Published: Friday, 4 Oct 2013 | 7:45 PM ET CNBC
CNBC October 6, 2013
When the fire department arrived, they observed standard procedure, which was to gain access to the source of the fire by puncturing holes in the top of the battery's protective metal plate and applying water. For the Model S lithium-ion battery, it was correct to apply water (vs. dry chemical extinguisher), but not to puncture the metal firewall, as the newly created holes allowed the flames to then vent upwards into the front trunk section of the Model S. Nonetheless, a combination of water followed by dry chemical extinguisher quickly brought the fire to an end.
It is important to note that the fire in the battery was contained to a small section near the front by the internal firewalls built into the pack structure. At no point did fire enter the passenger compartment.
Had a conventional gasoline car encountered the same object on the highway, the result could have been far worse. A typical gasoline car only has a thin metal sheet protecting the underbody, leaving it vulnerable to destruction of the fuel supply lines or fuel tank, which causes a pool of gasoline to form and often burn the entire car to the ground. In contrast, the combustion energy of our battery pack is only about 10% of the energy contained in a gasoline tank and is divided into 16 modules with firewalls in between. As aconsequence, the effective combustion potential is only about 1% that of the fuel in a comparable gasoline sedan.