To ensure the safety of the aircraft, and all those on board, passengers’ checked-in or hand baggage must not contain articles or substances that could pose a danger (some exemptions apply).
Batteries can short circuit and catch fire if they are carried loose in your bag. They must be protected against contact with other metal items (e.g. by being in their original packaging or own protective case) and carried in your hand baggage. Equipment containing correctly installed batteries can be packed in your checked baggage.