Here's why electric cars have plenty of grunt, oomph and torque

Here's why electric cars have plenty of grunt, oomph and torque
Nobuteru Taniguc drifting a Tesla Model S in Tokyo, Japan. Credit: MASUDA

Australian politicians, including Prime Minister Scott Morrison, have raised the question of electric vehicles' capacity for "grunt".

Now I'm by no means a "grunt" expert, but when it comes to performance, are far from lacking. In fact, Australian electric car owners have ranked performance as the top reason for their purchase choice.

The V8, fuel-guzzling, rev-heads, who are supposedly worried that electric cars mean they will be left driving around golf buggies, should first check out this drag race between a Tesla and a Holden V8 Supercar.

Spoiler alert: The Tesla wins, and by a fair amount.

Internal combustion engine vs electric motor

Internal engines and are very different. In an internal combustion , as the name suggests, small amounts of fuel are mixed with air, and are exploded to drive a series of pistons. These pistons drive a crankshaft, which is then connected to a gearbox, and eventually the wheels.

This is a rather simplified overview, but there are literally hundreds of moving parts in a combustion engine. The engine must be "revved-up" to a high number of revolutions in order to reach peak efficiency. The gearbox attempts to keep the engine running close to this peak efficiency across a wide range of speeds.

CarAdvice.com: Tesla Model S v Holden V8 Supercar v Walkinshaw HSV GTS Drag Race.

All of this complexity leads to a significant amount of energy being lost, mostly through friction (heat). This is why combustion engine cars are very energy inefficient.

So how are electric motors different? Electric motors are actually pretty simple, consisting of a central rotor, typically connected to a single gear. The rotor is turned by a surrounding magnetic field, which is generated using electricity. The added benefit of this design is that it can operate in reverse, acting as a generator to charge the batteries while slowing down the (this is called regenerative braking).

On the other hand, the electric motor reacts instantly as soon as the accelerator is pushed. Given the minimal moving parts, electric motors are also highly reliable and require little to no maintenance. Their simplicity also means that almost no energy is lost in friction between moving parts, making them far more efficient than .

Does simplicity translate to more or less grunt?

Combustion engines need to be "revved-up" to reach peak power and torque. Torque is a measure of how much rotational force can be produced, whereas power is a measure of how hard an engine has to work to produce the rotational force.

Here's why electric cars have plenty of grunt, oomph and torque

As shown below, the power and torque characteristics of a means that although a conventional car might have a top capacity of 120 kW of power and 250 Newton metres of torque, this is only when the engine is running at high speeds.

In contrast, an provides full torque from zero kilometres an hour, with a linear relationship between how fast the is spinning and the power required. These characteristics translate to a vehicle that is extremely fast at accelerating, with the ability to push you back into your seat.

What about pulling power?

For over a decade electric motors have been used in mining trucks, sometimes with a capacity greater than 100 tonnes, due to their powerful, instant torque and ability to pull large loads at slow speeds.

While most of these vehicles have been diesel-hybrids, fully electric mining trucks are now being introduced due to their high power-to-weight ratio, low operating costs, and ability to use regenerative braking to—in some cases—fully recharge their batteries on each mine descent.

Here's why electric cars have plenty of grunt, oomph and torque

Electric motors are also increasingly being used in shipping, again because of their ability to push large loads. In Europe, a number of short-haul electric ships are currently in use. One example is the Tycho Brahe, a 111 metre-long, 8,414 tonne electric passenger and vehicle ferry that operates between Helsingborg, Sweden and Helsingør, Denmark.

The future of grunt

The global transition to electric vehicles is underway. Australians must decide whether we want to capture the enormous benefits this technology can bring, or remain a global laggard, literally being killed by our current vehicle emissions.

While towing in fully electric vehicles is currently a challenge, in the near future this will no longer be the case with the introduction of long-range electric utes like the Rivian R1T and Tesla Pickup.

In the interim, alternatives also exist, like my own plug-in hybrid electric vehicle. It can tow, drive on the beach, and drive up to 50 kilometres on electricity alone. Charged using my home solar system or The University of Queensland's fast-charger, it means that more than 90% of my trips are zero-emission.

It is clear that electric cars can provide plenty of grunt for Australians, so let's make sure we are ready for an electric performance future.

