Abstract: Switching device and energy storage system The present invention relates to a switching device, which is capable of changing a connection state of at least two batteries of a high voltage energy storage system between a series connection and a parallel connection, and to an energy storage system comprising the switching device. The switching device (100) comprises a fixed bus bar arrangement, which comprises at least a pair of fixed input bus bars (140, 142) and a pair of fixed output bus bars (144, 146), and a move-able bus bar arrangement, which comprises at least one connection bus bar (130, 132).