Hello, I have had an AXPERT MAX II TWIN 11Kw inverter for a few months, and I am faced with the problem of the 90V of the MPPT controller during low sunlight, which can considerably reduce solar production.

I found a solution (apparently effective) simple and without modifying the inverter, to avoid this "sticking" at 90V. Maybe someone has already proposed this solution I did not look too much on the forum.

I noticed that when the photovoltaic panels are disconnected from the inverter and then reconnect the inverter, this releases 90 V and the mppt resumes normal operation.

My solution is to add a contactor in my case an ABB AF16ZB-40-00-22, an esp8266 D1 mini, an ACS758LCB-050B-PFF-T Current Sensor Module, a 2Mohms divider bridge and an ads1015.

The contactor is used to isolate the solar panels at night to avoid any overvoltage due to a night storm (my panels are 40 meters from the inverter = large antenna for EM lightning waves).
I also added a rule:
if Amperes > 0.7A and Volt between 80 and 100V for more than 2 minutes = disconnection of the solar panels then 15 seconds later reconnection.
The inverter goes back to 275v, in my case (2x8 panels in series/parallel for the moment) then the mppt controller resumes its normal work. (see picture)
Because in cloudy weather below 1.5/2A this remained at 90v as long as the sun did not hit the panels directly or the intensity did not rise higher.
 
With this modification it allows me to produce more than 2.5x more during low light(on my installation).

Hello, I have the same issue since a couple of year, I do the same, manually, disconnecting the pannels ant then reconnecting.

Did someone find any different solution?

Did someone tried to contact the maker?

 

Thank You.

Paolo.

 

I never got a response from either the manufacturer or the seller.

the problem arises less since I put several strings (two) in parallel, there are more amperes so the inverter "sticks" less.

otherwise since I also improve the system I use "solar assistant" and by the mqtt protocol I retrieve the current voltage data and cut if necessary.

the manufacturer does not answer I also asked if there were new versions of the firmware I never got an answer

Hey BR999,

that's same experience I've had with the manufacturer. It's weird because there are a lot of same inverters with different brands.

There is another thread here in this forum, try and look here,

https://powerforum.co.za/topic/20469-voltronic-axpert-vm-iv-bad-mppt-or-firmware-bug/#comment-174985

I'm going to read right now and maybe post something.

Bye!