  • Here's why electric cars have plenty of grunt, oomph and torque
    Power and torque characteristics of a typical internal combustion engine. Credit: Victor Barreto
  • Here's why electric cars have plenty of grunt, oomph and torque
    Power and torque characteristics of a typical electric motor. Credit: Victor Barreto
  • Here's why electric cars have plenty of grunt, oomph and torque
    A Mitsubishi Outlander PHEV (Plug-in Hybrid Electric Vehicle). Credit: Jake Whitehead

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Apr 16, 2019
As shown below, the power and torque characteristics of a combustion engine means that although a conventional car might have a top capacity of 120 kW of power and 250 Newton metres of torque, this is only when the engine is running at high speeds.


The same is true of electric motors. Power is a product of both torque and speed. At zero RPM you have torque but no power because the wheels aren't turning.

In contrast, an electric motor provides full torque from zero kilometres an hour, with a linear relationship between how fast the motor is spinning and the power required.


False. The power requirements increase in proportion to the rolling and air drag combined, which is somewhere between velocity squared and velocity cubed, depending on the vehicle.

This article is broadly speaking in the right ballpark, but gets the details wrong. One of the issues is that generating high torque at low RPM is very inefficient. Electric motors too need to "rev up".

Apr 16, 2019
And, while the motor itself may be able to generate high torques (for a while, before it overheats), the rest of the electronics cannot. A small-ish electric traction battery cannot provide the current to run the motor, because the efficiency of the battery is reduced at high discharge rates.

For example, if the safe continuous discharge current of your lithium-ion battery is 5 C and you have a 25 kWh battery, your continuous "power rating" for the battery is 125 kW or about 170 HP (minus conversion losses). If your battery is sized at 100 kWh, then you get 500 kW or nearly 700 HP as long as the battery is completely full. As the voltage drops, the continuous power output drops as well.

Hence, the power output of your electric car has almost nothing to do with the motor - it has to do with your battery, or, how much beating you're willing to give it. Small battery, little power, less "grunt", big battery, more grunt, and extra heavy on the price tag.

Apr 16, 2019
More precisely, if you take an individual cell with a nominal voltage of 3.7V, you can observe that it varies between 4.2 - 2.8 Volts, and so for example, a 1000 mAh cell with a 5C continuous rating can provide you with 14 - 21 Watts of power. The continuous maximum power output drops by 30% as the battery empties.

Furthermore, drawing high current out of the battery causes its voltage to drop. If the voltage drops below a certain threshold, the battery cell gets permanently damaged, so as the battery goes empty you also have to limit the amount of current drawn out of it.

Torque in an electric motor is a function of electric current going through it, which means your motor is losing both power and torque as your battery gauge goes towards zero. This is why "high performance" electric cars like the Teslas are gimmicks. They're pushing the batteries to the limit.

EVs can have good torque and performance characteristics: the limiting factor is the battery, not the motor.

Apr 16, 2019
One of the limitations of modern EVs is that they omit the gearbox, because of cost and weight/size reasons. It's already difficult enough to fit all the batteries, the battery cooling system, and their crash shields in the car.

Electric motors do not operate efficiently when they are slowed down electronically. The efficiency becomes terrible below 25% of the nominal design speed because high current is needed to maintain torque, but it is doing less actual work. The difference is lost as heat.

The single-speed gearbox is designed so that the same motor can drive the car up to 120+ mph. That forces the motor to run in the inefficient region below 30 MPH speed, and sustaining high torque to pull loads becomes an exercise of trying to keep the induction coils from melting, or the permanent magnets from demagnetizing from the heat, depending on the type of motor.

Apr 16, 2019
Electric motors too need to "rev up".


Eikka, did you even watch the video? The Tesla beat the million dollar racing car dude! How much "rev up" time are you talking, a nanosecond? a microsecond?

https://www.carth...-torque/

I don't know what your bizarre rambling complaints are about anyway. I hear you drive a POS, have never even been in a EV, and probably never will. So go away and let the rest of us do something about global warming and air pollution while saving money on gasoline and repairs and having a blast doing it.

Apr 16, 2019
@Eikka.

The opposite is true, mate! The lower the revs, the greater the torque of electric car motor! Are you unwittingly lying (to yourself and me); or do you really not understand the electric motor performance parameters?

Add the fact that there's much less noise pollution; no fuel vapour/exhaust pollution; very little vibration; much less tuning/maintenance etc; much less cost of energy/fuel; and better ageing/resale value; and cleaner/safer environment from less mining/transportation/burning of fossil fuels in the wider environment...

