Tesla adding underbody triple shield system to Model S to reduce risk of battery fires caused by impacts
In an effort to reduce further the already low risk of a Model S battery fire resulting from impact with road debris, Tesla Motors is outfitting new Model S cars (as of 6 March) with an underbody triple shield system consisting first of an aluminum bar; then a titanium shield; and finally a shallow angle solid aluminum extrusion.
Tesla will also retrofit the system, free of charge, to existing Model S cars upon request or as part of a normally scheduled service, wrote Tesla Motors CEO Elon Musk in a post on the Internet publishing site Medium. The action comes as an additional Tesla response in the wake of the two widely-reported Model S collisions in 2013 that resulted in underbody damage that led to car fires. Tesla had earlier provided an over-the-air software update to increase the default ground clearance of the Model S at highway speeds, thereby also reducing the odds of a severe underbody impact.
During the course of 152 vehicle level tests, the shields prevented any damage that could cause a fire or penetrate the existing quarter inch of ballistic grade aluminum armor plate that already protects the battery pack. We have tried every worst case debris impact we can think of, including 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.—Elon Musk
The rounded, hollow aluminum bar that is the first in the new line of defense is designed either to deflect objects entirely or, in the case of a self-stabilizing, ultra-high-strength object such as a three-ball steel tow hitch, absorb the impact and force it upwards forward of the battery pack. While this would pierce the plastic aeroshield and front trunk liner, the impact would cause no damage affecting safety. The car remains drivable during and after the impact.
The titanium plate is designed to protect sensitive front underbody components from being damaged and also aids in neutralizing the road debris.
The shallow angle solid aluminum extrusion is intended to handle any piece of road debris that has not already been deflected or crushed. The extrusion further absorbs impact energy, and ultimately would cause the Model S to ramp up and over the object should it prove incompressible or immovable.
Tesla also published three slow motion videos provided by on-vehicle high-speed cameras of a newly outfitted Model S destroying or deflecting potentially dangerous road debris: a three-ball tow hitch; a concrete block; and an alternator.
Musk said that the new shield system has only a 0.1% impact on range and does not affect ride or handling. Wind tunnel testing showed no discernible change in drag or lift on the car.