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More combustible than oil trucks? Battery technology route is key after an electric car burns instantly after collision, experts say

via:新浪科技     time:2023/6/6 8:02:20     readed:176

Cui Dongshu, secretary general of the Association, said to The Times finance that new energy vehicles are not more prone to spontaneous combustion than fuel vehicles, extreme events are caused by extreme causes, and now fuel vehicle accidents are relatively few people concerned, electric vehicle attention is particularly high, which is the product difference brings different attention.

The safety issue of new energy vehicles has once again triggered hot discussion.

According to the Hangzhou Public Security Bureau expressway traffic police detachment on June 5, 2023, A small ordinary bus with Zhejiang A license plate along the S2 Shanghai-Hangzhou expressway driving out of Hangzhou toll station, collision toll station facilities and fire, resulting in four deaths. At present, the public security authorities are further investigating the accident.

According to several media reports, the accident vehicle is suspected to be a joint venture brand pure electric model. According to the network surveillance footage shows that the accident vehicle is about to arrive at the toll station, the speed did not significantly reduce, but at a higher speed straight into the toll station platform. After a severe crash, parts of the vehicle flew everywhere, and then smoke came out of the body of the vehicle, and a few seconds later there was an open fire, and the fire quickly grew larger in a very short time.

碰撞后起火的新能源汽车 | 图源网传视频截图New energy cars caught fire after collision | figure source network video screenshots

Although the investigation into the accident is still ongoing, it has sparked heated public debate over the safety of new energy vehicles.

On June 5, Wang Hai, a senior industry insider, told Times Finance that the power battery of new energy vehicles has a high voltage inside. When the car has a violent collision, it is easy to cause the wiring harness, high voltage parts, battery cells and so on to fall off and dislocation, and the whole battery shell will be deformed, which is easy to cause positive and negative short circuit. This leads to a series of thermal runaway, thermal diffusion, and fire.

Zheng Kun, an engineer at the Fifth Institute of Electronics of the Ministry of Industry and Information Technology, analyzed in Environmental Technology that the safety problems of lithium-ion power batteries, which are high energy carriers, mainly focus on combustion or explosion. When lithium batteries short-circuit for some reason (mainly caused by abuse of high temperature, extrusion, overcharge and other conditions, or aging and manufacturing defects), the internal temperature will rise. Battery anode and cathode, electrolyte, diaphragm will occur chemical reaction, produce a lot of heat and gas, the battery itself thermal management is out of control, when the accumulation to a certain degree will cause the battery fire.

Other public information shows that, different from fuel vehicles, the pipelines in new energy vehicles are more complex, with more combustible materials. In the state of free combustion, the pipelines will last for about 90 minutes, and it may spread to the surrounding flammable objects, and the process is accompanied by the irritating smell of smoke. In addition, after the external open flame is extinguished, new energy vehicles are also prone to repeated reignition.

警情通报 | 图源网络Police blotter | figure source network

It is worth paying attention to that, in recent years, with the continuous expansion of new energy vehicle sales scale and ownership scale, more and more accidents of spontaneous combustion and fire after collision of new energy vehicles, especially pure electric vehicles. According to public information, the data of new energy vehicle fire accidents released by the Ministry of Emergency Management in the first quarter of 2022 show that there were more than 600 new energy vehicle fire accidents in the first quarter of 2022, with an average of more than 7 cases of fire accidents per day. The number of new energy vehicle fire accidents increased by 32% in the first quarter of 2022 compared with the same period in 2021, higher than the average increase of 8.8% in vehicle fire accidents.

So, with a large capacity battery of new energy vehicles, is it more prone to fire than traditional fuel vehicles, spontaneous combustion?

Song Jian, a professor at Tsinghua University's School of Vehicle and Delivery, said in a previous interview that the tendency to catch fire after a crash is a characteristic of new-energy electric vehicles. According to Song, fuel tanks and batteries work differently. The tank is a system closed to the outside world, so as long as the oil does not leak out, there will be no fire. Battery is different, its own both oxidant and combustible substances, once the fire consequences serious. "The battery doesn't need to be knocked out, it just needs to have a big enough impact to have the potential to catch fire."

On June 5, Cui Dongshu, secretary general of the Board, said to The Times finance that new energy vehicles are not more prone to spontaneous combustion than fuel vehicles, extreme events are caused by extreme causes, and now fuel vehicle accidents are relatively few people concerned, electric vehicle attention is particularly high, which is the product difference brings different attention. Previous research data shows that the accident probability of new energy vehicles is lower than that of fuel vehicles, and electric vehicles are generally safe.

Wang Hai, for his part, believes that the tendency to catch fire after a crash is characteristic of part of the power battery technology route, not the entire electric vehicle. As long as the thermal management and insulation of the power battery is done well, it is rare to see a large area fire, an entire power battery or a car catching fire, but more likely a single battery module is burned out, and fires can occur after a fuel car crash.

It is worth mentioning that the monthly sales and ownership scale of new energy vehicles are getting larger and larger. At this stage, safety is the top priority for the development of new energy vehicle industry, and all parties should try their best to reduce the occurrence of extreme events. Fu Bingfeng, executive Vice president and secretary general of China Association of Automobile Manufacturers, also said that all enterprises in the new energy vehicle industry chain should attach great importance to the safety of new energy vehicles, actively assume the main responsibility for the safety of new energy vehicles, do a good job in safety supervision and maintenance testing, establish and improve safety control and emergency handling mechanism, and timely discover and eliminate hidden dangers.

On June 5, the latest information released by the China Passenger Union showed that its comprehensive estimate of the wholesale sales of new energy passenger car manufacturers in May was 670,000 units, an increase of 11% month-on-month and 59% year-on-year. The China Passenger Federation predicts that in 2023, the sales volume of new energy passenger vehicles in China will be 8.5 million, and the sales volume of narrow passenger vehicles will be 23.5 million, and the annual penetration rate of new energy vehicles is expected to reach 36%.

In view of the extreme events caused by the thermal runaway of new energy vehicles in recent years, Wang Hai said that to avoid tragedies as much as possible, on the one hand, enterprises should go to a higher technological direction; In addition, there are many scenarios of power battery fire, such as spontaneous combustion after charging, static combustion, spontaneous combustion after soaking in water, spontaneous combustion after collision, etc. Manufacturers or automobile companies can consider writing the above scenarios into the battery or vehicle as a form of code, so as to actively eliminate the above scenarios as far as possible and reduce the occurrence of extreme events. Cui Dongshu believes that, on the one hand, safe driving, consumers should be responsible for their own safety, on the other hand, enterprises should also consider how to let consumers escape after extreme events, such a serious incident will not occur, all parties should on the current basis, as far as possible to increase safety protection.

For the relevant characteristics of new energy vehicles themselves, the relevant departments also have corresponding requirements. According to public reports, in January 1, 2021 from the implementation of the "safety requirements for electric vehicles", "safety requirements for electric buses" and "safety requirements for power batteries for electric vehicles" three mandatory national standards for electric vehicles, especially added the battery system thermal diffusion test, the battery system requires that after the occurrence of thermal loss of battery cells, no fire or explosion within 5 minutes, Allow time for passengers to escape safely.

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