question

sesshoumaru avatar image
sesshoumaru asked

On the calculation of the power values

Hello

My Victron system uses two power meters and has a fronius PV with AC-1-out coupled.


The first power meter is on the handover point to the grid, hence its configured as role gridmeter. Needless to say that the fronius is configurd as inverter. Now comes the tricky part. Before the Victron System came I had an AC-coupled Varta Element 6 battery. This battery I still have. I wired it like the Fronius - so its coupled to AC-1-out but with the second power meter which has the role "AC Loads".


I know this is already a bit odd. Yet I have four questions, which I hope somebody can enlighten me.

1)
How does the Cerbo calculate the values I see on the remote console? The values for PV and grid seem to be valid, but AC loads is always always 0 .. 200 and "Critical Loads" seems to be all what is pulled from AC-out (of the inverter).

2)
Can the Cerbo distinguish between loads on AC1-out and loads on AC2-out? I ask because "Critical Loads" seem to be both for. Regardless if I draw power from AC1/2-out, all seems to end under "Critical Loads".

3)
Obvious question: I know the Varta Element 6 is odd man out, especially AC-out coupled, but is "AC Loads" a good role for this? Or should I go for somthing else?

4)
I tried setting the Varta Battery Meter to role "PV Inverter", yes, it added to the Fronius, but I still had "AC Loads" in the diagram. What actually is the meaning of "AC Loads", compared to "Critical Loads"?


Odd questions, for an odd system...

cerbo gxESS
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2 Answers
shaneyake avatar image
shaneyake answered ·

Grid = Grid Meter reading

AC Loads = Grid - Inverter_Input

Critical Loads = Inverter_Input + Inverter_Power

The invert only has 1 current sensor on AC input. Inverter_Power is a calculated value.
AC Out and AC Out2 don't have sensors so use the Critical Loads calculation for both.

AC loads is any load between Grid and Inverter input.
Critical Loads are all loads on Inverter Output.

If you add a PV meter then

AC Loads = Grid - Inverter_Input + PV
Critical Loads = Inverter_Input + Inverter_Power + PV

4 comments
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sesshoumaru avatar image sesshoumaru commented ·
I just seem to have odd usecases, by adding the AC coupled Varta Element to the AC-Out side.

How comes the generator into picture? Its handled like "Grid"? Because the role "Generator" of my second meter seems to add the values to "AC Loads"? So it would be best to add the Varta Battery as role "PV"?

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shaneyake avatar image shaneyake sesshoumaru commented ·
You can only have a generator or grid active at once, not both. So generator won't really work. You can set the Varta as PV inverter which will make the loads display correctly but not your PV.
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sesshoumaru avatar image sesshoumaru shaneyake commented ·
Can I beg somebody at Victron to add a new Role "AC-coupled Battery on AC-out"? Which then appears as own icon, besides PV, so that all s nice and dandy? *lol*
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tobyfw avatar image tobyfw commented ·

Shouldn't PV be subtracted? If the PV meter is installed as in the documentation, it delivers positive values. Also, wouldn't the location influence the calculation (PV meter can be set to AC-IN1/2 or AC-OUT)



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sesshoumaru avatar image
sesshoumaru answered ·

Nobody knows how "AC Loads" and "Critical Loads" are actually calculated?
I set the energy meter for the Varta System now as role "Generator". It now shows up on AC Loads, I guess this AC Load actually means loads on AC-Input side? Because its shown to be connectect togather with "Grid".

Makes we wonder how to show "AC-out-1-loads" and "AC-out-2-loads" on the console.. or if its possible at all. Insights?

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