Tesla Motors Issues Official Statement on Model S Fire


Model S Fire

Model S Fire

Well, that didn’t take long.

Just moments ago, Tesla Motors issued its official statement on the recent Model S fire.

Below you’ll find the statement in its entirety, as well as a couple of back and forth emails between the Model S owner and Tesla.

Let the speculation now end…

Model S Fire

By Elon Musk, Chairman, Product Architect & 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

Below is our email correspondence with the Model S owner that experienced the fire, reprinted with his permission:

From: robert Carlson
Sent: Thursday, October 03, 2013 12:53 PM
To: Jerome Guillen
Subject: carlson 0389

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

On Oct 3, 2013, at 12:29 PM, Jerome Guillen wrote:

Dear Mr. Carlson:

I am the VP of sales and service for Tesla, reporting directly to Elon Musk, Tesla’s CEO.

I am sorry to hear that you experienced a collision in your Model S 2 days ago. We are happy that the Model S performed in such a way that you were not injured in the accident and that nobody else was hurt.

I believe you have been in contact with Justin Samson, our service manager, since the accident. We are following this case extremely closely and we have sent a team of experts to review your vehicle. All indications are that your Model S drove over large, oddly-shaped metal object which impacted the leading edge of the vehicle’s undercarriage and rotated into the underside of the vehicle (“pole vault” effect). This is a highly uncommon occurrence.

Based on our review thus far, we believe that the Model S performed as designed by limiting the resulting fire to the affected zones only. Given the significant intensity of the impact, which managed to pierce the 1/4 inch bottom plate (something that is extremely hard to do), the Model S energy containment functions operated correctly. In particular, the top cover of the battery provided a strong barrier and there was no apparent propagation of the fire into the cabin. This ensured cabin integrity and occupant safety, which remains our most important goal.

We very much appreciate your support, patience and understanding while we proceed with the investigation. Justin keeps me closely informed. Please feel free to contact me directly, if you have any question or concern.

Best regards,
Jerome Guillen I VP, WW sales and service

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39 Comments on "Tesla Motors Issues Official Statement on Model S Fire"

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“Vents built into the battery pack directed the flames down towards the road and away from the vehicle.”

Ironically, this safety feature made the fire appear much more spectacular from the outside. If a gas car were to have external flames like this, imagine what would be going on within the passenger compartment!

Well played, Tesla.

I think the fines and penalties for people that allow stuff to fall onto the roads should be raised dramatically! We are talking about people’s lives at stake!

Seriously. Punched the car with 25 tons of force? Holy smokes, that alone could kill someone.

25 tons isn’t as much as you’d think considering the situation. Basically it was the shape of the object which allowed the forward motion of the car to be converted into upward motion of the metal object. Kind of like when a person steps on a rake and the handle flies up and hits them in the face. Only, in this case it was the opposite. Instead it would be like pushing against the rake handle and having the rake push up into your foot. Had it been a human being, the human would have probably just been pushed out of the way, causing minor blunt force trauma. But since the model-S is pretty heavy and not designed to have the weight of the car lifted from a tiny area on the battery pack, well.. a puncture was the only option the forces of nature allow.

My question, if the puncture (which is greater than a 1/4″ to puncture a battery pack and a cell) occurs at an angle what force extracted the metal object with an apparently opposite force vector?

It sounds like the car “rolled over” the object, so presumably the continuing forward motion “removed” the object after the initial damage was done (or, who know’s perhaps even did more damange on the way out). In any case, it certainly seems plausible that it could take much more force to first puncture the battery pack’s steel plate than to remove the object from the resulting hole.

Again, I have experienced this with a rock in the road with my Miata. That rock was perhaps only 2″ higher than the underplate of my car, but there was nowhere for the rock to go, and it didn’t shatter. The result was the car being lifted off the ground, and the engine cross plate, an X shaped plate under the engine, being destroyed.

