2014 Tesla Model SEnlarge Photo
Tesla Motors announced this morning that it will fit three new underbody components to all Model S electric cars to add further protection against impacts from road debris, which caused a pair of fires in its cars last fall.
Those two Model S cars were severely damaged when their battery packs, mounted under the floor, were pierced by road debris and subsequently caught fire.
A third Tesla fire occurred in Mexico after a Model S was stolen, run off the road at high speeds, and through a reinforced concrete wall, tearing off wheels and totaling the car.
No one has been injured or killed in any Tesla fire; drivers were able to pull over, park the cars, and walk away following a warning from the cars' monitoring system.
The company pointed out in its announcement that more than 200,000 fires in gasoline cars occur in the U.S. each year.
On new cars since March 6
The company announced today that all new Model S vehicles built are being fitted with an additional triple underbody shield. Installation of the shield began March 6 for new cars built in its Fremont, California, assembly plant.
Tesla will also retrofit the shield to all existing Model S cars--numbering roughly 30,000, although the company declines to give production data--as part of a normally scheduled service call or at the request of owners.
The existing battery pack is shielded by a quarter-inch thick armor plate made of ballistic-grade aluminum. On top of the pack, a steel-and-ceramic firewall sits between the pack and the car's floorpan.
The new protective devices comprise three different elements: a hollow round aluminum bar, a titanium plate, and a shallow-angle solid-aluminum extrusion.
The aluminum bar acts to deflect or absorb impacts, which in the most serious cases will be directed upward ahead of the pack and into the car's front trunk area--damaging it, but protecting the battery pack further aft and keeping the car in control so the driver can pull over when damage is detected.
The titanium plate, which Tesla characterizes as "more commonly seen in aerospace or military applications," protects front underbody components and absorbs force from road-debris impacts.
Finally, the aluminum extrusion further deflects objects but also causes the car to ride up and over objects that won't move and cannot be compressed.
150 tests, no damage
The company released video from high-speed camera footage taken from more than 150 tests of the new shield, with the camera recording the impacts and deflections of various objects.
Those tests included impacts from a concrete block, a tow hitch and trailer ball, a steel alternator, and what it called "hardened steel structures set in the ideal position for a piking event, essentially equivalent to driving a car at highway speed into a steel spear braced on the tarmac."
With the new shield assembly fitted, none of these objects pierced the battery pack or caused any fires.
Tesla's announcement said the shields cut the range of a Model S by 0.1 percent--that would be less than 1 mile--but do not change the car's aerodynamic drag or lift, and have no effect on handling or ride.
Prior software update
Earlier this year, Tesla had sent an over-the-air update to its cars to raise the ride height at highway speeds, increasing the ground clearance to lower the chances of damage from road debris.
The company's announcement cited the "significant value to minimizing owner inconvenience in the event of an impact" and its desire to address "any lingering public misperception about electric vehicle safety."
The release, bylined by Tesla CEO Elon Musk, ended as follows: "With a track record of zero deaths or serious, permanent injuries since our vehicles went into production six years ago, there is no safer car on the road than a Tesla. The addition of the underbody shields simply takes it a step further."