Officials investigating a Tesla Motors electric car which caught fire outside Seattle, have reached the conclusion that the fire began in the battery compartment after it was impacted by a metallic object. The fire was contained and nobody was injured, but the design of the car made extinguishing the fire difficult.

tesla20s fire.png Tesla fire began in battery

The car in question, a Tesla Model S worth about $70,000, caught fire when a metallic object directly impacted the battery pack. The liquid-cooled, 85kW Lithium-Ion batteries are mounted in the floor of the car, and are of similar chemistry to the batteries which grounded the Boeing 787 Dreamliner earlier this year. The batteries in question have a high energy density, which means they can deliver consistent and long lasting electrical output, but at the cost of being fairly volatile. (The angry cousin of the Li-Ion battery, the Lithium-Polymer battery, is frequently referred to as the most dangerous battery in the world. If dented, it has been known to explode into a several thousand degree fireball.)

The fire began after the Tesla’s driver struck an object on the highway in the Seattle suburb of Kent. After exiting the highway, the vehicle became disabled and caught fire. Unfortunately, the damage caused by the fire was severe enough that the original damage made by the impact couldn’t be assessed. The design of the battery compartment has taken safety into account and the fire was contained to a small section of the front end, but that came at a price. Firefighter originally were not able to put out the fire, which reignited after a short time. To make matters worse, water seemed to intensify the flames. The firefighters switched to a dry chemical extinguisher, which also failed. In the end, they were forced to cut a hole in the body of the car to access the battery compartment, puncture the batteries and then pour water directly on top of them. That finally killed the flames.

2013 Tesla Model S rear three quarter 1 1024x640 Tesla fire began in battery

Beautiful car though. Might be worth a bit of a fire hazard.

While nobody was injured, the incident has taken a toll on Tesla’s reputation and stock price. Tesla previously touted the car as the world’s safest, but now, shares of Tesla Motors have fallen by 6% and R.W. Baird analyst Ben Kallo lowered his rating for the stock from “Outperform” to “Neutral.”

Via Phys.org