Reflection On Frequent Fires Of Electric Vehicles: Safety Standards Need To Be Speeded Up

A "fire" will be the recent momentum of the Xiaopeng car and the ideal car again "burning" hot search.

On August 11, a G3 car caught fire in Pazhou science and technology building in Haizhu District, Guangzhou. In the afternoon of the same day, Xiaopeng official response said, "after the company's personnel on-site preliminary investigation, the appearance of the vehicle is in good condition. After lifting and investigating in the store, it was found that the bottom of the battery box had obvious serious bumps and bruises, which led to serious damage to the battery. It was preliminarily determined that the cause of the accident was. It is worth mentioning that, behind the spontaneous combustion accident, it has just been three days since Xiaopeng auto officially submitted its IPO documents to the US securities exchange.

Coincidentally, the ideal car which has been on the market for a long time has also been exposed to fire accidents. On August 6, an accident occurred on an ideal one in Zhaoqing City, Guangdong Province, causing the vehicle to catch fire. Ideal official response said, "battery, range extender are normal. The cause of the accident was preliminarily determined to be that the suspected iron sheet was rolled up by the high-speed vehicle and penetrated the high-pressure oil pipe, causing fuel splashing and being ignited by high-temperature exhaust pipe. "

On August 13, a reporter from the 21st century economic report came to the smoke and fire area of Xiaopeng G3 and found no trace. A witness told reporters, "I don't know the cause of the accident, and suddenly smoke, growing bigger and bigger, and then the fire engine came and there was a small explosion." Another witness, Mr. Chen, told reporters: "at that time, the car stopped at the side of the road, and the owner seemed to be waiting for someone. As soon as the car started to smoke, the owner called the police, and soon the firemen and Xiaopeng's people came." Mr. Chen showed reporters the video he had taken at the scene. The white smoke was getting bigger and bigger.

The fire accidents of new energy vehicles occur frequently, and the quality problems emerge again. The problems behind them are more worthy of reflection.

Fire when the bottom is seriously bumped?

The reporter saw from the video circulated on the Internet that when the firemen arrived and laid the fire water bag, Xiaopeng G3 suddenly made two explosions, and the fire broke out from the bottom of the vehicle, and the crowd around kept a distance from the vehicle.

According to the official data of Xiaopeng, there are two versions of Xiaopeng G3. The g3520 version carries the Ningde era NCM 811 cell, with an energy density of 180wh / kg; the 400th version uses BIC or linkage Tianyi's cell. The specific model of Xiaopeng G3 and the type of battery used in the fire accident cannot be determined for the time being.

For the explanation given by the official of Xiaopeng automobile that "serious bumps and bruises lead to serious damage to the battery", netizens seem not to buy it: "bumping will cause fire? Didn't you test it before you left the factory? "

Indeed, Xiaopeng's explanation failed to answer the question that consumers are most concerned about - what degree of bumping will cause spontaneous combustion? And how to avoid this kind of collision?

"It is a special problem of electric passenger cars that the battery is injured by the collision of the chassis. We should take it seriously, prevent this kind of thing, and reduce the probability of this kind of thing to a very low level." On August 16, Wang Binggang, leader of the national new energy vehicle innovation project expert group, said in an interview with the reporter of the 21st century economic report.

Wang Binggang said that electric passenger car enterprises should seriously deal with the chassis collision problem, and can make efforts from three aspects: first, ensure the good passing characteristics of the chassis as far as possible in the design, and do not touch the obstacles when passing through the obstacles, and consider the selection of the actual parameters such as the minimum ground clearance and passing radius; second, the resistance between the battery pack framework and the shell in case of collision Third, we should formulate a reasonable test method to check through the actual test. The car is not a simple geometric object, and it is not enough to determine the design parameters only by calculation. When driving at a certain speed on the road, suspension and body will produce multi degree of freedom movement when passing through obstacles Some tests to check.

What is the reason?

As of the time of press release, the detailed analysis results of Xiaopeng's accident have not been released. It is worth noting that although the products of new forces of car manufacturing are frequently exposed to spontaneous combustion and other incidents, it is not only Xiaopeng and idealists who have quality problems with new energy vehicles.

According to the data of the State Administration of market supervision, in 2018, there were more than 40 fires of new energy vehicles, involving about 120000 defective vehicles of 33 models; in 2019, the average number of spontaneous combustion incidents of electric vehicles occurred every month, with brands involving Tesla, Weilai, Geely, Yundu and other brands; this year, GAC new energy, BYD, ideal, Xiaopeng and other brands had fire accidents, The quality problems of new energy vehicles have emerged.

The safety of electric vehicles can not be ignored. In many cases, the electric vehicle is a sudden fire without warning. At the same time, the fire speed is fast, the temperature is high, the spread is fast, it is easy to explode, and it is easy to damage the surrounding vehicles, resulting in huge losses.

In addition, every electric vehicle fire, broken axle and other "out of control" cases affect consumers' purchase intention and aggravate consumers' distrust of electric vehicles.

