Elon Musk : Electrons Are Less Flammable Than Gasoline

Elon Musk sent out his official response to a Tesla Model S catching fire this week, and, in typical Muskian fashion, it's logical, reasoned, and a tad bit combative. Which is probably how he should have responded.

His post on the Tesla website begins with some insight into how the fire actually started, including what that strange "metallic object" was that actually managed to puncture the armored underbody of the car:

A curved section that fell off a semi-trailer was recovered from the roadway near where the accident occurred and, according to the road crew that was on the scene, appears to be the culprit. The geometry of the object caused a powerful lever action as it went under the car, punching upward and impaling the Model S with a peak force on the order of 25 tons. Only a force of this magnitude would be strong enough to punch a 3 inch diameter hole through the quarter inch armor plate protecting the base of the vehicle.

From those facts alone it's almost incredible that a conflagration was the worst that happened. Most cars don't have armor plate on the bottom, and if a lever action had forced a sharp piece of metal through the passenger compartment you could be reading a much different story right now.

The downward-facing vents in the battery packed forced the resulting flames down towards the roadway and away from the vehicle, as designed, but firefighters failed to follow Tesla procedure in extinguishing the fire. Instead of just pouring water on the battery, they punctured holes in the pack which enabled the flames to vent upward and into the front trunk area.

Musk then goes on to tout the inherent safety of the Model S battery pack design, but the real kicker is his point about driving a car powered by gasoline:

For consumers concerned about fire risk, there should be absolutely zero doubt that it is safer to power a car with a battery than a large tank of highly flammable liquid.

Gasoline, in case you've never actually encountered a car before in your entire life in which case it is very impressive that you not only found a computer but then directed it to Jalopnik so a hearty bravo to you, catches fire. And, as we've tragically seen time and time again, gasoline-powered cars catch fire.

We've noted before that the drop in Tesla's share price that resulted from the news of the fire was in part because the technology used is so new, and that it's not like Ford's stock drops every time one of their vehicles catches fire.

To Musk's credit, the company also posted an e-mail from the owner of the Model S that caught fire, and he didn't seem too upset by the whole thing:

Mr. Guillen,

Thanks for the support. I completely agree with the assessment to date. I guess you can test for everything, but some other celestial bullet comes along and challenges your design. I agree that the car performed very well under such an extreme test. The batteries went through a controlled burn which the internet images really exaggerates. Anyway, I am still a big fan of your car and look forward to getting back into one. Justin offered a white loaner—thanks. I am also an investor and have to say that the response I am observing is really supportive of the future for electric vehicles. I was thinking this was bound to happen, just not to me. But now it is out there and probably gets a sigh of relief as a test and risk issue-this "doomsday" event has now been tested, and the design and engineering works.

rob carlson

I guess we can all get back to our electric future now.

Reprinted below is Musk's post, in full:

Model S Fire

By Elon Musk, Chairman, Product Architect, and CEO

Earlier this week, a Model S traveling at highway speed struck a large metal object, causing significant damage to the vehicle. A curved section that fell off a semi-trailer was recovered from the roadway near where the accident occurred and, according to the road crew that was on the scene, appears to be the culprit. The geometry of the object caused a powerful lever action as it went under the car, punching upward and impaling the Model S with a peak force on the order of 25 tons. Only a force of this magnitude would be strong enough to punch a 3 inch diameter hole through the quarter inch armor plate protecting the base of the vehicle.

The Model S owner was nonetheless able to exit the highway as instructed by the onboard alert system, bring the car to a stop and depart the vehicle without injury. A fire caused by the impact began in the front battery module – the battery pack has a total of 16 modules – but was contained to the front section of the car by internal firewalls within the pack. Vents built into the battery pack directed the flames down towards the road and away from the vehicle.

When the fire department arrived, they observed standard procedure, which was to gain access to the source of the fire by puncturing holes in the top of the battery's protective metal plate and applying water. For the Model S lithium-ion battery, it was correct to apply water (vs. dry chemical extinguisher), but not to puncture the metal firewall, as the newly created holes allowed the flames to then vent upwards into the front trunk section of the Model S. Nonetheless, a combination of water followed by dry chemical extinguisher quickly brought the fire to an end.

It is important to note that the fire in the battery was contained to a small section near the front by the internal firewalls built into the pack structure. At no point did fire enter the passenger compartment.

Had a conventional gasoline car encountered the same object on the highway, the result could have been far worse. A typical gasoline car only has a thin metal sheet protecting the underbody, leaving it vulnerable to destruction of the fuel supply lines or fuel tank, which causes a pool of gasoline to form and often 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.

The nationwide driving statistics make this very clear: there are 150,000 car fires per year according to the National Fire Protection Association, and Americans drive about 3 trillion miles per year according to the Department of Transportation. That equates to 1 vehicle fire for every 20 million miles driven, compared to 1 fire in over 100 million miles for Tesla. This means you are 5 times more likely to experience a fire in a conventional gasoline car than a Tesla!

For consumers concerned about fire risk, there should be absolutely zero doubt that it is safer to power a car with a battery than a large tank of highly flammable liquid.

– Elon