Hi Walde,
greetings from NRW. That looks like a very nice built.
I also started charging my packs from the grid in December as they got too low for my liking. The inverter still draws its 7W and all the PV production is used by the house. So I decided to give them a quick 30 min 500W grid charge every night (or every other night). Thankfully I can program that and don't have to do it manually.
It'll cost me 5€ over the course of the winter but it will also give me peace of mind.
Waiting for better days in February / March.
Love to see your videos.