Why do EV have low max speeds?
Discussion
I would guess that ICE cars need a high top speed to get the gearing right for motorway cruising but EVs don't have normal gears and the motor is the same volume whatever speed. You couldn't have an ICE with 100mph top speed as you'd be pulling 5k revs at 70 and need earplugs. Mainstream EV makers probably realise that 100mph is fine for most people.
Tycho said:
I would guess that ICE cars need a high top speed to get the gearing right for motorway cruising but EVs don't have normal gears and the motor is the same volume whatever speed. You couldn't have an ICE with 100mph top speed as you'd be pulling 5k revs at 70 and need earplugs. Mainstream EV makers probably realise that 100mph is fine for most people.
This and to maintain peak efficiency is probably a factor too.If your petrol car was at peak power rpm at 70 mph it would be pretty tedious.
So you gear for relaxed and economical cruising, which gives head room for higher speed.
An electric motor is satisfactory at full rpm, so it's geared for that.
Additionally sustained high speed autobahn driving would empty an EV battery, so it wouldn't be that useful a capability generally.
So you gear for relaxed and economical cruising, which gives head room for higher speed.
An electric motor is satisfactory at full rpm, so it's geared for that.
Additionally sustained high speed autobahn driving would empty an EV battery, so it wouldn't be that useful a capability generally.
Taycan/E-Tron GT have 2 gears on the rear motor, 1st gear for the fast launch acceleration, 2nd gear for the rest. Volvo have limited their cars, EV and ICE, to 112mph for a few years now, so EVs having a higher gear for a higher top speed and cruising isn't likely to happen. It's all about the acceleration now.
A lot of it is down to how relatively motors and petrol engines operate.
If you drive a petrol car with a max speed of 100mph, it's pretty unpleasant to drive at 70mph. The awful base model Vauxhall Crossland, so favoured by the hire car companies, has a top speed of just over 100mph, and sits at nearly 4000rpm at 70 as the feeble n/a 1.2 thrashes away to push its bulk through the air.
It needs a step up to a car with a larger engine, or a turbocharger, to get something which doesn't feel so out of breath just going down the motorway. A side effect of that is that the overall top speed is higher, though this extra speed will very rarely be called upon in a mundane car.
A mundane electric car (Nissan Aryia, Kia Niro, VW ID3 etc) will similarly be rarely driven above about 80mph, but, even if it does the only sign it's going nearly flat out will be how far the accelerator pedal is pushed down rather than any engine roaring away.
I'm sure they could spend more money to make an electric car go faster, but there's little point unless it's marketed as a "sporty" model.
If you drive a petrol car with a max speed of 100mph, it's pretty unpleasant to drive at 70mph. The awful base model Vauxhall Crossland, so favoured by the hire car companies, has a top speed of just over 100mph, and sits at nearly 4000rpm at 70 as the feeble n/a 1.2 thrashes away to push its bulk through the air.
It needs a step up to a car with a larger engine, or a turbocharger, to get something which doesn't feel so out of breath just going down the motorway. A side effect of that is that the overall top speed is higher, though this extra speed will very rarely be called upon in a mundane car.
A mundane electric car (Nissan Aryia, Kia Niro, VW ID3 etc) will similarly be rarely driven above about 80mph, but, even if it does the only sign it's going nearly flat out will be how far the accelerator pedal is pushed down rather than any engine roaring away.
I'm sure they could spend more money to make an electric car go faster, but there's little point unless it's marketed as a "sporty" model.
Some do have two speed gearboxes like the Taycan does on the rear axle, think the Lucid might as well.
Due tot he way electric motors produce their torque, you dont need a super low gear for setting off or a super high one for cruising, the power band is as wide as the rev range so you dont need to mitigate the deficiencies in power delivery with a gearbox.
That said, you can augment the characteristics to allow more flexibility by having two ratios, but little or no point having any more than that.
