“Safety is a positive feedback concept. It is not that we emphasize safety. It makes everyone feel that electric vehicles are not safe. Electric vehicles are still emerging industries that need constant innovation. They need social tolerance and reduce vulnerability. Two security incidents scared consumers away. The head of the 100-member association said at the Media Forum of the Summer Forum and Electric Vehicle Safety Report on August 12th. Denso Spark Plug,Auto Iridium Spark Plug,Spark Plugs For A Car,Iridium Spark Plug For Car LIXIN INDUSTRIAL & TRADING DEVELOPING CO.,Ltd , https://www.kgvsparkplug.com
At the exchange meeting on the same day, Ouyang Minggao, vice chairman of the China Electric Vehicle 100-member Association and professor of automotive engineering at Tsinghua University, pointed out that the safety of electric vehicles involves three aspects.
First, the battery industry, which is the most basic and core battery safety field, requires strict thermal management; the second is the charging industry, which is an emerging industry, which needs further regulation, wireless charging will be the future direction; third is the whole vehicle In the industry, due to the strict safety verification of electric vehicles and the overall quality, enterprises still need to pay attention to high-voltage motor systems, crash tests and waterproof and dustproof processes.
However, due to factors such as excessive number of bus companies and short product development cycles, electric vehicles have greater safety risks and require major supervision. When asked whether the ternary battery was suspended or not, the OUYANG Minggao said that the relevant departments are currently developing relevant safety standards.
Thermal runaway needs to be carefully evaluated
Battery safety is temperature dependent. "Battery is different from other components such as the engine. As the temperature rises to a certain temperature, the battery will start to produce side reactions. The side reaction will interlock to form a battery exotherm. To a certain extent, the internal short circuit, the diaphragm collapse, and the electrolyte burns. The temperature rises rapidly and the heat is out of control. When it reaches the maximum temperature, it will form smoke, fire or even explosion." Ouyang Minggao said.
Among them, three characteristic temperatures need to be noted: one is “spontaneous heat onset temperatureâ€; the other is “thermal runaway onset temperatureâ€, such as short circuit, large-scale combustion; the third is “thermal runaway†maximum temperature, such as internal core. The temperature reaches 900 degrees or even close to 1000 degrees.
"The battery can only work normally within a certain temperature range. The temperature is high and it is not good. If it is low, the battery capacity will not be released, and it will not be charged. This is caused by the polarization of the battery. In short, the battery If you are cold, if the battery temperature is too low, it will not work properly. Under high temperature environment, the battery will not work normally. The normal working range is within 45 degrees. If the temperature reaches 90 to 100 degrees, the problem will be generated. Caused a series of 'self-generated heat reactions'." Ouyang Ming Gao said.
"But some materials systems are out of control. The maximum temperature is only three or four hundred degrees. Some batteries only smoke. This is very related to the battery material system. The battery temperature indicators of different systems are not the same," he explained.
Although the battery materials are different, there will be a "spontaneous heat onset temperature". At this temperature, the battery will form a side reaction, which is generally an exotherm.
The exothermic reaction causes an increase in temperature, which in turn causes another side reaction, causing the temperature to rise again, forming a chain reaction.
When the temperature reaches 150-250 degrees, thermal runaway will occur, such as diaphragm collapse, electrolyte burning, etc., up to 900 degrees or higher.
Ouyang Minggao further pointed out that lithium batteries have safety hazards due to their characteristics, but it does not mean that electric vehicles must be unsafe. Therefore, in order to prevent the battery from running out of control, strict thermal management is required, and the battery temperature is always kept within the normal range from three aspects of heating, heat dissipation and heat insulation.
The so-called heat dissipation, in short, is to use the cooling system to dissipate heat. This system design is very complicated, and there are air-cooling, water-cooling and other heat dissipation methods. When the temperature is low in winter, heating is required, but heating is a relatively difficult system. The so-called heat insulation is when a battery has a thermal runaway condition. When the problem is not serious, heat insulation is required to prevent the occurrence of firecrackers. The same one heats up one by one, and the first battery is thermally conducted to the next battery, forming a chain reaction.
Electric vehicles drive energy transformation
As the overall level of China's charging pile industry is relatively backward, the threshold for product entry is low and the quality is uneven. Ouyang Minggao believes that it is easy to cause safety problems when charging batteries, and fully charged electric vehicles are more prone to safety accidents.
"If there is a problem with the battery management system, the charging pile may not respond in time. If the battery overcharge reaches 150%, there will be a big accident, and the battery will often be charged to more than 100%. In the short term, there will be no big problem, but the battery will be used for a long time. Life and safety will be affected," Ouyang Minggao said.
In addition, in the charging industry, the efficiency of wireless charging is gradually increasing. Wireless charging is high frequency, and the new generation of semiconductor power electronics is suitable for high frequencies, so its energy efficiency is not much lower than the traditional charging method.
"The emergence of a new generation of power electronic devices has made the development of wireless charging technology leaps and bounds. Its efficiency is improving. The efficiency of traditional charging methods is more than 90%. Now the wireless charging efficiency can reach more than 90%." Gao said.
But in terms of cost, current wireless charging is higher than traditional batteries. However, wireless charging will be greatly improved in terms of security and convenience, which can be reflected in the charging experience.
"After a period of heavy rain, the main problem facing electric vehicles is that the charging port is raining. If you use wireless charging, you can avoid this problem. In addition, using wireless charging, you can get off the car and go straight away, just like the gas station self-fueling now. Convenient, after the demand for charging experience is high, it will definitely require wireless charging technology." Ouyang Minggao said.
In addition, the development and application of wireless charging technology depends on a new generation of power electronics, but also rely on precise positioning.
"It's not that people are going to position, but to integrate with the intelligence of the vehicle." Ouyang Minggao said, "So the next development direction is two-way, car network integration. So the technical change in the charging side will be by cable. To the development of wireless, from one-way charging to two-way feeding, the power grid sends power to the car, and in the future, the car can also send power back to the grid."
Electric vehicles have been criticized and not environmentally friendly, because the battery itself is powered by coal-fired power, which also emits a lot of carbon dioxide. However, Ouyang Minggao thought that the story was not finished.
"The third industrial revolution" is about the future of electric vehicles is the use of energy, energy storage, energy-receiving terminals, that is, electric vehicles are energy terminals, information terminals, and logistics terminals. In this direction, wireless Charging will play a very important role." Ouyang Minggao believes that this is the perfect ending of electric cars.
Similar to Tesla's recent acquisition of Solarcity, the largest home solar company in the United States, Musk's goal is to use solar energy to charge electric vehicles and store excess power for later use. “Every household is a power plant. If there is more electricity, users can sell electricity when the electricity price is right in the grid. If the electricity is particularly cheap, you can buy electricity. When the grid is charged, the grid can be charged. The electric car is discharged. So if the story is about this level, it will not be said that the electric car is not clean."
Ouyang Minggao believes that the energy transformation will be completed in another 30 to 40 years, and the current solar energy conversion efficiency has reached 30%. When the cost is slowly reduced, large-scale application will be realized. “Solar energy and wind energy are intermittent energy sources. The best way to store energy is to use batteries.â€