Charging system provides energy supply for the operation of electric vehicles and is an important basic support system of electric vehicles, as well as an important link in the process of commercialization and industrialization of electric vehicles. With the rapid development of electric vehicle industry, charging technology has become one of the key factors restricting the development of the industry, and intelligent and fast charging method has become the development trend of electric vehicle charging technology.
There are different ways to classify electric vehicle charging devices. In general, it can be divided into vehicle-mounted charging device and non-vehicle-mounted charging device. Charging devices can be divided into contact type and induction type according to the different ways of charging the battery of electric vehicles. According to different charging modes, electric vehicles can be divided into slow charging, fast charging, power changing, wireless charging, mobile charging and so on. Next, the electric expert xiaobian will take you to understand several charging methods, the composition and functions of charging piles and charging stations, so that we can have a systematic understanding of electric vehicle charging and equipment.
Also known as conventional charging, vehicle charging, that is, the use of portable charging equipment equipped with the car to charge, can use household power supply or special charging pile power supply. That's what we use in our passenger cars today: on-board chargers and wall-mounted charging piles at home. Generally, the charging current is about 16 to 32 A. The current can be DC, two-phase AC, or three-phase AC. Therefore, the charging time ranges from 5 to 8 hours depending on the battery string capacity.
The disadvantages of conventional charging mode are very obvious. The charging time is long, but its requirements for charging are not high, and the cost of charger and installation is low. It can make full use of the off-peak period of power to charge and reduce the cost of charging; The more important advantage is that it can deeply charge the battery, improve the charging and discharging efficiency of the battery, and extend the battery life. Because of the longer charging time, can greatly meet the daytime operation, the night rest of the vehicle.
Quick charging, also known as ground charging, as the name implies, is a charging method that can be fully charged quickly. It directly charges the battery with high current through non-vehicle charging machine, so that the battery can be charged to about 80% of the power in a short time, so it is also called emergency charging. The fast charging model is represented by Tesla superchargers. The current and voltage of quick charge mode are generally 150-400A and 200-750V, and the charging power is greater than 50kW. This mode mostly uses DC power supply. The ground charger has large power and wide range of output current and voltage.
The quick charge has a very high charging speed, which is close to the time it takes an internal combustion engine to fill with fuel. But its charging method is to use pulse rapid charging. The biggest advantage of pulse rapid charging is that the charging time is greatly shortened. And can increase the appropriate battery capacity, improve the startup performance. However, the pulse charging current is large and the charging equipment installation requirements and costs are very high. In addition, the current and voltage of quick charging is high, which has a great impact on the battery in a short period of time, easy to make the active substance of the battery fall off and the battery heat up. Therefore, there are higher requirements on the protection and heat dissipation of the battery. Not every model can be charged quickly. No matter how perfect a battery is, long-term fast charging will ultimately affect its lifespan.
The quick charging mode is essentially the emergency charging mode, which aims to charge electric vehicles in a short time. Generally speaking, it is not recommended to use the quick charge mode for charging. And the quick charging mode is only supported by some models.
Also known as mechanical charging, in addition to the conventional direct charging of the vehicle, can also be used to replace the power battery to charge the battery. That is, when the power battery runs out, replace the low battery with a fully charged one. There are three modes to replace the battery pack from the car: pure manual mode, semi-automatic mode and robot replacement mode.
The replacement battery combines the benefits of regular and quick charging modes. The biggest limitation of the charging mode of replacement batteries is that manufacturers need to unify battery specifications, size and other standards, and they cannot guarantee the same performance of each battery pack, thus restricting its development. Another more important reason is that the market is monopolized by the State grid and there is no competitor, resulting in the lack of development of battery replacement charging mode.
Wireless charging mode does not need to transfer energy through cables, but uses electromagnetic induction, electric field coupling, magnetic resonance and radio waves to transfer energy. To adopt wireless charging mode, first install on-board induction charger on the car. There is no mechanical link between the electric receiving part and the power supply part of the vehicle, but the connection between the electric receiving body and the power supply body is more accurate.
Limited by technology maturity and infrastructure, electric experts believe that wireless charging technology cannot be applied in mass production for the time being. The mainstream wireless charging technology in the industry mainly uses electromagnetic induction and magnetic resonance to transfer power, but the magnetic resonance charging efficiency is higher, and the electromagnetic radiation intensity is lower than the intensity of mobile phone calls, more importantly, the sending coil and the receiving coil do not need to be very aligned, which is less than the electromagnetic induction.
The future of wireless charging is inconceivable. It will be possible to charge while walking, either from the power supply of the pavement or from the electromagnetic energy received in the car.
The ideal scenario for electric car batteries is to charge them while the car is cruising on the road, known as mobile charging (MAC). There is no need for electric car users to find charging stations, park their vehicles and spend time charging. The MAC system is buried under a section of road, the charging area, and requires no extra space.
Both contact and inductive MAC systems can be implemented. For a contact MAC system, a contact arch is installed at the bottom of the car body. By contacting a charging element embedded in the road, the contact arch can obtain a transient high current. When the electric vehicle cruises through the MAC area, its charging process is pulse charging. For inductive MAC systems, the vehicle-mounted contact arch is replaced by inductive coils, and the charging elements embedded in the road surface are replaced by high-current windings that generate strong magnetic fields. Obviously, the contact MAC doesn't appeal to people because of mechanical wear and the placement of the contact arch.
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