Had someone developed a decent battery 100 years ago, nobody would have bothered much with developing the IC engine the electric motor is perfect, elegantly simple, its just that the energy storage is still comparatively crap.
Due tot he way electric motors produce their torque, you dont need a super low gear for setting off or a super high one for cruising, the power band is as wide as the rev range so you dont need to mitigate the deficiencies in power delivery with a gearbox.
That said, you can augment the characteristics to allow more flexibility by having two ratios, but little or no point having any more than that.
Had someone developed a decent battery 100 years ago, nobody would have bothered much with developing the IC engine the electric motor is perfect, elegantly simple, its just that the energy storage is still comparatively crap.
I always though it was because ICE engines have a limited RPM range and narrower power band than EVs, so they need gears and a clutch to match speed of the road wheels to the engine.
EVs have an RPM range that would make a Honda proud so it means the designers can ditch the gear box, clutch etc.. Less to go wrong, instant response, more efficient drivetrain etc.. but the single fixed gear does mean a lower max speed. The faster/more powerful EVs get around it by having 2 gears to get a higher top end speed.
EVs have an RPM range that would make a Honda proud so it means the designers can ditch the gear box, clutch etc.. Less to go wrong, instant response, more efficient drivetrain etc.. but the single fixed gear does mean a lower max speed. The faster/more powerful EVs get around it by having 2 gears to get a higher top end speed.
Tycho said:
I would guess that ICE cars need a high top speed to get the gearing right for motorway cruising but EVs don't have normal gears and the motor is the same volume whatever speed. You couldn't have an ICE with 100mph top speed as you'd be pulling 5k revs at 70 and need earplugs. Mainstream EV makers probably realise that 100mph is fine for most people.
We can and do have ICE cars with top speeds above 200mph. The diesel in my daily driver is doing barely 2000 rpm at 70mph because it has a thing called a gearbox, and six forward gears.In one market in particular, Vmax is important - Germany. People will and do sit at a high speed for durations.
So you need to consider the impact of that. Because they want to use one gear (simpler, cheaper, better for driveability) it does mean the motor will spin high speed at high speed. This causes heat build up and can lead to motor demagnetisation.
Also need to figure in the effect on the power electronics - as speed increases, so does the switching frequency of the inverter. This heat gets high and difficult to deal with without really good thermal management.
So it's just simpler and cheaper to limit it. Some vehicles where top speed is important - look at Porsche Taycan - they will be designed around it. But it's more expensive.
So you need to consider the impact of that. Because they want to use one gear (simpler, cheaper, better for driveability) it does mean the motor will spin high speed at high speed. This causes heat build up and can lead to motor demagnetisation.
Also need to figure in the effect on the power electronics - as speed increases, so does the switching frequency of the inverter. This heat gets high and difficult to deal with without really good thermal management.
So it's just simpler and cheaper to limit it. Some vehicles where top speed is important - look at Porsche Taycan - they will be designed around it. But it's more expensive.
J4CKO said:
Some do have two speed gearboxes like the Taycan does on the rear axle, think the Lucid might as well.
Due tot he way electric motors produce their torque, you dont need a super low gear for setting off or a super high one for cruising, the power band is as wide as the rev range so you dont need to mitigate the deficiencies in power delivery with a gearbox.
That said, you can augment the characteristics to allow more flexibility by having two ratios, but little or no point having any more than that.
Had someone developed a decent battery 100 years ago, nobody would have bothered much with developing the IC engine the electric motor is perfect, elegantly simple, its just that the energy storage is still comparatively crap.
The battery is still the problem, because they are very heavy, very expensive, and in many EVs, still only give poor range, (unless a person buys a `very' expensive EV)Due tot he way electric motors produce their torque, you dont need a super low gear for setting off or a super high one for cruising, the power band is as wide as the rev range so you dont need to mitigate the deficiencies in power delivery with a gearbox.
