The connected chip of the 18650 lithium battery is on the protection board of the battery, as the name suggests, the protection board is to protect the lithium battery and prevent the lithium battery from overcharging and overdischarging. The relative function of the protection board of different manufacturers is not the same, but they have the basic role of preventing the battery from overcharging and overdischarging! Because lithium batteries are prone to danger after overcharging and overdischarging. Intersecting with lead-acid batteries, lithium batteries have more and larger safety risks, and it is flammable and explosive.