This Fronius PV inverter has about the same solar capacity and can do 4kw. At the time of this snapshot it should do at least 3700W. It is being throttled to just deliver enough current to carry the critical loads. Its output varies with the critical loads. Why? I looked around for a setting that can cause this but could not find it.
More history: This inverter was installed about two years ago and always delivered the maximum current while the battery needed to charge. The current not used up by the critical loads was used to send power through the Victron Multiplus to the batteries: Quite often the batteries were charging at much more than the PV charger was delivering.
Then we had to remove the Fronius from the installation, and ever since it was re-installed, it runs in this throttled mode.
In the second photo you see an example of Fronius charging the batteries through a Victron Quattro 3 phase system.
That looks normal to me. A tiny amount is being drawn from the grid (which is inevitable), all local loads are covered, and the battery is charging with the remainder. I assume you don’t want the surplus to go to the grid?
Or is there more capacity left for charging the battery?
There is this weird thing that happens sometimes, where the Multi doesn’t charge the battery harder, and the PV inverter therefore has no choice but to limit lest the power goes into the grid.
There is a hidden setting in the GX device, com.victronenergy.settings/Settings/CGwacs/PvPowerSetpointOffset, that controls the offset between what the Multi and the PV-inverter “fights” about. This is 200W by default. You could try increasing that. I assume you know how to?
The fronius is being throttled only to cover the critical loads. Like the control loop’s aim is to have zero current at the output of the MPII.
Previously the Fronius was only throttled to prevent pushing current to the grid. It generated a lot more power than required by critical loads. The excess power was used by the MPII to charge the battery.
So in the first graph, I need the fronius to generate 3800w, and the battery charging should be 5000w, with about 2000w being converted from the Fronius through the MPII to add to the battery charging current.
Here you see an old setup where the inverter was before critical loads, but it helped to charge the battery.
It uses either the grid meter (if you have one), or the AC input of the Multi as the control point. This is literally hardcoded and it cannot accidentally start regulating on the output.
Something else is going on.
You could try this, just as a test. Set the ESS AC power setpoint to something higher, say 500W. Then enable the feeding in of excess AC power, but set the system feed-in limit to 0W.
In that scenario, the Multi tries to pull the AC import up to 500W, while the PV-inverter will be adjusted to feed in everything until the grid gets to zero. That creates 500W to “fight” over, which should be enough to make everything increase power to their maximum points.
If that test works, then the problem is that the system reaches a kind of equilibrium where it all seems to balance out, except that it could have done better.
For the record, I have absolutely no idea how to fix it. Not without rewriting the entire thing. Which has to be done anyway… just not sure when.
It looks like the Multiplus was re-registered as a new device in VRM and the old device was deleted, so I can’t see the old data from last year. I can see my battery over same period and it was full every day.
I have a different system but one thing I find useful is to remove the CT (or disconnect it)
Do this on the fly to see if it’s causing the throttling…
I picked up a wiring faux paux on my system by doing this.
I don’t know what’s changed, but I see the battery is charging much faster than the PV charger is supplying. So it seems there is excess power from the Fronius being used to charge the battery today.
The indicated power on the Fronius is 1612W, which just about cancels out the 1635W of the critical loads.
But the battery is charging at 4789W while the PW inverter is only delivering 3387W, so where is the other 1400W coming from? Not from the grid, so it has to be from the Fronius! The power reading on the Fronius has to be wrong here.
I sold the property, and the new owner is not interested in the tech side of the solar system at all, so I’m just still checking it out. I built this system, @JacoDeJongh set it up for me and expanded it with the Fronius. Difficult to let go. So I can’t get to the system physically any more…
The more I look at this the weirder it gets. Look at the critical loads graph. It is zero overnight and then climbs to exactly mirror the power generated by the Fronius.
That’s just wrong. We don’t have any critical loads drawing power now, especially nothing that will increase like the sun rises. So the power indicators for both the Fronius and the critical loads are wrong.
These wrong measurements are also visible in the graphs: This increase with the sun rising is visible in the AC consumption.
There is a bug in the energy accounting code – I found it last week, it has been there for almost a decade – where sometimes PV production is accounted for twice, and then since consumption is the difference between grid and solar, it causes the consumption to mirror the production.
But this bug will only manifest if you have multiple PV inverters, and if you are playing around with the AC input settings. So it is probably not that.
Anyway, the new owner can ask for help through a legitimate support platform. That is the best way to go about this, and get it off your back. I’m happy to help you, but I will get in trouble for helping an acquaintance of a friend via a random forum
So I can’t get to the system physically any more…
