Looking at the FAA video I was curious why a CO2 extinguisher was not tested. CO2 changing state from a liquid, which it is in the extinguisher, to a gas gets very cold (I'm a wine maker and use CO2 as a cover gas all the time) generating solid CO2 (dry ice) which is pretty damn cold. As cooling the battery is the critical step...... I use siphon CO2 tanks where the liquid is expelled through the valve vs the gas from the top of the liquid as in a regular tank. Regular tank gets pretty cold also.