DETROIT — A federal safety investigation of the Tesla Motors electric Model S sedan announced this week comes at a critical juncture for the car and the company.
For the first time, regulators are examining whether the design of the high-end vehicle and its advanced lithium-ion battery pack are defective and the cause of two battery fires.
After garnering high praise for its styling, performance and eco-friendly electric power, the Model S will be the subject of scrutiny by the National Highway Traffic Safety Administration. Tesla’s chief executive, Elon Musk, said the company welcomed the inquiry.
At issue is whether the size, shape and chemical makeup of the car’s battery make it prone to fires when its lithium-ion cells are punctured in a collision.
Musk has repeatedly defended the design of the Model S, which won early accolades for its safety from regulators and independent publications like Consumer Reports. But the car has caught fire on three occasions in less than two months — twice in the United States and once in Mexico.
The Nissan Leaf, the best-selling all-electric car on the market, has had no reported fires.
A federal defect investigation can take months to complete and could include crash tests of the vehicle well beyond the ordinary government testing done on cars before introduction.
Tesla said it would increase the ground clearance of the Model S, and it also pledged to extend its current vehicle warranty to cover fire damage.
But those changes are not expected to divert the focus of the investigation, or minimize the potential for the safety agency to order structural changes and a vehicle recall.
“Adjustments or modifications of the vehicle will not affect the inquiry,” said Karl Brauer, an analyst with the auto research firm Kelley Blue Book. “That is out of Tesla’s hands now, and the range of potential outcomes is very wide.”
As a startup company in the keenly competitive global auto industry, Tesla has, until now, enjoyed remarkable early success with its Model S luxury sedan.
But the safety agency inquiry has raised questions about what was perceived to be one of Tesla’s greatest strengths — its technological superiority.
Musk has not retreated from his position that the Model S is safer from fires than vehicles with gasoline engines.
“There is a larger issue at stake,” Musk wrote in a blog posting this week. “If a false perception about the safety of electric cars is allowed to linger, it will delay the advent of sustainable transport and increase the risk of global climate change, with potentially disastrous consequences worldwide.”