packs having this type of corrosion.
In the beginning I would try to get my hands on anything 18650 Li-Ion, I have since become a bit more selective shall we say.
My first set of medical packs were some Phillips 14.4V packs with CGR18650CR cells in them. I got probably about 50 of these packs with 12 cells in them. I opened my first one and found the cells superglued together and extremely difficult to get out. Nevertheless I was happy as they were rated minimum 2150mAh and typical 2250mAh right in my window at that time of what I wanted.
This joy nevertheless came to a quick disappointment as I opened these packs, one after the other had these severely corroded cells in them.
Some of the packs were perfect but most had only maybe on average 6 good looking cells.
I salvaged what I could and found that many were not up to par.
I don't have any pictures of the corroded cells this was very early in my documentation (Nov 2018) but believe me they were bad.
And there was that funny lithium fruity solventy smell.
I also know now that they were manufactured in 2008 and 2009.
As you can see by the wrappers they looked terrible so the good ones were going to get a new skin anyway.
But that brings me to the question it seems that medical packs have a higher rate of corrosion than regular laptop packs.
I have seen and smelled the coffee spills the soda corrosion and the water spills but most of them have never quite been as bad as the medical packs. I wonder if it is the environment that these packs get used in? I mean not all medical packs have this issue. Could it be that these particular cells operate in a high Oxygen environment? Or is there some other caustic or acidic environment that exist in a hospital where these cells would be used. IDK.
But looking at your cell IDK man. It's like looking at the gas tank on your car and you know it's got a bunch of rust spots on it but it just doesn't leak yet.
Personally I would recommend not using any cells that have rust on them
I'm with Korishan on this I would be very picky about using any cell that has any surface damage i.e rust, dents, etc.
If you read the full spec sheet of many cell manufactures they warn against use if any rust is present.
My battery build is way too important to me to loose the whole thing because of a rusty cell. That is why on my first build the frankenstein battery I re-wrapped every cell, especially convincing is when you do find those cells with the hidden corrosion.
Wolf
Cell with hidden rust