What are the safety warnings when replacing the batteries?

Batteries can cause explosion due to fire or short-circuit, so you must not recharge, damage, disassemble, or heat batteries over 85°C, and prevent them from contacting water. If a battery leaks electrolyte, handle it only with suitable protective gloves, and if electrolyte contacts your eyes, rinse immediately with plenty of water and consult a doctor. Only use batteries of the same type and manufacturer, observe polarities, and do not mix new and used batteries. (Page 9)