Coulomb

I think that using the USB menu (pressing the appropriate keys on the display) puts the USB port into host mode, where it expects to talk to a "peripheral" such as a USB stick. Using a standard USB cable, the USB port presumably defaults to peripheral mode, so that the PC can be the host and they can communicate. This is probably the best way to connect between PC and inverter, since there is no USB to serial adapter required, and some adapters are not compatible. However, this only works IF the reflash tool has the USB "port" option. I think that many of the reflash tools for the '2809 chip do NOT have this option. Most if not all reflash tools for the '28066 processor use the Arena reflash tool, which seems to be more recent, and has the USB "port" option.

Yes. all the 82.xx firmwares should be compatible with your model that has 82.05 now. The latest and the only one with the MPPT fix is 82.63. I recommend using the RAR file from this post, that keeps all the files together, and makes it less likely that the wrong file will accidentally get used.

The PV production is looking OK for a dismal day, except that the current threshold seems way too high, at around 0.8 A. That's assuming that your top graph is MPPT2 voltage. I'll see how my time goes. Thanks for the recent firmware update files.

So '28066 then. Alas, I forgot that Axpert Max II 11kW firmwares are extremely rare. I only have one, and it's for '2809 and a Twin model. Sorry! As a point of interest, if you recall, what was the original firmware version it came with?

If I found the correct panels with a quick search, the Isc rating is 14.0 A, so two stings in parallel would be 28.0 A. The Imp is 13.11 A, so two panels would be 26.22 A. The Axpert VM III specs that I found say 27 A max, so this is very close to the max. The above, combined with "Bus voltage 1 V", is not good news. It looks like that solar charge controller failed in such a way that it shorts the DC bus (both MOSFET(s) and diode(s) shorted). But you may be able to disconnect that inverter's solar charger board, and allow it to work without that That's probably the panel short circuit current. That's the theory, but in practice, there are short periods of overshoot. My wild guess is that enough of these happened over time to eventually blow out the solar charger. Unfortunately, the fix could be very inconvenient: replacing all the panels with slightly lower power ones, which don't exceed the 27 A rating. Or just use a single string, perhaps 10 panels in one string (10S1P) instead of 7S2P. You might get away with 12S1P; carefully check the Voc and likely temperature range (the problem will be on the coldest mornings when the voltage is highest). Hopefully, the failed solar charger will not have taken out anything else in that inverter. It could be repairable if you can find the right people, and if not, replacement solar charge boards should not be too expensive. The hassle will be finding the exact right boards, and getting quality rather than cheap junk.

As I said earlier, I suspect it's badly unbalanced cells due to the inverter reading the battery voltage incorrectly for a long time. You choices are: * Wait and see. With the corrected battery voltage readings, it should balance over the course of several weeks, perhaps longer since the inverter was misreading the voltage for so long. If so, the battery should cut off gradually at lower and lower voltages, giving longer and longer run-times. * Balance the battery by hand. This requires you or someone else to open the case and clip on loads or a power supply, and will likely void the warranty. * Send the battery in for repair or replacement. It sounds like this could be a slow, expensive process. * Purchase another battery module(s), possibly while trying to get the existing modules repaired or replaced or balanced. Personally, I'd balance by hand, but I've had experience doing this before, and have the appropriate equipment.

What firmware versions are working for it? I need to know that to select the right '2809 or '28066 firmware.

I was just researching two different firmwares, both 43.05, and they are both either 2500W 24V or 1200W 12V. The VM firmware numbering is very confusing. Were you able to download the 20.44 firmware from my link? It at least has the capability of driving a 5 kVA 48 V model.

There is a chance that this post from 2014 (!) has some clues. BTW, is it really an Axpert King 7.2 kW? They are normally 5 kW, with some models 3 kW, and more recently 4 kW, and 6 kW. 7.2 kW suggests an Axpert Max.

I've not seen any, unless the 43.05 that you posted recently is one such.

I note that there is an older firmware version 43.05 whose hex file is dated 2022-10-11, and is different. The one above may be for the "premium" (refresh?) VM II model. Both 43.05 firmwares are only for 1200 W 12 V or 2500 W 24 V models. The older 43.05 supports both the QGMN command (returning 029, for VM II non-export), and QMN command (returning VMIII-2500 or VMIII-1200). The newer one above only has the QMN command, also returning VMIII-nnnn. It looks like they are trying to unify the VM2, VM3, and VM4 firmwares, at least to a degree. @Bassemubid, thanks for sharing the firmware update.

It could be that the bus soft start power supply is weak, or that there is too much load on the DC bus for the power supply to cope with in the allotted time. Both of these might cause the transformer to make an unusual sound. I wonder if the transformer has failed: either with shorted turns, or the ferrite core has cracked and now has too much air gap (these "transformers" are supposed to have an air gap to store magnetic energy). It is possible to try a transformer from another unit?

