LiFePO4 Over-Discharged

[SD-RV-Guy]

I upgraded my Class A motorhome to LiFePO4 battery banks to increase overall capacity. The battery bank is twelve 3.2v EVE prismatic cells in a 4s3p configuration with 3 individual BMS devices, one on each 4s. I had balancing concerns, and wanted the ability to see amperage draw and voltage of each 4s 12v group, so added an interior panel that displays voltage and amperage using a hall effect sensor attached to each. I figured that the loads from these 7-segment displays were so minuscule that I decided to bypass the BMS for monitoring.

Things were working great until we had a long stretch without sun here is southern California. When I checked on the RV after a few weeks in storage, I saw that the voltage of the cells were extremely low (6-10v). My main concern was checking to see if the RV would even start, and after doing so, current from the alternator to the coach batteries quickly brought them back up above 12v.

Unfortunately, I have no idea how long the batteries were in an over-discharged state or even how low individual cells may have gotten (1.5v, 2v, ?). Batteries have since seemed to charge completely just fine (14.2v) and there appears to be no bulging with the batteries themselves. What are the safety risks of continuing to use these batteries? I've read information regarding internal metallic formations and shorting. Obviously I do not want to continue using these batteries if they pose a credible fire risk.

 

[740GLE]

What’s the max charging current the alternator puts out to charge the LiFePO batteries? When cells are low it’s best to charge them slowly.

Also you use the same battery bank for starting the motor home?

What’s the starting current you see?

 

[SD-RV-Guy]

What’s the max charging current the alternator puts out to charge the LiFePO batteries? When cells are low it’s best to charge them slowly.

Also you use the same battery bank for starting the motor home?

What’s the starting current you see?

Unfortunately, the alternator did not charge them as slowly as I would have liked. They were being charged at probably close to 50A per 4s 12v group for the first 30 minutes. They were then charged at a rate of 15A-20A after that with the shore power charger. The batteries themselves are 280ah.

The motorhome has a separate chassis battery. There is a relay between the two that was manually activated by myself. In hindsight, probably not a good idea, but I did not know at the time that so much current would be provided.