Long Range EVs - What's Involved

[mkg3]

This article explains in simple terms what elements are most involved in increasing the range for any EV. The plot shows breakout of what consumes most energy at 70mph.

https://www.autocar.co.uk/car-news/electric-cars/inside-race-50mpkwh-secrets-long-range-evs

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[Zoidz]

That doughnut should be on the start up screen of every EV, lol.

Well, at least in the manual.

 

[ElGuano]

This seems totally in-line with the general consensus around EV efficiency.

By far the biggest factor is your speed. Going 70mph is probably 15% less efficient than 60mph, and going 80mph is 30-40% less efficient than 70mph.

HVAC is the next big one, if you can stand to turn down the heat/cold/fan without being uncomfortable, you'll see a noticeable improvement.

The big meta point that the chart doesn't address is the fact that EV drivetrains are SO EFFICIENT that every little thing matters more than with an ICE car. Window open You'll see it affect your range. Tire pressures just a bit low? That'll cost a few miles more. Run your AC? Big 20% hit. Go up a hill slightly? You'll feel it.

ICE cars with their 30-40% efficient drivetrains will see a much smaller percentage bump on these things, because they're already seeing massive drivetrain losses just to move the vehicle forward.

This is one of the reasons I always roll my eyes just a bit whenever I hear people recite "300 miles is more than enough!" Even if you take their literal words, they're not likely getting the 300 miles their vehicle is rated for, without making some pretty serious compromises to everyday driving.

 

[iansriv]

OP-thanks for posting this. Not sure about anyone else but, aerodynamics wasn't on the top of my list when I decided to get a car that was shaped like a brick.

 

[DayTripping]

I've drilled home the aero aspect in other posts. The Rivian is a fairly aerodynamic brick.

It is also why I call BS on the supposed new efficiency gains won't matter much at speeds that most of us drive well above the EPA cycles. The highway maxes out at 61 mph or so and averages 48, I believe.

 

[mkg3]

I've drilled home the aero aspect in other posts. The Rivian is a fairly aerodynamic brick....

Just want to clarify. While R1S has better than average Cd (drag coefficient), the frontal areal is quite large. As such, the actual drag force is quite hight.

Drag = Cd(frontal area*0.5*air density*velocity^2)

Like all 2 box SUVs, there is a huge base drag at the rear of the vehicle where the airflow is completely separated and Rivian did very little to mitigate that.

The small slope at the top and clean sweep upwards at the bottom (where the trailer hitch cover is located) help a little - very little.

It would have help much more if Rivian had put a downward spoiler (e.g., early Tahoe) at the top and diverters at he bottom to channel the air from the rear tires away directly from behind the vehicle..

It would have also helped if Rivian had put an external spare tire (e.g., Land Rover and the new Scout SUV) behind the rear hatch. In both cases, it reduces the base drag than what it is now.

 

[DayTripping]

Hard to get away from frontal area when you build a truck/SUV large enough that can actually carry stuff. It goes with the territory. It penalizes you even more as you go faster as drag goes up by the square of speed and HP required by the cube.

The aerodynamic drag basically goes vertical compared to everything else, as most of those are a more linear function and become far less as an overall portion of total drag as speed go up. If I need more range, I just slow down or take my Tesla.

This info is likely based on a sedan, not a truck or SUV. So we'd see more to aero drag and everything else a small portion of the overall drag profile. I can tell you there isn't a 20% difference between my usage of HVAC or not. Maybe in extreme cold I might experience but I haven't seen that happen to any of my EVs in Texas. The extreme hit causes about a 10% hit on my Teslas and less on my Rivian.

 

[SwampNut]

The HVAC must be highly variable depending on current weather, so it makes me suspicious of the whole thing. If you could gain 20% by just turning it off...yeah nah, not buying it. Maybe it includes the battery and motor cooling?

 

[electruck]

While there are definitely opportunities for incremental improvements in each of those areas, to truly get a meaningful increase in range without compromising utility, battery energy density is where the improvement will need to come.

 

[DCFC]

In my Polestar2, it shows the percentage of energy consumed by HVAC. I've never seen more than 10%, but I also live in SoCal. The easiest thing to do to extend range is drive slower as aero drag increases to the square of speed. Any cyclist knows this first-hand.

 

[beatle]

Cold temperatures are often to blame for higher energy consumption since we have to run the heat for the cabin and the battery, but it's also because the air is denser. I did an experiment in my Model S a few years ago where it was ~40F outside. I preheated the cabin and battery, bundled up, and left the HVAC turned off. I only used the seat heater. I found that my energy consumption didn't really change much from an identical trip I took in similar ambient temperatures when I set the cabin temp to 73.

All other things being equal, you're using 11% more energy to overcome drag when comparing some typical winter and summer temperatures. This table also shows the dramatic change in load at higher speeds.

Temperature	Air Density	Wind Speed (m/s)	Speed (mph)	Wind load (Newtons)
32F (dry)	127537​	35​	78​	450​
80F 60% RH	1.15273​	35​	78​	407​
32F (dry)	1.27537​	27​	60​	268​
80F 60% RH	1.15273​	27​	60​	242​

These calculations are from when I had my Model S, and I set the drag are of the S to 0.575999 square meters and atmospheric pressure to 1 bar. The Rivian will have higher drag and will take a bigger penalty with cold weather.

Some good links if you want to play around with the calculations (I am not an engineer):

https://www.engineeringtoolbox.com/wind-load-d_1775.html

https://www.omnicalculator.com/physics/air-density

 

[mkhuffman]

It would have help much more if Rivian had put a downward spoiler (e.g., early Tahoe) at the top and diverters at he bottom to channel the air from the rear tires away directly from behind the vehicle..

This is probably why Wakeshield has claimed a measurable highway range improvement when putting their topper on the T.
https://www.rivianforums.com/forum/threads/r1t-topper-shell-by-wakeshield.27670/

By the way, here is an excellent study regarding the aerodynamics of the R1T.
Rivian R1T Low Drag Coefficient Claims Analyzed In Virtual Wind Tunnel

 

[webfootdawg]

OP-thanks for posting this. Not sure about anyone else but, aerodynamics wasn't on the top of my list when I decided to get a car that was shaped like a brick.

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