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The Arrival of the Wheel Hub Motor

Update : Proteanelectric totally got it down. But they are not very active.

Road testing

A few years back we wrote a piece about wheel hub motors. These (electro) motors are located in the wheels of a car, and could make conversion of an IC car into a EV very easy, as they don’t have to use more space than the wheels already do. These wheelmotors are available for cars, heavy trucks and busses.

There’s enough space in a wheel hub to hold a powerfull electromotor


The wheel hub electromotor is a very old concept, many of the early cars where electric, and even then the idea of putting weight in the wheels made sense. The lower the weight, the better the car holds the road and the lighter the chassis mounted on the springs will be.

1900 Lohner-Porsche petrol-electric hybride

The wheel hub motors are used now in two super car concepts, and they may become the quick and dirty way to create a rolling EV chassis. One is the Rimac, the other the Quant. The 1088 HP Rimac uses conventional Lithium Phosphate batteries and has a range of about 370 mi or 595 km. These numbers are a bit out there though 😉

The other supercar is the Quant, it uses flow cell batteries, which is a first in cars. Flow cells are like wet batteries but the electrolyte is kept in a separate container, and fed to the electrodes when needed. This makes the output power independent of the total capacity of the system, so you can have low output power flow batteries holding thousands of kilowatthour and you can have high output holding only a few kilowatthour, and everything in between. Conventional batteries have storage linked to output capacity.

Because in flow cell batteries the power is stored in the electrolyte it is possible to ‘refuel’ it by replacing the discharged electrolyte with charged electrolyte. One drawback of this system can be that the electrolye is toxic, although in the case of the Quant one has been chosen that is non toxic.

As you can see the Quant uses four electromotors located in the wheels. The image also shows the two electrolyte compartments (in the case of Vanadium for example, the electrolyte in one container can accept electrons, while that in the other can offer them, causing current to flow through the electrodes to power the car). The car also uses supercapacitors, this is common in electric cars. Supercapacitors can store and release relatively small amounts of energy but do so extremely fast. They can thus match the dynamic requirements of driving a car, and are also used to catch the electricity generated while braking.

Above a Michelin Activewheel wheel hub motor where the coils are not integrated with the rim of the wheel. This may make it more shock resistant, and allow sourcing of electromotors from different sources. More changes to the car and suspension are needed though.

The spanish Volar-e is build on the Rimac chassis by spanish engineering firm Applus+Idiada. It also has four wheel engines, and maybe more similarities. It seems that the four wheel motor concept allows for flexible design.

We hope to see conversions of traditional cars using wheel hub motors, so that the transition from IC cars to electric won’t require a full replacement of every IC car with a new one. People are trying it and developing kits.

This story is about converting cars from internal combustion to electric, EV car conversion, hybrid drive, electric drive, wheel hub engines, or wheel hub motors.