That said, you can augment the characteristics to allow more flexibility by having two ratios, but little or no point having any more than that.
Had someone developed a decent battery 100 years ago, nobody would have bothered much with developing the IC engine the electric motor is perfect, elegantly simple, its just that the energy storage is still comparatively crap.
The battery is also just another type of fuel tank, and there is still the cost of the fuel which must be put into it to take into account.
If car buyers were told that the new car they were buying, had a very expensive fuel tank ,which does not even give the range of an equivalent ICEV. and which weighs the same (Heavy) regardless of whether it is completely full, or completely empty, and (like with ICEVs) a range goes down rapidly the more power is used for heavy acceleration, and higher speeds, at the start of a journey, they would be less inclined to buy an EV.
When the manufactures can produce an EV, that costs the same as its ICEV equivalent, has the same range as its ICEV equivalent, and weighs the same as its ICEV equivalent, and has re-sale prospects that are the same as its ICEV equivalent, they will switch to them in droves. The problem is, that to date NO such EV exists.
GroundEffect said:
In one market in particular, Vmax is important - Germany. People will and do sit at a high speed for durations.
Yes (some) people do in ICE cars. However the energy used per mile goes up with the square of the speed.So if you had an EV with a range of 200 miles at 75 mph, then it would be exhausted after 50 miles at 150 mph.
Stopping to recharge literally every 20 minutes isn't that convenient, so there's little purpose to such high speeds in an EV.
Note that the physics apply to ICE cars too, as my wife observed when we touring Germany, "Stopping for fuel again?", but the vastly greater amount of potential energy in 75 litres of super and the faster refuelling process means it's far less of a delay.
Pan Pan Pan said:
Tycho said:
I would guess that ICE cars need a high top speed to get the gearing right for motorway cruising but EVs don't have normal gears and the motor is the same volume whatever speed. You couldn't have an ICE with 100mph top speed as you'd be pulling 5k revs at 70 and need earplugs. Mainstream EV makers probably realise that 100mph is fine for most people.
We can and do have ICE cars with top speeds above 200mph. The diesel in my daily driver is doing barely 2000 rpm at 70mph because it has a thing called a gearbox, and six forward gears.EVs do not need two gear for all normal road use so why add the expense, complexity and potential additional points of failure?
The Porsche Taycan and similar performance cars have two gears to allow a much higher top speed which of course adds significant cost as the gear has to be able to change whilst under significant load as quickly and seamlessly as possible and if you have have the pleasure of driving the Taycan you will experience that change as seamless.
The top of the range Taycan is good for 190mph top speed and 0-124mph in 6.4seconds with 100 mph coming up in about 5 seconds.
Edited by Nomme de Plum on Monday 15th April 10:19
Pistonheadsdicoverer said:
PS: Should have said: Why do SOME EVs have low max speeds?
The max speed on the Nissan Ariya is 99MPH and I've noticed that mainstream EVs (except for Tesla) seem to have similarly low max speeds.
Is it because efficiency nosedives beyond a certain speed?
I think it's more an efficiency thing.The max speed on the Nissan Ariya is 99MPH and I've noticed that mainstream EVs (except for Tesla) seem to have similarly low max speeds.
Is it because efficiency nosedives beyond a certain speed?
Some EV's have decent top speeds. Model 3 Performance is 162 mph I think.
Pan Pan Pan said:
Tycho said:
I would guess that ICE cars need a high top speed to get the gearing right for motorway cruising but EVs don't have normal gears and the motor is the same volume whatever speed. You couldn't have an ICE with 100mph top speed as you'd be pulling 5k revs at 70 and need earplugs. Mainstream EV makers probably realise that 100mph is fine for most people.
We can and do have ICE cars with top speeds above 200mph. The diesel in my daily driver is doing barely 2000 rpm at 70mph because it has a thing called a gearbox, and six forward gears.samoht said:
If your petrol car was at peak power rpm at 70 mph it would be pretty tedious.
