Removing swollen LiPo cell?

[SleeperAgent]

Hello fellow e-bikers and world savers!

My first post so be nice

Last summer I bought a DIY kit from the (in)famous Conhismotor in china. (infamous because I, like many others thought we bought LiFePo batteries when they were in fact normal LiPos. How could I ever be so stupid to order some random junk from China?!) Well everything has worked mostly fine until I took the bike from winterstorage a few weeks back. I'd kept the battery at about 80 % during the winter months and even discharged in fully and recharged it again to about 80% a few times, as per common knowledge.

However, now when I started fiddling around with the battery and electronics I noticed that one of the LiPo-cells was partly swollen. Not the whole cell, just about 1/3 of it. And swollen pretty bad. It really looks like it's about to burst but It's now remained stable for over a week.

From what I understand this is not life threateningly dangerous but I'd rather not zip around town with a potentially hazardous battery between my legs.

What I would like to know is: do you think I can just rip that one cell off, and leave the rest of the pack as it is. This would lover the voltage from 48 to about 45.5 yes? And loose some amp hours of course. At least it's better than buying a new battery after only one season :-/ But is this doable at all or will this somehow damage the battery. And what about charging later on? I guess there's some silicon in the battery pack that keeps the cells balanced and tell the charger how many cells there are etc. Should I try to change it or reprogram it somehow?

What are your thoughts?

 

[wesnewell]

I may be totally off in left field, but from everything you've posted, it would appear to me that you do in fact have a lifepo4 battery pack using lifepo4 pouch packs, pretty much the same as most cheap lifepo4 packs use. I use lipo, and there's no BMS with it and it's much smaller and lighter than the packs shown on the diy site. They list their 48V packs as 16s, which is standard for a 48V lifepo4 pack. 16x3.65v=58.4V. A 16s lipo pack would be 16x4.2v=67.2V, which would blow most standard controllers. Even 15S lipo will blow some 48v controllers. 14s lipo is the max safe configuration for a 48v controller using 63V caps. I only use lipo, so I'll let someone else familiar with lifepo4 give you a definitive answer, but my guess would be not to worry about it too much, and not remove the weak cell unless you are going to replace it.

 

[liveforphysics]

There are many types of LiFePO4 LiPo cells.

Just because it's in a foil pouch that looks like an RC LiCoO2 LiPo cell doesn't mean its not using LiFePO4 chemistry inside the cells.


Honestly, I would prick that pouch with a pin, let it vent its gas and not be bulging, then seal over the pricked hole with some glue.

And if the packs performance sucked after that, then think about replacing it. But it might turn out just fine.

Also, who knows WTF those cells actually are or how stable they actually are, so be aware that anything from fire balls to poison gas or whatever could occur, but likely wont.

 

[dogman dan]

Yeah, try pricking it and sealing it back up, and see what happens. Removing that cell will only strain the others in the paralell group enough to cause an eary death.