Lifepo4 voltage

[Thisizwade]

Hey guys. I know there is a lot of discussion on this type of subject but i need help with a specific problem.

I have 4 100ah lithium wired in parallel.

My voltage will drop from 13.25 to 13.15 with only around 2% of the battery being used according to my victron monitor. Why would this be happening?

 

[richard cabesa]

What load is on when you see this drop?

 

[Thisizwade]

Between 2 and 4 amps

 

[OffGridForGood]

LFP 4s nominal voltage per cell 3.2 x 4 = 12.8
low voltage 3.0 x 4 = 12v
fully charged resting 3.4 x 4 = 13.6v
under load the voltage will sag,
with good quality cells,the sag will be small and removal of the load will quickly return the pack to original voltage.
with poor quality cells, the sag will be larger and removal of the load will slowly return to original voltage, or not.

 

[wholybee]

What brand batteries, and do you have a way to see the individual cell voltages? If you disconnect the 4 batteries, are they all charged to exactly the same voltage?

If the cells are out of balance, with one or two cells charged over 3.5V, and the other 2 cells below 3.5V, then a small change in SOC could create a large drop of total voltage.

I would disconnect the batteries, and fully charge each of them, then fully discharge them and check capacity. If you get 100Ah for each of them, then just charge them all to 14V, then reconnect them, and it should be fine.