"Before half a year, my family was not interested in the spontaneous combustion of electric vehicles, but I was not interested in them." Mr. Qiao, a Zhengzhou citizen who is planning to buy a car recently, chose to give up starting electric vehicles.

In fact, the analysis of the cause of electric vehicle fire is more complex. The defective product management center of the State Administration of market supervision once said that the electric vehicle fire may be related to electrical circuit, fuel cell, mechanical interference and external fire source, and some evidence will disappear or change during the combustion process, so the defect investigation is very difficult and the cause analysis is extremely complex.

Overall, the direct cause of electric vehicle fire may be thermal runaway. "In addition to how the battery system can prevent thermal runaway due to external impact, another important fire factor is whether the safety margin is sufficient? Insufficient safety margin directly affects the safety of charging. " Wang Binggang said that overcharging is an important cause of battery thermal runaway. In order to pursue energy density and driving range, some products raise the rated charging voltage of the battery system very high, which may be a very important reason for fire during and after charging.

"At present, the causes of the whole new energy vehicle safety problem are complex, including internal factors and external factors. From the battery itself, we should make breakthroughs in the thermal stability of materials, high-voltage resistance and overcharge resistance of single battery, and focus on the prevention of thermal diffusion of the system from the aspect of system integration. At present, it is difficult to completely avoid the internal short circuit caused by the manufacturing of single battery. We can reduce the accident probability through the improvement of technology. " Meng Xiangde, assistant chairman of China New Energy Technology Co., Ltd., said on August 15, 2020.

Safety standards will be issued in succession

According to the data of CAAC, in July this year, the production and sales of new energy vehicles completed 100000 and 98000 respectively, with year-on-year growth of 15.6% and 19.3% respectively, ending a 12 month year-on-year decline and achieving the first year-on-year positive growth so far this year. Xu Haidong, deputy chief engineer of CAAC, predicts that the domestic new energy vehicle market will sell 1.1 million vehicles this year, of which Tesla will account for 100000.

However, before the large-scale market-oriented promotion of new energy vehicles, there are still many pain points. "These pain points are all related to the power battery. According to the analysis, the main factors affecting consumers' purchase are: too high cost; anxiety about mileage; weak environmental tolerance of battery; long charging time, which is very inconvenient compared with refueling; product safety, at present, the fire and spontaneous combustion accidents of new energy vehicles have been widely concerned, which has affected consumers' confidence in purchasing new energy vehicles. In addition, second-hand new energy vehicles are also used Compared with fuel vehicles, the residual value is very low. " Meng Xiangfeng said.

Safety issue has become the key to the development of new energy vehicle industry, and has attracted the attention of relevant departments and industries. In order to promote the research on safety technology, after investigation and planning, the China Automotive Engineering Society and the electric vehicle industry technology innovation strategic alliance plan to start the research project of electric vehicle safety series standards, and carry out more stringent research on electric vehicle and battery safety related standards.

"Under the current technical conditions, there is no absolutely safe battery, but the safety of new energy vehicles can be guaranteed through system design and the establishment of continuously improved standards." On August 16, Zhao Lijin, director of Technical Standards Department of China Society of automotive engineering, told reporters of the 21st century economic report that, focusing on the safety technology of electric vehicles and power batteries, the society of automotive engineering of China finally selected four topics to carry out research, namely, safety risk monitoring and fault warning specification (operation process / charging process) of electric vehicle battery system, and electric vehicle The general quality specification for power battery products, the falling test evaluation specification for pure electric passenger vehicles, and the requirements and test methods for the anti-collision capability of the bottom of pure electric passenger vehicles.

Among them, the general quality specification for power battery products of electric vehicles mainly studies and analyzes the relevant technical and quality requirements (safety, reliability, life, cascade utilization, quality index, etc.) of power battery products for electric vehicles, and studies and formulates the general quality specification for power battery products of electric vehicles; the anti-collision capability requirements and test methods for the bottom of pure electric passenger vehicles are mainly investigated The bottom impact condition and safety failure of electric passenger car are studied. The bottom impact test method of pure electric passenger car is studied, including test conditions, items, damage evaluation, etc.

Zhao Lijin told reporters that the project was officially launched in November last year, and the research contents and research results of the standard were refined from January to March this year, and participants and enterprises for research and development were collected from April to June in China, and some vehicle enterprises and parts enterprises actively participated in the project. At present, the research work has started. It is expected that the first draft of the standard will be made by the end of this year, and further comments will be solicited next year. It is expected that it will be officially released as the group standard of China Society of Automotive Engineering (CSAE) by June next year.

"The last two (i.e. the evaluation specification for the drop test of pure electric passenger cars and the requirements and test methods for the bottom anti-collision capability) are relatively large in engineering quantities. In order to make a scientific and authoritative standard, each vehicle may prepare at least 10 vehicles for test verification."

Zhao Lijin finally told reporters, "we should not only do the test method well, but also refine and put forward the specific requirements after the test, so that many vehicle enterprises can refer to the method and requirements to do the test."