Coulomb

It looks like it might be a VM III (from the "V3 at the end of the model name), so you could try display (U2) firmware version 02.90, (ignore the DSP file), since you have little to lose, and I don't think you'll find 03.xx display firmware. As a point of interest, what was the display firmware version that didn't work?

You seem to have plenty of PV voltage. So try version 378.11; at worst it should get stuck at 200 V. But I suspect it will kick in at lower PV current than the present ≈2.5A. and ≈1.4A.

Yes, as far as I know. That presumably means that you have paralleling cards installed, and all the wiring is correct. I also assume that you must have the output mode of both set to PAR (parallel single phase mode). All I can suggest is that you check the output wiring (no neutral and live swapped, for example). Though I would expect fault codes if the inverter somehow detected that. You should have breakers on both AC outputs. Do you get AC out if you isolate one of the inverters? Are both inverters using the same battery?

It's version 75.85. It should work with your inverter.

Sadly, I have only one 75.xx firmware in my collection, 75.85. So IF it's a firmware issue, this might fix it. The hex file is dated June 2025, so if your inverters' manufacturing dates are later than this, don't bother with updating to this firmware. There is no way to go back to your 75.03, except by asking your inverter supplier for an update file.

I have no 03.xx display firmware at all. Is this for a clone? Is 03 perhaps a typographical error?

74.04 is the latest 74.xx firmware that I have. It does not support the QDOP command, so it won't allow setting 29 and two others to use SoC%. Sorry. I don't own one of these inverters, but I've read that you can only change these settings on the front display, not via monitoring software. Once set, you can do everything else via the monitoring software. I have not looked into this. Edit: BTW, from the looks of the label, I'd guess that this is a clone.

Glad you got it working, @bruno1975 I've not heard of needing to "restart" the inverter.

Thanks. I must have missed it.

It could be a firmware problem. What is the main (U1) firmware version?

No. The latest 60.xx firmware that I have is 60.10, from June 2024.

King II 5 kW models seem to pair with either 19.xx or 44.xx; I don't understand the difference so far. The latest 19.xx that I have, from October 2024, is 19.21. The only 44.xx that I have, from July 2023, is 44.33. If your King II is a Twin model, and/or the display is colour (usually round), then it will require different display (U2) firmware again. Perhaps 20.xx, 52.xx, or 57.xx. That's why I wish everyone asking for firmware would say what their existing firmware version is.

What brand are they? Is there a fault code (e.g. "F80") when the slave trips?

I just did a sweep of my usual sources, and there are no new MKS IV firmwares that I could find.

The display / BMS comms is likely the firmware that needs to be changed, however. The latest (of two) 57.xx display firmwares I have is 57.22. [ Edit: Oops, I now see that's just above in this thread. I just search once I know the firmware version. ]

The latest main MKS IV firmware that I have is 74.04. The latest 22.xx display and BMS comms firmware I have is 22.25. It's two years old, but should have support for lithium batteries, with suitable cables.

The only 89.xx firmware that I have is 89.05, but it's for 8kW models only. It's for an "Axpert WP" which I know nothing about. I don't have any 43.xx display firmwares at all. Sorry.

What is your present main (U1) firmware version? There are many VM II model variants.

I posted about 75.85 in response to one of your other posts. The oldest 39.xx display firmware I have is 39.16; your clone has quite old firmware. The latest Voltronic 39.xx firmware I have is 39.36. I have no idea if it will work in a clone. ==== This is display / BMS comms (U2) factory firmware version 39.36 for the Axpert VM IV and Axpert Max Twin. Do not use with any other model or version. Use at your own risk. The hex file is dated 09/1/2026. Firmware upload instructions for models with a colour 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(39.36).rar

Ah, you actually have 60.06. It seems that the latest 60.xx firmware is 60.10 (also available as x60.xx patched). But if you need the quiet fans, stick to 60.95, or its patched versions x60.96 (note the difference in the last digit; I erred with x60.95 and the fixed code is now called x60.96, even though it's still based on factory firmware version 60.95).

Patched firmware version x75.85: https://forums.aeva.asn.au/viewtopic.php?p=106587#p106587

Any more ferrules to be found??

It should be compatible, despite 82.07 being a few months later than 82.63. 82.07 has more complex checking of the EEPROM contents, which I think is an attempt to behave properly with various EEPROM layouts. 82.63 has the "presumed good" MPPT logic, meaning that it's not as good as patched MPPT firmware for solar production, but is better than most factory firmwares. The good news is that you can revert back to 82.07 if needed. There is also patched x82.07. That zip file also has factory firmware version 82.07. It would be good to hear from other owners running 82.xx firmware, to be sure of compatibility. I'm 99% sure that no harm will come of trying 82.63, and reverting if problems seem to arise.

There is a collection of some partial schematic traces here, including some of the paralleling boards. I came across this post, where a PIP-5048 owner fixed a fault code 80 issue by replacing paralleling boards.

This is on the edge of my knowledge, so treat accordingly. I'm uneasy about it. The replacement for the choke wires would obviously have to be quite high voltage rated; audio cables would break down quickly with catastrophic results. With respect to protective earth, one end of the inductor has a high dV/dt 50 Hz square wave of amplitude equal to bus voltage plus the PV voltage. The other end has that plus a ≈20 kHz square wave also with bus voltage amplitude. The capacitance from wire to braid will be low, but with all this dV/dt, the current will be significant. I worry that this current could increase losses in the two converters (the 50 Hz DC<->AC converter and the MPPT boost converter) such that they could fail under some conditions.