On the way to becoming an overnight sensation, something funny happened to the Tesla Motor Co. in the last couple of years. Three of its highly touted Model S sedans caught fire in on-road accidents, raising the specter of something dangerous lurking in the electric cars’ motors. Upon further examination, however, investigators found that the cause of the accidents was the undercarriage of Tesla vehicles striking metal debris on the road, which punctured the aluminum shielding designed to protect the sedan’s lithium-ion battery packs, causing something called “thermal runaway.”
The hand-wringing over just a few of Tesla’s new cars catching fire was enough to bring out the doom and gloom crowd on the Internet, who eagerly jumped on the incidents as proof that lithium-ion batteries in automobiles are inherently unsafe. The folks at Tesla first responded with words, with CEO Elon Musk writing on the company’s website that: “For consumers concerned about fire risk, there should be absolutely zero doubt that it is safer to power a car with a battery than a large tank of highly flammable liquid.”
Then Musk put his engineers to work to correct the design flaw. What they came up with is a better shield for the Li-ion battery pack in the front of the car. And the centerpiece of the improved shield, literally, is a plate of stamped titanium (weighing about 0.8 to 1.6 pounds).
According to a report in the Christian Science Monitor, the new shield is a three-part, “military-grade, aluminum-titanium solution” to the vulnerability, which Tesla enthusiasts have taken to calling Tank Mode. The California-based motor company has announced that “all Model S cars manufactured on or after March 6 will carry three extra layers of underbody protection, and Tesla service centers will retrofit existing cars free of charge,” according to the report.
The National Highway Traffic Safety Administration has since closed its investigation of the traffic fires, satisfied that the aluminum-titanium workaround (in addition to the quarter inch of armor plate already protecting the base of the vehicle) should remedy the problem, according to a report in The New York Times (free registration required).
“As the empirical evidence suggests, the underbody shields are not needed for a high level of safety,” Musk wrote recently. “However, there is significant value to minimizing owner inconvenience in the event of an impact and addressing any lingering public misperception about electric vehicle safety.”
The New York Times article states that Tesla made a good choice in selecting titanium as the material of choice for shielding its vulnerable battery packs from dangerous road debris strikes, because of the metal’s unique strength-to-weight characteristics. “The titanium plate prevents sensitive front underbody components from being damaged and aids in neutralizing the road debris,” Musk observed.
“The protective qualities of the underbody shields are substantial, but their effect on the overall structure of the vehicle is minimal” Musk added. “In total, the shields only have a 0.1 percent impact on range and don’t affect ride or handling. Wind tunnel testing shows no discernible change in drag or lift on the car.”
It sounds like a perfect use for a material with amazing properties.