A thermal water bag has been filled with galvanothermy energy conversion agent, which helps it to warm up quickly and keep warm for a long time. Commonly, after charging for 7-12  minutes, it can be used for 2-10 hours, which is 2 hours for hand warming or 10 hours for quick warming. It has automatic temperature control to avoid being overheated, starts heating when the light starts shining, and stops when the light is extinguished. The product is explosion and leakage-proof. The protection device installed inside can restrain air expansion, and the vinyl film and high-strength complex fiber guarantee no leakage of the proof.