[Riggald]

Autocar check out what effect driving style has on range, using a pair of I-Paces.

https://www.autocar.co.uk/car-news/features/jaguar-i-pace-test-does-driving-style-make-big-difference-electric-range

 

[sciencegeek]

Pretty interesting, somewhat reassuring, and confirming the predicted 200 mile range with 'normal' driving

 

[TotesMagotes]

Pretty interesting, somewhat reassuring, and confirming the predicted 200 mile range with 'normal' driving

Here's something I've been thinking about, mainly because I live in Colorado and will be driving my I Pace at elevations above 6,000 feet: I should get better range than I would at sea level, right? Unlike an ICE, an EV should not, in theory, see a decrease in efficiency due to lower air pressure. However, there should be significant gains vis a vis reduced drag (but only really accruing at highway speeds). Does anyone have any insight on this? I'm having trouble finding published real-world experience with EVs at altitude.

 

[I-PaceDave]

Here's something I've been thinking about, mainly because I live in Colorado and will be driving my I Pace at elevations above 6,000 feet: I should get better range than I would at sea level, right? Unlike an ICE, an EV should not, in theory, see a decrease in efficiency due to lower air pressure. However, there should be significant gains vis a vis reduced drag (but only really accruing at highway speeds). Does anyone have any insight on this? I'm having trouble finding published real-world experience with EVs at altitude.

Yes, the lighter should lessen aerodynamic drag, and no penalty on motor / engine power/efficiency like a naturally aspirated combustion engine experiences.

 

[Guy]

This is why airplanes fly above 30,000 feet. Less airdrag.

 

[I-PaceDave]

This is why airplanes fly above 30,000 feet. Less airdrag.

Yes, Exactly, but in an airplane, the wings also lose lift forcing higher speeds to avoid stall, and the engines lose thrust with thinner air to breathe. In some airplanes at higher altitudes the cruise speed / stall speed window gets pretty tight.

 

[sciencegeek]

I'm not an aerodynamicist but it would stand to reason that drag is linear with air density; density at sea level is 0.075 lbs/cubic foot, at 6000 ft it's 0.060. So that would seem to be a nice 20% less drag in Denver compared to Palo Alto, probably translating to some nice range extension, perhaps 10%ish depending on speed (more at higher speeds).

 

[TotesMagotes]

Thanks everyone. Since we agree, we're either all correct or we're all incorrect. Once I get the car, I'll see if I can gather some data to confirm this theory.

 

[bruintoo]

So the Red car that was driven modestly traveled 239 miles on a single charge. And the Blue car that was driven "dynamically" traveled 208 miles on a single charge. Which means the Jaguar published estimate range of 234 miles (currently on Jaguar USA site) is correct. Am I missing something?

 

[sciencegeek]

No not missing. That's exactly right. If you drive it like you want to drive a sporty car then you have a 200 mile range. If you're simulating driving a Prius you have a 240 mile range (or maybe more, heck!)

 

[sflgator]

Here's something I've been thinking about, mainly because I live in Colorado and will be driving my I Pace at elevations above 6,000 feet: I should get better range than I would at sea level, right? Unlike an ICE, an EV should not, in theory, see a decrease in efficiency due to lower air pressure. However, there should be significant gains vis a vis reduced drag (but only really accruing at highway speeds). Does anyone have any insight on this? I'm having trouble finding published real-world experience with EVs at altitude.

Correct me if I'm wrong but I'm fairly certain that EVs get better range on flat roads and decrease range when traveling up/down mountains. Your range in CO may not be any better despite the higher elevation just based on going up & down the terrain. I think the I-Pace EV tries (if selected) to find a route to your destination with the flattest roads.

 

[TotesMagotes]

Correct me if I'm wrong but I'm fairly certain that EVs get better range on flat roads and decrease range when traveling up/down mountains. Your range in CO may not be any better despite the higher elevation just based on going up & down the terrain. I think the I-Pace EV tries (if selected) to find a route to your destination with the flattest roads.

You're correct about that (at least I think you're correct). Even if the overall elevation change is zero over the course of the trip, multiple up/downs will deplete range. The act of going up a hill consumes significantly more energy than you can recapture with the regen going down a hill. My question was more a theoretical question about air pressure.

That said, the Front Range (metro areas) of Colorado is not as mountainous as most would initially think. For example, a common real world trip for me is 75 miles from my home in Colorado Springs (6200') to Denver (5280') and there is one hill in between (which crests at 7400'). Usually travelling at about 75mph. In theory, I should be able to make that round trip with a full charge, but I guess I'll find out.

 

[sciencegeek]

A couple of simple Gedankenexperiments:

1.
Let's say you're on the freeway traveling fairly fast.
The hill is not so steep, so you're not regenerating on the downhill; you're using energy on the downhill too.

On the way up you're using more energy
On the way down you're using less energy

Theoretically it's a wash because the potential energy you have to put in on the way up is exactly the same as the potential energy you're regaining on the way down. (NB: this is obviously independent of what type of engine you have, it applies to a ICE as well)

2.
Let's say it's a steeper hill. On the downhill you have a choice: A: you go so slow that the low wind resistance allows regeneration. B: you want to go fast so you put in energy to overcome drag. [On the downhill the temptation is to go faster but that increases drag.]

Hill or not: it's mostly about the wind resistance and how fast you choose to drive.

That said, there's probably some loss of efficiency because you're drawing more power on the uphill; uphill is as if you're slightly accelerating all the time.