On 2025/12/17 at 11:29 AM, rabihhatem said:

the company that sold me the inverter is long gone ... so that is a dead end for me.:

Try and find another Voltronic reseller in your country...

On 2025/05/20 at 1:44 PM, Kurtbe said:

hi Alexisis,

IF we are talking Max II, 8oooW, then the latest firmware is 81.08 and 22.25 for the display.
I have both official versions if you want them.

They also allow to programs 12 & 13 in SOC%.

However the apps do not seem to follow this.
Is there anyone who knows of an App that will allow to change the settings in SOC% instead of Voltage? (Not WatchPower, not Energy-Mate, nor Dessminitor can do it.)

Greetings, Kurt

Hi Kurt,

Are 81.08 and 22.25 the latest versions for Axpert Max II 8kW?

Where can I get them?

And the software to update the firmware?

Thanks in advance!

On 2025/05/20 at 1:44 PM, Kurtbe said:

hi Alexisis,

IF we are talking Max II, 8oooW, then the latest firmware is 81.08 and 22.25 for the display.
I have both official versions if you want them.

They also allow to programs 12 & 13 in SOC%.

However the apps do not seem to follow this.
Is there anyone who knows of an App that will allow to change the settings in SOC% instead of Voltage? (Not WatchPower, not Energy-Mate, nor Dessminitor can do it.)

Greetings, Kurt

Hi Kurt,

Do you know where can I get the last firmware versions and upgrade tuturial for Axpert Max II 8kW?

Thanks in advance!

On 2025/05/20 at 1:44 PM, Kurtbe said:

hi Alexisis,

IF we are talking Max II, 8oooW, then the latest firmware is 81.08 and 22.25 for the display.
I have both official versions if you want them.

They also allow to programs 12 & 13 in SOC%.

However the apps do not seem to follow this.
Is there anyone who knows of an App that will allow to change the settings in SOC% instead of Voltage? (Not WatchPower, not Energy-Mate, nor Dessminitor can do it.)

Greetings, Kurt

Hi Kurt,

Last September, I bought an Axpert Max II 8kW (image attached) with firmware versions 81.07 and 22.21.

I am experiencing the same problem that you apparently already went through. Parameters 12 and 13 are still related to battery voltage, instead of battery charge percentage. The lack of values between 48V and 49V does not allow for much resolution for the system to return to line mode.

I ask if you can help me find the latest firmware for my Axpert, and if is there is any procedure on how to upgrade them.

Thanks in advance!

I can confirm that 81.08 and 22.25 are still the latest firmwares available for the Axpert Max II 8kW '28066 non-Twin.

Firmware update instructions for models with a colour display.

Factory main firmware version 81.08 for the above. It does process the QDOP command.

Factory display firmware version 22.25 for the above. It does process the QDOP command.

Having both firmwares support the QDOP command means that settings 12, 13, and 27 will work with SOC% rather than battery voltage, provided that you are connected to a suitable battery with a supported BMS.

On 2026/01/11 at 11:20 AM, Coulomb said:

I can confirm that 81.08 and 22.25 are still the latest firmwares available for the Axpert Max II 8kW '28066 non-Twin.

Firmware update instructions for models with a colour display.

Factory main firmware version 81.08 for the above. It does process the QDOP command.

Factory display firmware version 22.25 for the above. It does process the QDOP command.

Having both firmwares support the QDOP command means that settings 12, 13, and 27 will work with SOC% rather than battery voltage, provided that you are connected to a suitable battery with a supported BMS.

Many thanks Coulomb!

I will test it as soon as I can!

On 2026/01/10 at 3:46 AM, jfmm said:

Hi Kurt,

Last September, I bought an Axpert Max II 8kW (image attached) with firmware versions 81.07 and 22.21.

I am experiencing the same problem that you apparently already went through. Parameters 12 and 13 are still related to battery voltage, instead of battery charge percentage. The lack of values between 48V and 49V does not allow for much resolution for the system to return to line mode.

I ask if you can help me find the latest firmware for my Axpert, and if is there is any procedure on how to upgrade them.

Thanks in advance!

Hi jfmm.

If you cannot find the Firmware files online: I can send them to you.
Greetings, Kurt

to Jfmm: If you are using windows 11 for the update you might need a driver in order for the upload cable to connect properly (depending on the chip version of the computer). If you experience any problem: feel free to contact me.

Kurt.

