Why do EV's in general have poor top speed

[Badger_Prof]

I agree with the title of this post that implies the top speed of EVs is bad. They are bad--i.e., too high. It is bad if people can drive a street car at over 100 mph. Just saying that "bad" is subjective. Perhaps the OP meant "not very high?" Yep, feeling jerky for some reason....

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[Draconfier]

First off. Let me apologize for the incoming wall of text..
Ok so some basic research for those that wish to Google it. (Also to limit the math and formula usage to explain it). Governing physics of electric motors deal with Faraday's Law, Lenz's Law, and the relationship of EMF and Back EMF (electro magnetic force).

These laws govern how an electric motor works. It explains not only the instant torque we feel when we apply the pedal when the vehicle is sitting still (no counteracting Back EMF) means all the voltage of the battery is applied to the motor with no initial counteracting force, hence why we get that huge sense of thrust and g-force from all that torque. However, as the motor continues to have current applied, the back EMF field starts to build. The laws referenced above basically state that eventually the amount of force or current that can be applied is finite as the back EMF is working to counteract the voltage going in.

Additionally we have two types of motors and different phases to those motors. Most BEVs (including the Mustang Mach-e) use a single phase synchronous electric motor. Once the limit is reached between EMF and Back EMF top speed is achieved, to apply more current risks destabilizing the permanent magnets present in the motor.. the reason this type of motor is used is because of its efficiency, and the same reason that most Teslas now (except the Model S) currently use this type of motor.

More efficiency means more range and lower cost. This speed limitation can be overcome by Two methods: introducing 2 speed transmission, where once a certain speed is reached the next gearing can kick in to take the electric motor to a higher speed without damaging the permanent magnets. (Think Porsche Taycan which has a 2nd speed rear motor).

The second method is a more complicated, more expensive, and less efficient method of a motor called induction motor or asynchronous motor. Because the motor is not synchronized to the rotor speed it can be phased as well as spin at a slower speed then the rotor allowing a higher speed to be reached without risk to destabilizing the magnets due to some of the current being supplied creating the initial magnetic field rather than relying on a permanent magnet to accomplish the same initial result. These types of motors are used in the Model S, which employs a 3 phase motor.

If you made it through all of that now you know the basics of why most EV's all have the same top speed, if they didn't govern a single phase permanent electric motor it would break the magnets by demagnetizing them when too much current was applied and our vehicle would be bricked permanently.

 

[IamIA]

The Chevy Volt has a smart transaxle design that allows the the traction motor to switch from 1:1 to 1:2 ratio at highway speeds.

so what? it is still maxing out at 100 mph

 

[hawkeye3point1]

so what? it is still maxing out at 100 mph

and I never got close to that, saving energy is my goal and using fewer kWhs at cruising speed is a plus in my book

 

[will]

I am more curious if over time electric cars will be tinkered with the way that non electrics are. I know a lot of people are hesitant in fear of “bricking” their vehicle, but that can’t last forever right? Eventually some people will get comfortable with modding software/ hardware for more performance gains or range gains, etc.

 

[2021mustangdan]

Would be nice if Ford offered acceleration boost for Mach-E like Tesla Model 3?

 

[SpaceEVDriver]

Why does the 1987 Chevrolet Chevette (94 mph--terrifying at that speed) have a lower top speed than the 1987 Mustang GT 5.0 (137 mph)? Why did the Pinto have a lower top speed than the Mustang of the same year? Why does the Rav4 have a lower top speed than a same-year Mustang top speed?

Why does the Bugatti Chiron (261 mph) have a higher top speed than the Mustang?
Why does the Rimac Nevera (258 mph) have a higher top speed than the Mustang?

Different purposes.

Why would you compare top speed of a Nissan Leaf to a Mustang (ICE or otherwise)? Their purposes are completely different. One is for driving around town, the other is for performance or at least pretend performance.

 

[robbinbadams]

My reply would be that unless your are driving on a track no one needs to driver faster than about 80mph...unless you are out west on the open highway or European autobahn.

i would say 100 mph is enough for anyone even in Texas.

 

[Cabel]

Does not explain why Tesla retains better high speed than others including base Model 3 rwd

Marketing. It is all about marketing. The only place on earth you can even legally use all that top end is on a German autobahn. I certainly don't need it going around the DC beltway.

 

[mr_raider]

First off. Let me apologize for the incoming wall of text..
Ok so some basic research for those that wish to Google it. (Also to limit the math and formula usage to explain it). Governing physics of electric motors deal with Faraday's Law, Lenz's Law, and the relationship of EMF and Back EMF (electro magnetic force).

These laws govern how an electric motor works. It explains not only the instant torque we feel when we apply the pedal when the vehicle is sitting still (no counteracting Back EMF) means all the voltage of the battery is applied to the motor with no initial counteracting force, hence why we get that huge sense of thrust and g-force from all that torque. However, as the motor continues to have current applied, the back EMF field starts to build. The laws referenced above basically state that eventually the amount of force or current that can be applied is finite as the back EMF is working to counteract the voltage going in.

Additionally we have two types of motors and different phases to those motors. Most BEVs (including the Mustang Mach-e) use a single phase synchronous electric motor. Once the limit is reached between EMF and Back EMF top speed is achieved, to apply more current risks destabilizing the permanent magnets present in the motor.. the reason this type of motor is used is because of its efficiency, and the same reason that most Teslas now (except the Model S) currently use this type of motor.

