AC200Max Solar Charging never reaching 100%

I have an AC200Max that was purchased when it was first released here in Australia in 2022.

Been very happy with it and until the last couple of days and have never charged it via solar as it was always being kept as a backup system when the grid goes down and has served this purpose very well.

I am now also utilising it for other duties and have noticed that even though it has an 800W solar array connected having a Voc of 92V, Vmp of 76.8V and Imp of 10.42A available the AC200Max reaches a charge state of between 99% to 97% and then decreases the PV input charge from say 700W to a constant 280W and never allows the AC200Max to reach 100%.

When you look at the battery status, when the PV wattage decreases from 700W to 280W it shows the battery BMS Status as in Standby. Then occasionally the BMS status switches back to a charging status for a very short period of time also increasing the PV input wattage to resume at 700W but then goes back to a BMS status of standby with the SoC between 99% to 97% and PV input of 280W.

By the behaviour of the BMS status it appears that the unit may be reaching a 100% charge status but never displaying it.

Whilst all this is occurring the AC inverter output is on with a constant load of 240W.

As soon as you remove the load, Soc changes to 100% and no PV wattage is obviously shown.

This AC200Max gets fully discharged and then recharged to 100% via T500 adapter every 3 months to recalibrate the BMS.

Software versions are as follows.
ARM v4008.02
DSP v4005.08
BMS v1010.07
Serial Number AC200M2205000207028

Hoping that there is a software update that can be pushed to rectify this from Bluetti?

Thanks for the response however the AC200Max doesn’t have a UPS mode.

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@DJR I will send a BMS firmware to your AC200MAX and you can update the firmware to test.

Thanks, when will that update be pushed please?

Installed update successfully and will observe over the next few days to see if this has rectified the issue, thanks.

I have observed the following regarding the new BMS Firmware update that Bluetti pushed to me.
It has sort of fixed the issue, but not really, I will explain.
Under a no-load condition, i.e. AC & DC switched off and when charging via PV input the AC200Max now reaches 95% then immediately within seconds jumps to 100%.
When you then turn on the AC and apply a small load, the unit drops very quickly drops from 100%, indicating to me that it never really was at 100%.
Maybe further investigation from Bluetti is needed please.

@DJR Thanks for your update. I will forward to technicians. If I got any update, I will let you know.

Thanks, if they don’t make any changes with a new update, I would prefer to roll back the update as at least it charged to 100% even if it said it wasn’t.

Just noticed that this strange charging behaviour is the same if you are charging from a Power Brick or PV.

@DJR Did you do a full cycle of charge and discharge after the firmware upgrade? Will it improve?

No not since the BMS update, will do it and report back soon.

I have cycled it twice and now the power brick light goes green however the AC200Max will only show 99%, and never displays 100% on screen, so BMS update doesn’t seem to be working correctly.
Please correct or allow a roll back to previous revision.

@DJR OK. We will help you roll back to version 1010.07. You will receive the version prompt of BMS1010.99. After the upgrade, it will actually return to 1010.07. After the upgrade, please notify us and we will delete the push in the background so that you will not continue to receive the prompt of 1010.99.

Appreciate your assistance.
I have checked and the prompt has appeared for BMS1010.99 which I will install later today my time as unit is presently being used and I am unable to interrupt the equipment it is powering.
Once this task has been undertaken, I will advise so you can stop the push for upgrade in the background.
Thanks again for the follow up and support.
Will be back in touch very soon.

@DJR Thanks for your update.

Just installed BMS1010.99 so BMS status is now 1010.07 please go ahead and delete the push for BMS1010.99 as discussed.
Again, thanks for trying to supply a fix and look forward to a possible solution to my issues when a next BMS is made available to all.

Bluetti can you please remove the push to update the BMS from 1010.07 to 1010.09.

Bluetti can you please remove the push to update the BMS from 1010.07 to 1010.09.

@DJR I’m sorry 1010.09 was pushed to all AC200MAX and we can’t delete delete the push in the background.