Fast charging can also be used in two modes of operation. One is the constant voltage fast charging mode. During the charging process, the output voltage of the charger remains unchanged. At the initial stage of charging, the voltage of the lithium battery terminal is relatively low, and the difference between the output voltage of the charger and the voltage of the lithium battery pack terminal is large, so that the charging current of the lithium battery is large.
During the charging process, the voltage of the lithium battery terminal gradually increases, the difference between the two voltages gradually decreases, and the charging current gradually decreases. When using this charging method, the stable voltage value of the charger output should be determined according to the terminal voltage of the single cell lithium battery. The other is a two-stage constant current fast charging method. In both phases, the charging current is a pulsed current having a determined amplitude. The charging current of the first stage is about 0.8C. When the terminal voltage of a single lithium battery reaches 2.5~2.6V, the lithium battery is automatically transferred to the second stage of charging, and the charging current amplitude drops to about 0.4C.