I have a time of use contract with hourly pricing, based on the day-ahead electricity market. So I also wanted to schedule charging, but I was somewhat disappointed that
- my charging station has no scheduling feature built-in
- my EV does have settings for this, but they act more as a suggestion. It would often charge when I didn't want it to.
Fortunately the charging station does support being controlled over modbus tcp/ip, so I was able to write some code and run it on a Rasperry Pi to control it. My control system fetches the prices and enables charging whenever they are below the configured maximum.
However, I now find that (because of my obsession with optimizing this) it is still very far from a hands-off solution. I find myself doing this:
- check electricity prices manually
- check car state of charge manually
- if prices are going to dip very low, figure out how much time will be needed to charge to 80%
- if prices are high, figure out whether I need to do a minimal top up anyway and how much, based on how much I think I'm going to drive
- choose a maximum price such that charging will be enabled during a sufficient amount of hours, based on the above
The main thing that's missing to properly automate this is a way to retrieve the EV's state of charge. But a charging station for home use will typically only support a simple PWM signal to tell the car how much current it can draw. No other communication is possible unless the charging station supports ISO 15118. Mine doesn't :-(
- my charging station has no scheduling feature built-in
- my EV does have settings for this, but they act more as a suggestion. It would often charge when I didn't want it to.
Fortunately the charging station does support being controlled over modbus tcp/ip, so I was able to write some code and run it on a Rasperry Pi to control it. My control system fetches the prices and enables charging whenever they are below the configured maximum.
However, I now find that (because of my obsession with optimizing this) it is still very far from a hands-off solution. I find myself doing this:
- check electricity prices manually
- check car state of charge manually
- if prices are going to dip very low, figure out how much time will be needed to charge to 80%
- if prices are high, figure out whether I need to do a minimal top up anyway and how much, based on how much I think I'm going to drive
- choose a maximum price such that charging will be enabled during a sufficient amount of hours, based on the above
The main thing that's missing to properly automate this is a way to retrieve the EV's state of charge. But a charging station for home use will typically only support a simple PWM signal to tell the car how much current it can draw. No other communication is possible unless the charging station supports ISO 15118. Mine doesn't :-(