Several charging methods and differences of new energy vehicles
There are many classification methods for new energy vehicle charging systems. According to whether the charging system is in direct contact with the public grid, it is divided into a contact charging system and an inductive charging system. According to whether the charging system is installed in the car, it is divided into EV on-board charger system and EV off-board charger system.
The EV on-board charger system is installed inside the vehicle. It has the advantages of small size, good cooling and sealing, and light weight. However, the power is generally small and the charging time is long; the off-board charging system is installed outside the new energy vehicle and has a large scale, It has the advantages of wide use range and high power, but it is large in size, heavy in weight, and not easy to move. It is mainly suitable for fast charging of new energy vehicles.
The use of different charging methods for the battery will have varying degrees of impact on the battery life, and the use of an appropriate charging method is of great significance to prolong the life of the battery.
Common charging methods for EV on-board charger include constant voltage charging, DC charging, phased charging, and pulse charging. In constant voltage charging, the charging voltage remains unchanged during the entire charging process, and the charging current gradually decreases as the charging time increases. When the charging current is less than a certain value, the charging stops. The entire charging process consumes less energy, can effectively avoid battery overcharging, and is simple to control and easy to operate.
At the beginning of DC charging, the power battery is charged with a constant current. When it is about to be fully charged, a constant low current is used for floating charge to fully charge the remaining power and compensate for battery self-discharge. When the charging voltage reaches the rated voltage, the charging is stopped. Constant current charging avoids the problem of excessive constant voltage charging current, and the current is always limited within the acceptable range of the battery pack.
Phased charging can be divided into two-phase or three-phase charging according to actual application conditions. The first stage is constant current charging, which uses high current to quickly charge the battery so that the battery voltage reaches a certain voltage value. Set the age according to the voltage of the power battery pack; the second stage is constant voltage charging, and continue to charge with a current smaller than the constant current. Charging the battery reduces the gas production of the battery; the third stage is floating charging, charging the battery with a trickle to ensure that the battery can be fully charged. When the control system detects that the charging current is less than a certain set value, the charging ends. Phased charging combines the advantages of constant voltage and constant current charging methods, which is beneficial to reduce the polarization of the battery and avoid the impact of overcharge and high current charging. At present, charging mostly adopts phased charging.
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