Lithium battery pack refers to the output of one or more lithium batteries plus a battery protection board with specific functions. Lithium battery packs consist of multiple cells to form a single physical module that provides higher voltage and capacity. For example, a battery module uses four cells in series to give a nominal 12V voltage or multiple cells. The parallel connection provides greater power—lithium battery components connected in series and parallel. Parallel battery packs require that each battery have the same voltage, and the output voltage is equal to the voltage of one battery. Parallel battery packs can provide stronger current. There are no excessive requirements for series battery packs, as long as the batteries are guaranteed. The capacity of the battery pack is about the same. The series battery pack can provide a higher voltage. A more complete lithium battery pack protection function should be composed of two modules: to protect the circuit substrate, and the other is to judge the substrate intelligently.