I’m wondering what the legal requirements to use EFBs like ForeFlight or Skydemon or similar for primary flight planning and navigation. If I remember correctly, I once heard about requirements on battery percentage, backup device, external battery or similar.
In particular, I’m interested in the situation in Germany, but I’m happy to hear about differences to other countries (e.g. FAA vs. EASA) as well. I’d be happy about hints on where to find regulations like these as well.