So you gear for relaxed and economical cruising, which gives head room for higher speed.
An electric motor is satisfactory at full rpm, so it's geared for that.
Additionally sustained high speed autobahn driving would empty an EV battery, so it wouldn't be that useful a capability generally.
Do a track day in a performance ICE and single figure mpg is a given. So you gear for relaxed and economical cruising, which gives head room for higher speed.
An electric motor is satisfactory at full rpm, so it's geared for that.
Additionally sustained high speed autobahn driving would empty an EV battery, so it wouldn't be that useful a capability generally.
Cruise along an autobahn at 160 kph + and watch the fuel disappear before your eyes. Drag increases at a square of the speed.
samoht said:
GroundEffect said:
In one market in particular, Vmax is important - Germany. People will and do sit at a high speed for durations.
Yes (some) people do in ICE cars. However the energy used per mile goes up with the square of the speed.So if you had an EV with a range of 200 miles at 75 mph, then it would be exhausted after 50 miles at 150 mph.
Stopping to recharge literally every 20 minutes isn't that convenient, so there's little purpose to such high speeds in an EV.
Note that the physics apply to ICE cars too, as my wife observed when we touring Germany, "Stopping for fuel again?", but the vastly greater amount of potential energy in 75 litres of super and the faster refuelling process means it's far less of a delay.
If somebody in Germany wants to cover 100 miles quickly and knows the car will do the job at almost any speed its capable of, why wouldn't they do 130mph if that's what keeping up with L1 involves.
I know from experience I can get from my house south of Shrewsbury to Heathrow in under 2 hours in the small hours. If I'm in a hurry I don't really care if I arrive there with 20% battery remaining instead of 50%, which is what I might manage if driving sedately. I can deal with that on the way back.
Pan Pan Pan said:
J4CKO said:
Some do have two speed gearboxes like the Taycan does on the rear axle, think the Lucid might as well.
Due tot he way electric motors produce their torque, you dont need a super low gear for setting off or a super high one for cruising, the power band is as wide as the rev range so you dont need to mitigate the deficiencies in power delivery with a gearbox.
That said, you can augment the characteristics to allow more flexibility by having two ratios, but little or no point having any more than that.
Had someone developed a decent battery 100 years ago, nobody would have bothered much with developing the IC engine the electric motor is perfect, elegantly simple, its just that the energy storage is still comparatively crap.
The battery is still the problem, because they are very heavy, very expensive, and in many EVs, still only give poor range, (unless a person buys a `very' expensive EV)Due tot he way electric motors produce their torque, you dont need a super low gear for setting off or a super high one for cruising, the power band is as wide as the rev range so you dont need to mitigate the deficiencies in power delivery with a gearbox.
That said, you can augment the characteristics to allow more flexibility by having two ratios, but little or no point having any more than that.
Had someone developed a decent battery 100 years ago, nobody would have bothered much with developing the IC engine the electric motor is perfect, elegantly simple, its just that the energy storage is still comparatively crap.
The battery is also just another type of fuel tank, and there is still the cost of the fuel which must be put into it to take into account.
If car buyers were told that the new car they were buying, had a very expensive fuel tank ,which does not even give the range of an equivalent ICEV. and which weighs the same (Heavy) regardless of whether it is completely full, or completely empty, and (like with ICEVs) a range goes down rapidly the more power is used for heavy acceleration, and higher speeds, at the start of a journey, they would be less inclined to buy an EV.
When the manufactures can produce an EV, that costs the same as its ICEV equivalent, has the same range as its ICEV equivalent, and weighs the same as its ICEV equivalent, and has re-sale prospects that are the same as its ICEV equivalent, they will switch to them in droves. The problem is, that to date NO such EV exists.
As EV range goes up, charging time and cost come down the bar will lower, they will work for more people. They arent for everyone right now, and ICE has downsides, its just we have lived with those for decades.
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