The invention relates to an apparatus (2) for state of charge compensation having a battery system (10) for providing electrical energy comprising a series connection of a first battery sub-module (13) and a second battery sub-module (13′) having a first voltage conversion module (20′) wherein the first voltage conversion module (20′) is electrically connected to the second battery sub-module (13′), and wherein an electrical component (30) can be connected to the first voltage conversion module (20′) and can be supplied with electrical energy from the connected second battery sub-module (13′), wherein the apparatus (2) has a switching device (26) for switching an electrical connection between the first battery sub-module (13) and the first voltage conversion module (20′) and wherein the apparatus (2) has a control device (11) which is designed to control the switching device (26) such that electrical energy flows from the first battery sub-module (13) to the second battery sub-module (13′) and/or that electrical energy flows from the second battery sub-module (13′) to the first battery sub-module (13).