A battery cell includes a first resistance change member having first and second terminals, a first power generation element including a first positive electrode, a first negative electrode, and a first electrolyte interposed between the first positive electrode and the first negative electrode, a first case enclosing the first power generation element and the first resistance change member, and first positive and negative electrode terminals. At least one of the first positive electrode, the first negative electrode, and the first electrolyte contains a first sulfur-based material. The first resistance change member contains a first resistance change material of which electrical resistance is changed by a chemical reaction with hydrogen sulfide. The first and second terminals of the first resistance change member are exposed to the outside of the first case, and the first resistance change member is not electrically connected to any of the first positive and negative electrode terminals.