Charging is an important step in the repeated use of batteries. The charging process of lithium-ion batteries is divided into two stages: a constant current fast charging stage and a constant voltage and current decreasing stage. During the constant current fast charging phase, the battery voltage gradually rises to the standard voltage of the battery, and then goes to the constant voltage phase under the control chip. The voltage no longer rises to ensure that it will not be overcharged, and the current gradually weakens as the battery power rises. To the set value, and the charging is finally completed. The power statistics chip can sample and calculate the battery power by recording the discharge curve. The lithium ion battery will change its discharge curve after being used many times. Although the lithium ion battery has no memory effect, improper charging and discharging will seriously affect the battery performance.