The invention relates to an energy storage device for generating an n-phase supply voltage, wherein n>1, comprising n energy supply branches connected in parallel, which are each coupled to a respective output connection of the energy storage device, wherein each of the energy supply branches has a plurality of energy storage modules connected in series. The energy supply branches each have a respective energy storage cell module, which has at least one energy storage cell, and a respective coupling device having first coupling elements, which are designed to selectively connect the energy storage cell module into the respective energy supply branch or bypass the energy storage cell module. At least one of the energy supply branches has at least one second coupling element, which is coupled between output connections of energy storage cell modules that are adjacent in the at least one energy supply branch and which is designed to connect the coupled energy storage cell modules into the respective energy supply branch in parallel with each other.