Coulomb

For other readers, I have answered this on another forum (55.xx main firmwares for the Axpert VM III 6kW(etc) non-Twin).

Ah! I overlooked that bit. Oops. Yes, the capacitor mod does seem like it won't explain that problem. It could be something to do with the buck converter; that "works harder" in those conditions. I can't think what exactly about the buck converter, though. Perhaps a weak IGBT? Weak gate drive?

The spikes from the fast changing potential of the PV wires seems to interfere with communications. The display talks to the DSP via serial lines. It's possible that this could also disrupt the BMS RS-485 commands as well. The capacitor mod seems to apply to many high PV voltage models, which is most if not all of the models made in the last several years.

My remaining question is why I was never able to connect to the chip via COM when the inverter was working. I could connect to the display, but that was it.On these inverters, you only ever talk directly to the display. The display is supposed to forward your commands to the DSP, amongst its own regular commands which try to keep the display up to date. When warning code 32 is in effect, that means that the DSP is not responding to commands sent from the display (either forwarding commands from the RS-232 port, or its own regular commands). With the wrong firmware in there, the DSP was never going to respond to anything, unfortunately. Yes, it's a pretty crazy setup. As for before the warning 32, I don't know.

That's "Ads" (equalisation Activation DiSabled). It's because you're not declaring a flooded battery; equalisation only makes sense for flooded batteries. So just ignore settings 30-36. Yes, it's confusing. Yes, there are different firmwares for the main (U1, DSP) firmware and the display (U2) firmware. There is also different firmware for the touch and button removable displays, as well as the colour versus removable displays. The ability to set three settings in SoC% depends on both the main and display firmwares. The latest 54.xx firmware I know of is 54.06, available here. For the display firmware, I'm guessing it's 22.xx, but please post your present display (U2) firmware version to be sure. Updating both will likely fix most of your problems. Sorry for the late response. Edit: Oops; I assumed that the latest 54.06 firmware would support the QDOP command, but in fact on checking just now, it does not. To get that to work, you will need an even later firmware; ask whoever sold you your inverter. Sorry for the false hope.

There is a link to Voltronics' communications tool in the link; search for the keyword "tool" without the quotes. It's likely, but not definite, that Sumry is a reseller, getting Voltronic to manufacture the inverters with the Easun branding on it. Or perhaps Easun do that subcontracting, and Sumry are reselling the Easuns. That's Voltronic's chosen approach: let someone else deal with customer service. There are dozens of such resellers and brands, as well as many illegal copies. The Easun SMG II models do look quite Axpert like, so the chances are good that this will work. Unfortunately, Easun seems to have started off as a clone manufacturer, so some of the older Easun models may not be genuine. But Easun have been around for many years now.

I and others have made many patched firmwares for working around the "stuck at 90V" issue. See What Patched Axpert Firmware is That?

This means that you have an inverter with a '2809 DSP chip. Unfortunately, 81.xx firmwares are only for inverters with the '28066 DSP chip. The 81.xx firmwares will call a calibrate function in the firmware very early on, in the first few milliseconds of operation. Unfortunately, the '2809 is an older chip, which does not have ROM memory at the address that the firmware calls. The result is that the DSP crashes. The only hope is to load a 54.xx Max II firmware (54.06 is still the latest available for your model) and start the upload at just the right instant so that the bootloader detects the start of the reflash before it runs the main firmware. See the If you Think Your Inverter is Bricked for clues on how to do this. Or use a JTAG device to flash the firmware, but that has its own issues as the firmware is password protected. Or buy a new control board for your inverter, but the hassle is getting the exact right card with suitable firmware on it, when there are so many variants that look nearly the same. If you buy it from whoever sold you the inverter, they should get the exact model number from you and hopefully supply the right card. I try to make this difference clear in my firmware posts, but I get that the whole thing gets confusing. Voltronic don't help themselves much with this; they could do a simple test before calling the calibrate function. Sorry for your difficulty, and I hope you can get it resolved soon.

Perhaps you mean that when the inverter switches from battery powering the load to AC input powering the load or vice versa some appliances drop out or lights flicker. This can happen because of the brief changeover period (some 10-20 milliseconds usually, i.e. one or two hundredths of a second) when there is no power to the loads. Axpert inverters have a special circuit that attempts to make this changeover quicker, closer to the 10 ms than 20 ms. But this only happens with certain settings and in certain circumstances. If it's really annoying, it might be worth running a small Uninterruptable Power Supply (UPS) just for the sensitive loads.

Another possible reason for warning code 32 is if the last firmware update was incomplete. In that case, the bootstrap loader program detects this situation, and rather than allowing the faulty firmware to crash, it stays running, waiting for another firmware upload. The bootloader is very simple, so it can't even let you know that it's running. So the inverter looks like it's totally bricked, other than the display, which runs totally separate firmware on another CPU, and it shows warning code 32 because all the commands it sends are timing out with no valid response. If this is the case, merely restarting a firmware upload will often start the reflash process again, and assuming that it eventually succeeds, the inverter will spring back to life. See If you think your inverter is Bricked.

