Tesla adds titanium shield to prevent Model S battery fires, ending federal probe

Following three reports last year of fires from punctured battery packs, Tesla Motors today revealed updates to its all-electric Model S sedan that it says should eliminate the chance a piece of road debris could cause a fire. The solution: More armor, including a titanium plate that the company's own tests show can withstand impacts from steel and concrete — an answer that was good enough for federal auto safety officials to close a probe without finding a defect.

Related video

In a public letter, Tesla CEO Elon Musk repeats his claim that the Model S is the safest vehicle on the road, noting that with some 35,000 cars in service there have been no deaths or injuries to date. But he's also careful to present the changes as upgrades rather than a safety improvement — which would trigger the legal requirements of a recall.

"We felt it was important to bring this risk down to virtually zero to give Model S owners complete peace of mind," Musk said.

But the changes also come after the National Highway Traffic Safety Administration opened a probe into the two fires; unlike other electric cars, Tesla mounts its battery pack on the bottom of the chassis, exposing it to more road debris.