Cells venting, normal or not?

teemust

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Sep 9, 2020
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I noticed a weird smell in my RV after charging and found that the smell comes from 2 cells I have (from 8).

photos show that 2 have something coming out of the pressure valve. One is for reference, rest are like that, clean.

Should I be worried or is this normal? They are not swollen, compared to the others. Its just the weird thing in the valve and smell, the smell also is not super strong or anything, just mild weird smell...

The voltage now is 3.34v in all the cells, but when I charge them they rise as do the rest, exactly the same.

edit. The batteries have been top balanced recently but the problem wasn´t these cells (2 other cells were quite a lot lower)
also don´t know does these matter so 8s Daly bms (150a24v common port) and 120aH cells
 

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stienman

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That is not normal, and those cells should be considered damaged. If you have a way to monitor them while charging you would likely find they are being overcharged.
 

teemust

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Damn, I did monitor them while charging and they didnt go higher than the rest. Also i have never charged without bms so I thought they would be in the safe limits.

Also wouldnt they bulge more before the valve opens up?

But are these safety risk now? thats the main concern...
 

teemust

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Sep 9, 2020
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Its an old daly so i cant change the settings, but my mppt is max charge 27v float 26.8v
and swelling is the same as on the others, If you press them agains each other theres maybe a few millimeters cap
 

upnorthandpersonal

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That is the real question. I'm running into the where, as in where do I dispose of these large cells. I cannot find a source locally and have only found 'for fee" sites hours away.

That's something I can't help with since that's location dependent. Over here I would just bring it in as dangerous waste to the local waste processing company.
 

upnorthandpersonal

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Ok, so the only thing I can think of if they were not overcharged is that they were on their side for some time and some electrolyte leaked to the valve which now came out. We know this was an issue with some Lishen cells, but yours look like CaTL, but I'm not 100% sure of that (make a picture of the QR code). If that is the case, and they are not overcharged (and the no swelling seems to indicate that), these might be salvageable. However you will have to do some charge tests (preferably outside) and do some very close up cell monitoring and verification...
 

RCinFLA

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Overvoltage charging is the most common cause of bloating but if cells have been overdischarged to very low voltage they can develope leakage dendrite paths that heat the cell when charging causing bloating.

It is possible a defect develops in the separator that causes leakage path. During manufacturing the cutting of copper and aluminum foil can create edge burrs that can damage separator. Too much compression can cause this.

Besides overvoltage, too much heat causes electrolyte to decompose and bloat cells. On these thick electrode type cells internal heating starts to become significant above about 0.5C amps of cell current during charge or discharging. At 1C discharge rate, a 280 amp-hour cell will have internal heating of about 35 watts which will get the internal electrolyte very hot. Older used cells will have greater self heating along with greater terminal voltage slump with load current. Prismatic cells packed together do not have good heat dissipation ability.

You might watch to see if cells with bloating have greater self discharge than other cells and if cells get warm when charging..

LFP cells are about as toxic as diesel or fuel oil. There is a small amount of fluorine but it is well captured in chemical bonds.
 
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teemust

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Sep 9, 2020
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I sent a message to the store and they answered immediately,
"Hello, this is normal,
Transportation, temperature difference, air pressure, don't worry"

I have been few weeks in Denmark where the moisture level has been +75% all the time but not sure about this one.

They havent replied to my question about the smell..

I only have and old phone so the photo is definitely not the best. I was trying to get a better photo but no luck there, taking close ups with my phone is almost impossible.

they answered: "The exhaust is normal, and it will return to normal after several times of use. These are all new grade a batteries without quality problems."
 

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RCinFLA

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The manufacturing process is aluminum/copper/separator layers are wrapped then placed in pouch with an electrolyte fill port. The electrolyte is then injected while the whole pouch is put under vacuum to draw in the electrolyte. Finally the port is heat sealed. Sometimes electrolyte does leakage out during filling process and remain on outside of pouch unless it is cleaned off. This could create the smell.

Some of the aluminum shell cases may eliminate the pouch just relying on the aluminum shell casing to seal the wrap.

I have not seen a domed vent port like you showed in picture. The pouch needs to be sealed,. You might try to gently push on the domed port to see if it is still under pressure or if gentle pressure causes it to collapse indicating the pouch seal has been breached.

If pouch is still under pressure what they say may be true. Evenually the CO2 gas will diffuse through pouch polymer. If the pouch is not sealed the electrolyte will go bad. It may take several months to a year for it to show in cell performance.
 

teemust

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The pouches seem to be intact. So all good I guess.

Thanks to you all for helping!
 

Gazoo

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they answered: "The exhaust is normal, and it will return to normal after several times of use. These are all new grade a batteries without quality problems."
The only way I would believe any venting is normal, for any brand of cell, is if the manufacturer stated it's normal.

I suggest finding out the manufacturer of the cells and contacting them directly.
 
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