In addition, with continuous breakthroughs in lithium-ion battery technology, the energy density and power density of lithium-ion batteries are improving in parallel. This not only increases the driving range of electric vehicles but also makes "fast charging," with refueling time comparable to that of gasoline vehicles, possible. Amidst the accelerated iteration of technological innovation, electric vehicle users are gradually bidding farewell to the long-standing "charging anxiety."
"Power sharing" charging pile method
The matrix-style flexible charging pile technology can meet both current battery charging needs and future battery upgrade requirements, preventing the repeated rebuilding and dismantling of charging stations.
By the end of last year, my country had 450,000 charging piles of various types, 14 times the number at the end of 2014, with a vehicle-to-pile ratio of approximately 3.8:1. However, while the construction of the charging network has progressed steadily, there is also a certain degree of structural supply shortage. Resource misallocation has led to the coexistence of "charging difficulties" and a large number of idle public charging piles. Furthermore, for a long time, most of the public charging piles for electric vehicles deployed in the market have been fixed-power charging piles, designed primarily to meet current automotive battery standards. 40kW, 60kW, 80kW, 110kW… As newly launched vehicle models become increasingly powerful, charging piles will face replacement or expansion.
The coexistence of electric vehicles with various power outputs is already a reality in the existing electric vehicle market. Therefore, improving the power compatibility of charging equipment is crucial for centralized charging stations. "Under the same charging current, when the voltage is increased to 1000V, if we still charge vehicles with a voltage platform of 350V, the power utilization rate using current technology is less than one-third of the original, resulting in extremely low equipment utilization," said Xiao Xia, Chairman of Shenzhen Autel Power Equipment Co., Ltd. "Charging pile technology can meet both the current battery charging needs and the future charging needs of 'battery upgrades,' preventing the repeated construction and demolition of charging piles."
It is reported that Autel's matrix-type flexible charging pile technology centralizes all or part of the charging modules of an electric vehicle charging station. Through a power distribution unit, the charging modules are dynamically allocated according to the actual charging power required by the electric vehicle. In other words, in charging stations using this technology, a single charging pile, after power sharing, can meet both 100kW and 300kW battery charging needs, ensuring that each new energy vehicle can be charged at maximum power. In Shenzhen, Autel has invested in, constructed, and operates more than 80 flexible charging pile centralized charging stations.
Li Zhigang, chief engineer of Autel Power Equipment, said, “Shared power is somewhat like shared bandwidth. Before the advent of charging piles, fixed-power charging equipment was like a fixed-bandwidth network. If the total bandwidth is 100 Mbps and there are 10 users, each user’s bandwidth is fixed at 10 Mbps. So even if many users’ broadband is not in use, the maximum bandwidth of other users is still 10 Mbps. Charging piles are like shared bandwidth, which can be dynamically adjusted according to the number of users and the bandwidth demand. If there is only one user, then his/her maximum bandwidth can reach 100 Mbps.”
Wei Jian, Deputy General Manager of Shenzhen Qianhai Aote Xun New Energy Service Co., Ltd., explained that the amount of electricity allocated to a charging terminal depends on the electric vehicle being charged. Aote Xun's technical team designed a massive computing system and established a cloud platform. After collecting big data on the identity information of hundreds of electric vehicles, they manage the data intelligently on the platform. The moment the charging gun is inserted into the charging port, all vehicle information is read and intelligently allocated for charging.
Since December of last year, the "Technical Requirements for Flexible Charging Stacks for Electric Vehicles," a standardized guiding technical document jointly formulated by the Shenzhen Municipal Market Supervision Administration and the Shenzhen Municipal Development and Reform Commission, has been implemented in Shenzhen. This is the first local standard in China concerning flexible charging stacks for electric vehicles. Shenzhen Autel Power Equipment Co., Ltd., a leading company in the power automation power supply sub-sector, was the lead drafting unit for this standard.
"For commercial vehicles such as taxis and trucks, the power adaptability of centralized charging stations directly determines the convenience of charging," said Ni Feng, deputy director of the International Department of NARI Technology Co., Ltd. "In the application scenario of centralized charging stations, charging pile technology has the characteristics of precise and efficient matching, and will undoubtedly have a great role to play."
Unlocking the Potential of High-Power Fast Charging
Generally, "fast charging" for electric vehicles refers to a charging technology that charges the battery from 0% to 80% in less than 30 minutes.
At a recent symposium on high-power charging pilot projects for electric vehicles, CATL demonstrated the charging process of its super lithium iron ion battery, which uses a "super lithium iron ion + high-energy-density fast-charging graphite" system. The product can be charged at "5C" speeds, and the demonstration showed it completed a charge from 20% to 80% in just 7 minutes and 12 seconds, while charging from 20% to 100% took only 13 minutes and 8 seconds.
