this post was submitted on 06 Jan 2024
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What was the EPA rated highway range? The 320 mile range is the EPA combined city/highway which you won't hit doing entirely highway but you would beat doing entirely city.
Most EVs he's tested hit or exceed the EPA range on this test. Even bricks like the EV9 exceed their EPA range in similar temps.
Why is the efficiency lower on highways?
Due to electric drivetrains having minimal fixed losses at low speed unlike internal combustion engines. Aerodynamic losses start becoming the largest factor for EVs at relatively low speeds (25-35 MPH) since other losses at so low. This shows up on tests as higher city efficiency and lower highway.
For an internal combustion engine you are burning a large amount of energy just to keep the engine running, so the slower the speed, the less distance traveled for the fixed amount of running losses and lower the MPG. It isn't until higher speeds (55-65 MPH) that aerodynamic losses become the largest factor. This manifests as lower efficiency in the city tests and higher highway.
It's also a factor that acceleration/deceleration in an ICE kills mileage. Highway tests maintain a constant speed. If you ran the same test at 35 mph, they would get much better mileage than at 55 (or 70)
Also regenerative breaking is not useful when you're maintaining constant speed on the highway, but a huge leg-up in the city
That makes sense, thanks.
There’s more air resistance at higher speeds.
That doesn't explain why ICE vehicles are much better efficiency-wise than EV ones at higher speeds, just why EVs don't do so well. Another post responding to me addresses it well.
Do you mean that ICE is more efficient than EV at higher speeds, or that ICE scales better than EV?
ICE vehicles have better MPG at higher speeds, EVs at lower speeds.
Neither. ICE reaches its best efficiency at higher speeds than EV does, but it is still less efficient than EV at all speeds.
Air drag
Aerodynamic drag increases with the square of speed. Other frictional losses might follow a similar pattern.
Cars have other sources of inefficiency too (such as idle power consumption), so all cars have a different optimum speed for maximum range (which depends on wind speed, direction & temperature too).