AC500 takes from grid less than gives AC out


I recently noticed that my ac500 (eu) +b300s started acting weird when working in ups mode.

I do not have solar panels, so the grid is the only charge method.

The max charging current is set to 10 amps.

Once it reaches 100% battery SOC, it takes less power from the grid than it gives to powered devices. Then, the battery soc drops to 99, 98, or even 96% (these levels I have noticed, maybe there are others), and it starts to charge again. After that, all starts over.

It started about 2 days ago, before that, I did not notice such behavior.

@Artur911 Did you update the firmware to the latest one? Could you please provide me with the SN and the firmware version?

Thank you for your quick response.

Yes, I have the last available updates,
IOT v9041.06, ARM v4048.02, DSP v4057.03, HMI 6052.07, BMS 1022.09
I’ll send You SN in a private message.

Looking forward to hearing from you.

At this moment the issue has disappeared by itself.

It takes about the same amount as it gives (+/- ~10W).
The only thing left is that the battery drops to 97-98-99% before it starts charging (used to it was mostly 99% and sometimes 98%), but as far as I’m aware it is ok.

Still, It’d be great to understand the reasons for this behavior and what actions I should take next time it happens.

One more interesting fact.

I also have ac200p.
Right now I’m having a blackout. I changed the max current on AC500 to 1 amp and connected it to the AC output of AC200P.

I don’t know who is lying more but check out the difference between what the ac200p and ac500 show.

Also, while I was writing this message, ac200p just now threw an error “019 bus over voltage”, and its AC shutdown. It has never happened before.

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@Artur911 I think this phenomenon is normal. The inverter is always in the started state. In UPS mode, there is self-consumption of electricity, so the power will drop to 99%, 98%, etc., and then start to charge again.

Dropping SOC is not a problem, I understand it.
The main question is, AC500 shows that it takes less than it actually does.
I realize that numbers are not accurate, but 199 VS 385 (first screenshot, grid vs AC out), and 139 VS 598 (AC500 input vs AC200P output) is quite a major difference, don’t you agree?

BTW this behavior came back again, I still have it, currently it shows that it takes 169W from the grid and 343W AC out. Seems like the watt meter is completely confused, I wonder if it can damage the battery or cause overload on the AC charging cable or wall outlet.

@Artur911 Regarding the problem of power display, it may be the difference between apparent power and active power.

@BLUETTI_CARE That is not it.
Apparrent power mesures in VA, Active power in Watts. The device screen says “W” as well as the app. And the smart outlet confirms that AC500 takes less than it gives.

I found a way to temporarily fix it:

  1. switch from Standard UPS to Customized UPS with SOC settings 90/90 (actually, anything lower than 95%)
  2. wait till the actual SOC value drops to less than 97%, for instance
  3. switch back to Standard UPS, and wait until it charges to 100%
  4. done. Till the next no-power situation (when I do not have the grid power) it will take what it gives (+/- 10W).

Next time I’ll have no grid power and then the grid will be back - the problem appears again, AC500 charges to 100% and starts to take less than it gives unless I repeat the steps described above. Or I just stop carrying about it till you fix the firmware (hoping it will not damage anything), I believe you will one day :slight_smile:

Hello. I hope you’re safe and have power.

The problem disappeared once again after I connected the second b300s battery.
About a week so far, all good.

Yet, here I am again.
Now there is another unexpected behavior, at least for me.

I would like to share this info with you, maybe there is a chance someone else has experienced it before.

It is not the initial issue I started the topic for, but it is strange as well, and also might have the same topic title.

I use bluetti-mqtt to collect some metrics from the power station 24/7 which are then sent to prometheus and used to build graphics in grafana.

Here you will find AC Power metrics (based on ac_input_power and ac_output_power),
as well as SOC metrics (total_battery_percent, pack_details1, and pack_details2),
and of course AC Voltage metric (based on ac_input_voltage).

The data is sent to mqtt broker each 1 second, processed via node-red, and prometheus scrapes data every 5 seconds.

As you can see on screenshots, at 20:36:40 AC500 started to take less than give (input vs output).
And it ended at 20:37:40.
It resulted in dropping SOC on both batteries and they started charging right afterward.
You can also notice that there was no decrease in grid voltage or any significant changes in power consumption.

Since I have set up system monitoring now, I see that it happens regularly, several times a day but no pattern was noticed. But there is always 1-minute drop of AC input and then SOC to 96-99%.

P.S. I also have configured predictive charge/discharge time. It took about 15 minutes. I know I’m not the first one pointing out this, but it’d be great to have it in the app as well.