On 2026/01/11 at 11:20 AM, Coulomb said:

I can confirm that 81.08 and 22.25 are still the latest firmwares available for the Axpert Max II 8kW '28066 non-Twin.

Firmware update instructions for models with a colour display.

Factory main firmware version 81.08 for the above. It does process the QDOP command.

Factory display firmware version 22.25 for the above. It does process the QDOP command.

Having both firmwares support the QDOP command means that settings 12, 13, and 27 will work with SOC% rather than battery voltage, provided that you are connected to a suitable battery with a supported BMS.

Thanks Coloumb, I updated both firmwares yesterday and it seems to be working fine.

I left "SOC back to utility" at 30% and "SOC back to battery" at 50%.

Since I'm far from this solar installation, I use the WatchPower app to make any remote changes.

I just noticed that in the WatchPower app, these parameters continue to show voltage values instead of SOC.

Is there any additional configuration that can be done?

On 2026/01/16 at 10:33 AM, Kurtbe said:

to Jfmm: If you are using windows 11 for the update you might need a driver in order for the upload cable to connect properly (depending on the chip version of the computer). If you experience any problem: feel free to contact me.

Kurt.

Thank you Kurt,

I already updated both firmwares yesterday and it seems to be working fine.

There's only one unresolved detail regarding the WatchPower app and parameters 12 and 13. They continue showing values in Volt instead of SOC!

On 2026/01/26 at 4:06 AM, jfmm said:

I just noticed that in the WatchPower app, these parameters continue to show voltage values instead of SOC.

Are you using the latest version of Watchpower?

Do the values make sense as battery voltages, or are they really SoC% displayed as if they were voltages? My vague understanding of this is that the relevant command always responds as SoC if certain conditions are met, e.g. if the DSP responds to the QDOP command. So I'm surprised that Watchpower can respond with sensible battery voltages.

Edit:

I left "SOC back to utility" at 30% and "SOC back to battery" at 50%.

Was that using the front panel?

Edited January 28Jan 28 by Coulomb

Hi Jfmm and coulomb,

When setting the SOC% values (in my case) it needs to be done on the ACTUAL converter (using the physical panel on the inverter) It cannot be done via any app.
After that, the inverter WILL react accordingly. HOWEVER: NONE of the existing Apps (as far as I know) will REPORT in SOC%. WatchPower, Energy-Mate and Dessmonitor (via a browser) Will ALL still report in Voltage terms. My guess is that Voltronic has changed from Voltage to SOC%, But that tha actual apps have NOT adapted nor upgraded.

On 2026/01/28 at 1:01 AM, Coulomb said:

Are you using the latest version of Watchpower?

I'm using Watchpower version 1.5.0.0. I don't know if it's the latest version.

On 2026/01/28 at 1:01 AM, Coulomb said:

Do the values make sense as battery voltages, or are they really SoC% displayed as if they were voltages? My vague understanding of this is that the relevant command always responds as SoC if certain conditions are met, e.g. if the DSP responds to the QDOP command. So I'm surprised that Watchpower can respond with sensible battery voltages.

I can say that the inverter is working according to what I set up (Return to grid: 30%, Return to discharge: 50%).

But the Watchpower screens show all the information in voltage! (please see the attached images)

On 2026/01/28 at 1:01 AM, Coulomb said:

Was that using the front panel?

Yes, everything appears correctly on the inverter display.

Hi Jfmm. this is EXACTLY what you can expect, and what I tried to explain before. The Axpert itself (via its own physical panel, WILL act according to SOC%, but ANY app or even Dessmonitor (via a browser) WILL continue to report in Voltage.
BUT: your Inverter WILL act according to the settings you made.
One can only hope that the apps or Dessmonitor will adapt shortly.
Kind regards, Kurt

On 2026/02/04 at 5:39 PM, Kurtbe said:

Hi Jfmm. this is EXACTLY what you can expect, and what I tried to explain before. The Axpert itself (via its own physical panel, WILL act according to SOC%, but ANY app or even Dessmonitor (via a browser) WILL continue to report in Voltage.
BUT: your Inverter WILL act according to the settings you made.
One can only hope that the apps or Dessmonitor will adapt shortly.
Kind regards, Kurt

Hi Kurt, I'm hoping to get to the facility where I have the axpert to install the Solar Assistant application, which, from what I understand, will allow me to manage not only the inverter but also the Pylontech batteries.

