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tcircuns asked

Two Multiplus II in series


I am working on installing a Multiplus II 48/5000 at my home, where I already have an on-grid photovoltaic inverter SMA Sunny Boy 4kW and I have some questions I haven't found answers anywhere:

1. Is it possible to install two Multiplus II inverters in series (one of them connected to the other critical loads output) with non-shared batteries? How should I configure them? That would enable me to add a new Multiplus II in the future with another new battery on grid-parallel mode connected to first Multiplus II critical loads output.

1.1 If 1. question is possible, should I configure second one to not exporting to grid? Or first one could use frequency shifting (or similar) to control how much energy could export the second one?

1.2 Continuation of 1.1 question. Would be possible to have SMA Sunny Boy 4kW connected to the same critical loads output than second Multiplus II, having both controlled by frequency shifting? Or that is not possible as maximum power would exceed Multiplus II maximum power?

It appears a similar configuration could be done by using CerboGX large firmware, to be able to use Node-red to control some inputs:
- first Multiplus II critical loads frequency (could be updated depending on first Multiplus II is able to receive more power from critical loads or it cannot accept many more
- first Multiplus II AC In grid status (availabe/not available)
And to be able to control some things:
- second Multiplus II power exportation limit, being configure to 0 power exporattion into second Multiplus II if grid on first Multiplus II is disconnected

I've seen some other questions about similar solutions, but they were trying to control batteries load between two Multiplus II at the same time at the same battery load. I'm not interested on that. What I'm looking for is to:
1. If second Multiplus II (with AC In connected to first Multiplus II critical loads AC OUT) has batteries fully loaded, then it will share power with the other one if the other requires it; if the other doesn't require it and external grid is connected, power could be exported to grid; and if the other doesn't require it and external grid is disconnected, 0 power export should be configured into second Multiplus II
2. If first Multiplus II (connected to grid and with second Multiplus II connected to it's critical loads AC OUT) has batteries fully loaded, if second Multiplus II requires power, first Multiplus II can provide that power as if it were coming from real grid

Multiplus-IIVenus OSNode-REDmultiple inverters
victroninseries.png (107.4 KiB)
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