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Tesla’s rapid crash analysis; will NHTSA come in?

On Tuesday, a Tesla Model S traveling at highway speed crashed into road debris, causing significant damage to the vehicle and resulting in a major vehicle fire. A video of the flaming wreck went Internet-viral (along with unwarranted EV fire hysteria), and Tesla stock shed up to $30 of its price per share at times during the next two days (about 15%). On Friday, Tesla Chairman, Product Architect & CEO Elon Musk posted a brief analysis of the accident and fire on the company blog. (The stock price began slowly climbing again.)

According to Musk and Tesla, a “curved section that fell off a semi-trailer ... 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.

...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.

Musk goes on to point out that there are some 150,000 vehicle fires per year in the US, and asserts that the Model S, with its lower energy density battery pack, has a much lower “combustion potential” than gasoline-fueled cars.

An unknown at this point—mainly because of the shutdown of the Federal government—is whether or not the National Highway Traffic Safety Administration (NHTSA) will open a special investigation into the crash and fire, as it did with the Volt fire in 2011. (Earlier post.) That fire resulted not from a real-world crash, but was a delayed reaction to New Car Assessment Program (NCAP) side pole impact testing.

The resulting detailed investigation took about two months (earlier post). As a result of the investigation, General Motors modified the vehicle structure and battery coolant system in the Volt to further protect the battery from the possibility of an electrical fire occurring days or weeks after a severe crash. (Earlier post.)

At the time, NHTSA noted that:

NHTSA continues to believe that electric vehicles show great promise as a safe and fuel-efficient option for American drivers. However, as the reports released in conjunction with the closure of the investigation today indicate, fires following NHTSA crash tests of the vehicle and its battery components—and the innovative nature of this emerging technology—led the agency to take the unusual step of opening a safety defect investigation in the absence of data from real-world incidents.

(As a side note, the NTSB investigation and Boeing response into Li-ion fires on the 787 took about 3 months to work through before the FAA cleared the Dreamliner for flight again.)



If the default training of first responders is improper in such situations, it would be good to have a way to get info to them in a timely fashion to alter their strategy appropriately.

On the other hand, this is no big deal if they don't.  Nobody's hurt, you replace the car.


Can battery packs be better protected against accidental foreign objects? Would light weight Kelvar or other puncture proof composite materials be better than 1/4 inch of heavy steel?


One thing's for sure, a Kevlar or carbon-composite bottom armor plate would be one hell of a rigid framing piece.  Use internal ribs and the top as structural elements and the body stiffness of the result would be very hard to match.


As @EP says, noone hurt, you just get a video on youtube and you need a new car.
Q: Should Tesla have a policy of replacing any cars that burn out in a crash ?
If they do, should they make it public.

As they say, there are lots of car flameouts / year and no one is marching on capital hill. So people have got used to the idea of cars burning out, as long as they don't get killed.

This is NOT like the Byd fire where 3 people were killed.

Tesla were very quick off the mark on this one. I wonder did they have a contingency plan ready so that when the inevitable fire happened, they knew exactly what to do ?


On the other hand, this is no big deal if they don't. Nobody's hurt, you replace the car.

This seems to be the case. Quote the owner: "I agree that the car performed very well under such an extreme test," wrote Carlson, who added, "I am still a big fan of your car and look forward to getting back into one."

Carlson also noted that he was a Tesla investor, and we're guessing he's not thrilled that his own car accident is hurting his stock portfolio.


Eventually, one could calculate the percentage of cars-vehicles, per type, make etc subjected to fires (per reason) per year?

Do the stats already exist?


The stats exist for USA from NFPA:

1. 287000 vehicles fires per year
2. 480 deaths per year
3. 1525 injuries per year
4. $1.3 B property damage per year

Main reasons:

1. Mechanical failures = 40%
2. Electrical failures = 18%
3. Intentional = 8%
4. Collisons = 3%
5. Other reasons = 5%

Did not find stats per vehicle model-make?


Yes, new lighter materials such as Kevlar 20 or 49 and/or nanotube fiber could be used to improve battery pack protection and reduce weight at the same time.

Surprise that Tesla has not done it already?

Bob Wallace

People in the BYD taxi were killed when another car going over 100 MPH slammed into it.

The fire started from a wiring short. It lit interior fabric. It spread to the batteries. Only part of the battery pack burned, it wasn't like a ruptured gas tank going up in a fireball.


The bottom of the battery pack was protected by a quarter inch armor plate. Really, under any normal situation that's overkill, this accident was a freak. Sure Tesla *could* beef-up the protection with thicker steel or kevlar but it's not magic, no matter how much you use there will always be some way to defeat it. Sooner or later another, bigger freak accident WILL happen (Murphy's law) and then what? A call for even MORE armor? When does it stop?

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