Coulomb

Sorry for the late reply; it's been busy here. That's probably the same as running 11 kW firmware on a 7.2 kW model. It will likely work, except that it won't protect itself from loads over 7.2 kW. Twin means exactly that: it has hardware and firmware to support an extra relay and output terminals. You can adjust settings for how and when the extra output comes on.

That's because the manufacturer stole the firmware and didn't contribute to the development costs. Voltronic firmware checks for clone-ness, and if so, brings up fault code 90 after 60 days of runtime. You might be able to rescue it. You should be able to find the existing firmware version by using the arrow keys until U1 appears at the bottom left of the display. Report any digits after that. I note that updating the firmware alone will not fix the issue. You need someone to patch the firmware to work around the clone test. Or get a legitimate firmware from whoever sold you the inverter, if they are still in business.

74.01 has not been patched, but the more recent 74.04 has. Patched firmware version 374.04 implements only the lowered current threshold. I've come to doing the "full set" of patches for later patched firmwares. It's still the original perturb and observe algorithm, but there is a special test for low PV power that they get wrong, so it gets stuck at the low MPPT voltage limit. You can try the above, and if you don't like it, you can revert to the original factory firmware version 74.04, or I guess use the hex file you posted.

Please post the main (U1) firmware version for the other inverter. The 90.xx firmware versions are all over the place. Sadly, the 7.2 kW models are not very popular any more, so there's not a lot of work done for them now. Generally, the latest factory firmwares don't fix the "stuck at 90V" issue. However, 69.70 (from March 2024) has the "presumed good" algorithm, so that's as good as you will get with factory firmware. You could try patched firmware version 269.61, but that's based on even older firmware (November 2022).

You haven't mentioned paralleling boards or cables. Are you using these? Some models have paralleling boards built in, or at least come installed from the factory. Without these boards and cables, the inverters can't co-ordinate properly. Also, some models aren't designed to be paralleled at all, e.g. the VM series. Please post your main (U1) firmware version so I can tell exactly what model these Kodak branded inverters are. Sorry for the late reply.

I'm not familiar with this model, but it sounds like a 24 V model similar to my 48 V models. These inverters have trouble with capacitors drying out. There is a thread on this, see for example the post below. But you or your repairer have to be familiar with electronics, obviously. https://powerforum.co.za/topic/14666-repair-of-axpert-inverters-a-journey-started/page/4/#findComment-150549

I certainly did with my ancient PIP-4048MS inverter (Axpert MKS 5K-48 PF1). Part of that is the fact that the transformer temperature sensor is now more directly in the air flow. But an iGrid model is quite different; I don't think you can conclude much from this.

At a very wild guess: Something corrupted the EEPROM, and now there are charge source settings set to take effect at a particular hour or set of hours. It could also be per-hour charge source priority as well. Yes, it happens at 31 minutes past the hour, but very likely the time was never set properly, and/or the time has drifted so now it thinks that 7:31am is on an hour boundary. Use whatever monitoring software you have, or the front panel, to reset the per-hour charge priority and output source priority. The "stuck at 90 V" issue is mostly fixed with patched firmware; few factory firmwares fix this problem. Voltronic seems to be blind to this and a few other problems with their firmware, for reasons that are beyond me. What main (U1) firmware are you running? There is patched firmware for most Max models to address this issue, and you can do it at home without the help of your supplier.

I don't believe that it matters for most inverters. The ones I'm familiar with have the same speed on both fans. VM models do seem to treat the fans differently, but if you swapped them I don't think it would make a real difference.

Firmwares for the smaller (≤ 1500 W) are scarce. Please post your existing main (U1) firmware version.

Is it a lead acid battery? If so, your inverter has probably been excessively draining it day after day, and 3 years is all you can expect from those conditions. Winter is a tough time for batteries too.

Yes. In this configuration, almost completely ignore the inverter's reported State of Charge. It's using lead acid logic, which is weak enough for a lead acid battery, and delusional for an LFP battery. Just use the LEDs on the battery modules for a low precision but far more accurate and useful SoC. Sorry for the late reply.

UPS AC input range also has tighter voltage requirements to use the AC input, typically rejecting the AC input if under some 170 VAC. Appliance mode will hang on to lower utility voltages.

I doubt it, as the system is fully off-grid and no generator was mentioned. It would likely be staying in SBU output source priority (basically, it will stay in battery mode). When the battery goes to float, there is a short period where the battery charge current goes to zero (depending on loads etc). At this point, the battery voltage is going to dip from the absorb voltage to the float voltage. The power flow will change from towards battery to away from the battery, so the buck converter will change from active (bucking) to "straight through". This will involve a change in bus voltage, I think. My guess is that the bus capacitors typically need to supply some of the load for a brief time; this could be the brown-out if they are not up to snuff. Check for bulging of both bus capacitors, or any other signs of stress. Measure their capacitance if you can. Decent replacements are a bit pricy, so I hesitate to say just replace them and see what happens. I imagine that they could be awkward to desolder too. The other possibility is some sort of problem with the buck transistor, its gate drive circuit, or the buck diode, though I think all that must be working for smoothly regulating the charge current. Perhaps those film capacitors on either side of the buck inductor.

