Electric car "fast charge" bid farewell to "charging anxiety", technology innovation in accelerated iteration

At centralized charging stations in Shenzhen, more and more electric car drivers are charging cars with multi-power compatible charging stacks. In addition, with the continuous breakthrough of power battery technology, the energy density and power density of lithium batteries have increased in parallel, which has improved the driving range of electric vehicles, and on the other hand, the replenishment time is comparable to that of fuel vehicles. It’s possible to fast charge. In the accelerated iteration of technological innovation, electric vehicle users are gradually bidding farewell to the long-standing "charging anxiety."

"Power Sharing" charging reactor solution

Matrix flexible charging reactor technology can not only meet the current battery charging requirements, but also meet the future "battery upgrade" requirements, avoiding the repeated withdrawal of charging piles.

As of the end of last year, China had 450,000 types of charging piles, which is 14 times that of the end of 2014, and the national vehicle-pile ratio was about 3.8:1. However, while the construction of the charging network is steadily advancing, there is also a certain degree of structural supply shortage. The mismatch of resources has led to the coexistence of “difficulty in charging” and the large number of idle charging of public charging piles. In addition, for a long time, most of the public charging piles for electric vehicles put on the market are fixed-power charging piles, and the design of charging piles is considered to meet the current standard of automobile batteries. 40kW, 60kW, 80kW, 110kW... As the new models are getting more and more powerful, the charging piles will face replacement or expansion.

The coexistence of multiple power electric vehicles is already a fait accompli of the electric vehicle inventory market. Therefore, in a centralized charging station, how to improve the power compatibility of the charging device is the key. "In the case of the same charging current, when the voltage is raised to 1000V, if the vehicle with the voltage platform of 350V is still charged, the power utilization rate of the prior art scheme is less than one third of the original, and the equipment utilization rate is extremely low. Xiao Xia, chairman of Shenzhen Aotexun Power Equipment Co., Ltd. said, "The charging reactor technology can not only meet the charge requirements of the current battery, but also meet the charge needs of the future 'battery upgrade', avoiding the repeated withdrawal of the charging pile. ".

It is reported that the matrix flexible charging reactor technology developed by Autoxun integrates all or part of the charging modules of the electric vehicle charging station, and dynamically allocates the charging module according to the actual charging power of the electric vehicle through the power distribution unit. That is to say, in the charging station using the charging reactor technology, after the same charging pile power is shared, it can satisfy the charging of 100 kW or the charging of 300 kW batteries, ensuring that each new energy vehicle can be charged at the maximum power. In Shenzhen, Autotech has invested, built and operated flexible charging reactors with more than 80 centralized charging stations.

Zhigang Li, chief engineer of Autox Power Equipment, said that “shared power” is somewhat like “shared bandwidth”. “After no charging reactor, a fixed-power charging device is like a fixed-bandwidth network. If the total bandwidth is 100 megabytes, there are 10 Users, each user's bandwidth is fixed at 10 megabytes, so even if there are many user broadband unused, the maximum bandwidth of other users is still 10 megabytes; and the charging reactor is like shared bandwidth, which can be dynamically adjusted according to the number of users and the required bandwidth. With only one user, his broadband can reach up to 100 megabytes."

Jian Wei, deputy general manager of Shenzhen Qianhai Autoxun New Energy Service Co., Ltd., introduced how much power can be allocated by the charging terminal, which is determined by the charging electric vehicle. Autostron's technical team designed a huge computing system, built a cloud platform, and intelligently managed the identity information of hundreds of electric vehicles after they were collected. When the charging gun is inserted into the charging port "handshake", the vehicle information is completely read out and intelligently distributed to charge the car.

Since December last year, the Shenzhen Standardization Technical Document “Electric Vehicle Flexible Charge Reactor Technical Requirements”, which was jointly organized by Shenzhen Municipal Market Supervision Administration and Shenzhen Development and Reform Commission, was implemented in Shenzhen. This is the first in China local standard for flexible charging reactors for electric vehicles. As the leading enterprise in the subdivision industry of electric power automation, Shenzhen Autotron Power Equipment Co., Ltd. is the lead drafting unit of this standard.

"For taxis, trucks and other operating vehicles, the power adaptability of centralized charging stations directly determines the convenience of charging." Feng Ni, deputy director of the international department of Guodian NARI Technology Co., Ltd. said, "At the centralized charging station. In the application scenario, the charging reactor technology has the characteristics of precise and efficient matching, which will undoubtedly be of great use.

Tap potential high power fast charge

It is generally believed that "fast charging" of electric vehicles refers to charging technology in which the battery is charged from 0% to 80% for less than 30 minutes.

At the pilot seminar on high-power charging of electric vehicles held recently, the Ningde era showed the participants the charging process of the super-iron lithium battery using the "super iron lithium + high energy density fast charge graphite" system. The product can be charged "5C", the demonstration process only takes 20% to 80% of the charge in 7 minutes and 12 seconds, and 20% to 100% of the charge, only takes 13 minutes and 8 seconds.

