LiFePo4 Battery drops from 22% to 0%

[TomC4306]

The BMS on my battery charges at 55

Closed loop. Tells the Sol-ark to charge at 55.0v until battery hits 54.5v, and then tells the Sol-ark to drop to 54.0 volts. So, yes it is the BMS controlling the charging.

Unless you are running 15S, your batteries are not getting a full charge.

I was replying to what you actually wrote.
BMS charges....
Not
BMS controls charging

 

[robby]

Unless you are running 15S, your batteries are not getting a full charge.

Why would you want to charge 16S Batteries past 54.5V to 55V max?

 

[Zapper77]

Why would you want to charge 16S Batteries past 54.5V to 55V max?

Top balancing

 

[robby]

Top balancing

Makes sense for that but not something I would do very often.

 

[ventura]

Of course. Why would you blindly trust the BMS to be set correctly? Even though apparently your BMS controls charging, it could have settings incorrectly set.
Also, SOC is NOT a measurement it is a calculated value. You can't use a meter and measure state of charge.
I'm quite certain there is no setting in your solar charge controller that says 100% or charge it to 80%, I'm pretty sure there's a voltage setting in your charge controller. What is that number?
YOU came HERE with a problem.
I am TRYING to help you answer and understand.
You know... DIY Solar Forum.

That literally is what is happening. Once i connected the BMS communication successfully, all the voltage values on the inverter changed to % values and from then the battery controls the charging through the inverter and the inverter only shows %.

I got the values from the interface though: 53.2V is the float and constant charge voltage. This is a LiFePo4 15S pack, meaning 15 cells instead of the usual 16. This is a rack battery, I would like to assume the built in BMS is configured correctly and I don't need to change these values.

Thanks for trying to help. I attached an image of the battery and the relevant part in the inverter's documentation.

 

[ventura]

I have had this problem a few times when 3 cells in a EG4 battery pack were out of balance and at a lower voltage than the rest.
The voltage on those cells hit the knees and suddenly dropped off lowering the pack voltage and SOC.
I had to balance the cells back and that fixes the problem.

Apprechiate your help, Charging to 100% atm.

 

[TomC4306]

Why would you want to charge 16S Batteries past 54.5V to 55V max?

Many, many tests done by Andy (Off grid garage) show that at 3.4 volts/cell the battery saturating to a full state is inconsistent, even with lengthy absorption times.
3.45 or 3.5 as a constant voltage charge results in a fully saturated battery always. At 3.45 absorption time needed to be a bit longer than at 3.5. I'm currently charging to 56, float 54

Here is a link to one of at least half a dozen videos where he explores a range of charge voltages and absorption times.
See playlists, battery tests.