Anyhow, mate, try to get a grip on your pessimism (or your biases from vested interests?) before (yet again) trying on your usual down-playing of benefits/economies from renewables/electrics; and up-playing your 'manufactured' and/or 'tortured' half-assed 'problems' that demonstrate your agenda all too clearly.

Sure, you can/should critique things, no problem; but at least try to make objective/informed critiques. Ok? Thanks. :)

Apr 16, 2019
The single-speed gearbox is designed so that the same motor can drive the car up to 120+ mph. That forces the motor to run in the inefficient region below 30 MPH speed, and sustaining high torque to pull loads becomes an exercise of trying to keep the induction coils from melting, or the permanent magnets from demagnetizing from the heat, depending on the type of motor.

@ Eikka-Skippy. Cher, you need to get back into the school. Electric drives have been around for over 130 or 120 years and we have gotten pretty good at it too. They have been used on trains and trolleys and boats and REALLY BIG dump trucks for longer than you have been a live,,,,, and without a multi-speed gearbox. When was the last time you saw a ship or trolley or train driver changing gears, eh?

Oh yeah, I almost forget. Really-Skippy got you on this one Cher,,, maximum torque is just before stall,,,, when you are talking electric motors.

Apr 16, 2019
@Uncle Ira.
Really-Skippy got you on this one Cher,,, maximum torque is just before stall,,,, when you are talking electric motors.
Then you better write to these folks and correct their knowledge base, Ira:
Thankfully, in electric motors, maximum torque is produced from the get-go. As a current flows through the electric motor, a related electrical charge causes an armature to rotate. These rotations within an internal magnetic field cause something called a back-EMF (electromotive force) which opposes the supply voltage.....The net overall force being applied to the wheels is therefore the difference between the supply voltage and the EMF. The back-EMF is proportional to speed, therefore the higher the speed, the smaller the net overall force is. This explains why the torque curve begins to diminish on an EV dyno graph as the car's electric motors are pushed into the upper ranges of their performance limits.


ps: You're still bot-voting, Ira? Not good, mate.

Apr 16, 2019
Then you better write to these folks and correct their knowledge base, Ira:
Thankfully, in electric motors, maximum torque is produced from the get-go. As a current flows through the electric motor, a related electrical charge causes an armature to rotate.
From the get up and go. Just at the beginning or rotation is maximun torque, Or another way of saying it, as the motor starts slowing due to a heavy and heavier load, the maximum torque is at the point just be for it do not turn any more. From the get up and go, is starting at the stall point Cher.

Nice try though, eh? I am the real engineer and this is a thing I know about. Stall in a motor is when the thing is energized and the shaft is not moving,,,,, that can be when it starts or when it stops from being overy loaded. Slower shaft speed, more the torque,,,,, faster the shaft speed,,,, Cher, the electric motor starts from a stall, but only real engineers would know that.

Apr 16, 2019
ps: You're still bot-voting, Ira? Not good, mate.


P.S. for you Really-Skippy. Non Cher it is not me. I have not been able to figure out how to make it do like it was on the automatical, And it's too much trouble on to chase you around and vote on each one separate. It must be somebody else who is in your troll-gang-bot-fan-club.

Apr 17, 2019
Welcome to this Electric Revolution

The simple solution TESLA implements
is
these field coils are induction motor coils
induction motor rotation depends on Frequency
this frequency changes
depending on the rotation of the Rotor
so
one and all
electric induction motors have gears
they infinitely change in frequency which is as an infinitely electronic automatic gear box
Welcome to this Electric Revolution in Frequency of Gears

p.s. straight from the horse's mouth from Tesla in The Lion Yard

Apr 17, 2019
@Uncle Ira.
The lower the revs, the greater the torque of electric car motor!
Just at the beginning or rotation is maximun torque, Or another way of saying it, as the motor starts slowing due to a heavy and heavier load, the maximum torque is at the point just be for it do not turn any more. From the get up and go, is starting at the stall point Cher.
Thanks for confirming what I said was correct all along, Ira. :)

ps: You're still bot-voting, Ira? Not good, mate.

P.S. for you Really-Skippy. Non Cher it is not me. I have not been able to figure out how to make it do like it was on the automatical, And it's too much trouble on to chase you around and vote on each one separate. It must be somebody else who is in your troll-gang-bot-fan-club.
You mean to say there's another bot-voting troll of your (allegedly former) calibre on the net, Ira? Wow! Still, at least you've come to your senses at last, cher Ira. Anyhow, Ira, your apology is accepted. :)

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