Fronius battery control?


while I unfortunately don’t own any Fronius inverter myself to tamper with, I’m trying to implement battery control for it.
There’s the powerflowchannelpakku channel to read what’s going into/out of battery but I want to enforce charging or discharging.
The Fronius Modbus document mentions a register ChaGriSet to allow for charging from the grid or not but I have not seen this in the binding.

By chance, has anyone played with or implemented battery control on a Fronius inverter or knows how that would work ? maybe @JimT ? (sorry for pinging you).


Unfortunately I don’t have a battery, and only a Fronius Symo inverter, not the Gen24 (Hybrid). If you know the json / API to control this, I’d be happy to add the capability to the binding.


I am for the time being setting up a spot market control system for our bigger electrical loads. This will certainly take a while. But after that I would really be intrested in the possibility to set the PV system battery charging from the grid on/off from the same control system using Modbus TCP or RTU. From the inverter webserver it is possible only to set it on or off but no timing is possible as far as I have tested.

Our PV system is all Fronius,

  • Fronius Symo GEN24 6kW Plus inverter
  • BYD 10,24kW battery
  • Ohmpilot
  • Wattpilot
  • Smartmeter

The battery grid charging would make it possible to charge the battery at night during the winter when the electricity spot price is low and then discharge at daytime high price period.

At these high energy price times such a solution would certainly interest many PV system owners with a battery.


Are you aware of the commercial energy management system I’m selling ?
It’s now working with Fronius inverters. Just battery control to do peak shaving does not work.
I have an idea what to try but it’s a lot of trial & error because vendor documentation is sparse or unclear. Would you be willing to help with testing ?

I visited your pages and briefly looked trough them. My German language knowledge is not very fluent so I have to spend a little more time to read all the text. I am living in Finland.

Are Ohmpilot and Wattpilot supported in your system?

It is true that more technical Fronius information is sparse, e.g. I have not been able to find the latest Fronius API document only the previous version. We have a ground heating pump fro a Finnish manufacturer Oilon and there is the same thing - a lot of digital in- and outputs, relay controls - but no documentation and poor technical support.

As I earlier said I am in the very beginning to set up my spot market control for our ground heat pump, water heater, EV charger and hopefully the on/off grid charging of the battery. So at this point I am not able to be involved in testing.

But for the future I am in principle interested in testing when the time is convenient.

Sorry I assumed you’re German because of your name.
I suggest you use Google or DeepL translator.

I don’t know these devices and the current OH Fronius binding does not offer access to these.
So they will continue to operate the way they’re configured now but off the shelf no the EMS cannot address them. However if you and/or I determine how to access them via Modbus (like I do for battery control) it should be simple to control .

Essentially you would only have to setup a box with my EMS (see and grant me access to your inverter via IP/Modbus.
I’d then access it through VPN and try to get things to work. If you’re proficient with openHAB you can help with and take part in that, if not your part would be just some monitoring tasks.

Meanwhile you can already take advantage of the running EMS. For example if your heat pump has a SGready interface you can connect it and "pre-"charge its heat buffer using excess solar power (which is even cheaper than spot prices are).