Why do Tesla need 2 motors for AWD?

[tintinfish]

Stupid question, but you know how for gas AWD cars, they only have 1 engine; so technically Tesla can implement AWD using just 1 motor, right? Why do they use 2?

 

[M3DS]

It is a design decision. It made more sense to add another motor than to provide a driveshaft and other bits. It also gives you redundancy and more control. And, why not?

 

[HAL2001]

And probably energy savings.

 

[GtiMart]

Being forced to have a single engine, ICE cars need to rely on center differentials with a driveshaft. There are losses in the drivetrain, there is weight involved, and that shaft takes room in the middle of the car (the middle "hill"). To output the same power in a single motor, that motor would need to be bigger too. I'd say it's simpler to electronically control the difference in wheel speed from front to back and decide on power output based on available traction, on top of saving that hardware, to use two motors.

 

[tstolze]

The battery is in the way of everything to connect the front/back drivelines.

 

[SabrToothSqrl]

you could use one brake assembly for all 4 wheels just as "easily"...

but yea, this comes down to cost/efficiency/control, etc.

 

[Effopec]

I read a teardown analysis that said that the cost of a Tesla motor was about $750. I'm sure much cheaper to add another than to add a drivetrain to the front (or rear) & all the associated changes that would require. Plus as others have said, you would lose valuable space where the battery pack sits.

 

[Clivew]

Because having one engine that drives all 4 wheels is a terrible design that adds complexity and weight, but is the only realistic architecture with ICE vehicles.

The best design would be an electric motor inboard of each wheel.

 

[bjrosen]

AWD is much easier to do in an EV then in an ICEV. Using a single engine requires complex mechanical linkages to deliver power to the front and the back wheels, balancing that power is a complex problem. With two motors the computer can chooses how much current is delivered to each motor and it can do it at the speed of light. An ICEV has a big hump down the center of the car for the transmission and the drive shaft, an EV doesn't. The two motors can be optimized for separate things, one for economy and one for performance. Tesla has different reduction gear ratios for the front and back motors, this gives them the effect of having a two speed transmission without having a transmission at all. The front and back regen brakes each have their own motor to drive, that gives you higher regen.

 

[Vines]

Because having one engine that drives all 4 wheels is a terrible design that adds complexity and weight, but is the only realistic architecture with ICE vehicles.

The best design would be an electric motor inboard of each wheel.

Imagine the insane levels of grip and maneuverability that 4 independent controlled motors could bring, especially with world class dynamic stability control.

 

[stopcrazypp]

Stupid question, but you know how for gas AWD cars, they only have 1 engine; so technically Tesla can implement AWD using just 1 motor, right? Why do they use 2?

There were some ICE cars that used two engines to achieve AWD also, but in a practical sense it's hard to have two engines (especially one front and one back) in a ICE car. Takes up all your cargo space, plus you have to deal with two emission systems.
Awesome Cars With Two Engines

In EVs it's easy to fit a second motor and is the better solution for all the other reasons people pointed out.

 

[joebruin77]

Imagine the insane levels of grip and maneuverability that 4 independent controlled motors could bring, especially with world class dynamic stability control.

Doesn't the Rivian pickup have this feature, with one motor at each wheel? As a result, it can do a "tank turn" and spin on its axis.

 

[theothertom]

Additionally, one is an induction motor, and one is a permanent magnet motor. They both have pros and cons but having both is, well....the best of both worlds.

 

[Perscitus]

Tesla actually needs 4 motors, one at each hub.

The late 2010s, early 2020s dual-motor compromise, it too shall pass.