It's not just phones. The Toyota Prius is also vulnerable at extremely low temps. From the owner's manual: "When the hybrid battery (traction battery) is extre

It's not just phones. The Toyota Prius is also vulnerable at extremely low temps. From the owner's manual: "When the hybrid battery (traction battery) is extremely cold (below approximately minus 22 degrees Farenheit [minus 30 degrees Celsius]) under the influence of the outside temperature, it may not be possible to start the hybrid system. In this case, try to start the hybrid system again after the temperature of the hybrid battery increases due to the outside temperature increase, etc." edit: of course, gasoline-only cars have a similar problem. Oil gets THICK at -22F and without an electric engine block heater, the starter may not be powerful enough to turn that engine over. At least you can put a phone inside your jacked to warm it up. Not so easy with an automobile.