Has the Tesla S’ Reputation as the Safest Car Gone Up in Flames?

Peter Els
Posted: 10/23/2013

Specialist automotive company, Tesla Motors has certainly made its mark as a manufacturer of safe, high performance electric vehicles. In May 2013 Consumer Reports magazine proclaimed that the Tesla Model S had outscored "every other car in our test ratings."

In August, the NHTSA awarded the Tesla Model S a Five-Star rating, with an overall Vehicle Safety Score of 0.42, for frontal, side, and roll-over crashes. This is the best score of any vehicle the agency has tested under a new rating system it began applying in 2011.

Full PDF Tesla_S_Fire


Although the NHTSA test has no specific battery tests, it’s interesting that in Tesla’s press release on their achievement they state: "The Model S lithium-ion battery did not catch fire at any time before, during or after the NHTSA testing. It is worth mentioning that no production Tesla lithium-ion battery has ever caught fire in the Model S or Roadster, despite several high speed impacts. While this is statistically unlikely to remain the case long term, Tesla is unaware of any Model S or Roadster occupant fatalities in any car ever."


A Tesla Model S experiences a battery fire after an accident


All this good news translated to a share price that rose from $35 on the 2nd of January to $184 in September. Everything was going well for the small company from Fremont, California... until a Model S was involved in an accident early in October. The resultant battery fire saw Tesla shares fall 6 percent in 24 hours, and drop a further $7.64, or 4.2 percent the following day.

Despite the fact that there were no injuries the news soon went viral and at $173.31Tesla’s market value dropped about $2.4 billion in two days.

Reflecting public and investors concerns was a rare analyst-downgrade when R.W. Baird analyst, Ben Kallo, cut his rating on the stock from "Outperform" to "Neutral:" Telling investors that while he's still bullish on Tesla's long-term prospects, the company has "significant milestones" during the next 18 months that come with risk.

Deutsche Bank analyst Dan Galves, summed up the prevailing sentiment when he stated; "Investors will be concerned because electric cars represent a new technology with a high sensitivity to safety risks."

This concern is not really about Tesla cars or even electric motor vehicles in general. For years now consumers have seen spectacular images of (Li ion) batteries catching fire in cell phones, lap tops and even aircraft: Being thus sensitised, any fire in an electric vehicle is big news – especially when the vehicle in question comes with such impressive safety accolades.

On face value and, judging by the spectacular videos posted on social media site YouTube, the Tesla Model S may well have an Achilles heel in its ability to withstand an impact to the batteries.

Did the Tesla Model S meet the design standards?

The Model S travelling at highway speed struck a curved metal object that had recently fallen from a semi-trailer. The geometry of the object created a powerful lever action as the car drove over it, impaling the underbody of the Model S. The force required to punch the 3 inch diameter hole through the quarter inch armour plate protecting the base of the vehicle is estimated to be in the order of 25 tons!

 photo Embed_undefloor_battery_pack_EV
Image credit: www.boronextrication.com

As instructed by the onboard alert system, the owner exited the highway and was able to leave the vehicle without injury. The impact damaged one of the 16 modules of the battery pack, causing a fire in the front of the vehicle. Notwithstanding the damage, the fire was contained to the front section of the car by the internal firewalls within the pack; while vents directed the flames down towards the road and away from the vehicle.

 photo Panasonic_Image_EV
Image credit: www.insideevs.com

When the fire department arrived they gained access to the source of the fire by making holes in the top of the battery’s protective metal plate and dousing the flames with water. For the lithium-ion battery used in the Model S, water is the correct retardant to use, however puncturing the metal firewall allowed the flames to vent upwards into the front trunk section. Nonetheless, a combination of water followed by a dry chemical extinguisher quickly put out the fire. At no point did the flames enter the passenger compartment.

In correspondence to the owner Elon Musk, CEO of Tesla Motors, points out that a typical gasoline car only has a thin metal sheet protecting the underbody, leaving the fuel supply lines and fuel tank vulnerable to destruction, which could result in a fire of far greater intensity than that experienced in the Model S. The combustion energy of a Li Ion battery pack is only about 10% of the energy contained in a gasoline tank and is divided into 16 modules with separating firewalls. Therefore the effective combustion potential is only about 1% that of the fuel in a comparable gasoline powered sedan.

Notwithstanding all the accolades and laboratory testing, the safety of the vehicle design and construction can receive no better confirmation of its safety than, what the driver of this vehicle described as a "doomsday" event that has now been tested, proving the design and engineering works.

Conclusion

With official Department of Transportation figures indicating one gasoline-vehicle fire for every 20 million miles driven, Tesla with one fire in over 100 million miles definitely deserves the awards bestowed on it. And in the case of the one fire they have experienced, the Tesla passed with flying colours.

After reviewing the facts it seems as if Tesla Motors investors also agree - Jefferies analyst, Elaine Kwei, boosted her Tesla price target to $210 from $160 after shares recently rose 2.1% to $184.72. The stock, which dropped 7% is still up by more than 400% this year.

Of more concern is the preparedness of bystanders and emergency rescue personnel in dealing with EV emergencies. Capt. Kyle Ohashi with the Kent, Wash., Fire Department said crews learned lessons from fighting the Tesla fire. For one, the dry chemical extinguisher seemed to work better than water to combat the blaze. And he said the department is now aware that accessing the battery pack in a Tesla is quite difficult.

Ohashi said firefighters may need a course on how to handle electric cars. He also said Tesla may provide guidance.


Sources

  • Wall Street Journal - Tesla Model S Is ‘Safer Than Conventional Vehicles’: Analyst.
  • Tesla Motors club forum – Post by "jdovi".
  • Tesla motors press release – "Tesla Model S Achieves Best Safety Rating of Any Car Ever Tested"



Peter Els is a technical writer for Automotive IQ


*Editor's Note
A 2nd Tesla S has apparently been involved in an accident resulting in a fire. The incident reportedly happened in Mexico and appeared to be quite a severe accident. The driver walked away unharmed.

Peter Els
Posted: 10/23/2013

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