Feb 15, 2020
Ordinary people think that electric vehicle charging is just like mobile phone charging, just plug it in, but in fact, the charging process of electric vehicle is much more complicated than that of ordinary household appliances. The first is the physical interface, which can’t be determined at will. The charging power of electric vehicles is relatively large, and there are communication requirements, so the charging interface of electric vehicles is much more complex than that of ordinary sockets: there are not only channels for transmitting current, but also channels for communication. In addition, because of the high charging power, it is easy to cause overheating and fire in the high current transmission, so there must be a standard for this interface. There are specifications for the specific size of the interface. Generally, there will be no case that the interface cannot be plugged in, but plugging in does not necessarily mean that it can be used normally. In order to use the interface normally, four types of performance are required: 1. Universality, to see whether the tolerance meets the standard, and whether different brands of things can be inserted; 2. Mechanical structure; 3. The material characteristics of the interface itself, such as corrosion resistance, fire resistance and heat resistance; 4. Motor test after power connection. The old national standard “connection device for conductive charging of electric vehicles” was issued in 2011 and implemented since March 2012, including general requirements, AC charging interface and DC charging interface. In fact, this is a more detailed standard, which specifies the use identification, temperature, structural requirements, plug-in force, mechanical strength and rolling of vehicles in detail. The DC and AC charging interface and signal logic are also described. Since the standard was issued at the end of 2011, it has played an important role in regulating and guiding the design, production and charging infrastructure construction and operation of electric vehicles. However, when the charging interface standard is specified, there are not many electric vehicles on the market, and there is not much practical experience. Therefore, some terms and technical details of the charging interface and communication protocol standard are not specified in detail. For some key parameters, several choices are often given, and the standard does not limit them, but gives recommended values. As a result, electric vehicle manufacturers and charging pile manufacturers often act on their own in detail. The result is that in the process of application, there is a problem that different vehicles and charging facilities are not fully compatible. Everyone’s products meet the charging interface standard. The plug and interface look the same, but they are not compatible. One brand of charging pile can only charge their own car, and other brands of cars can not be charged when they are taken over. The standard is not standard, the result is that the standard is meaningless. Just like we can’t use 110V circuit when we go abroad with 220V equipment, we can plug it in, but we can’t use it. This brings confusion to the manufacturers of charging piles and reduces the number of actual charging piles. There are three charging piles in one block of Mingming, and as a result, there is only one electric vehicle in Jianghuai. For the cars in Jianghuai, there is only one block, so the charging resources are greatly reduced, and the remaining charging piles are also a waste. Therefore, in 2014, the National Standards Commission officially issued the standard revision plan, and the automobile industry and the power industry cooperated to carry out many discussions and tests, so as to solve the compatibility problem. Compared with the old standard, the new standard has many improvements, including improving the voltage and current level, thus improving the charging power, shortening the charging time, adjusting the size of the signal pin and the mechanical lock, optimizing the connection sequence, clarifying the requirements of the electronic lock, and improving the charging safety But the most important change is in communication. The old standard only specifies the definition of different signals, while the new standard not only specifies the definition, but also specifies the transmission rate under various states, the determination of message timeout, the determination of maximum current output, as well as the failure and the end of message transmission. The new standard specifies that the communication rate between motor and BMS is 50 kbit / s and 250 kbit / s. However, the old standard only recommended a speed and did not enforce it. We still can’t confirm whether the transmission rate is not uniform when the electric vehicle shakes hands with the charging post, which causes the charging ports of various manufacturers to be incompatible and the charging fails. But it can be confirmed that the new standard is more detailed in terms of signal. Therefore, in addition to some minor upgrades, the biggest significance of the introduction of the new national standard is to solve the compatibility problem by further refining the regulations. The charging piles and vehicles made according to the new national standard can be interconnected regardless of brands. In the future, the charging of electric vehicles on the charging piles will be as convenient as that of mobile phones.