It’s not the exact answer for all situations 
Here is what I do
Firstly I use MQTT since it is faster than Modbus
The flow I use is: When the car is charging change ESS state to Keep batteries charged and then change to Optimized without BatteryLife when the car stops charging. (I do this because when the car is charging the electricity is cheap)
That may not work for you scenario but you could for example limit the inverter power output instead