On 2026/03/17 at 8:40 PM, jfmm said:

I don't know if it's worth cycling the string to wake up the MPPT, but in my case, this would be the condition to do so: "IF MPPT_current>1.0A and MPPT_voltage>95V and MPPT_voltage<105V THEN cycle"

Is it possible to do this through the internal reading of these parameters in the inverter, or will I have to add external electronics to read the current and voltage of the string?

If by "cycle" you mean restart the MPPT logic, the standard MPPT patches achieve roughly that. Have you tried patched firmware version 281.05?

On 2026/03/16 at 8:23 PM, Kurtbe said:

Have you got an idea of the percentage of power that we lose because of that issue?

It depends on so many factors. But from various posts with many MPPT performance graphs, it seems that on the worst days, you can lose something like 80% of available power for something like half the day. That's rare of course. Most days you probably lose 5-10%, and on the best days basically nothing at all.

Edited April 2Apr 2 by Coulomb

Sorry, late answer

Edited April 2Apr 2 by Kurtbe
mistake.

3 hours ago, Coulomb said:

If by "cycle" you mean restart the MPPT logic, the standard MPPT patches achieve roughly that. Have you tried patched firmware version 281.05?

It depends on so many factors. But from various posts with many MPPT performance graphs, it seems that on the worst days, you can lose something like 80% of available power for something like half the day. That's rare of course. Most days you probably lose 5-10%, and on the best days basically nothing at all.

Hi Coulomb, so far I have tried nothing. Mainly because I have the impression that there IS no patch for the MAX II 8kW. That is mentioned nowhere as far as I vcan tell. Only MAX 8kW seems to be available...

Greets, Kurt

4 hours ago, Coulomb said:

There is Patched firmware version 281.05 but it's a bit old. I should update it for 81.08 and several minimum MPPT voltages. Life has been busy this year.

But indeed there are no 54.xx for the '2809 DSP. I do have 54.06 now, so I could patch that if there is interest.

Now you see, that is where I get confused immediately... You quote a number: 281.05: IS that for the MAX II, or for the MAX? ANd I suppose the more recent version would be 281.08? But again: for the MAX II, 8kW?
Then you quote 54.xx. No idea What you are referring to. 2809 DSP... DISPLAY?
So I will not start messing about until I know 100% sure that I will be using the correct firmware.
I hope you understand that this is all "a matter of fact" to you, but I am a one-time customer for Axpert. I am far from stupid, But I am a trained psychologist. Not an engineer...😟

Thanks for understanding, Kurt

On 2026/04/03 at 12:10 AM, Kurtbe said:

that is where I get confused immediately... You quote a number: 281.05: IS that for the MAX II, or for the MAX?

My notes say that 81.xx are for the Axpert Max II, as are 54.xx, but for different DSP chips. These can't be mixed.

I haven't seen where you say what your existing main (U1) firmware is. My apologies if I missed it.

No need to apologize Coulomb. I am sure it boils down to me.

81.xx is for the Axpert Max II, as opposed to the 281.xx (which is NOT for the MAx II)? But i do not find a 81.xx...
Concerning the 54.xx, I am clearly in the 22.xx zone (if we are talking display). I have no idea what you mean with "existing main (U1) firmware"...
I guess I should apologize for being so ingnorant.

Sorry... Kurt

9 hours ago, Kurtbe said:

81.xx is for the Axpert Max II, as opposed to the 281.xx (which is NOT for the MAx II)? But i do not find a 81.xx...

81.xx is for some Max II 8kW models. 54.xx is for other Max II 8kW models. 281.05 is a patched version of 81.05, so it's suitable for all Max II 8kW models that are running 81.xx. The "x" here stand for any digit 0-9, e.g. 81.08 or 81.61.

9 hours ago, Kurtbe said:

Concerning the 54.xx, I am clearly in the 22.xx zone (if we are talking display).

