First, the lack of power, resulting in the stopwatch does not go, then it should be held in the sun, or charge the watch, if the charge is finished and does not go for a while, it may be the battery is broken. The photokinetic energy is to charge the battery of the watch through the built-in light source acquisition system, thus driving the watch to work. Its battery also has a life, if the battery is broken, it is recommended to replace.