Integrate a OpenEVSE charging station with a 9kWp Solar system?

I am a solar (PV and thermal) installer and electronics technician, but (yet) have no skills on Arduino or the like, I have done some code writing looong ago, but not in C++

Here is my problem: a friend and customer wants me to install a 9kWp solar PV system and he wants an electric car to be charged with it, and use as much PV electricity, and as little grid electricity as possible, because he can only sell the excess production off at a very low price.

Fine…but… when the sun doesn’t shine, I need to let the EV wait at first, then when the sun gets strong enough, I need to rev up the charging station, when a cloud passes by, I need to slow down charging again, and finally when the night falls and the car is still not full, I need to allow grid electricity to be used, while still not making the 3x230V/32 Amp house supply trip.

I could of course try do this with what I used up to now for thermal solar systems, the Technische Alternative UVR1611 / UVR16x2 controller, and two of the maker’s 3-phase power metering sensors, and interface to an off-the-shelf adjustable amperage charging wallbox, like the Hager Witty, (I can drive it’s potentiometer to modulate the allowed charge current).

I would tend to more or less track the PV’s production amperage, so as to not use any grid electricity, but at some point I also need to respect some predefined “best effort” end-of-charge time, like 6am next day, normally achieved by switching over to modulating the current taken from the grid, without overly pulling on the line, so that the house’s main breaker stays on. Best practice would be to start that at night tariff time 10pm, of course.

The thermal systems controller I normally use can’t really make “if by 6pm charge state under 80% - then - what?” type of decisions, it is not really built for that. I would rather need something like a PLC, but most of them are neither open source, nor cheap.

How would you go about it, starting from the OpenEVSE kit that I saw here? I would need to make the Open EVSE use 3 phases, but maybe that doesn’t take more than a 4-pole relay, while the EVSE assumes there is only one phase.

Any suggestion is welcome


Hi Johan,

Thanks for your interest.

The OpenEVSE and EmonEVSE both support solar PV divert (Eco Mode). You will require an emonPi to monitor solar PV then you just plug the car in then via the OpenEVSE web interface (live demo) select Eco mode and pause the charge. The EVSE will then wait until the solar PV is producing more than 6A/1.4kW (the minimum an EV can charge at) before starting a charge. See GitHub - OpenEVSE/ESP8266_WiFi_v2.x: ESP8266 WiFi for OpenEVSE Version 2.x

The EmonEVSE is available pre assembled, fully certified with a 3-phase option: EmonEVSE WiFi Connected EV Charging Station (Type-2) - Shop | OpenEnergyMonitor

Yes, l went back to the webshop just after postng, and saw a PV divert was mentioned.
In France, the electricity provider urges me to produce 3 phase current as of 6kWp, so I also need a 3 phase EVSE, so I don’t throw 2/3 of the PV production away. Is it possible to make a 3 phase OpenEVSE ?

The EmonEVSE supports three-phase:

Yes, I contacted them and they should quote me for a 3 phase system. Thanks for the info.

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