The AC full bridge (four IGBTs generating L and N outputs) are bidirectional. They can push or pull power depending on the phase of the sine wave with respect to the utility's, and push or pull VARs (reactive power) depending on the amplitude of the sine wave compared to the utility's. So for utility battery charging, or indeed any charging with these models, the firmware manipulates the phase to cause the power flow direction and amplitude (power amplitude, number of watts) required. But that power ends up in the bus capacitors, since that's at the other end of the full bridge (a DC <-> AC converter). If nothing loads the bus capacitors, they will quickly overvoltage, and other parts of the inverter have to step in and trip everything. But before that happens, the DC-DC converter, which is also bidirectional. pushes power towards the battery, keeping the bus voltage withing reasonable bounds. But the DC-DC converter has a fixed voltage ratio, set by the transformer turns ratio. Typically this is 8:1 or 7:1, though more recent models use something like 7.2:1. And the bus voltage is being buffeted not only my the full bridge running in reverse, but also the PV boost converter(s). The bus voltage can't be more than a volt or so lower than the present PV voltage. So the bus voltage is fluctuating. How to regulate the battery charge current in this situation? That's what the buck converter is for. When power flow is from the bus to the load, this converter is "straight through", i.e. the DC-DC high-side voltage is very near the bus voltage. But when the power flow is the other way, i.e. towards the battery, i.e. charging the battery, the buck converter is controlled to regulate the charge current. But the buck converter can only buck, never boost, so the transformed battery voltage always has to be less than the bus voltage. In other words, the bus voltage mustn't be allowed to fall too low. This can be done by fine tuning the exact power demanded from the full bridge. You can see that the inverter firmware is juggling a lot of balls at once.

No, that seems too low to me, assuming that the voltmeter can be trusted to within one percent or so. The voltage of the 12 V rail is determined by the width of the pulses in the main power supply. I would suspect parts around the 3-terminal voltage reference and the associated opto-coupler. But of course it could also be that something is still drawing too much current from the 12 V supply, and that's overloading it. Those sorts of faults can be a nightmare to fix.

My guess is that you've been lied to about the third inverter. It seems to be running non-Twin 8kW firmware. The lack of a second output is extremely strong evidence that it's not a Twin model. I don't know the internal difference between 8 kW and 11 kW models, but presumably some things are "stronger" in the 11 kW models. The chances of paralleling that third inverter successfully are negligible. Sorry. Maybe you can demand a real 11 kW Twin model, or a refund.

There are so many brands with products that look like Voltronic inverters. Some are legitimately rebranded but genuine Voltronic inverters, others are clones using illegal copies of Voltronic firmware, still others use illegal but modified or patched Voltronic firmware. Still others again are Voltronic-like but run their own firmware series, heavily influenced by Voltronic firmware, but not compatible. Best to post the firmware versions that you have now, and someone like myself may recognise it, or alternatively declare it non-compatible. Also, please post a photo of the sticker on the side (if any) with the barcode on it. It contains important clues about whether the inverter is a clone or not.

This firmware identifies as version 50.81, and a VM III. Yet the description says VM II. 3.5kW and 5.5kW are not standard Voltronic ratings, as far as I know. So unless your inverter comes with 50.xx and is rated at 3500W 24V or 5500W 48V, I would not attempt using it. It is also missing any support files, like the reflash tool.

It would be helpful to know at least what brand of inverter you are using. Sorry for the late reply.

Sorry, I've been really busy lately. I see that 45.14 is not widely published. [ Edit: There is a third firmware, the "display" or "communications" firmware, that could likely do with updating as well. Version 12.30 is probably the latest for your model, and I see that's not widely published either. Let me know if you feel the need for that. ] This is main (U1) factory firmware version 45.14 for the Axpert Max 7.2kW '2809. Do not use with any other model or version. Use at your own risk. The hex file is dated 05/11/2024. 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. MAX 7.2k 45.14.7z

Sorry for the late reply. Can you tell us the model of inverter you are using?

All I can tell you is that I have no firmware, display or main, later than the ones you already have. I have not had the time to study the BMS protocol part of display firmwares in any great detail.

If battery type is set to PYLontech, that should have no effect. Is the battery icon on the display flashing? That indicates that the battery's BMS is talking successfully to the inverter.

I'm not familiar with that battery. All I can suggest is later display firmware; that's what talks to the battery BMS. What is your display/comms (U2) firmware version?