It seems like dual motor EVs have significantly less range. Can’t dual motor EVs run in single motor mode to save range and only use the 2nd motor when absolutely necessary? The motor can’t weigh that much that it contributes to often 50mi difference in range.
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Can you give an example? Because the only EV that offers both (off the top of my head) is Tesla and the dual motor has 20% more range
When would the dual motor be “needed” in your estimation?
Even if you discount the raw performance benefits of it (HP, torque), dual motor also allows the car to be AWD which is useful at all speeds.
The main difference between a dual-motor EV and a single-motor EV is weight. Each motor weighs 100lbs+, plus all the necessary related components like extra wiring and controls can easily add up, so having fewer motors saves a pretty significant amount of weight.
In terms of pure power efficiency, there isn’t that much of a difference. Running 1 motor at 20kW or running 2 motors at 10kW each will use roughly the same amount of battery power because the power loss converting battery energy into mechanical energy will be roughly the same regardless of how many motors.
So if you have a fixed capacity battery, the amount of electrical power and thus the amount of mechanical power (and range) you can get out of it mainly depends on the weight and of the car. And since single-motor EVs weigh less, they get slightly more range.
As well as additional weight there is also additional mechanical friction with the extra parts of the drive system and motor.
It may even be possible that the motor not in use has to use a small amount of power to compensate for the additional friction.
As well as additional weight there is also additional mechanical friction with the extra parts of the drive system and motor.
It may even be possible that the motor not in use has to use a small amount of power to compensate for the additional friction.
They can! Polestar introduced that exact functionality on the 2023 version of the Polestar 2:
https://media.polestar.com/global/en/media/pressreleases/663202/polestar-2-brings-more-power-performance-and-range
A single electric motor will use less electricity to produce 200 hp than two motors will use to each produce 100 hp to the wheels. This is due to the energy loss in converting electrical energy into mechanical energy. There will be twice as many bearings involved (friction), twice as many wires/windings (electrical current loss), and twice as many gears/drivetrain points (inertia loss).
The performance upside is that doubling of components also means the entire vehicle can handle more total electrical current and will have twice as much traction (tire contact area) to the ground to better translate electrical power to forward vehicular acceleration and velocity.
Imagine a person riding a kick scooter. Now imagine TWO people riding a kick scooter, simultaneously. Now imagine only one kicking and the other just riding.
Other than due to more weight, some cars have the ability to mechanically disconnect the 2nd motor so the loss is minimized compared to the cars that didnt mechanically disconnect.
So the loss become minimal when the 2nd motor is mechanically disconnected. So the loss mainly due to weight
Adding to the other factors already pointed out, some electrical motors (such as permanent magnet synchronous motors) actually consume energy when they are spinning but not powered.
Motors also have a specific range in which they operate efficiently in. Dual motor EVs employ different motors in the front and rear to take advantage of this and allow the car to operate efficiently at slow and fast speeds.
An ELI5 electrical motor and a generator are essentially the same thing, just depends on if you’re giving electrical power to in and extracting kinetic power (rotation) out, or if you’re giving kinetic power in and extracting electricity out.
Simplifying for ELI5, even if the motor was not connected to anything, the pure act of spinning the motor (such as when the wheels of the EV are rotating at high way speeds) will cause rotational resistance in the motor that will require more energy to overcome. This energy is converted into heat inside the windings of motor, which is dissipated and lost.
For a ELI16, the magnetic flux of the motor as its moving causes induced electrical current in the motor windings which, unless you’re playing with superconducting exotic materials, will converted to heat due to electrical resistance.
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