EVs and gearboxes, why not?

Resident

Resident

Resident

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Can someone explain to me, simply, why manufacturers aren't fitting EVs with gears?

Am I thinking too simply. My thought is this:

For example if a direct drive EV needs to spin it's motor to 10k rpm to acheive 70mph using a fair amount of power then if there was a gearbox then surely you could introduce ratios in which 70mph is acheivable by 5k rpm, using less power.

If I'm taking less power from the battery then surely that would increase the range?

I mean I know there's the whole adding complexity and moving parts angle & losses due to the drivetrain but surely those would be negated by the possibilty of doubling range etc?
 
They ave a gearbox, its just single speed.
Taycan has a twin speed rear gearbox. Final sentence is why most cars dont have it - mainly the £££ extra.
 
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They have a reducer gearbox already. Usually 9:1-11:1 ratio to slow the motor and increase it’s torque

cost Vs benefit is the usual balance. And why many EV have a lower top speed vs power. They are motor speed limited
 
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I don't think the efficiency of an electric motor works quite the same way you might be expecting it to in comparison to an ICE either, so it won't necessarily benefit from being geared to try and achieve the lowest practical rpm in the name of efficiency the same way an ICE does.

The two gear setup in the Taycan for example I think is more about getting a ludicrous amount of torque to the wheels for low speed acceleration and then the 'second gear' is effectively the 'normal' single ratio an EV would typically use, rather than anything particularly concerned with efficiency.
 
The torque range of an electric motor is much wider than a combustion engine. They simply don't need them. Adding a gearbox with multiple selectable gears is just unnecessary weight, cost and added inefficiency.
 
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50-94% efficiency on a typical motor map. Keeping the motor in the sweet spot is pretty beneficial and is the next evolution of EV wet motor technology.
 
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Resident said:
For example if a direct drive EV needs to spin it's motor to 10k rpm to acheive 70mph using a fair amount of power then if there was a gearbox then surely you could introduce ratios in which 70mph is acheivable by 5k rpm, using less power.
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Might want to go back to physics class. :p
 
Bug One said:
The torque range of an electric motor is much wider than a combustion engine. They simply don't need them. Adding a gearbox for no-benefit is just unnecessary weight, cost and added inefficiency.
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Erm. They have a gearbox. An electric motor without one wouldn’t pull the skin off a rice pudding and be matched to about 900mph top speed
 
Simon said:
Erm. They have a gearbox. An electric motor without one wouldn’t pull the skin off a rice pudding and be matched to about 900mph top speed
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Don't be a pedant. You know what I mean. If you want to call a single speed reduction transaxle a gearbox - fine. But it's not the same thing you get in a combustion engine.
 
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Bug One said:
Don't be a pedant. You know what I mean.
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It’s not pedant, They have a gearbox because their torque is too low as a motor alone. It’s a key bit of EVs that people seem to miss.

I guess you meant multi speed gearbox but you are looking backwards, stuff coming will be multispeed to eek out even more efficiency. the extra weight etc is starting to make sense when range is so critical
 
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Simon said:
50-94% efficiency on a typical motor map. Keeping the motor in the sweet spot is pretty beneficial and is the next evolution of EV wet motor technology.
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Interesting, I thought they were generally consistently above 75%, hence there not being much benefit to trying to use multiple gears to aid efficiency - as they are effectively pretty much always in a 'sweet spot' anyway in BEV applications.
 
Simon said:
It’s not pedant, They have a gearbox because their torque is too low as a motor alone. It’s a key bit of EVs that people seem to miss.

I guess you meant multi speed gearbox but you are looking backwards, stuff coming will be multispeed to eek out even more efficiency. the extra weight etc is starting to make sense when range is so critical
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It is pedant. And you know it. If you really need it, I'll update my post to specify it. :rolleyes:
 
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I think that was a bit pedantic, to *most* people a gearbox is something that enables you to change gear ratios, what EV's have is more what people would be familiar with as a final drive ratio in your differential in your ICE vehicle.

But on topic i think these will come as although electric motors have a far wider efficiency band than a ICE there are still gains to be had if you can minimise the loses by the extra gears and bearings etc and make it cost effective. I wouldn't expect to see them on anything other than high end stuff for a while due to the cost.

Tesla kind of do this anyway but in a different way with their dual motor cars, they'll have a different reduction on the front and rear motor so one is more efficient at cruising speed, that may be the way some go as it's far easier to implement so maybe that'll be the way forward instead.
 
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My assumption is that electric motors don't need high RPM to achieve maximum torque, and can operate efficiently at a much wider range of RPM, so there's just no need. Keeps everything simpler.

I am driving for 8 hours with a mate tomorrow who is a gearbox engineer so may pick his brains to pass the time :P
 
Look at some electric motor torque curves.

Also my MEB cupra born won’t give full power to 25mph. So this instant torque at low speed is sometimes calibrated out to save mounts/ tyres etc
 
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I'm not sure cost has anything to do with it. The EQS is a £120k luxury EV, but it still has a single speed gear ratio.

It can do 137mph, 0-60 in 3.4 seconds and a 364m range. I'm not sure what selectable gears would give it that it doesn't already have?
 
Bug One said:
I'm not sure cost has anything to do with it. The EQS is a £120k luxury EV, but it still has a single speed gear ratio.

It can do 137mph, 0-60 in 3.4 seconds and a 364m range. I'm not sure what selectable gears would give it that it doesn't already have?
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Obvious. More efficiency
 
Simon said:
Look at some electric motor torque curves.

Also my MEB cupra born won’t give full power to 25mph. So this instant torque at low speed is sometimes calibrated out to save mounts/ tyres etc
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Mine is the same, it dials down the power until you get moving. It can disabled on the leaf by turning traction control fully off. Might be similar on the cupra.

Although your front tyres might not approve.
 
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