Coulomb

16 hours ago, starfleet said:

It looks like a clone of Axpert Voltronic MKS 3K-24.

Agreed.

16 hours ago, starfleet said:

WatchPower detects it as "Stand alone" Transformer with main CPU version 000SR.27.

As far as I know, no genuine Voltronic firmware outputs anything other than 000dd.dd where all 4 of the ds are digits. So this is custom, or more likely patched firmware (patched by the clone manufacturer, not anyone on this forum).

So it's really hard to guess what Voltronic model they might have copied. Because it's PF0.8 (rated power is 0.8 x rated VA), it's likely not a recent VM II model. It could be using an 8-bit processor, or it could use a '28062 DSP.

So sorry, I can't be of much help.

17 hours ago, pecov said:

Could you advise me how to proceed?

See If You Think Your Inverter is Bricked. Basically, you need to have faith, try many times, and perhaps vary the timing.

On 2026/02/20 at 4:34 AM, Maxsteel83 said:

qualcuno sa qualcosa?

You are more likely to get responses on this forum when posting in English.

Unfortunately, MKS III firmwares are rare for some reason, and I have no 63.xx MKS III firmwares at all.

Your only hope is to get a firmware update from your inverter supplier, unfortunately.

Edit: BTW, the MKS III models are very different from the VM III and VM IV models discussed in this thread. The firmware is literally twice as large for the MKS models, for example.

On 2026/02/17 at 1:13 AM, Adnano said:

Most part references around SG3525 seem to be the same as in this schematic: https://forums.aeva.asn.au/viewtopic.php?p=88434#p88434

BritishRacingGreen's schematic is from an Axpert Max, but I suspect as per the above, this circuit hasn't changed much over the years. His schematic is easier to follow too:

On 2026/02/15 at 7:59 PM, BritishRacingGreen said:

I could not locate any posts that led to a definitive solution.

? The AEVA repair page documents two solutions: replacement of the battery-side electrolytic capacitors, and replacement of the SG3525 chip itself. I note that the Axperts can be cranky about the brand of SG3525; best to replace with the same brand as existing, where possible.

On 2026/02/15 at 7:59 PM, BritishRacingGreen said:

Another possible fault could be a failed buck IGBT, but I have tentatively ruled this out because the body diode should still allow some discharge path from the battery to the bus. I hope this assumption is correct.

That logic sounds good to me. The buck stage only actively bucks when charging the battery (in these models, from either solar or utility).

Good luck, and let us know how it goes.

On 2026/02/13 at 11:04 PM, jevko said:

Maybe Coulomb can see it and tell which inverter it is for.

Yes, 78.10 is for the Axpert Max E 11kW '28066 Twin. It has the QDOP command, so it should be able to have settings based on SoC% (from the display at least, as long as the display firmware is recent enough).

As usual for "production" firmwares (minor version number < 60), it does not have the "presumed good" MPPT voltage control algorithm.

On 2025/08/28 at 9:13 PM, franlopez said:

I am trying to integrate with Raspberry Pi and Home Assistant but whenever I connect any serial on the serial port or an USB to retrieve the data,

You might be running into the issue where when sending commands to the USB port, you (sometimes?) have to send a maximum of 8 characters in a single command. So commands with more than 5 characters (so more than 8 when adding the carriage return and two CRC characters) should be split into two write commands one after the other. This might be fixed in later Python libraries.

On 2026/02/13 at 7:16 PM, BGD said:

can somebody confirm to me that i can flash the 245.11 over the 45.07, to fix the 90v issue ?

Yes, that's the only 7.2kW patched firmware in the x45.xx series. Unfortunately, it's a bit old now, so it's a fixed 120 V minimum MPPT voltage, which may not be ideal.

On 2026/02/13 at 7:16 PM, BGD said:

should i update also the display, or leave it as it is ?

There is no need to update the display firmware for this issue.

This is a clone, so it may not be possible to update the firmware at all.

What is the present main (U1) firmware version? Unfortunately, the sticker doesn't tell everything needed about the inverter, e.g. the chipset used.