With Axperts (it may be different with Infinis), when you have paralleled inverters, the inverters that are not connected to the battery are supposed to have battery type USE. That would prevent warning code 61 (no communications to battery BMS). You might have to change this setting on the front panel.

I've since found 52.xx firmware for the Axpert MKS IV '28066. It might be worth a try if you have earlier firmware than that (52.00, 52.01, 52.02, or 52.03). Available here. I have no idea if it will fix this problem.

There is a huge thread on it. Summary: Most Axpert Max firmwares (except for a few "experimental" ones), and all VM III and VM IV firmwares, have a bug where the PV voltage can get stuck at a low value, usually close to the bottom of the MPPT range (90 V or 60 V), particularly in low light conditions (early morning, late afternoon, cloud, and rain). In the morning, the voltage will eventually shoot up from say 92 V to say 276 V, tripling the PV power. All that time from dawn through to this voltage rise, you've been missing out on up to 2/3 of available PV power. In some cases, on cloudy days, you can miss out on 75% of available PV power. But on a sunny day, the loss might be negligible, depending on many factors. Georg594 pioneered a patched firmware that largely fixed this issue, with the downside that you end up with a fixed minimum PV voltage. So someone with 4S panels needed a different patched firmware than someone with 8S or 10S panels. I extended the patched firmware to other models. It looks like Voltronic have fixed the problem in a way that works for all panel configurations. But for whatever reason, they don't port the good code to "mainstream" firmwares. I'm able to recognise the presumed good firmwares, and list them here.

Thanks. That does look like an Axpert King II 6 kW, quite possibly genuine. Unfortunately, I have seen no firmware for it. Strange that the VM III and VM IV 6 kW models also have 60.xx firmware. I wondered if they tried to merge these firmwares, but QMN returns (VMIII-... as expected for VM IIIs and VM IVs), and there is no QGMN command, as expected for Kings and King IIs.

Thanks. Interesting that it uses a '28069, I'm not familiar with that variant. It seems to be a two core version of the '28066. It's not clear if they just could not obtain the single core chip, or if they are using both cores. Unfortunately, I've not seen any 75.xx Axpert Max II 11kW '2806x Twin firmwares at all. The label strongly suggests that it's a clone, so it's compatibility with Voltronic firmware is unknown. So the quieter fans sounds like the only option until a suitable firmware turns up.

Hi, just a correction that they are. They are supplied by Rubicon who has an agreement with Voltronic power. Ah! My bad. I keep confusing Synapse and Synergy. Synergy are the clones I was thinking of. Sigh. Having firmware in the Voltronic FTP domain certainly clinches it. So @Pieter v D, there should be no problem paralleling these. If you're not concerned about the stuck at 90 V issue, it may be safer to parallel 45.13 with 69.07, since these are both from early September 2023, so they are probably compiled from the same source code (and so should operate identically on their respective processors).

Shutting down at 25.0 V is not normal, no. I have a suspicion that the bad battery voltage reading at the inverter has chronically undercharged the battery modules, causing the cells to become severely unbalanced over time. It could be that with proper charging from now on, it may gradually get better and better. But unfortunately, that might take weeks. The severe unbalancing could cause the early shutoff, too. You might be able to speed up the balancing by opening up the battery modules and balancing the cells manually (charging the ones that are lower than average, discharging the ones that are higher than average). I have car bulbs for just this purpose, and a "lab" dual power supply with current limiting. But if there is any chance that you might need and be able to get warranty service/replacement, then this is obviously out of the question.

I think it's worth doing, but if lightning decides it wants to invade your house, the tiny gap from your breaker is unlikely to stop it. The best you can hope for is that most of its fury has found a path to earth somewhere else, so that there are "only" under a kilovolt at the utility cables, which the breaker can withstand.

That's one of the limitations of such suppliers. You are effectively surrendering the right to support.

Oh. Synapse are not genuine Voltronics, as far as I know. [ Edit: Wrong! I was confusing with Synergy! Sigh. See a few posts down. ] I think that they somehow effectively forked Voltronic firmware, and now may have diverged enough to make paralleling with a genuine Voltronic (such as a Kodak) unsafe. Sorry, I don't recommend it. I assumed that they would be two genuine Voltronic models, regardless of branding.

Can I ask why? As a point of interest, the 20.44 firmware came in a file and folder that suggested that it was 20.43. But the QVFW command (Query main Firmware Version) certainly returns 0020.44.

All I can suggest is that this is a poor clone that somehow isn't sending the right commands from the display processor to the main processor. However, what little I could see from the video suggested it is a genuine Voltronic. Can you post a photo of the sticker on the side? Also, what is the main (U1, DSP) firmware version? There is a small chance that this is fixed in later firmwares.

For all the 6 kW and 8 kW models that I'm familiar with, you'll need at least 4 panels in series; 120 V may not be enough for these models, at least to get started. It's just the way that they are designed. Almost every inverter capable of handling high PV voltage is like this. They buck the panel voltage and use that as the DC bus voltage. The DC bus voltage can't be isolated from earth. No.