How to deal with one cell that has low voltage?

[lukassteiner]

I have a 48v DIY Lifepo4 battery with 16 cells and a Daly BMS.

Before I used it, I top balanced it and it worked well for about a year.

Recently, I noticed that the BMS cut the load very quickly.
I was able to charge the battery fully again but then when I connected the load, the BMS cut it again.

Now, I disconnected the separate cells and measured their voltage.
Every cell has a voltage of 3.3v except for one that has 1.1V.

I charged this one cell manually with a DC power supply for a minute. When I measured it again, that cell was 3.0V.

What would you guys recommend to do?

What I though of doing:
Test the load of this one cell. I just don't know how.
Or replace this cell and top load all the cells again.
Or assemble the battery again and connect it to my inverter to test the load again with 48v.

attached are the specifications of my battery cells

 

[Nobodybusiness]

I have a 48v DIY Lifepo4 battery with 16 cells and a Daly BMS.

Before I used it, I top balanced it and it worked well for about a year.

Recently, I noticed that the BMS cut the load very quickly.
I was able to charge the battery fully again but then when I connected the load, the BMS cut it again.

Now, I disconnected the separate cells and measured their voltage.
Every cell has a voltage of 3.3v except for one that has 1.1V.

I charged this one cell manually with a DC power supply for a minute. When I measured it again, that cell was 3.0V.

What would you guys recommend to do?

What I though of doing:
Test the load of this one cell. I just don't know how.
Or replace this cell and top load all the cells again.
Or assemble the battery again and connect it to my inverter to test the load again with 48v.

attached are the specifications of my battery cells

I had this happen in one of my packs.

Turns out the cell just quit working for whatever reason.
It would charge to 3.65 but had no capacity behind it.

I ended up replacing it.

I’m not saying your is bad.

You can test it with a tester or a shunt to see what it’s reading.
There are smaller capacity testers on Amazon.

 

[Daddy Tanuki]

first realize those cells are at least 5 years old...(I am guessing these are either blue nylon case or gray nylon case) thats when CALB stopped making the 180 and 200SE battery's. so they were either used and resold after a year or two of use, or they are wharehouse queens.

I have the same cells and the dealer of course swore up and down they were brand new... remember its against international law to ship used batteries. so the seller will always swear up and down that they are new...

so chances are that particular cell got beat on a bit more or came from a different batch. if you can still find some of these cells I would advise to by a couple fo spares.

 

[lukassteiner]

Thank you guys for your answers. I ordered one new cell for 57USD, still pretty easy to get them here in Thailand.
They have a blue nylon case.

Will keep you updated how it went when it arrived.

 

[RCinFLA]

Check your cell connections first.

This type of issue comes up a lot due to poor bus bar connections.

If you are using bare copper bus bars in direct contact to aluminum cell terminals, they will corrode and pit the aluminum terminal surfaces over time. Should always use nickel plated bus bars to provide a barrier between copper and aluminum.

 

[Daddy Tanuki]

Check your cell connections first.

This type of issue comes up a lot due to poor bus bar connections.

If you are using bare copper bus bars in direct contact to aluminum cell terminals, they will corrode and pit the aluminum terminal surfaces over time. Should always use nickel plated bus bars to provide a barrier between copper and aluminum.

yes sanding. cleaning of the battery terminals, and a good antioxidant is an absolute requirement, that and nickel plated connections if you use ring terminals. if you use buss bars then nickel plated is best again as their is corrosion that occurs between copper and aluminum... especially in Thailand where the relative humidity is high. actual torqueing of the studs, and a lock washer are also absolute requirements.