Elon Musk defends Tesla electric car after fire

Chris Woodyard | USA TODAY

Show Caption Hide Caption Tesla car fire video burns stock Tesla stock fell after reports of the electric cars catching fire after striking road debris

Elon Musk took to his blog to defend the Tesla Model S electric car

He says the fire during the week could have been worse if the car was conventional

He says the battery pack was pierced by a metal object with 25 tons of force

Tesla Motors CEO Elon Musk, never shy about personally blogging in defense of his company's electric car, has taken to the Web against in reaction to fallout over a video showing a Model S that caught on fire.

Musk's reaction comes as Tesla shares fell during the week after the video started receiving thousands of page views. After the video came to light, shares fell from $190 to a low near $168. But then they started to recover, rising $7.67 Friday to close at $180.98.

Musk's bottom line is the accident outside Seattle that caused the Model S sedan and its battery pack to go up in smoke would have been far worse had it been a conventional gasoline-powered car.

"Had a conventional gasoline car encountered the same object on the highway, the result could have been far worse," Musk, who is also CEO of rocket maker SpaceX, writes on Tesla blog.

Just as authorities have reported, he says the Model S struck a "large metal object" as it traveled at highway speeds. It went under the car and struck with a force "on the order of 25 tons." He says the estimate is based on the result: a 3-inch hole through armor plate that compromised the car's battery pack.

But from there, he says everything went as it should. The car's "onboard alert system" directed to the driver to stop and get out. The fire was contained by firewalls within the battery pack. Vents in the pack directed the flames down and away from the vehicle.

The fire department followed the correct procedure in trying to deal with the fire by puncturing holes in a protective plate and shooting water into the pack.

If the same accident had occurred under a conventional car, the thin metal shielding around the gas tank or tubing could have caused gasoline to pool and burn the entire car to the ground.

"In contrast, the combustion energy of our battery pack is only about 10% of the energy contained in a gasoline tank and is divided into 16 modules with firewalls in between. As a consequence, the effective combustion potential is only about 1% that of the fuel in a comparable gasoline sedan," Musk writes.

He says in comparison to 150,000 vehicles fires a year, Tesla has now had only one out of 100 million miles driven. "This means you are five times more likely to experience a fire in a conventional gasoline car than a Tesla!"