The protection function of the lithium-ion battery is usually completed by the protection circuit board and the PTC. The protection board is composed of electronic components. It can accurately monitor the voltage of the battery cell and the current of the charging and discharging circuit at all times in the environment of -40 ° C ~ + 85 ° C, and timely Control the on-off of the current loop; the important use of PTC is to protect in high temperature environment to prevent the battery from burning, explosio