With all the hubbub about the Tesla Model S and whether or not the large battery pack is adequately protected from road debris comes the discovery of a patent, granted over a year ago, for a better-protected battery. Green Car Reports also discovered that like the rest of the Model S, the battery pack is plated in aluminum, not steel, and should hardly qualify as “armor.”
Model S owner David Nolan, writing for Green Car Reports, got under his car and tried to apply a magnet to the battery’s armor plating. The magnet did not stick, indicating that it was likely made of aluminum, like most of the rest of the car. While Tesla claims the quarter-inch aluminum armor is an adequate defense from road debris, two serious fires (the Mexican one doesn’t seem to count) seems to suggest otherwise.
The reason for using aluminum over steel is to save weight; a similar level of steel plating would add about 250 pounds to the curb weight of the Model S, though it would also be a good bit cheaper. Aluminum is a much softer metal than steel though, and even though the Army uses aluminum plating some six-times thicker on certain personal carriers, the plating is only rated to deflect small-arms fire and shell fragments. It just isn’t nearly as beefy as steel.
Amidst all this comes a patent application, granted to Tesla last October, for an improved battery-protection system that includes up to two-inches of egg carton-like crush zone in addition to either an aluminum or carbon fiber shield. On top of all of that is the suggested inclusion of a firewall that could withstand temperatures up to 1,800 degrees F.
It doesn’t appear that this design made it into production models, at least not yet, and it also suggests that Tesla knew that the quarter-inch aluminum armor wasn’t enough protection from either road debris or fires. While the Tesla Model S has performed admirably, these fires aren’t just going to go away, despite Musk’s insistence that there will “definitely not” be a recall. GM recalled the Volt for a single, much-less serious fire, adding extra layers of protection to the battery.
This is the first real test of Tesla’s longevity, and I think this story has only just begun.