Rather Than a battery it's run by a small photo voltaic panel to the watch face (the 'Eco Drive') and thanks to 'Atomic Timekeeping' it could declare to be the 'most precise watch in the world'. Mühle watches are admittedly big, but for those who don’t brain that, you’ve bought https://www.watchesworld.com/germanys-top-10-favourite-luxury-watches/