Who says it is steel? They said it was “armor” but the battery box is aluminum. A 1/4″ steel plate would be hundreds of pounds and be affected by road salts. Aluminum is not. Surely it is hardended aluminum but hardly “Armour” in the proper use of the term when speaking of armour you might install on a HumVee army vehicle sent into a battle zone or to protect from IEDs.

I disagree. As a physicist and engineer, I have a good understanding of how leverage could create 25 tons of force in the situation. However, if that had hit directly under a passenger (who presumably is buckled in, with no place to go), it could have been much more ugly. Or what if it had kicked up to a motorcycle riding in the next lane?

You better believe a direct hit with 25 tons would kill someone!

Dr. Kenneth Noisewater

Indeed, it’s not pretty when, say, a motorcycle goes around a corner and plows into a mattress in the left lane. I almost ran into one on the Ben Franklin bridge in Philly a few years back, luckily I was able to swerve and recover to avoid it..

Wow, that was a super quick and in-depth investigation by an independent party. Not.

I wonder what kind of napkin the 25 tons of force calculation was done on?

It seems Tesla is too quick to move past this event rather than studying it and learning from it. Even GM made design changes after a one-off event with the Volt.

The least Tesla could do is allow an actual investigation to occur then make an assessment.

The full investigation is ongoing…we’ll have more to report on that soon

“I wonder what kind of napkin the 25 tons of force calculation was done on?”

They calculated the force required to pierce the bottom plating. Since this pierced it then it must have hit with that amount of force.

“….They calculated the force required to pierce the bottom plating. Since this pierced it then it must have hit with that amount of force……”

You would think a Piercing would require a force per unit area. A barrier requiring 50,000 lbs of force per square meter to puncture would only require 5 lbs of force on a square centimeter. So I’m not happy about these numbers until I know more about the situation.

It looked like a decent sized fire to me. Questions would be, for one, if the rupture happened further back would it still have stayed out of the cabin?

As they said, finding metalic objects in the road is not that uncommon an occurance.

Musk gives the size of the hole: 3″ diameter = 45 cm2.
This translates to about 5 kN/cm2.
This assumes a roughly uniform impact (probably very optimistic) with the full force applied straight up, perpendicular to the pack (likely highly pessimistic, as the car was traveling at highway speeds).

This made me wonder about that “armor plate”; see my msg below.

Aluminum plate hit with a 40 pound 2″ faced hammer at 80mph might pierce it. The use of the term “armour plate” helped sway the thoughts of the readers into belief that the car is invinceable.

Dr. Kenneth Noisewater

Quarter-inch steel plate is proof against smaller caliber handgun rounds, and depending on what kind of steel it is, is effective against larger rounds as well (such as .45ACP). It can also protect against oblique strikes by larger calibers, but 30.06 and .308 will punch thru it.

Methinks having a thicker tungsten-carbide leading-edge skidplate that can bend or pulverize larger/denser road bits might help, but then again, how far do you go? Integrate 3D forward-looking radar into the adjustable suspension to have it rise over detected road hazards?

How do you know what the thousands of teslas workers are doing at the factory? are you really that stupid to think they aren’t investigating the car? they figured out what happened, moron

Dude, step back.

Good they provided more details.

However, Musk should be a bit more wary about self-congratulations. Counter-factuals (what would happen if it was an ICE car) are nearly impossible to prove.

And the ‘you are 5 times safer with a Tesla’ ending statement is misuse of statistics.

“And the ‘you are 5 times safer with a Tesla’ ending statement is misuse of statistics.”

Why? The rate of occurrence of fire was normalized by miles driven per car. Also, it was fairly clear that Musk meant “5 times safer” in terms of encountering a car fire. So, what is wrong with the claim? That current statistics would seem to bear it out.

Or, are you saying the “sample size” (just one fire in a Tesla) is too small? Nice try… the number of fires is not the sample size. The number of miles driven is the sample size.

