Hello @Paulha,
since the day before yesterday I now also have a PV system with KOSTAL Plenticore inverter. Of course I also wanted to have the data on my MagicMirror. The API of the inverter is not for the faint of heart, but I have managed a first throw.

You can find my new module here:
https://github.com/eckonator/MMM-Plenticore

The battery is not output yet, because my battery will be connected next week. Unfortunately I can’t test for it.

I am very happy about your experiences with my module.