Coulomb

It seems that the only 65.xx firmware available for the Axpert Max II 11kW '2809 Twin is 65.08. I can't quickly find the factory firmware, but patched firmware version x65.08, based on that factory firmware, is available below. It also includes the factory firmware, in case you don't want or trust the patches. Sorry for the very late reply; I've been very busy.

In the case of Axpert firmware, you also need to post what the present main (U1) version of firmware is. This nails down several possible variants that can't easily be discovered. Unfortunately, there is no easy way to find the latest firmware, but if you post here with this information, I usually respond. Alas, as has happened this time, sometimes I get very busy and get months behind.

For other readers: I answered this here, for what it's worth.

Yes, by running suitably patched firmware. Georg594 pioneered this for the Axpert Max 8kW, I and a very few others continue it for other models. Once you decide on a main firmware that suits your needs, I can patch it and post the patched firmware here. The patched firmware is not perfect, but my many accounts is vastly improved in low light conditions, and even some shading conditions. For completeness, factory main firmware version 55.10 can be found here:

This is main (U1) factory firmware version 55.81 for the Axpert VM III 1.5/4/6kW '28062 non-Twin. Do not use with any other model or version. Use at your own risk. The hex file is dated 18/11/2025. Firmware upload instructions for models with a removable display. This firmware does not process the QDOP command, so it does not support SoC% for settings 12,13, and 29. It does not have the "presumed good" MPPT logic. Edit: The hex file has "TWIN" in the name, but it's definitely a non-Twin firmware, as are the other 55.xx VM III firmwares. VMIII 4K_6K MAIN 5581.7z

This is main (U1) factory firmware version 55.79 for the Axpert VM III 1.5/4/6kW '28062 non-Twin. Do not use with any other model or version. Use at your own risk. The hex file is dated 08/10/2025. Firmware upload instructions for models with a removable display. This firmware does not process the QDOP command, so it does not support SoC% for settings 12,13, and 29. It does not have the "presumed good" MPPT logic. VMIII 4K_6K_5579.7z

This is main (U1) factory firmware version 55.11 for the Axpert VM III 1.5/4/6kW '28062 non-Twin. Do not use with any other model or version. Use at your own risk. The hex file is dated 11/7/2025. Firmware upload instructions for models with a removable display. This firmware does not process the QDOP command, so it does not support SoC% for settings 12,13, and 29. It does not have the "presumed good" MPPT logic. VMIII 4K_6K_DSP_5511.7z

The EEPROM will be all messed up. You will likely lose accuracy of measurements, and you might end up with fault code 90 eventually. I highly don't recommend this. I believe that it will work. The main problem with paralleling inverters with slightly different firmware versions is if they change the CAN bus message layout. This only happens rarely. Sadly I don't have the time to check this at present by comparing key parts of the firmwares. It's a quite tedious process, working with assembly language. It might be possible to run the inverters both with the output mode set to PAR, yet without actually paralleling the inverters, for a while. Make changes to settings, make sure that everything seems to work, and check that the difference between outputs is 20 VAC or less, preferably under 5 VAC. Use one multimeter with a lead on each active output for this. It's been a long time since I played with paralleling, so I can't be sure that the inverters won't complain about this.

These are patched firmware versions x78.09, based on factory firmware version 78.00 for the Axpert max E 11kW '28066 Twin. Do not use with any other model. The original hex file is dated 2024/11/04. This firmware works around the "stuck at 90 V" problem by changing the current threshold from 0.50 A to 0.10 A. It also fixes the premature float bug, and changes the reported version number to x78.09 (e.g. 278.09). The removable display will continue to show version U1 78 09. As is usual lately, there is a 200V version (278.09), a 150V version (178.09), and a 90V version (978.09), as well as the original factory version (dsp_original_78.09.inv). This version does not modify the derate at 360 V behaviour. I note that 78.09 has a completely different EEPROM address layout compared to 78.07, so do not use this version, or 78.08 (patched or factory), if your inverter came with 78.07. As far as I can tell, 78.08 and 78.09 use the same address layout, so you could go straight to x78.09 patched firmware if you are on factory 78.08 now. I produce both just in case there is some hidden difference, and to give users the choice. Use at your own risk; I cannot test this firmware as I do not own an Axpert Max. It has been "sanity checked" by disassembling the firmware and confirming that the intended changes are present. Firmware upload instructions. https://forums.aeva.asn.au/viewtopic.php?p=87767#p87767 Edit: "derate at 450 V" → "derate at 360 V" dsp_x78.09_patched.zip

