B230 discharging much faster than AC200Max

I have one B230 connected to an AC200Max, which I’ve been running for ~2 years. The manual states that the discharging sequence will pull alternately from B230 or AC200Max depending on which has higher charge, to keep all batteries at about the same charge level – but I’m no longer seeing this equalization occur.

  • In the past few months the B230 has been discharging much faster than AC200Max:
    After a few hours of no solar (at night), I might see AC200Max at 60% , and B230 at 30%.
  • Obviously, this 30% difference is problematic and shouldn’t occur (per the manual) : the AC200Max is supposed to discharge from its internal battery instead, when the B230 charge level gets much lower than the internal battery. This doesn’t seem to be occurring.
  • They both charge to 100% each day using solar, and discharge each night to an average ~30%.

1) Why would the B230 drop so much more than AC200Max, when they both start from 100%, given that the firmware is supposed to pull from the higher-% battery to keep them all approximately equalized?
2) How can I fix this?

I would suspect that the BMS is misinterpreting the battery voltage vs charge status. I know that on my AC300 with 4 batteries (purchased at different times) two of the more recently purchased batteries read differently than the original 2. What I need to do, and perhaps you as well, is completely discharge the entire system with a constant load (I’d be using a 1500 watt heater) until the system turns off. Now the system knows the 0% point of the batteries. Then, after waiting to allow the system to cool for a while, recharge the system at a constant rate with no load applied until completely full. Now the system knows the 100% point. It should now show the actual battery condition and you will see if it performs normally.

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Thanks. But, the manual states that the discharge switching depends on the charge percent (%), so the actual battery voltage (and how accurate it is) doesn’t matter.
That is, if a battery’s % – no matter how inaccurate – is lower than the other battery, then the other battery will continue discharging instead.
In this case, making the BMS more accurate doesn’t help.
Or, perhaps Bluetti mis-stated that, and the internal voltage is actually what determined which battery source is discharged or not?

@BLUETTI @BLUETTI_CARE Can you assist?

@jCs Is the BMS version 1017.04? If not, please provide me with the SN of AC200MAX and the firmware version, and I will push the firmware for you to test.

BMS: 1010.07
Unfortunately I can’t get a FW update, since i’m still on an experimental one for the past 1.5 years (which is needed so that the MPPT works properly in certain conditions), and this version hasn’t yet been pushed to the main code. So if I switch FW, the MPPT will stop working.

I’m more trying to understand the issue at the moment. Do you think this is a FW version issue?

@jCs For the firmware version of your AC200MAX, you can update it to 1010.08. Normally, the new BMS firmware will not affect the MPPT function

My AC200MAX and the two B230s have the same problem.
The batteries are rarely discharged evenly.
(all batteries 100% charged)
Usually the B230 Batterie Pack 2 is always discharged first, then at 80% total capacity the B230 Batterie Pack 3 is also discharged.
The AC200MAX is not discharged until the total capacity is around 60%.
However, there are also times when all batteries are discharged more or less equally, but this rarely happens.
The same applies when charging, the AC200MAX is always charged to 100% first, then the B230 Batterie Pack 3, and when this battery is at around 80%, the B230 Batterie Pack 2 is charged first.
Only when there is a lot of PV power, such as 500W, are all batteries charged at the same time.
When charging, sometimes a B230 suddenly jumps to 100% at around 60%
(always the same B230)
By Batterie Pack I mean the battery number in the display
AC200MAX BMS firmware 1017.03
Yes, the batteries are calibrated

@jockel66 I can push the firmware of 1017.04 for you to test. Please provide me with the SN.

AC200MAX SN: 2226000689171


@jockel66 would you mind updating here whether it fixed it for you or not? If you do update here, thanks in advance :slight_smile:

So, update BMS 1017.03 to 1017.04 and DSP 4005.07 to 4005.08 completed.
(always with beads of sweat on my forehead during the bluetti firmware update,
but it worked without any problems) :exploding_head:
The battery status has changed after the update.
Without recalibration of the batteries.
AC200MAX from 71% to 44%
B230 (2) 47% to 83%
B230 (3) 74% to 69%
I will continue to observe the charging and discharging behavior.

Graphics are from 21.01.2024 about 10 o’clock in the morning.
The DC output of the box was active on 20.01.2024 from 19.30 to 24.00.
After that, all batteries were switched off.
The AC200MAX then woke up again automatically at around 9.00 a.m. on 21.01 with the first PV sunrays.
At 9.25 a.m. I then switched the two B230 batteries back on. It hardly charged at all, it was cloudy.
------------------------------------------------------------------------------------------------------------------------------------------21.02.2024 15.38 Uhr

Graphics are from 21.01.2024 at 15.40 hrs.
Charging finished, DC output switched back to active.
You can now clearly see that the B230s are being charged almost synchronously,
the AC200 Max is still lagging a little behind.

Graphics are from 21.01.2024 at 23.00 hrs.
Doesn’t look bad.

Conclusion so far, charging and discharge has worked better with firmware 1017.04.
Data recorded via Homeassistant.

Thanks for sharing the update. It’d be great to hear another update sometime after you have more sun, and more cycles, since one day is still a small sample size.
Also, how are you using home assistant?