My CALB cells have swollen

[Usangira]

Measure voltage on each cell. They are likely below 2V per cell. I have same type blue plastic case cells and one bloated like that too. It was left sitting disconnected for a year and self discharged to 0.3V. Looks like same thing happened to your cells. In the future use some kind of battery trickle charger to keep them at 3.35 V per cell. Small 10W solar panel with linear regulator should work.

Yes...I have measured them. They are around 0.8-0.9V

Is there a way I can recharge them back to 2V to bring them to life ?

 

[740GLE]

Again IMO those cells are toast, as much as it sucks, cut your losses and move on.

 

[AntronX]

Yes...I have measured them. They are around 0.8-0.9V

Is there a way I can recharge them back to 2V to bring them to life ?

LFP battery has greater resilience against zero volt discharge than regular Li-ion. You can try recharging at 1 amp until they reach 2 - 3V. They may come back but at degraded capacity. You could also try compressing them but I don't know if that could make them less safe.

 

[brum]

Find out why they got to that voltage before going ahead. Either your BMS is not working as expected or the cells have very high self-discharge.

 

[Usangira]

Again IMO those cells are toast, as much as it sucks, cut your losses and move on.

That's 4

LFP battery has greater resilience against zero volt discharge than regular Li-ion. You can try recharging at 1 amp until they reach 2 - 3V. They may come back but at degraded capacity. You could also try compressing them but I don't know if that could make them less safe.

Ok...I will try to set a maximum charging current as suggested. I am just thinking how many days it will take to get to 3V for a 400Ah battery bank

 

[AntronX]

I am just thinking how many days it will take to get to 3V for a 400Ah battery bank

Probably few hours, maybe a day. If they do not get to above 2V at 1A charge or cannot hold that voltage for long then they developed internal shorts and are now scrap.

 

[RCinFLA]

Cells will bloat if discharged to very low voltage. Electrolyte stable limits is about 0.1v to 4.3v at 25 degs C. The voltage limits get tighter if temp is high.

If left highly discharged for some time they likely have grown lithium metal dendrites at anode negative electrode.

 

[AntronX]

If left highly discharged for some time they likely have grown lithium metal dendrites at anode negative electrode.

Yep, that's what I am worried about. They may appear fine at this time but could short circuit in the future and i guess could develop internal hot spots that could lead to a fire.

 

[Usangira]

I have tried to recharge the battery bank with some caution..... So far I have just pushed in 18KWH and still hungry for more, it is 20KWH storage.
Next test is discharging it, to see how much will be recovered

 

[740GLE]

Are the swollen cells holding a charge?

Dumping KWh into it means nothing if those bad cells bleed voltage off in minutes.

 

[Usangira]

Are the swollen cells holding a charge?

Dumping KWh into it means nothing if those bad cells bleed voltage off in minutes.

I hear you.... Thats why am saying I will discharge them tonight