Hi Tommy, I'm looking to do the same thing except just use the excess solar generation to charge once my home battery system has been charged. I believe that the Open Energy Monitor https://openenergymonitor.org/ should be able to provide a solution, although I have only just started looking into this and have not had time to look into it further just yet.
Tommy
I'm looking to charge my car with excess solar up to 70% and then the rest with free power I get from 9pm to midnight...
I guess with openEVSE not able to see the battery percentage there is no real way I can do this without something like HomeAssistant?