How Does The Tesla Model S Ace Safety Tests, But Catch on Fire?

The battery was the source of the fire, but the exact cause is unknown.

ByABC News
October 3, 2013, 3:30 PM

Oct. 3, 2013— -- Tesla's better-than-perfect safety rating was called into question based on a technicality. But a Model S owner in Seattle might have a bit more reason to question Tesla's safety record.

The car owner saw his high-performance electric vehicle catch fire on Tuesday.

Kyle Ohashi, a captain with the Kent Fire Department that responded to the fire, said an unidentified metal object hit the bottom of the vehicle. "The car gave the driver a warning to stop and pull over," he told ABC News. "He got out and smoke started coming out of the car, followed by the fire."

The Model S battery's 16 modules are located underneath the car, protected by a steel plate. "Each module within the battery pack is, by design, isolated by fire barriers to limit any potential damage," said Elizabeth Jarvis-Shean, a spokeswoman for Tesla Motors. "The fire in the battery pack was contained to a small section in the front of the vehicle."

The exact cause of the Model S fire is not yet known.

The Model S's steel plate keeps its battery protected during everyday driving. But it also made the fire department's job trickier, Ohashi said. "Typically when you have a car fire, it's relatively easy to access the battery," he said. "This battery was buried deeply in the front portion of the car, so gaining access to the fire was an issue."

This is the first known fire caused by a Model S battery, said Jarvis-Shean.

"Tesla has delivered more than 13,000 vehicles since June 2012," she said. "Those cars have driven over 83 million miles, and this is the first fire."

There were no fires observed during the crash tests performed with the National Highway Traffic Safety Administration (NHTSA), she noted.

"The Tesla Model S performed well in standard crash tests, yet what sounds like a relatively minor impact resulted in a fire that proved difficult to extinguish," said Karl Brauer, a senior analyst at Kelley Blue Book. "This points to the wide variety of crash results that can't be tested in a lab."

Are Electric Cars At Risk?

Jeff Chamberlain, deputy director of the Joint Center for Energy Storage Research at Argonne National Lab in Illinois, said that like in any other battery fire, it comes down to a short circuit.

"If you puncture any battery, whether it's lead-acid, alkaline or lithium-ion, you'll create a short circuit and make connections across interfaces that you should not be making." he said. "When that short occurs, it creates heat and energy, which causes the fire."

Tesla's battery differs from other electric and hybrid cars, Chamberlain noted, and its design actually lowers the risk of fire propagating. "The Chevy Volt has 288 battery cells that are about the size of your hand," he said. "The Model S uses a different set of cells and has between 8,000 to 11,000 of them. When you divide those cells up the way Tesla did, the [risk] of fire spreading goes down."

According to a report by the Federal Emergency Management Agency, an estimated 194,000 highway vehicle fires occur each year, across all types of vehicles.

ABC News reached out to NHTSA for comment about the Model S. "During the federal government shutdown, some key agency functions have been discontinued until funding is restored," the agency said in a statement. "Functions funded by annual appropriations are suspended, including safety defect investigations, field crash investigations, review of consumer complaints and notification of new vehicle and equipment recalls." business reporter Susanna Kim contributed to this report.