Tesla Cybertruck gets less than 80% of advertised range in YouTuber’s test::A YouTuber took Tesla’s Cybertruck on a ride to see if it can actually hit its advertised 320-mile range, only to find out that its could only reach 79% of the target. When YouTuber Kyle Conn…

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3 points

Why is the efficiency lower on highways?

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1 point

Air drag

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14 points

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.

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3 points

Idle losses are real but not very substantial in a modern engine compared to the bigger factor you’re missing which is that in city driving tests there is a lot of speeding up and slowing down, ICE vehicles throw away all the energy used to slow down as heat in the brakes which makes city cycles particularly inefficient while an EV captures that energy through regenerative braking, dramatically reducing the net cost of those momentum changes.

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1 point

Regenerative braking only can recapture something like 2-5% of lost energy. The bigger factor is exactly what the other person said.

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1 point
*

Ah, good point, the speed changes for ICE results in lots of energy wasted as heat instead of being recaptured. That would certainly be the largest loss for an ICE in the city cycle.

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2 points

Also regenerative breaking is not useful when you’re maintaining constant speed on the highway, but a huge leg-up in the city

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4 points

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)

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3 points

It has the aerodynamics of a brick

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0 points

Aha yes, but what about other EVs?

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1 point

So does the EV9, but it exceeded the EPA range in the same test.

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1 point

This was a highway test though, not how EPA test the ranges

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1 point
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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).

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