1, the switch is broken;
2, the internal line has a virtual solder joint;
3, the carbon brush is not long enough or the spring is broken
Change the battery! Drill power is large, full charge or use time is not long, the reason is that one of the sections (most of the failure is a section) or several sections of the internal resistance is large, the battery is a series combination of high-discharge rate cells, discharge current is large, internal resistance voltage drop, a cell voltage drop is large, the output voltage is lower than the protection board protection voltage (2.8v), protection board protection, Power off..