Dr. Wang Lei, an expert in energy storage technology and founder of Eco flow, said, "Ultra-high-voltage DC technology is used for ultra-high power charging. In an image, it is dumping electricity into the battery." The unit "C" in "5C" refers to the charging rate, which can be understood as the charging and discharging rate. The charge-discharge rate of a lithium-ion battery determines how quickly the energy can be stored in the battery, or how quickly the energy in the battery is released. The current of "1C" is completely 1/1 = 1 hour from full charge to discharge; "2C" is 1/2 hour, that is, 30 minutes; 5C is 12 minutes. It is generally believed that the "fast charge" of an electric vehicle refers to a charging method in which the charging current is greater than 1.6 C, that is, a technique of charging from 0% to 80% for less than 30 minutes.

The core technology of lithium battery fast charging is to speed up the movement of lithium ions in the positive and negative electrodes through chemical system and design optimization without affecting the life and reliability of the battery. Dr. Shengwei Wang, the person in charge of the fast charge project of Ningde Times New Energy Co., Ltd., said that in the negative graphite surface, Ningde era adopted the "fast ion ring" technology, which is equivalent to creating a high-speed runway on the graphite surface, which greatly accelerates lithium ion in graphite. The layer is embedded, and the modified graphite combines the characteristics of super fast charge and high energy density. In addition, the heat dissipation rate inside the battery is also an important factor affecting the rate performance. If the heat dissipation rate is slow, the accumulated heat during charging and discharging at a large rate cannot be transmitted, which will affect the reliability and life of the lithium ion battery. The fast charge product developed by Ningde era is equipped with a self-developed thermal management system, which can fully identify the “healthy charging range” of fixed chemical systems in different environments and broaden the operating temperature range of lithium batteries.

"The demand for high-power charging is very clear. There is an urgent need for vehicles such as commercial vehicles, taxis, and network-related vehicles at home and abroad. Especially in large cities such as Beijing, shanghai, Guangzhou and Shenzhen, where parking spaces and charging pile resources are scarce, it is difficult for owners. When the parking space is found, there will be a strong demand for high-power charging.” Feng Ni said, “But the high-power fast charging products above 300kW are in the initial stage in the world, battery heating, equipment volume, safety isolation, etc. The technical problems still need to be optimized. From the maturity of technology to the maturity of the market, there is still a long way to go. In addition, infrastructure supporting issues such as charging station construction and power grid supply have yet to be resolved.

Management and services need to be more refined

Experts said that in order to promote the healthy development of electric vehicles, intelligent and refined management of charging services is the general trend.

China has been ranked as the world's largest producer of new energy vehicles for three consecutive years. As of the end of last year, the cumulative sales of new energy vehicles in China reached 1.8 million units, accounting for more than 50% of the global cumulative sales. "According to market trends, after 2020, there will be more and more high-power electric vehicles of more than three hundred and four hundred kilowatts." Feng Ni believes that "no matter whether it is a charging reactor or a battery itself, there is no problem in technology." In addition, although early operators did not consider power expansion, in recent years, more and more operators have reserved space for expansion in centralized charging stations. "After the emergence of more power charging requirements, stations, piles, and piles are all can directly expand capacity - increase the corresponding module can be."

Yongdong Liu, deputy director of the China Electricity Council's Standardization Management Center, said that in the way of charging, the trend of electric vehicles in the future will be the long-term coexistence and mutual integration of "private charging and charging piles daily slow charging" and "public fast charging and charging". “For urban families who use electric vehicles for commuting, they use private charging piles to charge at home after work. Long-term slow charging can meet most of the needs; using fast charging at charging stations will be a necessary supplement.”

The optimization of the charging field management system is expected by many experts. Feng Ni cited an example of a cooling scheme for a charging station power module. The mainstream cooling module of the power module has water-cooling and air-cooling modes. The former has a long service life and high reliability, but the price is expensive. The latter is inexpensive, but has high environmental requirements, and is prone to dust clogging due to long-term use. The "domestic bidding" is a mechanism that allows many operators to adopt the air-cooling mode, but it needs to be replaced in less than two years. The comprehensive cost of use is higher than the use of water cooling." Feng Ni said.

In Yongdong Liu's view, there is still much room for development in the installation and management of private charging piles. "Many residential areas, especially old ones, cannot be universally installed due to limited power distribution capacity and unmatched properties; and the use of technology platforms to implement and manage charging during low-voltage periods is yet to be further promoted." The intelligent and refined management of charging services is the trend of the times.

"We talk about charging technology and management and service improvement today, all of which are based on the healthy development of electric vehicles." Feng Ni said, "The most fundamental driving force of electric vehicles still comes from electric vehicles themselves, from the ecological adjustment of the entire industry chain. And change. What we are most concerned about is that after the relevant subsidies are cancelled, the desire of users to spontaneously consume and use electric vehicles is strong, which is the key to the long-term development of the entire industry."

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