Investigation concludes fire in BYD e6 collision caused by electric arcs from short circuit igniting interior materials and part of power battery
An investigation into the cause of the fire involving a BYD e6 electric taxi resulting from a fatal traffic collision in China earlier this year (earlier post) concluded that electric arcs caused by the short-circuiting of high voltage lines of the high voltage distribution box ignited combustible material in the vehicle including the interior materials and part of the power batteries.
In the accident, a driver crashed a Nissan GT-R into a BYD e6 electric taxi, and then collided with a separate gasoline taxicab. The e6 hit a tree before bursting into flames; the 3 occupants of the e6 were killed in the crash.
The investigating team—comprising 13 experts from specialized technical institutions including China Automotive Technology and Research Center, Research Institute of Highway Ministry of Transport, Tianjin Fire Research Institute, Fire Brigade of Guangdong Province and North Vehicle Research Institute and Shenzhen Academy of Metrology and Quality Inspection—found no flaws in the safety design of the vehicle, according to the summary of results released by BYD.
In early June 2012, the Shenzhen Academy of Metrology and Quality Inspection was authorized by its supervising authority to organize the work related to quality examination on the electric taxi involved in the accident on 26 May. The team began a special quality investigation focused on five areas: the complete car; the collision; power battery; fire; and traffic accident investigation. The investigating team concluded that:
The sports car involved in the accident was travelling at the approximate speed of 242 km/h (150 mph). Although the vehicle decelerated as a result of braking, it still severely collided with the e6 electric taxi in front of it, which was going at the approximate speed of 81 km/h (50 mph) in the same direction, at a speed of 183 km/h (114 mph). At the time of collision, the relative or difference in speed of the two vehicles exceeded 100 km/h (62 mph). After the collision, the e6 electric taxi lost control and skidded to the right front, and its rear hit a big tree on the road side leading to a serious column collision. The extent of intrusive damage reached 1050 mm, resulting in the damage to the e6 electric taxi, killing 3 people and burning the vehicle. The type and severity of the accident was extremely rare.
In the course of the two serious collisions, the bodies of the three passengers inside the e6 electric taxi “suffered severe damage which exceeded the endurance limit of human bodies.” The collisions inflicted fatal injuries on the three passengers.
As a result of the two severe collisions, the rear end of the e6 and its battery compartment were seriously deformed, and the power battery pack and high voltage switchbox were severely compressed, causing damage to part of the power batteries and short-circuit. High voltage lines of the high voltage distribution box and the body of the car short-circuited, producing electric arcs which ignited the combustible material including the interior materials of the vehicle and part of the power batteries.
The e6 electric taxi is one of the products in the State Vehicle New Products Announcement catalogue which has passed the tests conducted by the relevant state testing authorities, including tests in connection with vehicle collision safety, electric system safety and battery safety, and complies with the relevant national standards and requirements.
In the accident, the power batteries of the vehicle did not explode, and 72 single cell batteries (accounting for 75% of the 96 power batteries) did not catch on fire. The designs of the battery system in relation to the installation layout on the vehicle, the insulation protection and the high voltage system are reasonable, according to the investigators. No flaws in the safety design of the vehicle were revealed.
Further, part of the aluminum alloy casing and battery plate of 24 single cell batteries (accounting for 25% of all the power batteries) was burnt by fire but the setting of battery plate remained well-arranged and there were no cracks apparent.