AC500 + 3xB300S: 2 Problems with Battery and PV Charge

AC500S S/N: 2241000084770

  1. I observed that when discharging from 100% to 0 the Battery Level on the first battery was 20% and on the second battery was 1% and after about a minute both were 0% and the AC500 switched off.
    Discharge Power was just about 150W, so the first battery should have lasted much longer.
    I did 2 full charge/discharge cycles, but the problem is still the same.
    Any Ideas ?

  2. I disconnected the second battery and charged the first battery from 0 to 100% via 3A Grid charge over night.
    Then is disconnected the first battery and connected the second battery and tried to charge it via PV from 0 to 100% but above about 90% the PV Charge went down from 2200W to about 650W and after the second battery reached 97% it immediately switched to 100%.
    Why is that sudden Limit of the PV Input and then the sudden jump from 97 to 100% ?

DSP: 4047.06
ARM: 4048.02
HMI: 6052.04
BMS: 1022.09

1 Like

There are already a few topics here about this problem.
Using the search function is always a priority in a forum.


I know that cases and just want to report to Bluetti that there are still problems, otherwise they think everything is fine.
And the PV Problem can most likely only be solved by a Firmware update which has to be pushed manually specific for that S/N…

I had an EP500Pro before which has a single battery and a single BMS.
There I did 2 Full Cycles at the Beginning and never had such problems for nearly 2 years until I replaced the EP500Pro with the AC500+2xB300S.
It seems the problem is if you have more then one Battery/BMS.
But this should be possible to fix via Firmware.

I have the same problem with my AC300 + 4×B300.
It is system-related that different SOC values ​​are displayed.
The percentage values ​​are not measured, but calculated or more or less estimated.
They depend on the usually different charging/discharging powers.
These are not distributed absolutely evenly across all batteries, for whatever reason.
This is particularly the case when charging via PV.
Take a look at my posts. I have already commented extensively on the problem there.
Bluetti is supposedly working on the problem with a specially adapted software update, but I don’t believe they can manage it.

Greetings Joachim
Ich habe das gleiche Problem mit meinem AC300 + 4×B300.
Es ist systembedingt, daß unterschiedliche SOC-Werte angezeigt werden.
Die Prozentwerte werden nicht gemessen, sondern errechnet bzw. mehr oder weniger geschätzt.
Sie sind abhängig von den meist unterschiedlichen Lade/Entladeleistungen.
Diese werden nicht absolut gleichmäßig auf alle Akkus verteilt, warum auch immer.
Das ist insbesondere beim Laden über PV der Fall.
Schau dir mal meine Beiträge an. Dort habe ich mich zu der Problematik schon ausgiebig geäußert.
Bluetti arbeitet angeblich an der Problematik per speziell angepasstem Softwareupdate aber mir fehlt der Glaube, daß die das hinbekommen.

Gruß Joachim

My Problem is NOT that the 2 batteries have different SOC. That is understandable that is quite difficult to balance 2 or more BMS.

My 2 Problems are:

  1. Battery 0 showed 20% and battery 1 was flipping between 0 and 1%. Then I just went 1 floor up to get my mobile phone to take a video from that symptom.
    But when I came back the AC500 was off an BOTH batteries were down to 0% with just about 150W load within 1 Minute.
    I did 2 full manual cycles just a month ago and in between there were als 2 or 3 times that the battery was completely discharged to 0 because 2 days without sun.
    I have exactly the same PV environment which I used with the EP500Pro for about 1,5 years and the same charging/discharging environment but with the EP500Pro I never hat the problem that it discharged completely from 20 to 0% in one minute.
    So I guess the BMS Firmware was working better in the EP500Pro then the BMS Firmware in the B300S.
    Therefore I am reporting that problem.

  2. Why is the PV Input throttled to about 650W as soon as the battery reaches 90% if I only connect 1 battery ?
    I Just did the a full charge via PV from 0 with only the other battery connected and again the PV Power went down from 1900W to 650W at the moment the battery was charged to 90%.
    For me that is a firmware Bug and therefore I reported it here.

@OpaleTrotzig Let me check with the technician. If I get any update, I will let you know ASAP.


  1. How are the two battery packs connected? Are they connected symmetrically, or are they connected to the same interface of the AC500? It is recommended that you connect them symmetrically, which will help balance the SOC between the two packs. If they are “stringed” together and connected, the far-end battery pack has a longer connection line and a larger resistance, so the current will be smaller than the near-end one (the far-end battery pack discharges slower than the near-end battery pack);
  2. Trickle charging, that is, the charging current (or charging power) will be limited when it is almost fully charged. The jump from 97% to 100% is also a normal SOC end correction (industry standard 5% error).


  1. The two battery packs are connected symmetrically.
    But that does not explain why one battery was down from 20% within a minute.

  2. Trickle charging:
    a. Why is it only implemented if I connect only one battery ? With 2 Batteries it does NOT happen.
    b. trickle charging is normally only used between 99 and 100% to keep the charge.
    But the Throttling from 2100W to 650W starts already much lower at 90%,
    c. If trickle charging is implemented, then it is usually mentioned in the user manual. Why is it not mentioned ?
    d. I have used an EB70, an AC200Max, and a EO500pro. None of the throttled the PV Input when the battery reached 90%. Why with the AC500 and why ONLY if one battery is connected ? That does not make sense !!!