Oh, yes, a 6.4mm thick “armor” plate, sounds great… Wait, what is it made of?
Something softer than whatever that “curved, metal object” was, but beyond that?

A solid steel sheet like this would weight close to 300kg, and it could sustain far more than 25 tons over 45cm2 (the size of the hole as announced by Tesla). So that’s almost certainly not it.

Maybe some honeycomb, aluminum sheet? This would offer very good rigidity for the weight, but not much protection against puncture.

Anyone knows?

At any rate, Musk repeating how thick that plate is, without giving any data as to what it actually is, is a bit disconcerting.
His statement, while definitely interesting and IMHO positive, seems very carefully crafted to only reveal (and insist on) favorable data.
Hopefully we’ll learn more in the coming days/weeks, such as, what that “metal object” was.

The plate is aluminum.


Anyone can use the term Armour and make it sound super strong. Hardened annodized aluminum is quite strong but we of course do not know how the 25 tonnes of force was computed and even if this is marketing math, structural engineering math or made up with a number based on some multiple of the count of human fingers.

Then the post goes on to equate driving an ev is five times less likely to end up with a car fire than an ice vehicle. More marketing “verbiage” and has no place in terms of this incident. That is simply extrapolation based on one data point which is innumeration at best. It isn’t even able to be turned into statistics properly. But it sounds good.

Dr. Kenneth Noisewater

Well, it’s hard to fault extrapolating on a single datapoint when all you have is a single datapoint. There is yet to be a fatality in a Tesla due to accident, so do we not even mention that since extrapolating from that would mean dividing by zero?

A threshold question, if the “curved section” was strong enough to exert 25 tons of force to pierce the 1/4″ battery pack case and then pierce the battery cells, why didn’t it stay embedded in the battery pack case?

Dr. Kenneth Noisewater

Because other road debris knocked it free?

Just relaying an experience. I was driving on the why an awheel and tire from an 18 wheeler bounced over the freeway divide and smashed into the car one lane to my right about 50 feet ahead. The car immediately burst into flames and unfortunately the driver was fatally injured and the drivers seat was found compressed against the rear of the car.

No car in the world, not even a Tesla could have prevented that. Why other than luck it was not in my lane is something I think about a lot.

I agree with Elon that the Models S did great in this instance and most likely but not assuredly fared better than a gasoline car would have.

A very lucky driver in an awful circumstance of chance.
Good job driver and Tesla.

for some reason the second sentenced got garbled. sorry about that!

Please Elon show to the ICE lovers what a 25 Ton impact can produce on a gas full of gasoline, diesel, propane gas.
Thank you…. I ordered my Tesla S today

Congratulations! (I’m jealous!)

Am I the only one who thinks this will have no effect on the bad press? The car going up in flames makes much better news than the dry explanation…

The car didn’t go up in flames. It’s very obvious from the video that the fire was isolated to the front. The video is actually a good thing for Tesla since it shows it wasn’t a lucky escape.

Agreed the 5x safer is a misuse of statistics. The Tesla Model S has simply has not run enough miles to make that meaningful. It will take many million more miles (years’ worth actually) to make that statement within a healthy confidence interval. It’s the only wart in an otherwise excellent response.

One data point cannot infer proper statistics. But, for marketing and press releases, sounds great.

The Tesla performed exceptionally well under that encounter.
Gives me greater faith in how well they are constructed.


It may be just me but I’m ok with the headline “Vehicle strikes debris on highway, driver safely navigates off road, no injuries, car bursts into flames”

One more experience, one more improvement opportunity.
In this case there is nothing wrong with the Aluminum armor plate but what could be done is to give some more distance between the armor plate and the actual start of the battery pack bottom. In a word, kind of create a crumple zone between the armor plate and the actual battery pack. It doesn’t have to be 4 inch but something like one or two would probably make a difference.
This said, it would make the bottom of the car one or two inch thicker as well and there is not necessarily place for that, although certainly one inch could probably be acceptable.