Identical setup 
I checked a little and found this thread. It hints that f.ex. the Wallbox has an RS-485 port which seems to be used to chain multiple wallboxes together so that the total draw is less than some value.
I would bet that the RS-485 is able to set the max current at any given time (assuming somebody reverses it)… and I did a search:
- this is promising. Some reversing of the RS-485 protocol
- Supposedly an ESPHome component to communicate with wallbox
- Thread on more modbus with ESPHome to communicate. This thread also hints at a Powermeter, an “EM300” that supposedly can do something with the Wallbox.
I’m hopeful. Great thread (I don’t have an EV yet - I’m still planning…)