Hi there,
my system is working perfectly fine since I have it (6 months or so) but this winter it began to have this “imbalance charging/discharging” symptom reported apparently several times before in this forum.
Example: at this moment my battery #1 SOC=51%, battery #2 SOC=29%, while the average of the two displays 40% (of course).
There is no way to visualize the SOC curves individually per battery but I have the feeling that one charges/discharges more frequently than the other…
I suppose this is due to the low solar exposure at this time of the year + my batteries sure never reaching 100% charge but barely 75% on sunny days. Still, I find it strange that the two batteries do not get exploited equally, at least to insure equal stress and therefore equal lifetime…
One remarkable thing is that these days in winter I charge the batteries a lot from grid during no-peak time, whereas this never happens in summer : grid is quasi-never used because the sun power alone is enough to charge the batteries 100% and also power my installation most of the time during daylight (and batteries enough to supply the night) => in summer I never saw disbalance!
→ Could this be an explanation? Like grid source cannot charge 2 batteries at once so priority is given to one (always the same) and therefore results in misbalancing the two …? 
In any case, any clue from @BLUETTI_CARE will be appreciated!
Now, the other very, very strange thing I discovered through this is that : if I swap the 2 batteries/connections; the SOC figures reported by the AC300 dont get swapped !!!
Practically speaking here is the testing I made 1 hour ago:
AC300 port BAT-01 is connected to battery pack #1
AC300 port BAT-02 is connected to battery pack #2
Battery info : SOC(1)=61%, SOC(2)=38%
Powering the system OFF
AC300 port BAT-01 reconnected to battery pack #2
AC300 port BAT-02 reconnected to battery pack #1
Powering the system back ON
Battery info : SOC(1)=61%, SOC(2)=38% … same thing as before swapping … whereas of course I expected it to tell me the opposite : SOC(1)=38%, SOC(2)=61% … !
@BLUETTI_CARE can you explain this??
Here is my info:
AC300 s/n AC3002309000181363
Versions apparently up to date : IoT=v9041.10, ARM=v4037.07, DSP=v4053.20, BMS=v1021.11=same for the 2 batteries.
Hi @LLaurent, Regarding the SOC (State of Charge) imbalance issue, we have requested a BMS firmware update for your system, and the update will be pushed within 12 hours. Please proceed with the upgrade tomorrow. Make sure to connect only one B300 battery at a time for the update and complete the process twice to update both batteries.
After the upgrade, you will need to recalibrate the batteries.
Please follow the steps below to recalibrate it:
- Please discharge all the power (charge AC & DC appliances with the power station) until the SOC is 0%, turn off the machine, and leave it for 3 hours till it cools down.
- Please charge it again, please do not load any device when charging it, and do not interrupt it while in charge.
You can click this link for reference.
Please let us know if it does help.
As for the unchanged SOC (State of Charge) readings of Pack 1 and Pack 2 after switching ports, this is normal. The AC300 system recognizes and memorizes each B300 battery. Even if the connection port or sequence is changed, the original Pack 1 will still be identified as Pack 1.
Regarding the better charging performance in winter, many customers have noticed this, and there are several reasons:
1/ Temperature Impact: Solar panels, inverters, and batteries are all affected by high temperatures. Excessive heat increases the internal resistance of batteries and reduces energy output. In contrast, cooler winter temperatures allow the solar system to operate more efficiently, improving charging performance. Ideally, the entire system should be kept at around 25°C.
2/ Better Light Penetration: Winter air typically contains less moisture and dust, resulting in better light transmission and improved solar panel efficiency. Additionally, the lower sun angle in winter enables the solar panels to receive sunlight more directly, enhancing power generation.
3/ Improved Heat Dissipation: The cooler temperatures in winter provide better heat dissipation for the solar system, allowing it to maintain more stable output power.
Let us know if you need further assistance!