I believe that it's a clone, which is not the same thing. They could have left off all sorts of things. The shutoff circuit is quite simple; it basically has to be U8 (per the schematic trace) or what drives it. Try shorting that opto collector to emitter; the power supply should shut off and stay off. Restarting continuously sounds like bad capacitors in the power supply. You could try replacing the usual suspects.

The later display firmwares relented and removed the warning altogether. The latest available 25.xx display firmware is 25.16:

It could be this issue:

Yes, that's the idea. There are a few very old models that did not have this feature, manufactured before about 2015.

The manual says that U03 means "Document inside the USB disk with wrong format." So it might be that the USB stick has the wrong format (FAT32 / NTFS / other), or the file is corrupted, perhaps by not "ejecting" it in Windows before removing it. Try reading the file with a text editor like notepad. The first three lines should be: :02000004003DBD :20800000761B0005ABBDA8BDA0BDC2BDC3BDFF6929425616767EA025761F02929235520166 :20801000EC04923662056F1F56BF08362B35761F01BF1A050002761F02920B36ED14923746Updating by USB stick seems not to be as robust somehow. Consider using a USB to RS-232 converter.

It would be nice to update to higher power for free, wouldn't it? But it's hard to tell what subtle changes they have made that makes the 11 kW model deserve its rating. Maybe the printed circuit board tracks are thicker, maybe there is some capacitor that has increased in size, that no-one has noticed. Certainly, I would not do it, and certainly, doing so would void your warranty. The latest 81.xx firmware for the Axpert Max II 8 kW '28066 non-Twin is 81.08, available here:

This is not my area of expertise. But my guess is no, it's not safe in the long run; this seems like the worst kind of penny pinching to me.

See also: https://forums.aeva.asn.au/viewtopic.php?p=104621#p104621 That's assuming that all the high PV voltage solar controllers have much the same circuit; I believe that this is the case.

I'm very late to this party, sorry. The above commands are all long ones. There is/was a bug with some USB drivers such that when you send more than 8 bytes at once, it fails. If you send them in segments of no more than 8 characters at once, it works. It's good to hear that you have updated the kernel and that it works now, so that this segmentation is no longer needed.

My guess is that 28.xx is display firmware for one of the Voltronics ESS (Energy Storage Systems, i.e. battery modules). It seems to have many extra and unusual commands, so I'd say for now at least it's not intended or safe to "update" an Axpert display. Edit February 2026: I didn't have specifically version 28.03 to examine when I said the above. Now that I look at it briefly, it seems to be a perfectly normal VM III (etc) display firmware. It looks like there are other 28.xx that are for the ESS; 28.xx seems to be yet another firmware version number range overlap.

Sorry for the very late reply. That appears to be a clone, so it's impossible to know what is in there, and hence what it might need. Your best bet might be to try the latest available Axpert VM III firmware, 41.18. The latest 02.xx display firmware for Axpert VM IIIs is 02.89, available here: This is main (U1) factory firmware version 41.18 for the older Axpert VM III 1.5/3.0/3.2/5.0/5.2kW '28062 non-Twin. Do not use with any other model or version. Use at your own risk. The hex file is dated 15/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. VMIII MAIN_4118.7z

Hopefully you are well sorted by now. If not, suitable firmwares are available here: https://powerforum.co.za/topic/29708-collection-of-dsp-axpert-firmware-for-vm-iii-twin-and-vm-iv-twin/ The new VM IIIs and VM IVs somehow use the same firmware.

Presuming that these are 4 kW 5 kVA (there are other 52.30 firmwares, unfortunately), then your best option is to run 3 x 73.70e fully patched firmware (NOTE: do not run factory firmware version 73.00, 72.70 max). If your inverters aren't this old model, please post a photo of the barcode sticker. Sorry for the very late reply.

Sorry for the extremely late reply. I don't seem to have any 7.2kW patched firmwares that defeat fault code 90. If you are still interested, please PM me with what minimum MPPT voltage you want, and I'll see what I can do.

Assuming that this is a firmware issue (I don't know), unfortunately the latest available firmware for this model is 60.10 (almost certainly older than what you already have), and 25.16 (the same as what you have). There is however a 68.13 firmware, hex file dated September 2025. This may or may not work for your model, see the thread below to decide. @Tarek Yag, you may want to include this one in your wonderful thread. This is main (U1) factory firmware version 68.13 for the Axpert VM III 1.5kW, 4kW, and 6kW '28062 Twin. Do not use with any other model or version, although if your inverter comes with 60.xx, it may work, see above. Use at your own risk. The hex file is dated 22/Sep/2025. Firmware upload instructions for models with a removable display. This firmware processes the QDOP command, so with suitably recent display firmware, it should support SoC% for settings 12,13, and 29 when connected to a suitable battery's BMS. VM III_TWIN_6813.7z