Fox ESS used as a PV inverter for the Victron ESS

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t3mschm2d asked Mar 7, '24

Fox ESS used as a PV inverter for the Victron ESS

Hello community,

I'm currently planning a conceptual PV system for a friend of mine. We want to use a mixed system with a 12kWp AC coupled FOX Ess PV inverter, a 9kVA three phase Victron MPII system with 30kW/h Pylontech US5000 and a 5kWp DC coupled Victron MPPT. I have some experience with all the Victron components so this should be no problem BUT I have never used a Foxx ESS PV Inverter. We would like to use the Foxx inverter as it is quite competitive in terms of price and performance. Does anyone have experience of running a Foxx ESS inverter on a Victron ESS system? Due to the fact that Foxx ESS inverters are able to communicate using Modbus TCP with the SunSpec data structure, I assume there should be no problem for the Cerbox GX to detect the inverter, right?

PS: The Fox ESS inverter is placed at AC-IN so no worries about Overloading the 3 times 3kVA MPIIs :D

ESS Pylontech

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Alexandra ♦ commented · Mar 08 at 06:38 AM

@t3mschm2d

Since it isn't listed as supported, you may or may not win with Comms to the Cerbo.

You could just add a supported energy meter and meter it to the Cerbo that way. I assume that is why you want it connected.

It won't need to frequency shift the Fox really on the input. I would assume as well that you are also wanting to feedback that already would have its own ecosystem for that?

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t3mschm2d Alexandra ♦ commented · Mar 08 at 01:09 PM

Oh ok, I haven't found the list of supported components. Could you share the link to it?

If it doesn't work natively, I'll have to use an external energy meter, but that should be absolutely fine :D. I do not need frequency shifting for power regulation.

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ejrossouw commented · Mar 08 at 08:05 AM

@t3mschm2d I am curious to understand why AC coupled PV, apart from price. Do you require a total of almost 24kW during the day? My thinking, if you start with a clean slate, DC-DC charging is more efficient and when you have a daytime grid failure, the DC charging can continue when the AC PV shuts down. Furthermore, if you have critical loads connected, the loads will benefit from the solar and with finally with DC PV there are no limit as with AC coupled PV on the output.

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t3mschm2d ejrossouw commented · Mar 08 at 01:19 PM

Hi @ejrossouw , thanks for your interesting input on this topic. I totally agree that the MPPT DC-DC converters are more efficient for charging the battery, and if I needed a robust off-grid system they'd absolutely be my way to go. But I have a non-negligible amount of AC loads that run primarily when there is sunlight (Smart Energy Management System) --> e.g. EV charger. I'll be installing this system in Germany, where grid stability is really high, so the off-grid part can be a bit undersized. The system I'm planning will be installed on a roof area that's fairly easy to work with. So if I see that my friend needs more DC-DC MPPTs, it's no big deal to just install some more pv-panels on the roof :D (With my design I'll be able to go up to 200A of DC-DC MPPT for charging the battery).

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