More efficiency means more range and lower cost. This speed limitation can be overcome by Two methods: introducing 2 speed transmission, where once a certain speed is reached the next gearing can kick in to take the electric motor to a higher speed without damaging the permanent magnets. (Think Porsche Taycan which has a 2nd speed rear motor).

The second method is a more complicated, more expensive, and less efficient method of a motor called induction motor or asynchronous motor. Because the motor is not synchronized to the rotor speed it can be phased as well as spin at a slower speed then the rotor allowing a higher speed to be reached without risk to destabilizing the magnets due to some of the current being supplied creating the initial magnetic field rather than relying on a permanent magnet to accomplish the same initial result. These types of motors are used in the Model S, which employs a 3 phase motor.

If you made it through all of that now you know the basics of why most EV's all have the same top speed, if they didn't govern a single phase permanent electric motor it would break the magnets by demagnetizing them when too much current was applied and our vehicle would be bricked permanently.

Do electric motors actually output enough power to push them through the air? I'd figure they would be drag limited long before they hit the the current limits.

 

[Raymondjram]

Compared to my Mustangs in the past, it seems EV's in general have poor top speed EXCEPT Tesla, why ?

Tesla Model 3 RWD base. 139 mph
Tesla Model S 162 mph
Mach-E Select/Premium 112 mph
Mach- E GT 124 mph
Chevrolet Bolt EV 2LT 90 mph
Nissan Leaf Plus 98 mph
Mini Cooper SE 93 mph
Kona Electric 103 mph
Ioniq 5 115 mph

2007 Mustang GT 149 mph
2021 Mustang GT 159 mph

Because responsible EV manufacturers want their customers to respect speed limits and drive safely. If you want to drive faster, go to a racetrack. Personally, I will NEVER exceed speed limits. I drove a 1967 Chevy Camaro RS and a 1974 Ford Mustang Mach-1 so I know what speed driving is.

Tesla is crazy! That is why the have the highest death records.

 

[Kevin P]

Because responsible EV manufacturers want their customers to respect speed limits and drive safely. If you want to drive faster, go to a racetrack. Personally, I will NEVER exceed speed limits. I drove a 1967 Chevy Camaro RS and a 1974 Ford Mustang Mach-1 so I know what speed driving is.

Tesla is crazy! That is why the have the highest death records.

If you never exceed speed limits on the interstate, you are a rolling roadblock. And dangerous.

I don't believe there was a 74 Mach 1,FWIW.

 

[ponydsp]

Hum… I wonder if I can use these exact words next time I get pulled over… maybe not, I’ll just keep doing what I’ve been doing… 5 miles above speed limit or if I need to go somewhere fast, I’ll be the second or third fastest on the road…

If you never exceed speed limits on the interstate, you are a rolling roadblock. And dangerous.

I don't believe there was a 74 Mach 1,FWIW.

 

[phidauex]

On the MachE, as with most EVs, it is just the single speed transmission and the max RPM of the motors.

The Borg Warner drives have a 13,800 RPM max speed.

The AWD Non-GTs have a 9.05 rear drive ratio and a 10.0 front drive ratio. At the 113mph top speed, the front motor will be going about 13,200, just shy of the redline.

The GTs have the same motor front and rear, with the same 9.05 ratio, so at their top speed of 124 mph they will be spinning about 13,150 RPMs, also just shy of the redline.

I doubt you could squeeze much more out of them, because if the car coasted to another mph or two on a downhill you could easily exceed the motor design speed.

To make them faster you'd need a taller drive ratio (get top speed, but sacrifice acceleration), use a 2 speed transmission (add cost and maintenance), or use a motor with a higher RPM (possible with future improvements, or using different motor designs, but all come with tradeoffs).

Honestly I'm completely happy with these top speeds - there is no reason to go that fast unless you are literally racing, and the cost/weight/maintenance/efficiency savings from a singlespeed drive greatly outweigh the dick-measuring benefits of a higher top speed that you'll never see except on a sheet of paper.

 

[Draconfier]

Do electric motors actually output enough power to push them through the air? I'd figure they would be drag limited long before they hit the the current limits.

Well not push, but definitely pull. Here's some information about the Rolls Royce Spirit of Inovation.
The 24 ft (7.3 m) span aircraft is powered by three high power density electric motors driving a single three-blade propeller spinning at 2,400 RPM, designed and manufactured by YASA,[2] running at 750 volts and delivering over 400 kW (536 hp) combined from its 6,480-cell battery pack with cork insulation.[6] Its cooled battery pack should have the highest energy density for an aircraft and should allow a 320 km; 170 nmi range.[2]

https://fortune.com/2021/12/04/roll...ecord-spirit-of-innovation-air-taxi-business/

https://www.bbc.com/news/uk-england...he plane set records over,330 mph) over 15 km.

An all-electric aircraft built by Rolls-Royce has broken two world speed records.
In November 2021, The Spirit of Innovation hit an average of 555.9 km/h (345.4 mph) over 3 km, and 532.1km/h (330 mph) over 15 km.
A third record attempt, for the fastest climb to 3,000m, reached in 202 seconds, is still going through the verification process. If approved, it will break the current record by 60 seconds.
A maximum speed reached, that of 387.4 mph (623 km/h) - which would make it the fastest electric vehicle ever - was not part of the official record submission.
The aircraft uses a 400kW electric powertrain - the equivalent of a 535 BHP supercar.

Rolls-Royce, whose aerospace headquarters are based in Derby, said the propulsion battery pack was the most power-dense ever assembled for a plane - enough to charge 7,500 phones.

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