Most of those flashlights use capacitors to temporarily store charge. In fact, the manual mode is that the magnet cuts the magnetic induction line in a group of coils to generate charge, which converts mechanical energy into electrical energy. In fact, the working principle of pressing is that the magnetic induction line is cut to generate charge, most of which is stored by a capacitor to drive a bright led to emit light. Time is short. The same mechanical energy is converted into electrical energy. This kind of weak electricity can't charge the battery at all, because this kind of power generation mode is inefficient and can't support the charging current of ordinary rechargeable batteries (normal chargers are hundreds of milliamps, and the electricity generated in that way can only reach tens of milliamps at most, and a 600-milliamp battery can't exceed ten hours) and people's physical strength is limited. You can't hold it for hours. It is recommended that you use solar cells to charge. At present, the polysilicon solar cell with an area of about 17-25cm can generate a current of 5v and several hundred ma. If you don't speak well, please give me more advice. Just like a radio in Desheng, it generates electricity by hand. The principle is very simple, that is, the big gear drives the small gear, and then drives the micro-generator to generate electricity. This technology is more practical because of the characteristics of radio (not consuming much power). You said that the mobile phone generates electricity manually, for emergency use. Don't be too efficient > The most important thing is that people should take the initiative. Solar cells are generally (5.5v.80ma) and can be used to charge mobile phones. It will be cheaper if the company buys it. Of course, it depends on where you are. I made a solar cell phone charger with a charging current of 240ma and 60 yuan, which is cheap. Stand by for more than 20 hours after charging. The market sells for one or two hundred yuan.