On 2026/02/10 at 3:12 AM, Palawan said:

U1 : 73 03

I am looking for firmware with smart fan control.

Fan control doesn't seem to be Voltronics' strength. I have no idea which Max 11kW '28066 non-Twin firmware has the best fan control, but the latest is 73.83, see below.

There is also 73.78, a little older, available here with original (unpatched) and various patched versions for mitigating the "PV stuck at 90 V" issue.

This is main (U1) factory firmware version 73.83 for the Axpert Max 11kW '28066 non-Twin. Do not use with any other model or version.

Use at your own risk. The hex file is dated 29/May/2024.

Firmware upload instructions for models with a removable display.

This firmware does not process the QDOP command, so even with suitably recent display firmware, it will not support SoC% for settings 12,13, and 29 when connected to a suitable battery's BMS.

DSP_73.83-20250606T033303Z-1-001.zip

On 2026/02/09 at 6:10 AM, mull said:

But the air filters are at the top!

Ah. My experience is with models with no filter, sorry.

On 2026/02/08 at 8:32 PM, Palawan said:

My actual is U1 : 56 09 and U2 : 25 06. I see there were already lot's of discussions on this platform about what should be the best version .. But not easy to see the forest through the trees. Lot's of firmware versions have been reviewed. What should be the best version for me ? I am looking only for a good smart fan control.

I don't own a VM model, but it seems that VM III and VM IV firmwares, at least for the 4kW and 6kW models, are interchangeable. The following post suggests that version 70.00 has good fan support, at least for a VM IV Twin:

If your present main (U1) firmware version is 78.xx, then yes, otherwise no.

On 2025/08/02 at 10:27 PM, Coulomb said:

Version 12.30 is probably the latest for your model, and I see that's not widely published either.

This is secondary (display, U2) factory firmware version 12.30 for the Axpert Max and Axpert King II (NOT the original King 1), non-Twin. Do not use with any other model or version.

Use at your own risk. The hex file is dated 08/10/2024.

Firmware upload instructions for models with a removable display.

This firmware processes the QDOP command, so with suitably recent main firmware, it should support SoC% for settings 12,13, and 29 when connected to a suitable battery's BMS.

Remote Panel_Reflash_MCU(12.30).rar

21 hours ago, Palawan said:

Is someone having experience with this is issue ?

I have no experience with use of these inverters.

But what it sounds like to me is that when there are clouds, there is a sudden drop of PV voltage, resulting in a sudden drop of bus voltage. At that time, the main power supply may "skip a beat" or ten. Other power supplies cope with this by having decent sized capacitors to "ride through" these periods, but the display, which relies on the "12 VAC" from the main power supply (often called HFPWR or similar, for high frequency power, may not be coping, as the capacitors are undersized, or perhaps dried out with age.

Has this problem been evident since new?

The Ouyads seem to be clones, and it's not clear whether the problem is the main power supply skipping too many beats, or the display not coping with the skips. Replacing the larger electrolytics in the display with decent quality parts may cure the problem. Unfortunately, there is no schematic for the display boards that I'm aware of, so it may be difficult choosing the right value capacitor, and/or making it fit.

This may be one area where clones are not as good as the original.

On 2026/02/03 at 6:15 PM, Jesus Abril said:

currently on 71.03

All I can tell you is that 71.03 is the only 71.xx file for VM III/IV Twin in my collection. So the safest path of updating to a later 71.xx is not available to you.

So unless you can get a suitable update from your inverter supplier, you'll have to try one of the other VM III/IV firmwares from this topic, and hope that it doesn't brick your inverter or damage it, and pick one that a reader says is quieter.

Hopefully, if all else fails, you can revert back to 71.03 from here. But there are no guarantees, unfortunately.

If I had time, and I currently don't because of a family issue, I might be able to figure out what the quiet firmwares do, and back patch it to 71.03. But that's also a lot of work.

@Jalil Ahmad, these appear to be low resolution thumbnails, with details hard to read.

Could you repost the originals, perhaps in a zip file? Especially part 2 of the control board, which I don't have so far.

Thanks in advance.