The software runs on a Raspberry Pi and is much more complete than WatchPower.

Let's see how it goes!

14 hours ago, jfmm said:

Hi Kurt, I'm hoping to get to the facility where I have the axpert to install the Solar Assistant application, which, from what I understand, will allow me to manage not only the inverter but also the Pylontech batteries.

The software runs on a Raspberry Pi and is much more complete than WatchPower.

Let's see how it goes!

Yes, That is indeed an option and a solution. To me it is however too tech and would involve learning skills that seem somewhat steep.
I am happy with the way it now runs: I have setup the %SOC on the Axpert itself, and the apps now allow me to read (but not change) the %SOC from the app.
In this country the price of electricity is a complicated matter. I have therefore built a setup to adapt to that. I have installed a timer and a relay switch that is connected to the Axpert. If the batteries drop below a certain percentage SOC, then the relay will be activated and connect my system to the grid. But ONLY if the timer allows it.

If this setup fails to provide power, and the Axpert shuts down, then an Automatic Transfer Switch will connect me to the grid. Thus, ensuring power at all times.

If you are interested:

Specific in my situation (whereby the house is 100% dependent on electricity, no other energy available): The grid price here is based on two principles: The amount of power that you might require at any one time (for example 40Amps), and the actual electricity that you consume divided in day/night zones. If you consume 0 Wh, but have a 10kW connection you would pay something in the region of 60€/month. If you have a 3kW connection, it would be something like 8€. The price of that connection is high during the day, much lower at night. The actual consummation of power is divided into 3 daily zones. The cheapest being from 00 to 08 am. Three 'middle' zones and 2 expensive zones. Weekends are cheapest zone throughout.
This is how I have setup my system:

The axpert will provide 8000 W (34A), which is plenty. And normally during the day the batteries combined with the solar power will provide that. Therefor during the day, I CAN connect to the grid but it will only provide 3kW. But this happens rarely. During the night I have a 5kW connection. In total I pay about 9€/month for this.
In normal circumstances, I end up with nicely charged batteries at the end of the day. These will last me until the morning, usually still having 30%SOC. That makes up 80 to 85% of all days: no grid, only sun and batteries.
But the sun does not shine every day... So, from time to time, I need backup from the grid. Clouded days (mostly in winter) make up the colder days. Meaning that in the evening I might require some heating (heatpump will consume about 2,5 to 3 kWh). If I monitor that so as to keep the batteries above 10% before midnight, then at that moment the relay will open and send power to the batteries. I allow 2500 to flow to the batteries (with the app), and if the weather forecast predicts subsequent cloudy day, I will let an appliance run at the same time (Dishwasher, laundry, filter pumps, etc.). When the SOC reaches 60%, charging stops. This allows for heating in the morning if needed. If during the day, the batteries do not charge (no sun), then the timer will allow to charge between 2 and 6 pm (the middle-priced zone). This will again provide 60% SOC at 6 pm (in theory), If I cook before 6, then the 60% will normally suffice for the rest of the evening.
If there is NO power anymore from the batteries or the sun, then the ATM will connect me to the grid at any one time (limiting me to 2.5 kWh during daytime and 5 during the night).
The combination of all this results in few connections to the grid, but when I do, it is almost always during nighttime, allowing for sturdy charging of the batteries, but at a very cheap rate. exceptionally I will connect to the grid during daytime, but at a slightly higher price.

There are only three downsides to this setup: 1: When the Axpert shuts down before midnight, it needs to be reset manually, or it will not charge during the night (it will however start itself up again when it 'reads' solar power from the panels in the morning). And 2: when the grid connects during the day, the batteries will hardly charge at all. As long as the Axpert receives the slightest bit of sun, it will hardly allow the batteries to charge but rather provide the energy to whatever one consumes in the house. It will not send its maximum power to the batteries (because of the setting: Solar, Batt, Utility). and finally, 3: whenever connected to the grid, there is little power available, so heavy consumers cannot be used simultaneously.
If I could find a solution for problem 1 (Axpert starting up when if 'sees' grid power) and 2 (allowing fast charging during sunshine), to me, it would then be a perfect system.

SO, admittedly this is not a perfect system. But it works, and with some monitoring in winter, it provides for a very cheap bill and a huge saving on CO² production. My bill varies between 12€ (just for the connection) to 55 something in a dark and cold month. (This winter being December: 203kW, of which 180 at cheap rate 0.17€. Including electrically heating up the solar boiler twice).

