There are two ways to charge electric vehicles, AC charging and DC charging, both of which have a large gap in technical parameters such as current and voltage. The former has a lower charging efficiency, while the latter has a higher charging efficiency. Liu Yongdong, deputy director of the Joint Standardization Center of China Electric Power Enterprises, explained that the “slow charging” that is often referred to as “slow charging” basically uses AC charging, while “fast charging” mostly uses DC charging.
Charging pile charging principle and method
1. Charging principle of charging pile
The charging pile is fixed on the ground, uses a special charging interface, and adopts a conduction method to provide AC power for electric vehicles with on-board chargers, and has corresponding communication, billing and safety protection functions. Citizens only need to buy an IC card and recharge it, and then they can use the charging pile to charge the car.
After the electric vehicle battery is discharged, direct current is passed through the battery in the opposite direction to the discharge current to restore its working capacity. This process is called battery charging. When charging the battery, the positive pole of the battery is connected to the positive pole of the power supply, and the negative pole of the battery is connected to the negative pole of the power supply. The voltage of the charging power supply must be higher than the total electromotive force of the battery.
2. Charging pile charging method
There are two charging methods: constant current charging and constant voltage charging.
Constant current charging method
The constant current charging method is a charging method that keeps the charging current intensity constant by adjusting the output voltage of the charging device or changing the resistance in series with the battery. The control method is simple, but because the acceptable current capacity of the battery gradually decreases with the progress of the charging process. In the later stage of charging, the charging current is mostly used for electrolyzing water, generating gas, and causing excessive gas output. Therefore, the stage charging method is often used.
Constant voltage charging method
The voltage of the charging power source maintains a constant value throughout the charging time, and the current gradually decreases as the battery terminal voltage gradually increases. Compared with the constant current charging method, its charging process is closer to a good charging curve. Fast charging with constant voltage, because the electromotive force of the battery is low at the initial stage of charging, the charging current is very large, as the charging progresses, the current will gradually decrease, so only a simple control system is needed.
Post time: Dec-02-2022