In het Engels.
Victronsupplies a great system for energy storage. We built a 3x15 kWh battery from 314 Ah cell LiFePo blocks. This is a little small in relation to the 44 solar panels on our all electric house.
We do have a heatpunp and two electric cars.
Victron delivers several schemes to run a net connected an ESS.
The obvious simple choice for us would be a dynamic energy contract with Victrom DESS (Dynamic energy storage system).
However all the Victron efforts to make DESS work, is does not deliver all the time what you would expect. DESS always starts an hour too early charging the battery. On a summer day the battery is just full when the lowest price arrives. And Victron has no option to influence the scheme when you expect planned high loads during the day. Also dealing with ever more frequent negative prices is hard for DESS.
So we therefore us a mix of DESS at days it may work and Loxone control on 'difficult' days. Difficult days are for example:
- Electric car charging.
- Dealing with maximum consuption during negative prices
- Winter operation (Loxone does peak shaving, which Victron has not)
This blog is intended to help other users of Victron and Loxone. Victron offers a lot of documentation. But there is more between the lines of their books and it is a puzzle about the right kind of connection from Loxone to Victron.
NB: Our system has the external Meter measuring net currents to allow it to maintain a certain net setpoint from Victron.
And our solar panels (Enphase system) are AC connected.
The 45 kWh battery is limited to 200 A (10 kW charging or discharging)
1 Interfacing Loxone and Victron
We are going to explain in this chapter the minimum set of registers required to control Victron energy absorption or delivery from Loxone.
Operating mode
Loxone works fine with Modbus over ethernet. And Victron does have such an interface if you enable it in the GX Cerbo, the control system for the 3x Victron Multiplus II units
There are two relevant victron documents to understand the Victron structure:
- The Excel with all the available registers 
And there is a manual describing the various operating modes of Victron, being: Standard, Time shifted and External control..
This last document should help, but actually it confuses. Victron presents the various modes and registers, but does not tell that most of the registers to control Victron ALWAYS work. And that knowledge simplifies life a lot.
After a lot of testing from Loxone to Victron, it turns out that Mode 1 is always fine. There is with the current SW (V3.72) no reason to switch Operating mode. Leave it always at 1 (Register 2902)
Energy Balance in Victron
If DESS is off, the system operates in ESS (Mode 1) meaning that the system maintains a net power input to ths house of 0 Watt, as good as possible.
So there are several cases in this scenario:
1) Few sun: Energy for the house is take from the battery. If more energy is needed than the battery can supply or if the battery is at minimal SOC, the AC net will supply the missing energy.
2a) More sun (up to 14 kW on a sunny day) than needed in the house: The surplus is charged into the battery. If there is more than the battery (10 kW) can take the rest is supplied to the net.
2b) If the battery is full and more solar energy than needed in the house, the rest is supplied into the net.
So Victron controls the battery charging and dicharging in such a way that these above cases are fulfilled.
Enabling battery charging and discharging.
A next important aspect to be able to control is when the battery is allowed to charge or discharge.
After the explanation of the Victron system as a whole in the previous section it is clear that you sometime want to limit the battery from cahrging or dicharging.
Maybe you want a full battery to charge the car during the evening.
In our case we have a Dynamic energy contract with hourly varying prices. In the Netherlands must companies charge a high fee with Standard energy contracts if you have a lot of solar panels.
With a Dynamic contract you may have strongly varying prices over a day, but no fine when delivering energy back to the net. You get the full hourly price when you deliver energy to the net.
On 1-1-2027 that changes again for the Netherlands. If you deliver back, you do not receive the energy tax of 0,10 euro back anymore.
So certainly to the future you want to be able to control the bagttery charging and discharging.
Basically Register 38 disables charging when set 1. Register 39 disables discharging when 1.
However after an update of the Cerbo GX firmware end of 2025, register 39 seemed not working anymore. The work around is shown below by using registers 2701 and 2702. (I should test if register 39 is working again)
Controlling AC power
The last ingredient for controlling the Victron systemis the AC power setpoint.
Intially we have been following the manual with the control mode description and tried using Mode 3 (External) and the AC setpoints via 37, 40 and 41 and an Loxone side PID loop
This worked fine, but was probable more comples than needed.
I figured that register 2700 does the same job for the 3 phases via the Victron control loop equally good. This register is decribed for mode 2 (Time shift) but does work always with the current Cerbo firmware.
The Clock I added for simple control power control during negative prices
So far this first draft to interface Loxone and Victron.
Last remark:
We do have a Solcast forecast in Loxone for expected sun today and tomorrow. As well Loxone has the Hourly prices. But the Spotprice component has unfortunately too few information to make a kind of proper planner replacing the Victron DESS.
So se introduced a simple winter mode called Piekschaven (Peak shaving) that conserves as much as possible energy in the battery to feed the house and not deliver back to the net
And for summer and normal price profiles (no negative prices, no car charging) we use DESS or the Clock to control AC net power during the day.
Will be continued as experience grows...