Another problem with aiming for very high altitudes is that you need to have several hour long flights to be able to reach those altitudes and really gain anything.
A typical climb/descent rate for a passenger jet is 1500 to 2000 feet per minute. So for a normal flight, going up and down to 35k will take close to 40 minutes. Going to 55k will take an hour.
So this means you can't start small and focus on cityhoppers with the fancy high-flying electric planes, you have to go straight for competing with the heavy jets.
It's not very difficult to put batteries in a heat controlled chamber.
A lot of RC guys are doing it with high altitude long range RC planes. Distances over 500km at 15km are already happening on 10kg planes.
Wind and temperature aloft forecast includes the note: "TEMPS NEG ABOVE 24000" and omit the minus sign.
With normal lapse rates (3.6℉/1000 feet), you're gonna need a heater in any general aviation airplane.
Single engine airplanes tend to use exhaust heat to heat outside air as a heater, so no fuel consumed. For airplanes that use a combustion heater, fuel use needs to be considered in flight planning. Therefore I'd expect the same for electric powered airplanes.
Me too, but it's pretty chilly at >35,000 feet up, where most commercial jets fly. Batteries really don't like the cold.