Electric car requirements for charging technology
Although the construction of electric car charging stations is affected by different factors, their construction methods and construction requirements need to be determined according to actual conditions. However, with the gradual promotion and industrialization of electric cars and the increasing development of electric car technology, the technical requirements of electric cars for charging stations have shown a consistent trend, requiring charging stations to be as close as possible to the following goals.
1) High security
The main factor affecting the safety of electric cars is the charging process of the battery. The inconsistency of the battery’s technical status is one of the basic characteristics shared by all types of batteries, which is mainly manifested in the capacity error, internal resistance error and voltage error of the battery. The consistency error of a few batteries is not obvious, but the capacity error, internal resistance error and voltage error of the electric car battery pack composed of dozens or even hundreds of battery cells will become prominent.
In the charging process of an electric car, it is impossible to sequentially charge the battery cells, but to charge the entire battery pack. During the charging process, due to the internal resistance error, the voltage across the battery cells in the entire battery pack forms an error. The larger the internal resistance error, the more obvious the voltage error formed. Although the charging voltage at both ends of the entire battery pack will not exceed the rated voltage, the voltage at both ends of an individual single battery may exceed its rated voltage, which will easily lead to uneven charging of the battery pack and different charging capacities of the single batteries. If the voltage error of the battery is too large, it may exceed the safety capacity of battery charging, causing the battery to overheat and cause a safety accident. Therefore, the charging device for electric cars must have technical measures to prevent the battery system cell voltage and temperature from exceeding the allowable value to improve the safety of the electric car charging process.
2) Fast charging
Compared with nickel-metal hydride and lithium-ion power batteries with good development prospects, traditional lead-acid batteries have the advantages of mature technology, low cost, large capacity, and good load-following output characteristics, but they also have low specific energy and continuous charging. The problem of short driving distance. Therefore, under the current situation that the power battery cannot directly provide more driving range, if the battery charging can be realized quickly, it will solve the Achilles heel of the short driving range of electric cars in a sense.
3) Universal charging
For a long period of time, batteries used in electric cars will still coexist with multiple types of batteries. Various types of electric cars have different battery capacities and voltages. Under the market background of the coexistence of multiple types of batteries and multiple voltage levels, charging devices used in public places must have the ability to adapt to multiple types of battery systems and various voltage levels, that is, the charging system needs to have charging versatility. The system should have charging control algorithms for multiple types of batteries, which can match the charging characteristics of different battery packs on various electric cars, and be able to charge different batteries.
At present, the electric car charging device and the battery charging control algorithm of the electric car are mainly completed by the docking agreement of the two systems. In order to be able to charge different electric cars, the charging device used for electric cars must be able to adapt to the various needs of electric cars . Therefore, in the early stages of the commercialization of electric cars, relevant policies and measures should be formulated to standardize the charging interface, charging specifications and interface protocols between charging devices used in public places and electric cars.
4) Intelligent charging
One of the most critical issues restricting the development and popularization of electric cars is the performance and application level of energy storage batteries. The goal of optimizing the intelligent battery charging method is to achieve non-destructive battery charging, monitor the battery discharge state, and avoid over-discharge. The purpose of extending battery life and energy saving. The development of the application technology of charging intelligence is mainly reflected in the following aspects:
① Optimized and intelligent charging technology and chargers and charging stations;
②Calculation, guidance and intelligent management of battery power;
③Automatic diagnosis and maintenance technology of battery failure.
5) Efficient power conversion
The energy consumption index of electric cars is very important. To measure the energy consumption index of electric cars in commercial operation, it is necessary to not only examine the energy consumption indexes of electric car driving systems, but also to pay attention to the utilization rate of electric cars obtained from the power grid. The energy consumption indicators of electric cars are closely related to their operating energy costs. Reducing the operating energy consumption of electric cars is one of the key factors to promote the development of the electric car industry. Therefore, improving the power conversion efficiency of the charging device and adopting a high-efficiency charging device are of great significance for reducing the energy consumption of electric cars. The main technical measures to improve the energy consumption efficiency of the charging device are to select a high-efficiency converter circuit topology, improve the power factor of the charging device, reduce the AC component of the output current as much as possible, and adopt an efficient charging control algorithm. For charging stations, considering the power conversion efficiency and construction cost, priority should be given to charging devices with many advantages such as high power conversion efficiency and low construction cost.
6) Integrated charging
With the requirements for miniaturization and multifunctionalization of subsystems, as well as increased requirements for battery reliability and stability, the charging system will be integrated with the electric car energy management system as a whole, integrating transfer transistors, current detection and reverse discharge protection, etc. Function, a smaller and more integrated charging solution can be realized without external components, thereby saving layout space for other parts of electric cars, greatly reducing system costs, and optimizing charging effects and extending battery life.
7) Little impact on battery life
The battery of electric cars accounts for the main part of the cost of electric cars. The power batteries of most electric cars account for more than half of the cost of the entire car, and some even exceed 65% of the cost of the entire car. Therefore, the service life of the battery greatly affects the operating cost of electric cars, which is also one of the key factors restricting the development of electric cars. If the performance of the on-board battery of an electric car deteriorates prematurely, the driving range of the electric car will be greatly shortened, affecting normal use. If the battery life ends early, the battery needs to be replaced for electric cars. Once the battery is replaced, it will cause a great burden for electric car operators. The battery life is not only related to factors such as battery manufacturing technology, manufacturing process, and battery group consistency, but also directly related to the performance of the charging device. The selection of a charging control strategy that does not harm the battery and a charging device with stable performance is a reasonable way to ensure that the service life of the battery reaches the design index and prevent premature damage to the battery. It is also one of the important technical measures to reduce operating costs.
8) Simple operation
The operation of the electric car charging device must be simple and convenient, so that all users can complete the operation independently. Since electric cars are applied to the masses, although there are technical requirements and technical guidance documents, it cannot guarantee that each user’s learning and understanding ability is at the same level, and it is impossible to increase more personnel to charge electric cars. service. If the operation of the charging device is cumbersome and complicated, it will inevitably require more high-quality technical personnel and increase management costs.