I have an offgrid 3x Multiplus II 48/15000 VA 3 phase system.
Due to battery limitations, I am maxxed out and cannot add more batteries, which I need.
I have purchased 3x 48/8000 VA MultiPlus II, and will create a separate system (lets call it System B) on the same property (200 meters away from System A).
Beyond the ability to add more batteries, I will have redunancy in case one system is down, for service, fire, etc.
My concept is to have system B, be connected to System A, via the AC In of System A.
Similarly, I am thinking to connect System A to System B, via the AC Input of System B.
In this way we can share power back and forth depending on which system has available battery capacity.
The systems will have different AC loads and wiring. SO they are completely separate systems and do not share any loads, etc.
Will this work? Potential issues?
And then lets throw in this curveball, I have a diesel genset currently on AC input of System A, this input will no longer be available. Hmmm
I think the solution would be cascading the systems.
System 1(A or B) is the main source of Power and System 2 is connected to the Input of system 1.
So system A is the main source of power. If there is left over power, system 1 can export it to 2.
If the batterys of 1 are emty, the power comes from 2
A cascade set up is unsupported officially. (Edited: Yours has a weird -and dangerous -twist to it as poonted out by Marc)
What is possibly a safer option is splitting the DB and running things as totally separate systems.
Correction
This is already a separate system. There is a simpler way.
Maybe create a cascade with a manual bypass switch to bypass system 2 for when system 2 is out-of-service.
System A out → System B in → B out → bypass switch position 1 (i.e. Hager SFT440) → devices
System A out → bypass switch position 2 (i.e. Hager SFT440) → devices
System A is cinfigured as a normal offgrid system with PV
System B has a ESS config with energy meter between A and B
In this config, you can even switch off system A if no loads are present, system B is unable to handle them, or battery B is empty or full. This will safe some Power.
With the bypass switch you can use system A, when B is down.
Behind this are the loads and PV
Interesting, thank you. As far as switching off a sytem, we can’t do that both systems would have critical 24 hour loads on them (water pumps, security system, alarms, emergency lights. etc)
It is caused by the communication of the BMS (Type of battery would bve nice to know). There is a maximum number per bus.
Connecting additional batteries in parallel to increase capacity is not a problem in itself, but the communication cannot be connected. Or the data must be merged, e.g. via the Pylontech LV-HUB
