Help with a 12v LiFePo

[rrleesb]

I built two 12v battery packs using 280ah cells and a JK BMS (JK B2A8S20P). They were both working well then one would not charge/discharge. I assumed I had a bad BMS after I cycled the BMS and tried emergency mode and still no charge/discharge. I replaced the BMS and I'm still getting the same results. Any ideas where to start troubleshooting?

I have factory settings for LiFePo except for cells (4), AH (280), and charge rate (100)

I've taken voltage readings on the cells with my multimeter:
Battery from main Pos to neg: 12.9v
Cell 1: 3.1vdc
Cell 2: 3.2vdc
Cell 3: 3.2vdc
Cell 4: 3.1vdc

 

[mikefitz]

factory settings for LiFePo

They are not ideal settings for LiFePO4 in the BMS. It should not prevent the battery from operating but the high volt protect values are too high. Low temperature charge protection values are also incorrect.
Suggest fixing these issues and checking your other BMS for similar incorrect values.

 

[rrleesb]

They are not ideal settings for LiFePO4 in the BMS. It should not prevent the battery from operating but the high volt protect values are too high. Low temperature charge protection values are also incorrect.
Suggest fixing these issues and checking your other BMS for similar incorrect values.

Do you have settings you recommend?

 

[rrleesb]

It's just weird that it was working then stopped. I made no changes to software or hardware.

 

[mikefitz]

settings you recommend?

Settings depend on recomended values provided by the cell manufacturer and generally accepted values by users. JK with their manuals suggest typical values for Li ion, LiFePO4, and LTO , it may be your supplier provided the BMS set up for Li ion.

Others responding to your post may offer alternatives but these values may be a starting point,

Start balance 3.45
Cell OVP 3.60
Cell 100% 3.50
Cell OVPR 3.45
Cell UVP 2.60
Cell UVPR 2.85
Charge UTPR 5.O deg centigrade
Charge UTP 0.0

 

[rrleesb]

Any other ideas why this thing won't charge or discharge? It's an expensive paperweight at this point.

 

[mikefitz]

thing won't charge or discharge?

As a test, will the cells charge/discharge directly, bypassing the BMS?
Try Installing the working BMS on the suspect battery.
Assuming you have checked all Interconnections in the battery and ancillary items, fuses/breakers, then itseems you have a faulty BMS. Replacing with the known working unit should resolve the issue.