Good News and sharing a bit my experience.
Last summer we got our first EV (an VW E-Up) and I started to dig into the topic of how to charge the EV intelligent if the power supply setup is configured as an island and by that no measurement data is available from an grid meter telling me the current feed in /overproduction.
I was seeing forward to the Victron Wallbox, its availability and functions but as good things take their time – I build my own system until it is available.
I am living in an residential house with 19,5 kwp PV and a 3phase Multiplus II 5000 system, system is configured as Island system and mostly unplugged from the grid.
The problem:
As usually if the batteries are full the Victron system will throttle the PV Output to the exact amount of energy used by the house and as result it is very difficult the find out which quantity of power currently would be available if not reduced.
For the EV Charging I of course need this information in order to enable the EVSE (control unit for EV charging and communicating with the car) to adjust dynamical the charging speed/amperage supplied to the car according to the current PV potential production.
My solution was an light intensity sensor (BH1750) for measuring the Realtime LUX / Irradiation value from the sun. This sensor data is send via MQQT to the automation system and recalculated to an value equaling the potential max output of the PV system in watt, every second.
By subtracting the current house load from the potential PV production I get wattage available for charging the car (in Ampere).
The automatization system is doing this calculation every minute and updates the EVSE with the currently available amperage for charging (dynamic EV charging).
Additional of course there is an start /stop automatization implemented.
If the car is plugged in the car will start charging in the morning if the house battery is above an certain SOC and if a certain potential PV output was available for a certain time. If all conditions are fulfilled the charging will start with 1 phase @ 6A. From this moment on every minute the availability of potential PV production will be checked and the amperage ramped up from 6A up to 16A in steps of 1A until the system has equalized
In case of an rain shower or cloud, the system will ramp down in steps of 2A per minute until again the load equals the produced power.
In case the weather forecast is good (clears sky forecasted for the day) the system would start automatically with 2 or even 3 phase charging giving it an charging speed of up to 11 kw per hour.
I am very happy, it was a long way but at the end the automatization is reliable and the user interface (IOBroker Vis application) gives me all adjustment and visualization possibilities i need.
For building you need basic knowledge in:
MQTT and Modbus, ESP8266 programming, IOBroker or other Middleware, Electrical skills for building the type 2 plug charging hardware
For the future I am seeing forward to the Victron Wallbox and its functions as I will need an second Wallbox for the second EV but until then I am very happy with the system and its full and integrated automatization.
If you have an better idea or where to find data giving me information about the potential PV output - lets discuss
Greetings
janek
