Huge delta: Battery 1 SoC and Battery 2 SoC after a day of discharging (Nexa 2000 & Nexa 2000 EBM)

[fbsfelony]

Hello,
first of all - great work, thank you very much!
There seems to be an issue with the balancing of both batteries, so not really an issue with GroBro but with the firmware of Growatt. Hoping that @Lisugu00 (or someone else) can help with that.

My setup:

• Nexa 2000 (two months old), FW 14.12.14.11.9000.4019
• Nexa 2000 Expansion Battery (one week old)
• Home Assistant, GroBro 2.7.2, Mosquitto
• Battery Management set to 15%–100%

The issue:
The Nexa discharges Battery 1 (base unit) significantly faster than Battery 2 (expansion battery). After just one week of operation, the delta between both batteries grows every night. Yesterday it was 17%, today already 25%. At the point where the system stops discharging, Battery 1 is at around 10–15% while Battery 2 still has 35–40%.
The root cause seems to be that the minimum SOC protection in the app works on the total SOC (average of both batteries), not on the individual battery SOC. So the system keeps discharging until the average hits the threshold, by which point Battery 1 is already well below it.

My workaround via Home Assistant:
To protect Battery 1 from going too low, I set up an automation in HA that blocks discharging when any of the following conditions is met:

• Total SOC drops below 20%
• Battery 1 SOC drops below 15%
• Battery 2 SOC drops below 15%

Discharging is only re-enabled when all three are above their respective thresholds again. This works around the firmware limitation but obviously means I'm losing usable capacity from Battery 2 every night, since the system stops earlier than it theoretically could.

Questions:

• Is the unequal discharge behavior a known firmware issue?
• Is there any register or configuration option that enables per-battery SOC protection instead of average-based?
• Would a full charge/discharge cycle help balance the two batteries over time, or is this a permanent BMS behavior?

Any insight would be greatly appreciated!
fbsfelony

[simical]

Well it seems I have the same problem, and I'm watching it further.
I have set the BMS to 15-90%, and sometimes one battery goes to 100% while the other is at 80%.
So I have set some automations:

• First the PV-Zero-Point-Feed (Nulleinspeisung?) with my Shelly 3em.
• Second with checking if one of the two batterys is below 15%, then set mode to 1 (Battery first)
• Third witch kicks off the Zero-Point-Automation when both batterys soc is over 20%.

Yesterday I changed in the GroBro-App the setting for mqtt forwarding to Growatt Cloud, and suddenly both batterys are nearly the same SOC.
On the screenshot we ware seeing both SOCs of the two batterys over one / five and 10 days.

I have the firmware 14.12.14.11.9000.4019, the Noah is from 11/25 and Nexa from 05/26.
So I looking some days with the setting for forwarding the messages to the cloud and than change back to see if there is the old behavior.