Left 105Ah Lifepo4 battery, came back to two heavily swollen cells.

[blipohm]

Hi,
I had a battery balanced, had disconnected the BMS but left cells in 4s 12v config. (4 x 3.2v 105Ah lifepo4 cells)
I came back after 3 months to find that 2 cells had swollen by 60% (I could not believe how much).

My question is, would it be a factor that I had disconnected the BMS?
The cells were cheap to begin with, I assume that is probably the main reason for swelling.
When I took the BMS the battery would have been at 95% charge.

Thoughts?

Thanks in advance!

 

[robby]

If I am understanding you correctly, you removed the BMS and the batteries just sat there with nothing charging them. If that is the case then they should have been fine for 3 months. The only way I can see them swelling is if you left them charging.

 

[blipohm]

If I am understanding you correctly, you removed the BMS and the batteries just sat there with nothing charging them. If that is the case then they should have been fine for 3 months. The only way I can see them swelling is if you left them charging.

I think it's purely a case of bad cells, just never experienced it before .. I just didn't know if having a BMS or not attached or not would make much any difference.
Cheers

 

[MisterSandals]

When I took the BMS the battery would have been at 95% charge.

What do you consider 95% charge?
What is the voltage of the swollen cells (mostly a curiosity)?

No cell constraint or compression? What happened to bus bars? Have a pic?

 

[chrisski]

I think it's purely a case of bad cells, just never experienced it before .. I just didn't know if having a BMS or not attached or not would make much any difference.
Cheers

Was there any load on the batteries, or any charge device? Was there a battery monitor? Were these stored in a hot place? Was this a second life system like Tesla batteries repurposed from a wreck? Why do you think they swelled?

Cells would normally for things like listed above, not just sitting there.

Its a big mystery.

 

[blipohm]

What do you consider 95% charge?
What is the voltage of the swollen cells (mostly a curiosity)?

No cell constraint or compression? What happened to bus bars? Have a pic?

No pic. Battery tried to be a banana, busbars bent up so that last 2 cells were in the air. I would say the two swollen cells, swelled to double the size overall.
No compression.
I disposed of the cells straight away without taking a voltage as they looked like they might blow!