Intermittent wireless charging coil Wireless charging coil at that time, the preferred choice for intermittent charging of cell phones, MP3s, and laptops was the conventional charging method of connecting one end to AC power and the other end to a rechargeable battery for portable electronic devices. This method has many bad luck. First, repeated plugging and unplugging will only damage the joint. Others can also pose a risk of electric shock. Therefore, contactless induction chargers were born at the end of the last century and quickly attracted attention from all walks of life with their convenience, low cost and no wiring. Therefore, wireless charging, high energy transfer efficiency and portability have become one of the research directions for charging systems.