Sadly I've bloated / pillowed my cell in the first few days, doing a capacity test and charging it afterwards.
My charger was possible set to CC (constant current)
Anyways, I was "lucky" to be able a new 152Ah cell with my next order.
Since then, several months have passed and I have been using the pillowed cell for tons of other things.
Always nice to have a 3.2v battery
In those months, more of my 152Ah cells got little or more bloating.
And some of the 280's start also.
I've done a TON of research on this topic.
It
is perfectly normal behaviour!!!
The cells are not damaged.
Yes, it looks funny / strange / concerning.
Capacity wise, life cycle still the same.
Lithium-ion are notorious for this.
The problem with them is not so much with safety or capacity, it's the shape.
Mobile phone screen get cracked, or the battery cover no longer fits.
In RC, the pouch no longer fits in the plane / car / drone / whatever..
Capacity wise... Not a problem!!
Puncture it, that is a problem and where the
fear originates!
With lithium ion, those gasses are flammable. That is what makes lithium ion dangerous goods to transport, and even responsible for plane crashes.
In event of a short, the cell heats up, makes loads of gasses, breaks and the rest is a small spark that egnite the explosive flammable gass.
Lucky we have Lifepo4!!
Not lithium ion!
I can not advise to inhale the gass escaping from the vent, that probably is nasty. But it's
NOT flammable!!
On this forum there are several YouTube videos showing lifepo4 abuse. Shot at, punctured, shorted (100ah can give 1300A), burned for half an hour, etc etc etc.
No explosion, no fire, no flames.
Boring actually!!
Even a full short of a fully charged 100Ah was almost boring to watch.
Naturally, it bloated, the vent bursted, you see gass escaping. That was it..
No spectacular things like with lithium Ion. Boring...
And... After this full short and vented cap, the cell still works. I can't say anything about the rest of the life cycle, but it did work!! Amazing!
Some background information on the gassing, this part is the same for lithium ion and lifepo4.
During the initial charge there is a special section in the pouches to collect the gasses that's formed, and sealed + cut after this first charge.
True, not all lifepo4 have pouches inside, some have layers that aren't sealed in a pouch, only in the cell
(What is fine also!)
How they technically do this at those cells, I don't know. Most likely they place the vent after initial charge.
Many people compress their cells, even
@Will Prowse shows this in his videos.
That isn't only just to keep the cells nice together, it's also to prevent bloating!!
Newer lithium-ion pouches for RC have a tiny bit reinforcement, enough to prevent the bloating.
CALB cells have strong plastic housing, to prevent this from happening.
Our Eve cells??
Almost nothing!
Thin, flexible aluminium.
Even the slightest bit of gass will make it bloated.
This doesn't mean that there is no bloating force in the CALB cells, there still is.
The housing is built to withstand this force. That's all.
We are all (myself included) using cells with paper thin walls without any protection against bloating, and complain when it does...
That's actually kinda stupid.
The cells aren't wrong or bad, we are.
We are abusing the cells outside specifications.
These cells are intended to be compressed mounted, not stand alone.
It's our lack of knowledge how to properly use the cells that makes them look funny.
Not broken, not defective, not dangerous.
This is NOT lithium ion!!!
I have used my cell a lot the last 3 months.
I even had it back in my battery array for a few weeks, replace a "healthy" cell.
My array is 3* 152 and one 280Ah per parallel set, 16 in series.
736Ah or roughly 37.5 kWh
No difference at all! (In terms of usage)
I have less bloated cells then the one I pillowed, it makes my array look funny.
That's all.
It looks different. Correct.
Can you still use? Yes you can!!
Can you still use it like the "healthy" (not bloated) cells? Yes you can!!
And you should.
besides having some gass inside there is absolutely no change in the internal chemistry or capacity or whatsoever.
The fear originates from lithium ion battery. Not lifepo4.
If you have a hard time believing this, please do a search on YouTube for lithium-ion and lifepo4 battery abuse.
You'll find the lifepo4 boring compared to the sparks and explosions that happened with lithium Ion.
De-bloating..
That's an interesting test.
I don't think I can safely de-bloat my pillowed cell.
The other cells that have some mild bloating like yours, I think it is possible.
I am going to try.
The steps are simple:
Compact!
Use 2 metal or wooded sheets (or other strong material) and compress the cells together.
I'm using aluminium strips and threaded rods to do this, for all my cells.
4 in a parallel set, 16 series.
I will put some syrofoam between the cells.
And compact.
Don't overdo it!!!
Gass can turn back to liquid in higher pressure.
The gassing is normal.
Being not compressed is not (or have strong walls that can handle the internal pressure without bloating)
A full battery is supposed to have more gass then discharged one.
Also, most gassing occur during charge or fast discharge.
Logically, at lower SOC the pressure should be less.
Perfect time to tighten the sheets a little more.
After several cycles it should be possible to tighten a little more, using the same force as used the first time.
The tension / pressure reduces as the gass is slowly getting back to liquid.
That is in theory.
I am going to do this, once my bus-bar project, melting copper and pouring in casting, is finished.
(Sadly, that goes a lot slower than hoped!)
I was "stupid" to ignore the advice given by
@Will Prowse , to compact the cells.
I'm fairly confident that "re-pressuring" the cells will give them more their original shape back, but most of all, prevent the cells that are not yet bloating, to do so.
Seeing the videos of lifepo4 abuse and the time it takes before the vent burst, it can handle quite some pressure.
Just normal behaviour for Lifepo4 cells that aren't compressed placed (as they should be) to start bloating.
Nothing to worry about.
Safe to use.
Same lifecycle.
Just look funny.
It is NOT Lithium ion !!