Do Electric Aircraft Face Lapse Rate Challenges?
By Scott Spangler on January 22nd, 2024
Beyond worrying about the heating bill and bundling up for the sub-zero trek to the mail box, reports about how much of America has been dealing with the polar waterfall has stimulated an unexpected question: Given the reality that cold weather quickly sucks the electron life out of batteries, will electric aircraft face lapse-rate challenges?
While watching a TV news report about desperate owners trying to revive their cold-sucked dead Teslas in Chicagoland, what immediately popped into my head was the reality that the ambient temperature in a standard atmosphere surrenders (lapses) approximately 3.5 °F or 2 °C per thousand feet up to 36,000 feet, which is approximately –65 °F or –55 °C. Above this point, the temperature is considered constant up to 80,000 feet.
That’s a lot higher than today’s prototype electric flyers now aviate, but I’m looking forward to their airline goals. But the temperatures at the airline’s cruising flight levels are a lot colder than it has been for the past week or so in much of the United States, roughly double our weeklong Wisconsin windchill. (This begs another question: Do batteries suffer from windchill, or is that just reserved for mammals? Google says it doesn’t.)
Installing battery warmers on these aircraft seems to be a logical solution, but they, too, would be electric, which would increase the draw on the storage system’s power reserves. And then there would be the added weight, the primary foe of power efficient flight. Battery temperature not only affects output, it has a negative effect on recharging the battery.
Electric vehicles, it turns out, have two batteries, one high-voltage and the other low, like the 12-volt battery that fires up an internal combustion powerplant. Apparently, like a vehicle that runs on dead dinosaurs, an electric vehicle with a cold-sucked 12 volt needs a jump to recharge its high-voltage counterpart more efficiently. Without the proper preparation, it seems, a recharge that takes an hour in milder temps can take four or five times longer when it’s cold. Not that airline turn-around crews need another time-suck challenge.
The Cold Weather Best Practices in the Tesla Model 3 Owner’s Manual was eye opening. Just as ice and snow on an airframe is detrimental to flight, on an electric car, its “moving parts, such as the door handles, windows, mirrors, and wipers can freeze in place.” This includes the charging port. “In extremely cold weather or icy conditions, it is possible that your charge port latch may freeze in place. Some vehicles are equipped with a charge port inlet heater that turns on when you turn on the rear defrost in cold weather conditions. You can also thaw ice on the charge port latch by enabling Defrost Car on the mobile app.”
This assumes the vehicle still has some battery power left, not to mention the phone needed to run all the vehicle’s apps. I’m sure the electrical aviation engineers are working on all these challenges, and all the others I’m unaware of. I wish them well. The sun has warmed the outside temperature to a positive single digit, and the mail truck just delivered, so it’s time to bundle up. –Scott Spangler, Editor
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