Steering the Marstek Venus D with Homeassistant while your EV charges with a go-e Wallbox

A plug-in battery with zero feed-in and an 11 kW wallbox don't get along: the moment your EV starts charging, the Venus D happily dumps its entire capacity into the car. Here's how I used Home Assistant, the go-e Charger API and Modbus to make the battery cover only my house.