EG4 Battery SOC - Large Discrepancy

[SolarGear]

Hi All,

I recently had my 2x indoor wallmount batteries balancing for a few weeks. The min and max cell voltages are pretty close, but the SOC is showing quite a bit different - 1 pack seems to be at a much higher SOC. Firmware has been updated, top balanced and I have tried running them in open comms for a few weeks based on voltage. Batteries seem pretty close for 1 to 2 cycles, then go completely out of whack. When batteries reach around 20%, 1 may be at 18%, another at 22% and the last one at 30% Any suggestions?

 

[Q-Dog]

I don't trust the built in VOC meters. Your cell voltages seem pretty close so I don't see a problem with the info presented.

Can you show a diagram of your wiring?

 

[timselectric]

Actually, being within 4% of each other is exceptional.
Count yourself very lucky.

 

[TM48]

If you have EG4 inverter(s) I'd recommend you go back to closed loop. My three wall mounts are never that far apart but I reach 100% most days so it balances often. How often do you enter balance mode?

 

[SolarGear]

Right now

If you have EG4 inverter(s) I'd recommend you go back to closed loop. My three wall mounts are never that far apart but I reach 100% most days so it balances often. How often do you enter balance mode?

Right now, I am cycling the batteries every other day, depending on how much sun I get and how far up they are able to charge. The batteries are currently running in closed loop comms

 

[Quattrohead]

Yes the SOC reported by each battery will drift over time, but as long as the voltage stays very close you are good.
The batteries need to hit 100% and stay there for at least half an hour at least weekly to minimize this reported drift.

 

[wpns]

Yes the SOC reported by each battery will drift over time, but as long as the voltage stays very close you are good.
The batteries need to hit 100% and stay there for at least half an hour at least weekly to minimize this reported drift.

Indeed. Remember it’s REPORTED drift, not real.