A mobile c-arm X-ray apparatus is described. The mobile X-ray apparatus includes an electrically operated X-ray source. The mobile C-arm X-ray apparatus also includes an electrical energy storage device having a high current-capable accumulator. The electrical energy storage device includes a first electrical terminal electrically connected to the electrically operated X-ray source and a second electrical terminal used by a system energy supply. A method for operating the mobile X-ray apparatus is also described.