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Fires caused by thermal runaway and the subsequent recall of new energy vehicles are becoming an important cause of new energy vehicle recalls.

According to data from Dr. Xiao Lingyun, head of the High-tech Products and Quality Assurance Institute of the Defective Product Recall Technology Center of the State Administration for Market Regulation, by the end of 2023, China had implemented a total of 2,842 automobile recalls, involving 103 million vehicles. Among them, there were 268 recalls of new energy vehicles, involving 5.7 million vehicles, and 81 recalls directly related to fires.

Battery thermal runaway is one of the main causes of fires in new energy vehicles. This phenomenon is usually manifested as a sharp rise in battery temperature during vehicle use, which is difficult to control. The internal causes of this situation may include internal short circuits, aging, overcharging or over-discharging of the battery, and external causes may involve collisions, extrusions, external short circuits, and external heating.

Further analysis shows that among the more than 270 new energy vehicle fire cases disclosed last year, only about 10% of them were caused by collision, while more than 50% of them were caused by fire during charging or static state. This data emphasizes the fire risk in non-collision situations, especially the risk closely related to battery thermal runaway.

In order to further study and solve this problem, the China Automotive Engineering Research Institute and the Tianjin Fire Research Institute of the Ministry of Emergency Management jointly established a joint research laboratory for automobile fire safety. The laboratory conducted a detailed analysis of new energy vehicle fire incidents in recent years.

The research results show that in addition to factors such as traffic accidents and bottom collisions, battery thermal runaway is one of the most relevant causes of battery fires. These research results provide an important scientific basis for formulating effective fire prevention measures.

According to the Xin Kuaibao report, statistics on the number of new energy vehicles and fires in China in the past three years show that the fire rate of new energy vehicles has dropped from 1.85/10,000 in 2021 to 0.96/10,000 in 2023, showing a significant improvement in safety. In contrast, the fire rate of fuel vehicles remains at around 1.5/10,000. It is generally believed in the industry that the improvement in the fire rate is attributed to the continuous research and improvement of battery thermal runaway issues.

Safety use guidance is also considered an important part of electric vehicle safety management. Improper use behaviors such as the bottom of the vehicle being supported or scratched, and long-term soaking in water, may trigger thermal runaway of the power battery. Therefore, strengthening the use guidance of electric vehicles is crucial to preventing fires.

In 2020, the Ministry of Industry and Information Technology promulgated three mandatory national standards for electric vehicles, including a thermal diffusivity test for battery systems, requiring that after a battery cell has thermal runaway, the battery system must not catch fire or explode within 5 minutes to ensure that occupants have sufficient time to escape.

On July 15, 2024, the China Consumer Product Quality and Safety Promotion Association issued the group standard "Electric Vehicle Safety Assessment Method Part 1: Vehicle Thermal Diffusion Protection". The standard focuses on battery thermal runaway and has formulated 11 specific indicators covering four key dimensions: safety tips, emergency rescue, fire protection, and data linkage.

Min Zhaoyuan, director of the National New Energy Vehicle Quality Inspection and Testing Center (Chongqing), pointed out that this evaluation method comprehensively and objectively evaluates the safety performance of the vehicle in the event of thermal runaway from four dimensions, how to extend the escape time of passengers, and whether key components such as doors can be opened normally after thermal runaway occurs to ensure that passengers can escape smoothly.

It should be noted that the assessment of the Consumer Promotion Association is currently in the public stage of the first part, which means that as the market share and ownership continue to increase, the safety assessment of electric vehicles will still be a process of continuous updating and further refinement.

Relevant experts also pointed out that the details of the battery's protection capabilities need to be further explored in the future. For example, in a collision accident, can the mechanical protection function of the battery pack effectively prevent the battery from being squeezed? In addition, the structure and materials of the battery itself also need to be continuously innovated and optimized to improve the overall safety level.