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Autoweek (and other car news outlets) summarize some independent testing: https://autoweek.com/article/green-cars/how-much-does-cold-weather-cut-electric-vehicle-range-quite-bit-aaa-study-finds
AAA partnered with the Automotive Club of Southern California's Automotive Research Center for its tests, which allowed it to run drive-simulating dynamometer tests in 20-, 75- and 95-degree Fahrenheit temperatures in a controlled laboratory setting. This is way more scientific than anything we'd be able to achieve toodling around in an EV in Detroit the next time a polar vortex hits.
A handful of key points pulled from the report:
- The increased use of HVAC systems in extreme temperatures has a bigger impact on EV range than decreases in battery pack efficiency caused by the temperatures themselves.
- Moreover, while both extremely hot and extremely cold temperatures affect range, you'll incur a significantly larger penalty when heating up a cabin than you will cooling one down. Compare that 41 percent decrease at 20 F to a mere 17 percent decrease at 95 F.
- The BMW i3s saw the biggest reductions in range in both hot and cold conditions, losing 50 and 21 percent of range in cold and hot conditions, respectively.
- The Nissan Leaf was the most versatile, losing 31 and 11 percent of range in cold and hot conditions, respectively.
The other test cars, Tesla S, eGolf and Chevy Bolt fell between these extremes. The article includes a link (pdf) to the original report with many more details. Worth reading if you live outside southern CA and are considering an electric car.
This AC is considering an electric car, and I'm fortunate enough to have an attached garage to keep it warm-ish, probably above freezing, even if the outside temp gets down to 0F (-18C) which is a typical low for my location. That means that any trip will start with a cool (not cold) battery & cabin...but after parking outdoors at my destination(s), I'll have a reduced range for the trip home.
(Score: 4, Informative) by Arik on Thursday May 16 2019, @06:11PM (1 child)
It doesn't heat or cool, it just transfers hot or cold from one place to another.
If you want to cool, then it needs somewhere to dump heat. A radiator, more or less. It makes you cool by transferring the heat from where you are, to the radiator. The colder that radiator on the outside is, the more efficient this process becomes. But if the radiator is hot, then this doesn't work well at all.
And it works exactly the same in reverse. If you want to *heat* the inside of the car with a heat pump, then you're still going to be using the radiator to do it, only now the HOTTER the radiator the better it works.
In an internal combustion engine, this can still work fine, even in nasty cold weather. That engine has to thermal cycle and build up a good bit of thermal energy to reach operating temperature, and it keeps right on making heat afterwards which must be radiated away. If you don't use that to heat up the car then it will have to be radiated out another way anyway.
One of the nice things about electric motors in other contexts is that they *don't* really put out much heat. Yes, there's friction, there's some radiation of thermal energy, but it's nothing like what happens with an internal combustion engine, there's no getting up to operating temperature and heat radiated is much less. In warm weather this is great, it means you aren't wasting a lot of energy heating up that engine block. In cold weather, though, it means you can't rely on the engine as a source for heat.
If laughter is the best medicine, who are the best doctors?
(Score: 2) by aclarke on Friday May 17 2019, @03:23PM
Air-to-air heat exchangers are pretty well-proven technology. They're a fairly efficient way to heat, even in freezing temperatures, although their efficiency drops with the temperature, just as an air conditioner's efficiency drops as temperature rises.
Perhaps they're too bulky or heavy or expensive to put into a car, but they're used regularly in buildings.