Tesla battery fire raises safety concerns about electric cars
Investors fret, experts calm as incident shows shield around battery needs strengthening
When debris on a North American freeway pierced the battery of a US$70,000-plus Tesla Model S and touched off a raging fire this week, it raised new safety concerns for electric-vehicle owners.
Electric vehicles have scored well in US government tests of front and side crashes - the Model S earned the highest score possible. But Tuesday's incident demonstrates that real-world driving could reveal some vulnerabilities that don't show up in laboratory testing.
"The safety challenges related to electric cars are still in the early stages of being tested and addressed," said Karl Brauer, senior analyst at Kelley Blue Book.
Tesla said the driver hit a large metal object in the road, which damaged a battery cell and caused a fire. The company said the car acted as designed by containing the blaze in the front of the car.
Still, experts said on Thursday that while incidents like this will happen again, they are rare. And electric cars are still safer than those with petrol engines that haul around a tank full of flammable petroleum. The Tesla fire also shows carmakers need to bolster the shields around batteries, and that firefighters need more training to deal with electric car blazes. Electric vehicles make up less than 1 per cent of the cars sold in the US.
Tesla says this is the only fire ever to happen in one of its batteries. Although a Chevrolet Volt made by General Motors caught fire two years ago after a government crash test, neither GM nor Nissan, which make the top-selling electric cars in the US, know of any real-world blazes in their vehicles.
"If you think about what you'd rather be close to, 10 gallons of gasoline or a battery pack, I'd pick the battery pack every day," said Giorgio Rizzoni, director of the Centre for Automotive Research at Ohio State University, where he is a professor of mechanical and electrical engineering.
An internet video of the Tesla fire spooked investors and caused a sell-off. Tesla shares fell 6 per cent on Wednesday, and they closed on Thursday down US$7.64, or 4.2 percent, at US$173.31. Even so, if an investor purchased a share of Tesla at US$35 on January 2, they're sitting on a gain of nearly 400 per cent. Tesla has dazzled Wall Street by selling more vehicles than expected and posting its first quarterly net profit earlier this year.
Tesla said that, in the incident in the Seattle area on Tuesday, the Model S warned the driver of problems from the collision. He pulled off the road, smelled smoke and saw flames. A company spokeswoman said the fire originated in a battery cell damaged in the collision, and the car's design prevented the fire from spreading.
Thomas Habetler, an electrical engineering professor at the Georgia Institute of Technology, theorised that the highway debris punctured a shield and a battery cell, causing a short-circuit, bypassing fuses and electrically linking one battery terminal to another.
Habetler and Rizzoni said electric cars are designed to withstand blows from debris. Fires are so rare that this one shouldn't give anyone pause if they're considering buying one, they said.