No, these are all "main" or "DSP" firmwares. On the front panel, the display version numbers are displayed at the bottom with U2 before the 4 digits of the display firmware, e.g. "U2 22 12“ indicates display firmware version 22.12.

There are two (occasionally three) firmwares in these inverters. The "MPPT stuck at 90V" issue concerns the main firmware, which is displayed on the front display (with appropriate presses of up or down buttons) with "U1" in front of the main firmware version number, e.g. "U1 81 05" indicating either factory firmware version 81.05, OR patched firmware version 281.05. You can only see the full 281.05 version number from monitoring software, like Solar Assistant.

So if you can find and report your main (U1) firmware version, I can help more.

Edited April 8Apr 8 by Coulomb

Hi,

I don't know how, but my panels with 2670 Wp were producing over 3350 W today for a moment!! Reflection in the clouds?!!

On 2026/04/02 at 3:10 PM, Kurtbe said:

I hope you understand that this is all "a matter of fact" to you, but I am a one-time customer for Axpert. I am far from stupid, But I am a trained psychologist. Not an engineer...😟

You don't need to be an engineer to have an engineering hobby

On 2026/04/02 at 11:04 AM, Coulomb said:

If by "cycle" you mean restart the MPPT logic, the standard MPPT patches achieve roughly that. Have you tried patched firmware version 281.05?

No, I just updated to the latest firmware version that you recommended in a previous post in this thread.

By cycle I mean switch off and on, physically disconnecting the cable coming from the panels. It seems to wake up the MPPT algorithm!

I'm even testing a script on a Shelly to detect the low power state in the MPPTs. It reads the MQTT topics in Solar Assistant and as soon as it detects the low power state it tries to "wake up" the algorithm, turning the panels off and on again.

Another output from the Shelly will control a contactor at the inverter's AC input to completely disconnect it from the grid whenever it is operating above the return to grid threshold. This way, I will save between 0.6 and 1 kWh per day from the grid just from the inverter's consumption.

A fourth output from the Shelly will control the availability of power for EV charging, taking into account several conditions, such as SOC status, load, battery drain, PV power, time of day, etc.

Next month I'm going to install 7 panels on MPPT 2, increasing the current power from 2670 Wp to 5915 Wp. Until then, I'll leave the Shelly algorithm running without controlling anything yet, to see if the outputs are switching correctly. I hope to avoid unpleasant surprises this way...

On 2026/04/02 at 11:04 AM, Coulomb said:

It depends on so many factors. But from various posts with many MPPT performance graphs, it seems that on the worst days, you can lose something like 80% of available power for something like half the day. That's rare of course. Most days you probably lose 5-10%, and on the best days basically nothing at all.

In my case, with just one MPPT, I'm losing around 0.5 kWh on a sunny day and much more on a cloudy day.

Edited April 9Apr 9 by jfmm

On 2026/04/08 at 4:11 AM, Coulomb said:

So if you can find and report your main (U1) firmware version, I can help more.

Thank you Coulomb,
U1 81.08 is the current firmware (But I knew that all along: I uploaded it myself). I have never updated with any patch so far, out of fear of getting it wrong and messing things up.

The display runs on 22.25, both of which are probably the latest firmware versions for the MAX II. The converter has the 28066 Chip.

13 hours ago, jfmm said:

Hi,

I don't know how, but my panels with 2670 Wp were producing over 3350 W today for a moment!! Reflection in the clouds?!!

That can occasionally happen if the sun hit the panels in the optimal way, AND the ambient temperature is low. That is when you get the highest output.

You don't need to be an engineer to have an engineering hobby

True, But I'm sure it helps... 😉

In my case, with just one MPPT, I'm losing around 0.5 kW on a sunny day and much more on a cloudy day.

Thanks for the feedback, I guess that for me that is similar.

Hi,

I currently have the automatic "wake-up" mechanism working.

When the MPPT voltage is between 95 and 105 V, and the current is above 0.5 A, the MPPT input is switched off for 1 second, which causes the MPPT voltage to rise and consequently the power as well.

