Rusty cells


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bbbbrass

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Jan 17, 2022
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Hi all, new to this. Do you ever clean the ends of cells that have some rust? I’m getting lots of power tool packs and some have a little rust. Not sure if I should clean or just toss.

Thanks!
 

Oberfail

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If i can wipe it away, i keep them.
If the rust is deeper, i toss the cell. A rusty cell is a big hazard.
 

Korishan

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Rust can be very dangerous. Well, not the rust, but what it does to the cell.
Cells are nickel plated steel. The nickel doesn't rust, but the steel does. So if rust has started to happen, that means that the nickel plating has been compromised.
If the the casing isn't pitted where the rust was, then you may be able to just cover it with something, like clear nail polish, or wrapping in kapton tape or something else that can keep the cell from getting into contact with oxygen. Otherwise, the rust will return.

All in all, I would recommend only using cells that have rust spots as testing cells. Do not use them in a production environment like a power wall, or some other build where they will be tucked away, wrapped up tight, non-visible, etc. Otherwise they can't be monitored and could lead to a really really bad day.
 

OffGridInTheCity

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In addition, I pay particular attention to rust on the positive end - as this may compromise the gas-pressure-escape cut-off protection from working - e.g. that little diaphragm that pushes up on gas pressure disconnecting the +. Mainly I toss rusted cells.
 

cak

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I also find lots of rusty cells in tool packs and usually they don't test well so get tossed anyways but I would only use them for side projects like Krishan said and only then if the rust originated from other parts of the pack and not the cell itself(often it seems like one cell or the plating is the part that rusts not always the cull you are wanting to use.
 

bbbbrass

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I found these is an old dell laptop pack. Is this cell leakage?
IMG_5399.jpeg
 
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cak

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Ones that bad I don't even attempt to put it into by rejected cells energy recovery killer where I draw them down to 0v. Not worth the risks and the recyclers can deal with it in it's own bag of similar damaged cells.
 

Korishan

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Toss that cell, asap. If there's still a voltage on it, try to discharge it down to nothing before trashing it though.

Take a 100-mOhm resistor, or a 5V flashlight bulb, and solder wires with a neodymium magnet on the ends. Then attach that to the cell(s) and let it sit for a couple days to make sure all energy is depleted.
If no magnets, then take a cell holder and dedicate it to just that purpose and solder in a resistor or bulb. The bulb would probably be preferable as you can visually see when it's done, as it won't light up anymore.
Then to finish it off, you could then take a wire and shortcircuit the ends. But only do that after you've depleted it as far as possible with the other means first.
 

italianuser

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Feb 25, 2020
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I remember @Wolf finding rusty cells which didn't show any rust if not removing the plastic cover, the shrink.

What I do, not to re-shrink all the cells (nice idea though... all the same, choose nice colours, yes nice indeed :)), when I find a rusty cell is this: I'm quite sure that potentially all cells with that same lot number could be rusty (even if no rust can be seen without removing the shrink). And, in these cases, I do remove all plastic covers from these cells having the same lot number printed on them.
 

hbpowerwall

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I used to think the most likely cause of that was AirConditionsers battery warm home cold or vice versa causing condensation over time
 

bbbbrass

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Jan 17, 2022
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Found several Sanyos in radio packs with rust on the positive ends, and nothing else in pack rusty.
 

bbbbrass

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Jan 17, 2022
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Yep! It smelled a bit like when a tab breaks open the end of a cell. Pack was from 2004, still can’t ID cells. All recycled already.
 

OffGridInTheCity

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I'm processing these medical packs from Battery Hookup - and I'm running into a number of cells like this:
1644349689668.png
1644349722145.png

where the corrosion is around the top ring but doesn't extend into the positive top area.

Here's one that is 'not that bad' - but still, has corrosion
1644350135565.png



There's no sign of water of fluid from outside the wrapper - these appear to be 100% under the wrapper and insulator top ring. Some of these are so bad I'm tossing, but 2/3 of them are mild and are testing OK - e.g. 95% original capacity and IR seems OK.

In this case, you have to pop the cells out of the wrapper to get them loose - so its 'right in your face' as you see the raw cell. Maybe in other cases this has occurred and I just didn't notice it under the wrapper.

What is this corrosion? - is it possible for the internals to spew out and cause this?!? and if so, how can they test OK?

Thoughts welcome :)
 
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Korishan

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Corrosion, rust, can happen with just high humidity in the air. It doesn't have to come into contact with drops of water. I know this, because I live in Fl. We have high humidity on the regular. And I've had things rust being on the porch, w/o any rain for weeks. Just from the 80+% humidity on a daily basis.
And if the cells were in a cool area, and then moved outside, then condensation can occur which would actually suck the water under the wrapping.

Problem with rusting on these cells is that once rust is visible, that means that the outside protective layer has been compromised. These cells are iron casings, they are magnetic. These sheets are then subjected to electroplating of nickel. This basically makes them resistant to moisture. But for any number of reasons, this coating could possibly not be as thick as it should be. Nickel does corrode over time. And when it breaks down enough to allow water to reach the iron, red rust can develop, and quickly.

Personally I would recommend not using any cells that have rust on them. Especially if that rust is near the Pos end and the cap. This puts the built in safety valve at risk.
However, if there is rust anywhere else, it could be coated with something else that would help protect it. Clear fingernail polish would be something that could do this. Just don't use it where you'd solder/spot-weld, obviously.
Another option, if the rust is along the sides, you could put some oil on the cell, put a shrink wrap on it, and shrink the wrap. The oil would get trapped and push out any air bubbles, and help keep moisture from encroaching the cell casing under the wrap. Wouldn't need much oil, just enough to gloss it. Oil as in 2-in-1 oil, or thin coat of vaseline, or something of the sort.
 

Wolf

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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.
1644378689216.png
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.
1644381158452.png
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
 
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OffGridInTheCity

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Corrosion, rust, can happen with just high humidity in the air. It doesn't have to come into contact with drops of water. I know this, because I live in Fl. We have high humidity on the regular. And I've had things rust being on the porch, w/o any rain for weeks. Just from the 80+% humidity on a daily basis.
And if the cells were in a cool area, and then moved outside, then condensation can occur which would actually suck the water under the wrapping.
OK I'm going with this explanation - e.g. external humidity on 'defective metal casing' is causing this corrosion rather than damaged electrolyte spewing gas thru the vents.

Further, its the outer case metal that wraps around the top that seems damaged / allowing corrosion. The middle/positive metal is a separate piece of metal and doesn't have any corrosion. These pieces of metal were likely manufactured separately so just because the outer metal is defective (allowing corrosion) doesn't mean the positive portion is defective.
1644550097373.png


Finally, the cells are testing good! and I just hate wasting them...

Since humidity / rust will continue in my battery bank I'm going to wipe on WD-40 Corrosion Inhibitor on the rust and top ring rust area to stop it / protect from future corrosion and use these cells :)
1644549792151.png
1644549302282.png

This WD-40 stuff is fantastic. I sprayed is on my galvanized pipe threads when I screwed together the PV array framework in the back yard and after 2 years of weather exposure - still no rust on the threads. Used it on some places on the cargo trailer - and after a year, similar good results.

I would not recommend this decision to anyone!!! But wanted to share what I'm going to try. I may be able to do a follow up at some future point :)
 
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