The voltage of the charging power supply remains constant throughout the entire charging time, and as the voltage at the battery terminal gradually increases, the current gradually decreases. Compared with constant current charging method, its charging process is closer to the optimal charging curve. Fast charging with a constant voltage, due to the low electromotive force of the battery in the early stage of charging, the charging current is large. As charging progresses, the current will gradually decrease, so a simple control system is required.
This charging method electrolyzes very little water, avoiding overcharging of the battery. However, excessive current during the initial charging stage has a significant impact on the lifespan of the battery and can easily cause the battery plates to bend, resulting in battery failure. Given this drawback, constant voltage charging is rarely used and is only adopted when the charging power supply voltage is low and the current is high. For example, during the operation of a car, the battery is charged using constant voltage charging method.