Dr. Wang Lei, an energy storage technology expert and founder of Ecoflow, explained, "Ultra-high power charging uses high-voltage direct current technology; figuratively speaking, it's like pouring electricity into the battery." The "C" in "5C" refers to the charging rate, which can be understood as the charge/discharge rate. The charge/discharge rate of a lithium-ion battery determines how quickly electrical energy can be stored in the battery or how quickly it can be released. A "1C" current takes 1/1 = 1 hour to fully charge and discharge; "2C" takes 1/2 hour, or 30 minutes; and "5C" takes 12 minutes. Generally, "fast charging" for electric vehicles refers to a charging current greater than 1.6C, meaning a charging time from 0% to 80% is less than 30 minutes.
The core technology of fast charging for lithium-ion batteries lies in accelerating the movement of lithium ions between the positive and negative electrodes through chemical system and design optimization, without affecting cell lifespan and reliability. Dr. Wang Shengwei, head of the fast charging project at CATL (Contemporary Amperex Technology Co., Limited), stated that CATL employs "fast ion ring" technology on the graphite surface of the negative electrode, essentially creating a high-speed track on the graphite surface. This significantly accelerates the embedding of lithium ions into the graphite layer, resulting in a modified graphite that combines super-fast charging with high energy density. Furthermore, the internal heat dissipation rate of the battery is also a crucial factor affecting rate performance. If the heat dissipation rate is slow, the heat accumulated during high-rate charging and discharging cannot be dissipated, impacting the reliability and lifespan of the lithium-ion battery. CATL's fast charging products are equipped with a self-developed thermal management system that can fully identify the "healthy charging range" of the fixed chemical system under different environments, thus expanding the operating temperature range of lithium-ion batteries.
“The demand for high-power charging is very clear. Both domestically and internationally, commercial vehicles, taxis, and ride-hailing vehicles all have an urgent need for it. Especially in megacities like Beijing, Shanghai, Guangzhou, and Shenzhen, where parking spaces and charging piles are scarce, car owners will have a strong demand for high-power charging when it is difficult to find a parking space to charge their vehicles,” said Ni Feng. “However, high-power fast charging products above 300kW are still in their infancy globally. Technical issues such as battery heat generation, equipment size, and safety isolation still need to be optimized. There is still a long way to go from technological maturity to market maturity. In addition, there are still infrastructure issues to be resolved, such as the construction of charging stations and the power grid supply.”
Management and services need to be more refined
Experts say that intelligent and refined management of charging services is an inevitable trend in order to promote the healthy development of electric vehicles.
For three consecutive years, my country has been the world's largest producer and seller of new energy vehicles. By the end of last year, my country's cumulative sales of new energy vehicles reached 1.8 million units, accounting for over 50% of global sales. "Based on market trends, after 2020, there will be more and more high-power electric vehicles with capacities of 300-400 kilowatts or more," Ni Feng believes. "There are no longer any technical problems with either the charging piles or the batteries themselves." Furthermore, although operators didn't consider power expansion in the early stages, in recent years, more and more operators have reserved expansion space in centralized charging stations. "When the demand for higher-power charging emerges, stations, charging piles, and charging stations can all be directly expanded—simply by adding the corresponding modules."
Liu Yongdong, deputy director of the Standardization Management Center of the my country Electricity Council, said that in terms of charging methods, the future trend of electric vehicles will be the long-term coexistence and combination of "daily slow charging at private AC charging stations" and "public fast charging for supplementary power." "For urban families who commute by electric vehicle, long-term slow charging at home using private charging stations after get off work can meet most of their needs; using fast charging at charging stations will be more of a necessary supplement."
Optimizing the management system in the charging sector is something many experts hope for. Ni Feng cited the example of power module cooling methods in charging stations. The mainstream cooling methods for power modules are water cooling and air cooling. Water cooling has a long service life and high reliability, but it is expensive; air cooling is inexpensive, but it has high environmental requirements and is prone to dust blockage after prolonged use. "The 'lowest bidder wins' mechanism in domestic bidding has led many operators to adopt air cooling, but these systems need to be completely replaced in less than two years. In the end, the overall cost is actually higher than using water cooling," Ni Feng said.
According to Liu Yongdong, the installation and management of private charging stations still have significant room for development. "Many residential communities, especially older ones, cannot widely install charging stations due to limited power distribution capacity and lack of cooperation from property management companies; and the practice of using technology platforms to promote and manage charging during off-peak hours also needs further development." Intelligent and refined management of charging services is an inevitable trend.
"When we talk about improving charging technology, management, and services today, it's all based on the premise of the healthy development of electric vehicles," said Ni Feng. "The most fundamental driving force for electric vehicles still comes from the vehicles themselves, and from the adjustments and changes in the entire industry chain ecosystem. What we are most concerned about is how strong users' desire to spontaneously consume and use electric vehicles will be after the relevant subsidies are canceled. This is the key to the long-term development of the entire industry."
