①The standard of electric car charging system
At present, the construction of electric car charging stations is small in scale and small in number, and most of the related technologies of electric car charging stations are still in the initial stage of practical application. The international standard for electric car charging systems is mainly IEC61851:2001 issued by IEC. The standard includes three parts, namely general requirements (part1), requirements for the connection of electric cars and AC/DC power supplies (part2-1), and electric cars and AC/DC charging stations (part2-2).
The lack of integrated technology for power supply, charging and storage battery system application and related standards and specifications is still the main weak link in the promotion and application of electric cars, which brings great difficulties to the next development of electric cars and the unified planning of charging facilities. There is no mature product for the charging station monitoring system that can ensure the normal operation of large-scale charging stations. There is no unified standard for the communication protocol and communication interface between the charging station monitoring system and the charger, and there is no information connection between charging stations.
②Standards for charging connectors for electric cars
1) CHAdeMO fast charging socket
CHAdeMO is the abbreviation of CHAdedeMove. It is a CHAdeMO socket supported by Japan’s Nissan and Mitsubishi Motors. CHAdeMO translates from Japanese and means “charging time is as short as a tea break”. This DC fast charging socket can provide a maximum charging capacity of 50kW. The CHAdeMO fast charging socket is shown in Figure 1.
Electric car models that support this charging standard include: Nissan Leaf, Mitsubishi Outlander plug-in hybrid, Citroen C-ZERO, Peugeot i ON, Citroen Berlingo, Peugeot Partner, Mitsubishi i-MiEV, Mitsubishi MINICAB-Mi EV, Mitsubishi MINICAB —Mi EV truck, Honda Fit electric version, Mazda DEMIOEV, Subaru Stella plug-in hybrid, Nissan eEV200, etc. Both Nissan Leaf and Mitsubishi i-Mi EV electric cars have two different charging sockets, one of which is suitable for the basic J1772 connector, and the other is for the CHAdeMO standard connector in Japan.
The fast charging method used by CHAdeMO is shown in Figure 2. The current is controlled by the car’s CAN bus signal, that is, while monitoring the battery status, it calculates the current value required for charging in real time, and sends a notification to the charger through the communication line. The fast charger receives the current command from the car in time and presses the specified value Provide current.
The battery management system monitors the battery status while controlling the current in real time, which fully realizes the functions required for fast and safe charging, and ensures that the charging is not restricted by the versatility of the battery. In Japan, 1,154 fast charging stations built in accordance with CHAdeMO standards have been put into use. In the United States, charging stations built with CHAdeMO standards have also been promoted. The latest data from the US Department of Energy shows that there are 1,344 CHAdeMO fast charging stations in the United States.
The advantages of CHAdeMO fast charging socket are: in addition to the data control line, the CHAdeMO fast charging socket also uses CAN bus as the communication interface. It has superior noise resistance and high error detection ability, communication stability, high reliability, and good charging safety records. Affirmed by the industry.
The disadvantages of CHAdeMO fast charging socket are: CHAdeMO fast charging socket was originally designed with a charging output power of 100kW, and the connector is very heavy, but the output power during charging is only 50kW.
2) Combo socket
The Combo socket can allow slow charging and fast charging of electric cars. It is currently the most widely used socket type in Europe. Audi, BMW, Chrysler, Daimler, Ford, GM, Porsche, and Volkswagen are all equipped with SAE (American Society of Automotive Engineers) Developed charging interface. This type of socket is also compatible with the Mennekes type. The Combo socket is shown in Figure 3.
On October 2, 2012, SAE committee members voted to pass the revised draft of SAE J1772 and became the only official DC charging standard in the world. The introduction of this standard is to change the status quo of mixed charging systems and enhance users’ enthusiasm for purchasing electric cars. The core of the standard for DC fast charging based on J1772 revision is ComboConnector.
The previous version of the standard (developed in 2010) clarified the specifications of the basic Jl772 basic AC connector used for AC charging, and the charging level is low (AC Level1 is for 120V, Level2 is for 240V). This basic connector has been widely used today and is compatible with Nissan Leaf, Chevrolet Volt, and Mitsubishi i-Mi EV electric cars. In addition to all the original functions, the Combo Connector in the new version of the J1772 standard formulated in 2012 also has two additional pins, which can be used for DC fast charging, but it is not compatible with the current production of old electric cars. This set of SAE standards comes from many major automobile manufacturers, so their goal is to hope that the charging time of this set of fast charging devices can be comparable to the refueling time, that is, when using DC charging, the charging can be completed within 10 minutes. This requires the charging station to provide a current with a voltage of 500V up to 200A.
