I'm trying to control a charging station with a raspberry pi. The software is almost finished by there is something missing in the electrical architecture of my CS. The EV is connected to the CS with a three-phase alternating current.

When I connect the vehicle to the CS the charge starts (the charge begins automatically without login with a password or without any kind of authentication).

I want to be able to control the charge, so if I send a request to my Rpi, I want the charge to be stopped even if the car is still connected to the CS, or charge at any time I want with the car still connected to the CS (stop the current between the CS and the EV)

How could I do that? I was thinking of adding breakers between the CS and the connector, but how could I control breakers from my Rpi? Or are there another electric components who could this job? I feel I am missing something in the electrical architecture but not sure what it is.

  • $\begingroup$ How do you control the charge based on the state of charge of the battery? $\endgroup$
    – Solar Mike
    Commented Aug 5, 2022 at 8:02
  • $\begingroup$ Note, cross posted here: electronics.stackexchange.com/q/630066/152903 $\endgroup$
    – Solar Mike
    Commented Aug 5, 2022 at 8:28
  • $\begingroup$ Well I don't control it yet, I want to control the voltage given to the car first. After that I will see how to get the SoC of the EV $\endgroup$ Commented Aug 5, 2022 at 8:34
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    $\begingroup$ "I feel I am missing something" You are but experimenting with high power 3 phase power circuitry is not a safe way of building up your missing expertise. What are you trying to achieve by controlling your charger? Can this really not be done with existing commercial products? $\endgroup$
    – Graham Nye
    Commented Aug 5, 2022 at 10:15
  • 1
    $\begingroup$ @CarlWitthoft Actually, this is only true with DC charging stations ("fast chargers). Single phase AC (and I assume 3-phase) charging stations use a pilot signal from the station to the car. This is a square wave with varying duty cycle to control how much amperage the car is allowed to draw. There is also a protocol where the car connects different resistors across the pilot signal to control the application of AC power to the car. $\endgroup$
    – DoxyLover
    Commented Aug 6, 2022 at 6:23

1 Answer 1


I cannot give you a complete answer but since no one else is answering, I'll take a crack.

If you want to actually control power to the charging station, you need to use contactors. These are special relays designed to control high-amperage AC power. There are actually contactors inside the charging stations to control application of AC power to the car.

However, I don't recommend this. The car electronics may become upset if power is suddenly cut while it's charging and then may refuse to continue charging until reset.

A better approach would be to interface to the charging station controller. Single phase AC stations use a fairly simple protocol between the station and the car to allow the station to verify that a car is connected and to control how much current the car is allowed to pull. I assume that 3-phase stations work similarly. This is described here: Wikipedia. This signaling involves a +/-12V pilot signal. This is a square wave from the station with varying duty-cycle to control how much current is allowed. The car places varying resistances across the pilot signal to indicate when it is ready to accept AC power.

If you are unable to interface to the controller, an easy approach would be to insert a relay to interrupt the pilot signal between the station controller and cable or connector. With the relay open, the station and car should should both think the cable is disconnected or charging is not allowed.


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