The vision of a car ablaze is startling. As the number of hits on the burning Tesla video climbed over two millions, people inevitably began to raise safety concerns. Elon Musk, the founder of Tesla Motors, responded on the company's blog with some facts about the damage sustained in the accident, the construction of the vehicle's battery, and the resulting fire.
Musk explained that damage to the armor plating on the bottom of the vehicle was inflicted by contact with debris of a specific shape that resulted in a lever action, puncturing the bottom of the Model S. He noted that 25 tons of force would be required to make the three-inch-deep puncture in the quarter-inch-thick armor plating.
Don Sadoway, a professor of materials chemistry at MIT and a leading advanced battery technology and energy storage expert, says that this event is incredibly rare. "Large format batteries are not intrinsically problematic and can be made to stand up to abuse, and I view this situation as an outlier event. The chances of running over something that actually punctures the underbelly of a car are small."
Upon detecting the puncture, the car's control system warned the driver to pull over and exit the vehicle, which he did without injury. At that point, fire broke out in one of the car's 16 battery modules. Musk pointed out, "At no point did fire enter the passenger compartment." This statement was true even after fire department personnel punctured the firewall in order to allow the fire to spread upwards, as seen in the video.
To further relieve fears of battery fires, Musk went on to compare the combustion potential of the Model S battery system to a typical internal combustion engine. "In contrast, the combustion energy of our battery pack is only about 10 percent of that contained in a gasoline tank and is divided into 16 modules with firewalls in between," he noted on the blog. "As a consequence, the effective combustion potential is only about 1 percent that of the fuel in a comparable gasoline-powered sedan."
Citing the National Fire Protection Association's statistics, Musk explained that combustion engines currently experience fires at a rate of one fire per 20 million miles driven. In contrast, Tesla has shown one fire per 100 million miles driven.
Sadoway agrees with that assessment, and says that this incident should not be a deterrent to adoption rates. "Unfortunately, we do see cars catch fire. There are accidents regularly where you see highly volatile fluids pouring out onto the road and catching fire. That doesn't stop people from buying them though. If you open the newspaper and see that there was a collision and that one car caught fire, you might say, 'Wow, that is too bad,' then go out and hop into your car and drive. If it is new technology that it happens to, people pay more attention.
"From my perspective, the bigger problem with lithium batteries is the cost. You don't see them widespread because the cars that are purely electric right now are far too costly to appeal to the general public. They won't have that attraction until we get one on the showroom floor for a total less than 20 thousand dollars.