4 ms·

I don't know, consumers are told lots of wacky counter-intuitive things about "how to eke performance out of technology in practice". Think of the way that lots

by dbuxton 14y ago

I don't know, consumers are told lots of wacky counter-intuitive things about "how to eke performance out of technology in practice". Think of the way that lots of people like to repeatedly run their laptop batteries down because they think that it helps preserve battery life, even though that hasn't been true for about a decade. However I think that your comment about thermodynamics is revealing because it seems to me that the real point of this article is that driving an electric car requires consumers to learn a lot (about entropy!) and think very differently from driving a normal car. It sounds frankly stressful to drive, even if everything works perfectly. That's where I think the real damage is.

stcredzero 14y ago
My solution would be to only use half the stated range. It would be perfect for me, even so.
gus_massa 14y ago
You don't need a Thermodynamics Ph.D. to understand this. Moreover the normal (gas) cars have the same behavior. So it's annoying that a car expert don't know it. You get the best mpg at a constant speed of ~50mph, and it's better with the cruise control because it reduce the times that you need to accelerate or decelerate. If you go too fast, the mpg drops because you need more fuel to compensate the additional resistance. If you accelerate and brake (for example in a city), the mpg drops because you need more fuel to accelerate and when you brake the energy goes away as heat. The advantage of the regenerations brakes is that some of the energy that is "lost" as heat braking is stored and used again to accelerate. This is not magic. It doesn't make braking lossless, it only recycles part of the energy so accelerating and braking is not so bad (it's only bad). This is well known for the electric and hybrid cars (I think that there are some tries to do something like this for gas cars, perhaps store the energy mechanically, I'm not sure.) I think that the recommendation was (paraphrase) "If you are going to drive inside a city, it's better to turn off the cruise control." The articles that he understood something like (paraphrase) "It's better to drive inside a city than in a highway with cruise control." It's very surprising that a car expert can understood this so totally wrong that it look like it was a willfully misunderstandment.
- danielweber 14y ago
  Moreover the normal (gas) cars have the same behavior. ... You get the best mpg at a constant speed of ~50mph This isn't true of EVs. The engine in a gasoline powered cars are around 15 to 25 percent efficient, and the hotter you put them, the more efficient they are. However, air resistance increases as speed increases. The peak efficiency depends on a few things, but most cars you'll find it around 40-60 mph. EVs don't have engines, they have motors. They are about 90% efficient, regardless of your speed. But they have the same air resistance issues. So EVs really do perform better at lower speeds. Even the Prius will show better city mileage than highway mileage, and that's only with a little bit of battery+motor.

by dbuxton 14y ago

stcredzero 14y ago

My solution would be to only use half the stated range. It would be perfect for me, even so.

gus_massa 14y ago

You don't need a Thermodynamics Ph.D. to understand this. Moreover the normal (gas) cars have the same behavior. So it's annoying that a car expert don't know it. You get the best mpg at a constant speed of ~50mph, and it's better with the cruise control because it reduce the times that you need to accelerate or decelerate. If you go too fast, the mpg drops because you need more fuel to compensate the additional resistance. If you accelerate and brake (for example in a city), the mpg drops because you need more fuel to accelerate and when you brake the energy goes away as heat. The advantage of the regenerations brakes is that some of the energy that is "lost" as heat braking is stored and used again to accelerate. This is not magic. It doesn't make braking lossless, it only recycles part of the energy so accelerating and braking is not so bad (it's only bad). This is well known for the electric and hybrid cars (I think that there are some tries to do something like this for gas cars, perhaps store the energy mechanically, I'm not sure.) I think that the recommendation was (paraphrase) "If you are going to drive inside a city, it's better to turn off the cruise control." The articles that he understood something like (paraphrase) "It's better to drive inside a city than in a highway with cruise control." It's very surprising that a car expert can understood this so totally wrong that it look like it was a willfully misunderstandment.

danielweber 14y ago
Moreover the normal (gas) cars have the same behavior. ... You get the best mpg at a constant speed of ~50mph This isn't true of EVs. The engine in a gasoline powered cars are around 15 to 25 percent efficient, and the hotter you put them, the more efficient they are. However, air resistance increases as speed increases. The peak efficiency depends on a few things, but most cars you'll find it around 40-60 mph. EVs don't have engines, they have motors. They are about 90% efficient, regardless of your speed. But they have the same air resistance issues. So EVs really do perform better at lower speeds. Even the Prius will show better city mileage than highway mileage, and that's only with a little bit of battery+motor.