This is patched firmware versions x78.08, based on factory firmware version 78.08 for the Axpert max E 11kW '28066 Twin. Do not use with any other model. The original hex file is dated 2024/6/24. This firmware works around the "stuck at 90 V" problem by changing the current threshold from 0.50 A to 0.10 A. It also fixes the premature float bug, and changes the reported version number to x78.08 (e.g. 278.08). The removable display will continue to show version U1 78 08. As is usual lately, there is a 200V version (278.08), a 150V version (178.08), and a 90V version (978.08), as well as the original factory version (dsp_original_78.08.inv). These versions do not modify the derate at 360 V behaviour. [ Edit February 2026: I was confused! These DO have the current limit set to start at a PV voltage of 450 V, which is the patched behaviour, since I started with cuba.cz's already-patched binary, and added my "stuck at 90V" etc patches to that. Factory firmware starts the 100A charge current limit at 360 V. Sorry for the confusion! ] I note that 78.08 has a completely different EEPROM address layout compared to 78.07, so do not use this version, or 78.09, if your inverter came with 78.07. As far as I can tell, 78.08 and 78.09 use the same address layout, so you could go straight to x78.09 patched firmware if you are on factory 78.08 now. I produce both just in case there is some hidden difference, and to give users the choice. Use at your own risk; I cannot test this firmware as I do not own an Axpert Max. It has been "sanity checked" by disassembling the firmware and confirming that the intended changes are present. Firmware upload instructions. https://forums.aeva.asn.au/viewtopic.php?p=87767#p87767 dsp_x78.08_patched.zip

For other readers, you can usually figure it out from the main (U1) firmware that your inverter came with (in the first post, this is 72.03), and searching the following post for the major version number (in this case 73, the number before the dot) in this post: What Axpert firmware is that?To find a patched firmware for your inverter, search the major version number in this companion post. But beware of the overlap of version numbers! What patched Axpert firmware is that?

Are you saying that you have two invrrters with the exact same serial number? I suppose some clones might do that.

You probably won't find an accurate schematic. Most of the 5kVA models are much the same inside, with the exception of the Kings' rectifier module. So you might get some value from a schematic trace like this one: https://forums.aeva.asn.au/viewtopic.php?p=88434#p88434

Those are custom made parts. You can't buy them from ordinary electronics parts sellers, as far as I know.

I assume that it has been running all night before dawn? That sounds like it might be a power supply issue to me. Check and/or replace the usual suspects, per this post. But it could also be something to do with the high PV voltage solar charge controllers. I don't know much about those, sorry. See the repair topic for possible clues.

Is this before or after you updated to what was supposed to be 281.05? I've done a quick check on the 281.05 patched firmware and it seems that it should show 281.05 on monitoring firmware. If that's how your inverter came, that's really weird. It should update to 281.05 by following the usual update instructions.

If these are the original versions, with the small non-removable displays, congratulations on having some of the oldest Axperts still running! I think that my 9 year old inverters came with 72.70. Both of these older models can run patched firmware version 73.00e (note: do not run factory firmware version 73.00 with no letter after it; it will eventually stop with fault code 90. This was one of the first firmwares to implement fault code 90). https://forums.aeva.asn.au/viewtopic.php?p=70827#p70827 If you don't want patched firmware for whatever reason, I think you should be able run version 72.90, if you can still find it somewhere. I would not run 72.xx and 53.xx in parallel, even though it may let you try. Of course, you need the appropriate paralleling boards and associated cables.

My suggestion is to always replace all 8 on one side of the H-bridge, since the short circuit will have given the opposite transistors a very hard time, if they are still working at all.

The instantly switching off suggests to me a power supply collapsing. Check or replace all the usual suspects in the power supplies. Most of the power supplies seem similar, so this post probably applies: https://powerforum.co.za/topic/14666-repair-of-axpert-inverters-a-journey-started/page/4/#comment-150549 As for schematics, I'm not aware of one for your specific model. But others may be close enough, e.g. https://forums.aeva.asn.au/viewtopic.php?p=88434#p88434

I'm not aware of any genuine Axperts with the round screen and 4 kW Twin. But there are so many models these days. Can you post your present main (U1) and display (U2) version numbers. Sorry for the late reply.

This looks like it might be an Axpert or clone. Can you post the main (U1) and display (U2) firmware versions, if they are so called?

Fault code 90 is specifically designed to thwart clone makers who steal Voltronic firmware and undercut their sales. Unfortunately it is the purchaser that gets punished, not the clone manufacturer. I'm away from my main computer at present, but I may have a solution. PM me as I'm really busy at present. Edit: It looks like merely updating to factory firmware version 73.78 will work, or patched firmwares based on that. All available here: This seems to be a clone, and they appear to be using E firmware with a II display. I don't know what the ramifications of this are; perhaps the RGB lighting won't work, perhaps something serious. I'd say you have nothing to losing trying one of the above firmwares.

450mA? These units make no sense. Perhaps you mean 450 V and 200Ah? For the battery capacity setting, it's not specified directly, but will affect the maximum charging current setting.

Sorry, I'm running extremely late with replies. Your inverter claims to be a VM III, but I'm not seeing a removable display. Is there one? Without a removable display, there is no ARM processor to talk to the BMS and to offer battery types of PYL and so on. I would also expect the U2 firmware version number to be 02.xx.

I very much doubt it, that's a very low voltage. Also, the high PV voltage models require pulses from the DSP, and it would be trying to regulate bus voltage, not battery voltage. So almost certainly you can't use the "wrong" type of solar charger. As for which models do which, just check the PV charging specs. The voltages will tell the story.