A monthlong investigation found no design defects on the all-electric taxi involved in a fatal accident that caught fire and claimed three lives on May 26.
The report by a 13-member investigation team said that 25 percent of the 96 battery units in the taxi - an E6 all-electric car made by Shenzhen-based automaker BYD - burned in the accident but didn't explode.
"The car's battery system was appropriate in terms of installation and layout, insulation and the design of the high-voltage electricity system," Wu Zhixin, head of the investigation team, told reporters on Friday.
However, the batteries and the high-voltage distribution box in the taxi were seriously damaged after two major crashes that resulted in short circuits, which caused the fire that made two holes in the car's roof, Wu said.
The taxi was hit in the rear left tire by a Nissan GTR sports car at about 242 kilometers/hour at around 3 am.
"The sport car's speed was reduced after the emergency brakes were activated but it remained at a level between 183 and 195 km/h when the collision happened," Wu said.
After it was hit by the sports car, the taxi, completely out of control, crashed against a tree at the roadside in 3.5 seconds, Wu added.
The investigations found that the victims were killed by the crashes rather than by the fire as some people had suspected.
"The accident was cruel and rare. Our virtual tests showed that both crashes were fatal to the taxi driver and the two passengers in the rear seat," Wu said.
The results from the second virtual test - when the taxi hit the tree - showed that the Head Injury Criterion, a major measure for the risk of head injuries in car accidents, stood at about 5,000 for the driver, roughly 8,000 for the passenger in the rear left and more than 4,200 for the other passenger in the rear right.
According to a standard accepted in Europe, a figure over 1,860 indicates that the car's occupants couldn't have survived the accident, Wu said.
In a reaction to the suspected explosion noises allegedly heard in some video clips of the crash, Wu said that some of the noises were from the rescue personnel when breaking the car windows, while the rest were caused when the safety valves of the batteries were activated.
The investigation was organized by the Shenzhen Academy of Metrology & Quality Inspection.
The deadly accident aroused concerns over the safety of all-electric cars, especially in the city of Shenzhen, where about 300 units of E6 taxis are in operation.
It also sounded a note of caution among some in the global auto industry as an increasing number of automakers are starting to build electric cars and plug-in hybrid cars, most of which rely on technology similar to the one used in BYD's vehicles.