It's working correctly, however, I'm going to try another approach instead of interrupting the input. Although the interrupted power is around 50 W, a load interruption is never good for the electronics...

Therefore, instead of cutting off the input, I'm going to apply a momentary load of a resistor in parallel with the input, in order to simulate shading. I hope it works.

Attached are the voltage, current, and power graphs of the MPPT before and after applying the input cut-off automation.

Edited May 6May 6 by jfmm

Hi,

I installed the second set of panels on the MPPT2 about a week ago.

Since then, once or twice a day, the inverter has been behaving strangely.

For no apparent reason, the inverter stops powering the loads for brief moment (maybe half a second) and stops working in off-grid mode, connecting to the grid for the next 10 minutes, after which it returns to off-grid mode.

Here's a screenshot I took from Solar Assistant at the time of one of these events.

Has anyone else experienced this or read about it to explain what the cause might be?

Thanks in advance.

Edited May 6May 6 by jfmm

Almost all measurements seem to be going low for that one measurement period, even battery voltage and one of the temperatures. Real temperatures don't plummet tens of degrees in seconds. That suggests to me that the inverter has lost power to the measurement circuitry.

How old is the inverter?

Is your climate hot?

It may be that the power supply capacitors have dried out, and the extra panels had little to do with the change, other than shaking things up a bit. This post has details for a 5 kVA model; 8 kW models are likely quite similar, possibly with parts moved around a bit.

Edited May 8May 8 by Coulomb

On 2026/05/08 at 11:35 AM, Coulomb said:

How old is the inverter?

Hi Coulomb, thank you for your quick reply.

The inverter was purchased in September of last year and went into operation in December of last year. It hasn't even been running continuously for 5 months yet.

On 2026/05/08 at 11:35 AM, Coulomb said:

Is your climate hot?

No. Temperatures are never very high because the installation is 600 meters away from the sea.

Currently, we are in the middle of spring, and on a sunny day like today, the temperature at two o'clock in the afternoon is around 19 degrees Celsius.

Even in summer, it is very rare for temperatures to reach 30 degrees Celsius.

On 2026/05/08 at 11:35 AM, Coulomb said:

and the extra panels had little to do with the change

I realize there is a coincidence with the installation of the second group of panels. With only one group of panels (2670 W), the abrupt variation in power due to cloud shading did not have as much impact on the system. Currently, the impact is greater because the total power has increased to 5785 W.

However, the problem has mainly occurred under low load conditions, around 300 W (residual load of the house), both in the morning when there is still little sun, and when the inverter starts to reduce the battery charging power, as it is already almost fully charged.

The event happened on 10 of the 14 days since the second group of panels came into operation. Before, it never happened.

On 2026/05/08 at 11:35 AM, Coulomb said:

It may be that the power supply capacitors have dried out

Since the inverter is practically new, could it be a problem with the capacitors? If so, could it be a manufacturing defect, or does the brand use very low-quality capacitors?

Should I give up on this type of inverter before I have some other kind of problem?

I don't know if you can see it in the attached image, but the event occurs where you see a small peak on the red line, which corresponds to the 10 minutes that the inverter switches to line mode.

Edited May 12May 12 by jfmm

11 hours ago, jfmm said:

the installation is 600 meters away from the sea.

This could be the root of the problem. These inverters do have conformal coating on the underside of the PCBs, but connectors and other exposed electrical metal can succumb to the corrosion from salty air. It could be worth spraying various parts with contact cleaner or moisture displacement spray, if you're willing to open the unit and void warranty.

Being purchased only last year, dried out capacitors are very unlikely. These inverters come with capacitors of moderate quality: not the worst junk types, but also not the longest life parts either (which cost more).

It's hard to say whether you need to switch to a higher quality inverter, and I don't know what brands are best at resisting salty air.

I believe that I have the same converter. And I am also relatively close to the sea. And my converter is actually placed outside, and temperatures here can rise up to 40°C. So far it's been performing very well since more than 3 years now...