Hi guys. I'm new to this forum so I'm sorry if I ask for help in the wrong section.

So here is my problem.

I bought two MUST Solar PV1800VHM 5Kw Inverters that I installed in parallel mode. I m now working on integrating them in my home assistant installation. Before connecting them in parallel mode I was able to get data from each one with a separate USB-RS485 converter as the Modbus ID is not configurable (I guess it's hard coded ). Now when I put them in parallel mode I got the same data from the two converters even if I keep only one connection and trying to plug it in any of the two inverters ( and it seems that the data is coming from the slave in all cases). I wonder if the master (or any of the two)  change its adress in parallel mode 😕??? Also I think that the data is transiting through the parallel modules???? Any of you guys have already this issue?  Any help is appreciated.

 

Also I think that the data is transiting through the parallel modules????

I can't tell you anything specific about PV1800s. However, I believe that the PV1800s started out as Axpert clones, then sort of "forked" and became their own thing. But I suspect that the paralleling hardware is much the same as with Axperts.

Axpert paralleling cards transmit CAN bus messages to each other. Special messages transmit data from each slave over this CAN bus. Each machine has memory for each of up to 9 machines; itself and up to 8 others. Data is compressed somewhat, so one 16-bit word might store data for two, three, or more pieces of data. There are commands like QPGS that take a machine number as a parameter. QPGS0 always refers to the master; QPGS1 to one of the slaves, and so on up to QPGS8. This machine number digit is used as an index into this table of data for each machine. A few of the fields of the QPGS response are totals for each connected machine. So that way, each machine can report the main data from the others.

So perhaps there is a MODBUS register for the machine you want to get data for, or maybe there is a whole set of MODBUS registers for each paralleled machine.

I finally managed to solve the mystery and guess what, I was right that the master was changing its Modbus adress (wasnt hard to find). I fact I told myself that if the two inverters keep the same adress on the same bus there ould be a conflict and I would have no response.. So I tested address 5 and it worked. Why 5 ? well already why do they put a fixed adress 4 in thier thing.

In short for those who like me would be faced with this problem you have the solution.

And I would to thank you Coulomb for your explaination it makes things more clear.