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Making old EVSE smart by tampering the CP-signal?


I want to make my old OpenEVSE (and another dumb charger) smart, so I can remotely start/stop charging for the cheapest hours. This is not possible to control in my EV's so I must make the charger do this task.

I have read a bit on how the CP signalling works. My idea is this:

  1. Install a zigbee relay inside the charger station
  2. The relay switches between the CP-signal from the EVSE and a signal that says to stop charging (9V DC?).
  3. The 9V (?) is picked from a 9V source in the EVSE or a 12V output with a resistor to reduce it to 9V.
  4. This means the relay switches between PWM and 9V DC to be sent to the car

Do you think this can work?
  1. Will the EVSE handle the lost communication with the vehicle when the relay switches from the PWM-signal to 9V DC?
  2. Will the car handle the lost PWM -> 9V DC and stop charging without going to error-state?
  3. Will the EVSE continue to send the PWM signal when the relay cuts the connection to the car?
  4. Will the car resume charging when the relay switches back to PWM?

Or any other solution you think can work to make a cheap hack for zigbee/zwave control for start/stop charging?

Best regards

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