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NHTSA Ends Tesla Fire Inquiry After Automaker Adds Battery Shield

March 31, 2014

The National Highway Traffic Safety Administration (NHTSA) ended its investigation into the fires involving the Tesla Model S electric car last week after Tesla announced an upgrade that would better protect the vehicle’s batteries.

The agency closed their probe without seeking a recall after they found no defect trend with the Model S. It started an investigation after two electric cars in the United States and another in Mexico caught fire last year. The U.S. fires were caused by road debris damaging the vehicle’s huge battery pack, which is located along its base. As for the Mexico incident, the fire was the result of a high-speed crash.

No one was hurt in all three reported incidents. The passengers were able to get out of the car before the fire began.

Tesla initially addressed the problem with an upgrade in November. The Palo Alto, California-based automaker provided a software upgrade to allow greater default ground clearance at highway speeds and in turn reduce the risk of road debris severely damaging the car’s underbody.

In an effort to put car owners’ minds at ease, the company also extended warranty coverage to include vehicle fires.

However, Tesla sought to offer a better solution to the problem to give all its customers peace of mind and has finally come up with the fix that will prevent fires—and recalls—in the future. In an article posted on the automaker’s website and, Tesla Chairman and Chief Executive Elon Musk announced the latest design change of the Model S.

The latest design change involves the addition of a triple underbody shield to the aluminum armor plate that already protects the battery pack.

The added protection consists of three shields. The first shield is a “rounded, hollow aluminum bar.” The second shield is a titanium plate. The third and last shield is a “shallow angle, sold aluminum extrusion.”

According to Musk, the aluminum bar is made to deflect debris or at least “absorb the impact and force it to pike upwards well forward of the battery pack.” The titanium plate, whose material is often used in aerospace or military purposes, is designed to prevent the underbody from being damaged by debris. Lastly, the aluminum extrusion is designed to further absorb impact energy. It is that which will allow the car to drive over an “incompressible and immovable” object.

The blog post comes with three animated .gif images that show how the added protection secures the battery pack from the likes of a three ball tow hitch, solid concrete block and steel alternator.

The NHTSA seemed happy with Tesla’s fix. The agency noted in its website that impacts with road debris are common and predictable, but expressed satisfaction with how the carmaker determined a solution.

“Tesla’s revision of vehicle ride height and addition of increased underbody protection should reduce both the frequency of underbody strikes and the resultant fire risk,” the agency said in a statement.

In the post, Musk said that all Model S units made after March 6 are equipped with the triple underbody shield and that all existing Model S units will be retrofitted with the additional protection free of charge upon the owner’s request or when the vehicle is brought for scheduled maintenance.

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