LFP charge behavior

[pjones]

Hi,

Pretty new to lithium batteries and want to understand it a little better. I am monitoring cell voltages in a 8s pack (the 24V BYD packs) and noticed that at a certain point, the individual voltages of the pack oscillate a lot, and this occurs after a certain voltage threshold has been hit. I'd like to understand why this happens, and if this is caused by the SCC (EPEver 3210AN, if I recall correctly). Is this normal? Thanks

 

[snoobler]

It's most likely your SCC modulating current to maintain battery absorption voltage. BMS cell balancing MIGHT be coming into play, but they appear to be all moving with one another.

Here's what my Victron absorption phase looked like today:



It's about 0.2V in the little bit of chop you see.

 

[pjones]

Thank you Snoobler. I just looked at the SCC, looks like I didn't pull in amps for the battery side, I'll watch that and see if it matches what you've described. I have the PV side, which looks a little weird, there are cycles where the PV voltage spikes and current drops to 0. This seems too extreme for MPPT behavior?