> Car fuel tanks are made of something like 1-2mm steel. Many, many car fuel tanks are made of plastic. It's the position of the tank in the car rather than t

> Car fuel tanks are made of something like 1-2mm steel. Many, many car fuel tanks are made of plastic. It's the position of the tank in the car rather than the material involved that's important. This is a hard problem for Tesla to solve because their batteries are bigger by volume, really heavy, don't get lighter as they discharge, and don't shape as easily as a liquid, so the bottom of the car is the only really good place for one. That's why Tesla used the "heavy armor" approach and actually -do- have several mm of metal located beneath the battery, but no armor is perfect.