Coulomb

Before this point, everything sounds normal. Not using all the available solar power has been a common problem with Axpert firmwares. I don't know the 24 V models well, but I collect most such firmwares that I come across. What is the present main (U1) firmware version? I'd love to get a Rand for every time I've posted that question.

I very much doubt it. Fault code 51 is one of the more mysterious codes, caused by various seemingly unrelated things, but always (?) hardware related. See the list of links to posts here; the links are sorted by fault code: https://forums.aeva.asn.au/viewtopic.php?f=64&t=6007#repair

If you mean when the AC-in and AC-out ports are no longer connected, do the Axperts bond AC-out neutral to earth, the answer is yes. Though there is a screw inside that apparently can be removed to thwart this, so check with a multimeter that AC-out neutral connects to earth when the inverter is totally unpowered.

Yes, those high PV voltage models are nearly always non-isolated (certainly for all Axperts). So there is a large 50 Hz potential between PV- and earth. PV+ would also be lethal even at night, I would think. Presumably, non-earthed rails would get some fraction of that from capacitive coupling. Always disconnect PV panels from a running inverter, even at night, to work on them. The PV inputs are not passive!

Ah! I'd forgotten that Georg594 had done that F90 patch. That should work for that specific model (Max E 8kW '2809 non-Twin), but no other (not 7.2, 10, or 11kW; not the II models, not the '28066 models, and not the Twin or Duplex models). And of course, that firmware won't have any updates that have happened since July 2022. [ Edit: Duo → Duplex ]

No. As far as I know, no factory firmware version for any Voltronic Axpert model whatsoever has ever gotten it right. Almost every patched firmware that I make has it, as it's a one byte patch, once you know where to patch.

True, but the planet is completely unliveable well before then.

Yes, that's correct.

Oh, boy! Another VM III or VM IV Twin firmware version number range! I have no other 76.xx firmwares at all. So I have no other 76.xx firmwares to compare it with. Honestly, the best clue about the age of a firmware is the date stamp for the hex file inside the firmware update archive file. Would it be possible to upload the whole firmware update archive file? Or at least check the date of the hex file inside the archive? Thanks for the hex file. Sorry I can't be more helpful.

That's a board for accelerating relay switch-over. I believe that when you use the AC input range (UPS? I forget), then this board is somehow involved. It seems like it has damaged parts on it. There seem to be SCRs or TRIACs on that board; it's pretty mysterious to me. It looks like the DSP squirts some I²C or SPI data at the control chip on this board. I believe that it's possible to run without this board, though relay speed may be affected, and strange things may happen if you select the faster AC input range option. It may be possible to buy a replacement board. I don't know if those boards are different between 5 kVA models and 8+kVA models, so you need to be careful to get the right version of the board. Sorry I can't be of more help; these boards rarely seem to fail. I bet that makes you feel special 😧.

Inverex specific firmware is rarer than standard Voltronics firmware. As far as I know, these Aerox models are made by Voltronics, but with customisations for Inverex, e.g. the display is different to that of Axperts. They also have slightly higher rated power; it's not clear to me whether the hardware is beefed up a little to accommodate these higher ratings. The only firmware in my collection explicitly labelled as Aerox is for a 24 V model. This surprises me; I have vague recollections of several of them. What is your present main (U1) firmware version? That might help me to track it down.

72.05 is indeed the latest factory (not patched) King 1 main firmware that I'm aware of. This is the latest fully patched display firmware for the King 1s, but it can only be used with a fully patched main firmware such as 72.00a, as Weber points out above. It's based on factory display firmware version 02.83, which is not the latest. The latest display firmware that I know of is 02.87, available here (along with 72.05).

The capacitor goes directly across the PV input terminals. If your old capacitor is working, it nominally has 3.3x the capacitance, so that's presumably better. But these may be safety capacitors with fusible foil, which may lose capacitance as they encounter voltage transients, say from nearby lightning. Ideally, measure the capacitance of both and use the one with the highest remaining capacitance. Some multimeters have a capacitance range, though some struggle with the higher values. 3.2uF should be ok though. Beware of residual voltage on those capacitors! Measure on a voltage range and discharge with a resistor if necessary. The last 10V or so can be discharged by shorting the leads.

