Hi 
!
I’m afraid this is not going to be as straight forward as you’d like. See New Fronius UI Integration with Multi Inverters - #2 by farmio and the link provided there.
If you really need more frequent updates in HA (Inverter not controlling the charger directly / via its IO port) I’d probably go for Modbus as the HTTP-API is not super fast / reliable and the Modbus people say theirs is. See Integration of a Fronius Symo Gen 24 plus Inverter via Modbus TCP