Simply talk about the working principle of apple pencil, you know why you need to charge, the traditional capacitor pen is conductive material conduction to achieve the transmission of electrical signals, but the apple pencil is an active emission of electromagnetic signals, and the transmission of multiple frequency bands of signals through cross-scanning and analysis to provide pen writing accuracy. And for different devices will automatically correct the signal to do adaptation, so the accuracy of apple pencil can be said to be pixel level.
In addition, in order to simulate the writing characteristics of different tools (such as simulating brush calligraphy), the pen is also added to the gyroscope, or even more than one. So the apple pencil is not only what we call a pen, but more like a sophisticated electronic product, it is not surprising that it needs to be charged.