A battery system comprising at least two battery modules, wherein each battery module consists of at least one battery and a controllable first switching apparatus, which is designed to connect the respective battery module into a current path of the battery system or to electrically bridge the respective battery module, comprising at least one controllable second switching apparatus, which is designed to electrically connect the at least two battery modules in parallel or in series and comprising a control device, which is designed to control the controllable first switching apparatuses and the controllable second switching apparatus as a function of the requested electrical power. In addition, the present invention discloses a method of operating a battery system.