I seems I am running into an issue with a setup, which surprises me:
Following components:
Multiplus II
Cerbo GX
MPPT Charger
Bus-BMS-Battery.
The issue/goal:
When connected to shore power (and DC power from Batteries and/or MPPT charger is sufficient), I want to prioritize DC energy over shore power.
Simple with the Virtual switch to ignore AC input (if DC Voltage/Battery SOC high, or Inverter power draw low).
And her it becomes tricky: In case Inverter is near overload, the grid shall support the inverter (only SUPPORT, NOT turn inverter off and switch over).
If desired, while connected to the grid, I want to set “one full charge” from the GX device (or VRM, etc), similar as in the 1. Solar and Wind installation.
Simplified Example (Inverter with 3000W rating):
Virtual switch set to ignore Grid until power demand exceeds 2500W.
Once 2500W power demand exceeded (and as long as there is sufficient energy on the DC side) the grid shall only support the inverter:
Inverter shall continue to deliver the 2500W, and the grid only take from the grid the excess above 2500W.
How do I realize that?
From a technical perspective, the Multiplus should easily be able to manage the required functionality. Reasoning: If PowerAssist (with grid side AC input limit set to any low number for texting purposes), the inverter is running together with the grid, just working the other way around (Inverter supporting Grid, where I want the Grid to support the inverter)…
If you enable “ignore ACin”, then its going to ignore it, even if it means going into an overload. If you want to switch back to mains then you need to disable “ignore ACin” first and let the system switch to mains again.
I would not use ignore AC, but rather regulate the input current limit, for example through some nodered.
There is more to it. In the option among other settings one can select, that grid is ignored up to a defined inverter load, and then it would not go into overload.
You could, but in my case I have no desire to (artificially) limit the input, because in case of low Battery and no PV input, I would artificially limit my shore power, while I might need (and could) use more.
@Basti AC ignore can be programmed to kick in e.g. based on load or voltage. I set it up on my test bench units with AC ignored and when I hook up the heater, it will switch to passthru before overloading. I set the power slightly lower than the peak of the inverter to avoid the overload. It is a great feature for use with my 800VA testvunit and allows occasional use of a heater an kettle as example as it is a touch crude for constant switching. It is also important to note that a voltage drop on the battery can affect the system under heavy loads and a low SOC so it may require some testing and tweaking.
Only ESS will do what you want e.g. make up for a shortfall when the e.g. the 2400W peak of the 3kVA is exceeded. In an off grid scenario the system will only passthru and charge, but cannot invert. You may experience power assist which will use power from the battery to support a limited AC input?
But what you do and describe is not what I was looking for. I wanted to make sure I always use DC power (if available) up to the inverter limit, and if excess is needed, only then I will draw the excess from grid.
Unfortunately my dealer must have misunderstood, because originally I was told that would work, but I must not have been clear enough (or he was thinking ESS). From a technical perspective I can understand the limitation without a proper grid code, because what I am looking for would require sync with the grid… Before I was under the impression that the Multiplus can always be in sync with the grid, was not aware about the limitation without the grid code (for moving installations, maybe even across countries).
So bottom line: If Multiplus is setup with no grid configuration, then what I was looking for is not available. Topic most likely could be closed.
