The charging requirements of lithium batteries are different from nickel-cadmium nickel-metal hydride batteries, and the rechargeable lithium battery cell voltage is 3.6V (some battery blocks may be nominally 3.7V). With the full charge, the lithium battery voltage will slowly rise, which is also a sign to judge whether the lithium battery is full, and the general manufacturer recommends that the charging voltage be 4.2V (in the case of a single lithium battery).