This morning Tesla’s CEO, Elon Musk, announced that, in response to three vehicle fires last year, Tesla is adding additional shielding to the undercarriage of its Model S electric car. Two of the fires started after the cars ran into objects in the road, damaging the lithium ion battery. The last occurred when the driver ran into a concrete wall going 110 miles per hour, Musk said.
In the announcement, CEO Elon Musk said the changes weren’t needed for safety, noting that no one was hurt in the fires. The fires developed slowly, allowing passengers to get out of the car, and didn’t spread to the passenger area of the cars. The National Highway Safety Administration is investigating the accidents.
Lithium ion batteries can catch fire if damaged—a short between the positive and negative electrodes can cause overheating and ignite the solvent-based electrolyte. Electric vehicles are still in their infancy, and some experts have worried that battery fires could give the technology a bad name.
The new shielding adds to the quarter-inch-thick aluminum plate that already protects the battery. Here’s how Musk describes it:
The first of the three shields is a rounded, hollow aluminum bar that is designed to either deflect objects entirely or, in the case of a self-stabilizing, ultra high strength object, like a three ball steel tow hitch, absorb the impact and force it to pike upwards well forward of the battery pack. This pierces the plastic aeroshield and front trunk liner, but causes no damage affecting safety and the car remains in control and driveable before, during and after the impact.
This is followed by a titanium plate, which has exceptional strength-to-weight properties and is more commonly seen in aerospace or military applications. The titanium plate prevents sensitive front underbody components from being damaged and aids in neutralizing the road debris.
By this point, the vast majority of objects will have been deflected or crushed. For the rare piece of debris that remains intact, we added a third shield, which is a shallow angle, solid aluminum extrusion that further absorbs impact energy, provides another layer of deflection and finally causes the Model S to ramp up and over the object if it is essentially incompressible and immovable.
Tesla provided some impressive video of the shielding deflecting or demolishing a steel trailer hitch, concrete block, and an alternator, without, Musk says, allowing significant damage to the battery.