https://blog.wongcw.com/2020/09/11/%e6%b2%83%e7%88%be%e6%b2%83%e5%ae%a2%e8%bb%8a%e8%88%87batteryloop%e5%90%88%e4%bd%9c%e8%ae%93%e8%88%8a%e9%9b%bb%e6%b1%a0%e9%87%8d%e7%8d%b2%e6%96%b0%e7%94%9f/