The advantage of the Combo socket is: The biggest advantage of the Combo socket is that in the future, automakers can use a socket on their new models. It is not only suitable for the first generation of smaller basic AC connectors, but also for the second generation of smaller size. Large Combo Connector, the latter can provide both DC and AC current, charging at two different speeds respectively.
The disadvantage of the Combo socket is that the Combo socket needs the charging station to provide a maximum voltage of 500V and a current of 200A in the fast charging mode.
3) Tesla socket
Tesla has its own set of charging standards, which claim to be able to charge more than 300 kilometers in 30 minutes. Therefore, its charging socket can reach a maximum capacity of 120kW and a maximum current of 80A. The Tesla socket is shown in Figure 4. At present, Tesla has 908 super charging stations in the United States, and in China, Tesla has also established 7 super charging stations.
In order to better integrate into various regions, Tesla plans to abandon control of charging standards and adopt national standards of various countries.
Advantages of Tesla sockets: advanced technology and high charging efficiency.
Disadvantages of Tesla sockets: Contrary to the national standards of various countries, it is difficult to increase sales without compromise; after compromise, the charging efficiency will be compromised, and it is in a dilemma.
4) CCS standard charging socket
In order to change the current state of chaotic charging interface standards, the eight major American and German manufacturers Ford, GM, Chrysler, Audi, BMW, Mercedes-Benz, Volkswagen and Porsche released the “Combined Charging System” in 2012, which is “Combined Charging System”. CCS” standard.
The “joint charging system” can unify all current charging interfaces, and use one interface to complete four modes of single-phase AC charging, fast three-phase AC charging, household DC charging and ultra-fast DC charging. Both home and outdoor charging piles can use this type of charging socket (slow charging method) that can provide a maximum of 32A AC current. The CCS standard charging socket is shown in Figure 5.
SAE has selected the joint charging system as its standard. In addition to SAE, the European Automobile Manufacturers Association (ACEA) has also announced the selection of the joint charging system as the DC/AC charging interface, which will be used for all plug-ins sold in Europe from 2017. Electric electric cars. Since Germany and China unified the charging standards for electric cars, China has also joined the European and American camp, bringing unprecedented opportunities for the development of electric cars in China.
The advantages of the CEE standard charging socket: BMW, Daimler, and Volkswagen, the three German automakers, will increase their investment in electric cars in China, and the CCS standard is more beneficial to China.
Disadvantages of the CEE standard charging socket: electric cars that support the “CCS” standard, either have a small sales volume, or have just begun to sell.
5) GB/T20234 socket
In 2006, China issued the “General Requirements for Plugs, Sockets, car Couplers and car Jacks for Conductive Charging of Electric cars” (GB/T20234-2006). This national standard specifies charging currents of 16A, 32A, 250A AC. The connection classification method with 400A DC mainly draws on the standard proposed by the International Electrotechnical Commission (IEC) in 2003, but this standard does not specify the number of connection pins, physical dimensions and interface definitions of the charging interface. In 2011, China introduced the GB/T20234-2011 recommended standard, replacing part of the content in GB/T20234-2006, which stipulates: AC rated voltage does not exceed 690V, frequency 50Hz, rated current does not exceed 250A; DC rated voltage It does not exceed 1000V, and the rated current does not exceed 400A. The GB/T20234 socket is shown in Figure 6.
Advantages of GB/T20234 socket: Compared with the 2006 version of the national standard, more charging interface parameters have been calibrated in detail.
The disadvantage of GB/T20234 socket: the standard is still not perfect. In addition, it is only a recommended standard and is not enforced.
Auto companies in various countries have gradually realized that “standards” are the key factor that determines the development prospects of electric cars. In recent years, global charging standards have gradually shifted from “diversification” to “centralization.” However, in order to truly achieve uniform charging standards, in addition to interface standards, communication standards are also required. The former relates to whether the connectors are consistent, and the latter affects whether the plug can be energized. There is still a long way to go to unify the charging standards for electric cars, and car companies and governments of all countries need to further “liberate” before electric cars may have a future.