(1) Constant-Current Charging
Constant-current charging refers to charging a battery at a fixed current rate. When charging with a single current value, an excessively low charging current results in an overly prolonged initial charging phase. Conversely, an excessively high charging current causes the battery's charging voltage to become too high during the later stages, subjecting the electrodes to significant stress.
(2) Constant-Voltage Charging
Constant-voltage charging maintains a fixed charging voltage throughout the process. While this method can automatically adjust the charging current based on changes in the battery's State of Charge (SOC) during charging, its drawbacks are significant: charging speed is slow. In the initial charging phase, excessively low battery voltage can cause the charging current to become too high, potentially damaging the battery, shortening its lifespan, or even rendering it unusable.
(3) Constant Current-Constant Voltage Charging
Constant current-constant voltage charging is currently the most widely used charging method for lithium batteries. This method involves first charging at a constant current until the battery voltage reaches a predetermined voltage level, after which the battery is charged at a constant voltage. During the constant-voltage phase, the charging current gradually decreases. When the current drops to near zero or 0.02C, the battery is considered fully charged. This method combines the advantages of both constant-current and constant-voltage charging: it ensures the initial charging current does not exceed the battery's rated current during the constant-current phase, while improving charging efficiency during the constant-voltage phase.
(4) Pulse Charging
Pulse charging refers to charging the battery with a constant pulsed current. The initial stage involves constant-current charging with a low current. Once the battery voltage reaches a predetermined voltage level, pulse current is applied to continue charging. This method provides ample time for depolarization, enabling the battery to store more energy.