Let me know how the Solar Assistant works out!
Regards, Kurt

On 2026/02/14 at 9:59 AM, Kurtbe said:

Yes, That is indeed an option and a solution. To me it is however too tech and would involve learning skills that seem somewhat steep.
I am happy with the way it now runs: I have setup the %SOC on the Axpert itself, and the apps now allow me to read (but not change) the %SOC from the app.
In this country the price of electricity is a complicated matter. I have therefore built a setup to adapt to that. I have installed a timer and a relay switch that is connected to the Axpert. If the batteries drop below a certain percentage SOC, then the relay will be activated and connect my system to the grid. But ONLY if the timer allows it.

If this setup fails to provide power, and the Axpert shuts down, then an Automatic Transfer Switch will connect me to the grid. Thus, ensuring power at all times.

If you are interested:

Specific in my situation (whereby the house is 100% dependent on electricity, no other energy available): The grid price here is based on two principles: The amount of power that you might require at any one time (for example 40Amps), and the actual electricity that you consume divided in day/night zones. If you consume 0 Wh, but have a 10kW connection you would pay something in the region of 60€/month. If you have a 3kW connection, it would be something like 8€. The price of that connection is high during the day, much lower at night. The actual consummation of power is divided into 3 daily zones. The cheapest being from 00 to 08 am. Three 'middle' zones and 2 expensive zones. Weekends are cheapest zone throughout.
This is how I have setup my system:

The axpert will provide 8000 W (34A), which is plenty. And normally during the day the batteries combined with the solar power will provide that. Therefor during the day, I CAN connect to the grid but it will only provide 3kW. But this happens rarely. During the night I have a 5kW connection. In total I pay about 9€/month for this.
In normal circumstances, I end up with nicely charged batteries at the end of the day. These will last me until the morning, usually still having 30%SOC. That makes up 80 to 85% of all days: no grid, only sun and batteries.
But the sun does not shine every day... So, from time to time, I need backup from the grid. Clouded days (mostly in winter) make up the colder days. Meaning that in the evening I might require some heating (heatpump will consume about 2,5 to 3 kWh). If I monitor that so as to keep the batteries above 10% before midnight, then at that moment the relay will open and send power to the batteries. I allow 2500 to flow to the batteries (with the app), and if the weather forecast predicts subsequent cloudy day, I will let an appliance run at the same time (Dishwasher, laundry, filter pumps, etc.). When the SOC reaches 60%, charging stops. This allows for heating in the morning if needed. If during the day, the batteries do not charge (no sun), then the timer will allow to charge between 2 and 6 pm (the middle-priced zone). This will again provide 60% SOC at 6 pm (in theory), If I cook before 6, then the 60% will normally suffice for the rest of the evening.
If there is NO power anymore from the batteries or the sun, then the ATM will connect me to the grid at any one time (limiting me to 2.5 kWh during daytime and 5 during the night).
The combination of all this results in few connections to the grid, but when I do, it is almost always during nighttime, allowing for sturdy charging of the batteries, but at a very cheap rate. exceptionally I will connect to the grid during daytime, but at a slightly higher price.

There are only three downsides to this setup: 1: When the Axpert shuts down before midnight, it needs to be reset manually, or it will not charge during the night (it will however start itself up again when it 'reads' solar power from the panels in the morning). And 2: when the grid connects during the day, the batteries will hardly charge at all. As long as the Axpert receives the slightest bit of sun, it will hardly allow the batteries to charge but rather provide the energy to whatever one consumes in the house. It will not send its maximum power to the batteries (because of the setting: Solar, Batt, Utility). and finally, 3: whenever connected to the grid, there is little power available, so heavy consumers cannot be used simultaneously.
If I could find a solution for problem 1 (Axpert starting up when if 'sees' grid power) and 2 (allowing fast charging during sunshine), to me, it would then be a perfect system.

SO, admittedly this is not a perfect system. But it works, and with some monitoring in winter, it provides for a very cheap bill and a huge saving on CO² production. My bill varies between 12€ (just for the connection) to 55 something in a dark and cold month. (This winter being December: 203kW, of which 180 at cheap rate 0.17€. Including electrically heating up the solar boiler twice).

Let me know how the Solar Assistant works out!
Regards, Kurt

Wow, what a complex setup!