BTW. I never reported a problem with a jump from 97% to 100%, Only from 20% to 0%.


  1. It’s also possible that the SOC display is wrong and we want to confirm this. If you have a symmetrical connection, there may be a problem with the consistency of the cells in one of the battery packs.
  2. If there is a problem with the consistency of the battery core, it will cause the power to be limited in advance and enter the so-called “trickle charge” during charging. From this case alone, the main reason may be a series of phenomena caused by problems with the consistency of a single cell in the battery pack.
    a. When one battery and two batteries are connected in parallel, the trickle charging current will definitely be different.
    b. Trickle charging usually occurs between 99% and 100%, which is for small, single batteries. B300S is a battery system composed of many cells connected in series and parallel. The battery pack is charged to different voltages to limit different powers. This is also a complex strategy. It is not comparable to a single battery.
    c. The manual does not mention very specific power limiting strategies under normal circumstances.
    d. Different models will not have exactly the same charging power strategy, and even different software versions will have differences.

By the way, a jump from 97% to 100%

I suggest you connect AC500 with a B300S separately, and then charge or discharge normally to see if there is any SOC jump to determine which battery pack may have the problem.

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Sorry for the late reply, I was on vacation.

Regarding the Jump from 97% to 100%: I watched it again and at that time the battery1 was at 100% and the battery2 was at 95%. Just seconds later the battery2 jumped to 100%.

I watched the charging a few times and the battery2 was always lacking behind, like battery1 showed “charging” and 94% while battery2 at the same time showed 74% and “standby”. Or battery1 was 98% and “charging” battery2 was 78% and “charging”.
Then battery1 stayed some time at 98% and battery2 charged slowly to 88%.
Then battery1 changed to 99% and battery2 slowly charged to 100% and then battery1 charged to 100%.

Is that normal that there is about 24% difference between the 2 batteries during charging ?

I disconnected battery2 and discharged/charged battery1 completely and the same with battery2.
Discharge capacity was about 2,67kwh for battery1 and 2,65kwh for battery2.
Is that ok for 3072kwh capacity each ? I bought the AC500+2xB300S end of September 2023.

I discovered a really annoying problem when discharging to 0% for BMS Training.

If I have only one battery connected it immediately start to charge in the morning when the PV starts.

But if I have both batteries connected then only ONE batterie is charged when the PV starts to charge.
I have to MANUALLY push the button in front of the second battery to be able to charge it again.

Before the BMS Training ONLY the first battery started to charge after the PV comes back.

Since the BMS Training not ONLY the second battery starts to charge when PV is back.

This is really annoying, BLUETTI_CARE please forward this Bug to the development team.

@OpaleTrotzig We have a new BMS firmware version of B300S. The firmware will sent to you in 6 hours. You can update the firmware of the battery pack, and then do a discharge and charge cycle to check if it works.

I just upgraded both BMS to 1022.10 and start a discharge cycle.
Do I need to charge/discharge each battery alone or can I do the full discharge/charge with both batteries connected ?

@OpaleTrotzig charge/discharge each battery alone should be better.

I did a complete Cycle with both batteries connected and one with each battery alone.
It seems that the battery levels are more synchronised between the 2 batteries.

But the most annoying problem that there is always only one of the towo batteries are set to online and start charging still remains.
A few month ago only battery 1 was the only one switched on, currently it is the battery 2 which is only switched on after the PV starts to charge in the morning after a complete discharge cycle.

This Problem has not changed with this firmware update.

That’s something I tried long ago as an experiment when I first bought it, but for whatever reason the AC500 would not turn on, using only one of the two AC500 connectors.
It’s now all connected as in your pics with 6 batteries.

Strange: Yesterday I was up early before the sun came up and i connected the grid to charge the empty batteries and BOTH batteries started to charge.

Over night I did again a complete discharge and when the PV came up in the morning only Battery2 started to charge.

So it seems that the problem that only 1 battery is charged only exist if I charge via PV.
But this is the main reason why I (and many others) bought the Bluetti Powerstation.

There is also another problem with that scenario: When I discovered that the battery1 was not charged the battery2 was already 19%.
After manually switching on the battery1 it started to charge from 0% and the battery2 started to DISCHARGE.
So it seems that the battery1 is only partly charged from the PV and mostly from battery2.
That is not very good for the battery health and increases the battery wear.

Please inform your engineers about that single battery not charging problem and that it seems to happen ONLY when charging via PV which nearly everybody does with the Powerstation.

Here are Screenshots from that shows that battery2 is discharging while battery1 is charging even though the PV Input (764W) is much higher then the AC Output (135W) and I would expect that both batteries are charged and not that one battery charges the other battery:

@OpaleTrotzig I have reported the problem to the R&D department and they are investigating the cause. I’ll let you know if there are any updates.

Can you push the update to my same setup please?AC500 + 4x B300S)

AC500 S/N: 2241000302755


@Razowski Is there any issue with your machine? And please provide me with the current firmware version. Thank you.