Feds close investigation of Tesla battery fires

FREMONT, Calif. (KGO) -- The National Highway Traffic Safety Administration closed the investigation into Tesla electric car battery fires after the company agreed to install more shields beneath the cars.

Dramatic video of a Tesla Model-S going up in flames was one of the literal and figurative sparks that led to an investigation by the federal government. The company says there have been three fires involving Tesla Model S. One after a high speed crash and two after the cars hit debris in the road, piercing the car's underbody and battery. This morning, CEO Elon Musk announced in his blog that the company has been outfitting all Teslas in production since March 6 with a triple underbody shield. That includes a hollow aluminum bar, a titanium plate, and a solid aluminum extrusion.

Consumer Reports explains what this means for the driver.

"If you run over something on the highway, Tesla claims that this added protection, it's going to push things out of the way rather than going through the battery pack," said Consumer Reports Sr. Auto Engineer Tom Mutchler.

All of these changes were done reluctantly by Musk. He has stated all along that the underbody shields are not needed for a high level of safety, but the public misperception fed by disproportionate coverage by the media led to the investigation and resulting changes.

He wrote this morning: "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."

Musk says this is not a recall but Tesla service will retrofit for free. The shields of the 22,000 vehicles sold through February upon request or during a normally scheduled service.

Even after the fires, Consumer Reports picked the Tesla Model S as the best car overall for 2014.