An apparatus (1) for determining the aging of a battery cell (2), the battery cell (2) having at least one galvanic element (3) for converting chemical energy into electrical energy and a housing (4) which surrounds the galvanic element (3) and has a wall (8) formed at least on one side of the galvanic element (3), comprising at least one length sensor (5) for sensing a length change of the galvanic element (3), the aging of the battery cell (2) being able to be determined via the length change of the galvanic element (3).