Yes, in my country, the system is very similar. But besides the very high energy costs, the area where I have the solar system installed experiences constant power outages, which even cause damage to some appliances. Since I have a constant consumption of around 300W due to the video surveillance system, alarm, motion lights, network rack, weather station, and two refrigeration units, I opted to install the solar system to be almost self-sufficient when the house is empty.

However, I wasn't very satisfied with the WatchPower App when I realized that firmware updates didn't allow remote configuration of SOC values. Furthermore, the inverter's Wi-Fi connection dropped regularly, returning online after a few minutes, the data storage capacity is very limited, deleting all information older than a month, access to this information is also difficult—some days the information simply disappears—and it doesn't display any consumption graphs.

Regarding the Solar Assistant software, not many skills are required because, in reality, there's not much science to it…

I acquired a 1GB Raspberry Pi 4, added a DIN rail mounting box and a power transformer, added a 32GB SD card, loaded the operating system image onto the card (which is available on the website), and purchased the connection cables between Raspberry Pi/Axpert and Raspberry Pi/Pylontech, as well as the lifetime software license.

The setup is extremely easy; you just need to configure the internet connection and the USB ports.

It runs in the browser, but it can also be installed on Android or iPhone and has a completely different presentation from WatchPower.

It's possible to access a large number of graphs, zoom in/out, it allows some automation, it allows access to the health status of the battery cells, and of course, it allows remote configuration of the SOC for grid return!

Since I configured the system only two days ago, I'm still learning the software's features! But I can already see that I made a good choice.

I've attached some screenshots I took of the system below.

Yes, it seem

On 2026/02/18 at 11:19 PM, jfmm said:

Wow, what a complex setup!

Yes, in my country, the system is very similar. But besides the very high energy costs, the area where I have the solar system installed experiences constant power outages, which even cause damage to some appliances. Since I have a constant consumption of around 300W due to the video surveillance system, alarm, motion lights, network rack, weather station, and two refrigeration units, I opted to install the solar system to be almost self-sufficient when the house is empty.

However, I wasn't very satisfied with the WatchPower App when I realized that firmware updates didn't allow remote configuration of SOC values. Furthermore, the inverter's Wi-Fi connection dropped regularly, returning online after a few minutes, the data storage capacity is very limited, deleting all information older than a month, access to this information is also difficult—some days the information simply disappears—and it doesn't display any consumption graphs.

Regarding the Solar Assistant software, not many skills are required because, in reality, there's not much science to it…

I acquired a 1GB Raspberry Pi 4, added a DIN rail mounting box and a power transformer, added a 32GB SD card, loaded the operating system image onto the card (which is available on the website), and purchased the connection cables between Raspberry Pi/Axpert and Raspberry Pi/Pylontech, as well as the lifetime software license.

The setup is extremely easy; you just need to configure the internet connection and the USB ports.

It runs in the browser, but it can also be installed on Android or iPhone and has a completely different presentation from WatchPower.

It's possible to access a large number of graphs, zoom in/out, it allows some automation, it allows access to the health status of the battery cells, and of course, it allows remote configuration of the SOC for grid return!

Since I configured the system only two days ago, I'm still learning the software's features! But I can already see that I made a good choice.

I've attached some screenshots I took of the system below.

Yes, it seems to fit you well! What country are you based in? (I am in Spain with One system, and that is the one which I referred to.)

On 2026/03/03 at 4:21 PM, Kurtbe said:

Yes, it seem

Yes, it seems to fit you well! What country are you based in? (I am in Spain with One system, and that is the one which I referred to.)

The installation is located on the coast of Portugal, south of Lisbon.

I know I'm new to this, and I'm probably facing situations that are common in inverter firmware with MPPT.

Is it normal for the MPPT to fix the panel voltage at around 100V during the first hours of the day, wasting a large amount of energy? Why doesn't it behave the same way at the end of the day?!

Please see the screenshots I took of Solar Assistant.

Hi Jfmm,

I never fully understood that issue either because it is rather technical. But for what I do understand it seems to be typical for the Axpert inverters. Their software seems to have been written in that way.
That is why Coulomb has written so many 'alternative' software (Patches) which seems to deal with that issue.

This is what AI says about it:

What you are referring to is known in the solar community as the "PV sticky at 90V/100V" problem (also called the "90V bug"). While often confused with the premature float bug (which affects battery charging), this is a specific flaw in the MPPT algorithm of Voltronic inverters, particularly the Axpert MAX and MKS4 series.