What is your main (U1) firmware version? That will tell me exactly what model of Axpert inverter you have.

At a wild guess, I'd say you have capacitors drying out, perhaps in the Solar Charge Controller.

How old is the inverter?

On 2026/01/26 at 7:18 PM, Livid said:

after turning it on it displays the F03 (battery overvoltage) error

That's what the user manual says. But a quick scan of one of the King 1 firmwares seems (at a quick glance) to be associated with battery under voltage. If so, that would explain the fault code with such a low battery voltage reading. Unfortunately, at present I don't have the time to investigate fully.

So then it's a matter of why the battery voltage is reading so low. It could be one or more of the battery voltage sense resistors going high value. These high value SMD resistors subject to moderate voltage for long periods of time seem to fail more often than average.

If it's the -12 V rail, then that would affect many readings. Do other readings seem reasonable?

On 2026/01/19 at 4:35 PM, Tony777 said:

It cycles like this continuously.

I'd say it has to be one of the transistors associated with the start circuit, or the associated resistors:

So Q10 or Q9 in the above.

Or possibly the SCC's opto coupler (if present) is shorted. Try removing the 2-pin cable from the Solar Charge Controller to the main board.

On 2026/01/26 at 4:06 AM, jfmm said:

I just noticed that in the WatchPower app, these parameters continue to show voltage values instead of SOC.

Are you using the latest version of Watchpower?

Do the values make sense as battery voltages, or are they really SoC% displayed as if they were voltages? My vague understanding of this is that the relevant command always responds as SoC if certain conditions are met, e.g. if the DSP responds to the QDOP command. So I'm surprised that Watchpower can respond with sensible battery voltages.

Edit:

I left "SOC back to utility" at 30% and "SOC back to battery" at 50%.

Was that using the front panel?

On 2026/01/11 at 9:53 PM, BobH said:

The Inverters reported 21.7kWh for last night; they under-read significantly.

They're probably reporting output power, i.e. AC-in less losses (assuming no AC charging). Each 5 kW inverter uses around 50 W when inverting; about 15 W when not.

On 2026/01/10 at 11:58 PM, Maurorr said:

After patching firmware, parameters 12 & 13 are no more manageable in % SOC , only in voltage mode

Ah yes. 72.75 happens to be the first one that implements the QDOP command.

On 2026/01/10 at 11:58 PM, Maurorr said:

Please , have you notice if this older release does not support QDOP commands ?

Yes. I see that now.

But 72.75 has what I have come to call the "presumed good" MPPT algorithm. Though I see that it only ever seems to be available in the "experimental" firmwares, i.e. those numbered xx.yy with yy ≥ 60. So you were definitely getting the stuck at 90 V issue with 72.75?

If so, I might as well patch 72.08, which is a "mainline" version (yy much less than 60). It also handles QDOP, and is a few months later than 7275. I also have 72.75, so I could patch that instead, but if it doesn't solve the stick at 90 V issue properly, I can't see the point.

Thanks in advance for any data.

I can confirm that 81.08 and 22.25 are still the latest firmwares available for the Axpert Max II 8kW '28066 non-Twin.

Firmware update instructions for models with a colour display.

Factory main firmware version 81.08 for the above. It does process the QDOP command.

Factory display firmware version 22.25 for the above. It does process the QDOP command.

Having both firmwares support the QDOP command means that settings 12, 13, and 27 will work with SOC% rather than battery voltage, provided that you are connected to a suitable battery with a supported BMS.

This is main (U1) factory firmware version 51.04 for the Axpert MKS III (PIP-5048MGX) 5kW '2809 non-Twin. This is like an Axpert MKS II with a removable display. Do not use with any other model or version.

Use at your own risk. The hex file is dated 17/Aug/2023.

Firmware upload instructions for models with a removable display.

This firmware does not process the QDOP command, so even with suitably recent display firmware, it will not support SoC% for settings 12,13, and 29 when connected to a suitable battery's BMS. The RAR password is "flash", without the quotes.

MKSIII_Inverter_Main_Reflash_Ver71.17 pw flash.rar