60.95 is from mid January 2024; I don't know what date 60.07 has. If the machine's sticker is February 2024 or later, 60.95 is probably not a later firmware. Sorry for not pointing that out earlier. BTW, "MCU" usually refers to the display firmware, not the main (DSP) firmware.

Ah. This is awkward. Fault code 90 means basically "clone detected". Voltronic got tired of having the clone makers undercut their products while using Voltronics' intellectual property (the firmware),without paying for it. From the label, I can immediately see that this is a clone, not a rebranded Voltronic. So the firmware is doing what it's supposed to, which is to stop working after 60 days runtime if the firmware detects that it's not operating in a genuine machine. Unfortunately, updating the firmware will not solve the problem; there are values stored in EEPROM that won't change with the firmware update. At best, you'll get another 60 days from it, then fault code 90 will reappear. This is the downside of purchasing a clone. I do wish that Voltronic would make it easier to spot clones, however. Many people, probably yourself included, would buy these without realising the situation. The right way to get this resolved is to have your supplier provide proper firmware that the manufacturer has written and is supporting. Unfortunately, the chances of this are small. There are other ways of resolving this, but I don't want to discuss them as I don't want to be seen to be supporting clone makers. Edit: BTW, the brand "MPPT Solar" is deliberately made to sound like a legitimate brand (in this case, MPPSolar). I can't find it now, but MPPSolar had a web page warning against this clone brand.

I'm not aware of any other available 84.xx firmware updates, other than 84.00. 84.00 is only 2 months old. I have no other 70.xx either, and 70.00 is 14 months old now.

That's from February 2024, so it's later than anything else I have, including 60.89, 60.90, and 60.95. It's also later than 70.00. However, 39.16 is not the latest VM IV round display firmware; that's 39.26 here.

The 41.xx firmwares are out of order. The latest one I know of is 41.07 (later than 41.17 and even 41.08, yet still almost 3 years old). 41.07 can be downloaded from here; ignore the very old display firmware that comes with it. There is a small chance that this problem has been fixed in firmware. "Fan spin program" appears in a folder name, so there may be fixes to the fan speed control as well. Given the age of your machine (over 6 years since manufacture in May 2018) it's also possible, though quite unlikely, that some part has dried out internally that is preventing utility charging from working, and the fact that it happened just after you update firmware might be co-incidental.

Check to see if it has the equivalent of a "battery type" setting. Axpert inverters, which yours doesn't appear to be, have options such as FLD and AGM (lead acid), but also PYL (Pylontech, RS-485 only), SOL (Soltaro?), WEC Weco), LIA/LIB/LIC (these seem to be some sort of standard protocol, hopefully the BMS people will know about them), and so on. Just the list of those options should be all that they need to know.

Yes, or the front panel. Sadly, I have no King II 68.xx firmwares in my collection.

That looks vaguely like an Axpert communications board. you can pick up inexpensive comms boards from Ebay or Ali Express etc, though it might be a challenge to mount it, as yours seems to have only one mounting point. This post says that Mustek South Africa carry some. This post has a comparison of the various comms boards for Axperts.

What is the present main (U1) firmware version? That sounds like a 6.2kW King II, but the firmware version will confirm.

That seems too much less than battery voltage to me. But I don't know the 24V models well enough to know for sure. Me neither.

Are you using a cable between the King's display and the BMS of the battery? If not, the inverter will not be aware of the true state of charge of the battery. It will guess based on battery voltage, and will assume that it's a lead acid battery. Are all the battery level LEDs on when the inverter stops charging? There are several known issues with your very old firmwares, so updating those is the first thing to do.

Then you need a protocol manual; search the files section for several. If you just want a basic monitoring program, you can download WatchPower for free. You might even have an out of date version on a CD-rom that came with the inverter. There are other monitoring programs, some free, some inexpensive and worth the small one-time cost, e.g. Solar Assistant. I don't use any of these myself. Edit: I'm assuming that this is an RCT branded Axpert inverter. I don't recognise the model name; maybe it's something else rebranded as RCT. If so, please disregard the above.