This is what AI says about it: What is happening?

In the early morning or during low-light conditions, the MPPT tracker starts up but fails to find the optimal operating voltage (Vmp) of your solar panels. Instead of climbing to the panel's ideal voltage (e.g., 250V–300V), it remains "stuck" at a very low voltage, typically around 90V to 100V.

• Yield Loss: Because the inverter is operating far below the panels' efficiency point, you might only get 100W of power when you should be getting 800W or more.

• The "Kickstart" Effect: The bug often persists until a sudden change occurs, such as a cloud passing by or the user manually cycling the PV switch. This "shocks" the MPPT into performing a fresh scan and jumping to the correct higher voltage.

Why does it happen?

The firmware's MPPT logic is overly cautious. At low light, it stays at the lowest possible voltage to avoid "crashing" the string if the current drops. It essentially gets trapped in a "local minimum" and lacks the logic to regularly scan for a better power point at higher voltages.

Solutions and Workarounds

• Patched Firmware: This is the only true fix. Community developers (notably "Coulomb" on the Power Forum) have released modified firmware for specific models that corrects this MPPT behavior.

• Hardware Workaround: Some users install a smart relay or contactor that automatically disconnects the PV input for 15 seconds if it detects the voltage is stuck between 80V and 100V with low current. This forces a reboot of the MPPT tracker.

• System Design: Increasing the number of panels in a string can sometimes pull the operating point further away from the "sticky" 100V zone, though this does not fix the underlying software error.

• SBU Priority: Changing the output source priority (e.g., to SBU mode) can occasionally trigger more frequent MPPT refreshes in certain models, though results vary.
  
  So maybe we should get some "lessons" in what this is exactly all about... 😉
  I am sure that Coulomb can help us understand better.

Greets, Kurt

On 2026/03/10 at 12:39 AM, jfmm said:

Is it normal for the MPPT to fix the panel voltage at around 100V during the first hours of the day, wasting a large amount of energy?

It's not "normal", but it is common on many Voltronic Axpert inverters with the high PV voltage rating, which is almost all of them these days.

I have a big post about patched firnware, see the section on MPPT stuck at 90V. It tells you what patched firmwares are available for particular models.

Voltronic do have several firmwares that do OK with this issue, but none of them seem to be "mainline" firmwares with version numbers like xx.yy where yy < 60. But it seems that Georg's original patches work best. I merely adapt his patches to many Axpert firmwares for many models.

On 2026/03/10 at 12:39 AM, jfmm said:

Why doesn't it behave the same way at the end of the day?!

There does seem to be a way that the bug manifests towards the end of the day, though it often seems to be less noticeable there compared to mornings.

As to why the bug is there at all, my guess is that these MPPT chargers run off PV power, so in the morning, it's important not to demand too much PV power, as you may "strangle" the weak PV power needed to run the charger's electronics. Power electronics running on marginal power supplies is not a good thing, so they have special code to prevent this. As the AI suggests, it seems over cautious the way it does this.

I have to say it's somewhat flattering to have AI mentioning my forum name directly 😊. Now if we could somehow train it to point to my patched firmware post directly, that would be wonderful.

Hi Coulomb,

I am sure that you will become world-wide known soon now that AI is spreading the word! 😁

It is a pity that there are no patches out there for the Max II 8kW.

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

Hi,

From what I understand, the patch is only available for the first version of Axpert Max 8kW.

In my case, since I'm only using one of the MPPT's with 2670 Wpeak, I'm losing about 0.5 kWh per day.

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?

Hi jfmm,
I have practically the same setup for the moment. 1 MPPT, 2700Wp. I am in the process of adding a West-East setup of 8X 600Wp. and connect those to the 2nd MPPT. This would allow to produce earlier in the morning and later in the evening, providing full batteries for the night and airco/heating and charging the car during the day.
If you lose about 0.5 per day, then that is probably comparable to what I lose. Once I use MPPT 2, it will at least double. On a 10kW battery system, this is 10%, which is significant.
It would be nice to be able to test the difference with a patched version, but indeed, the Max II is not in the list.

As to your question, that is beyond my scope. But you can ask Coulomb, he will probably be able to help out.
Good Luck, Kurt

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

It is a pity that there are no patches out there for the Max II 8kW.

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.