Published on October 16th, 2012 | by Zachary Shahan


In-Wheel Electric Drive — FTW!

October 16th, 2012 by  

We’ve covered the idea of in-wheel electric drive or electric motors once before. Clearly, there isn’t a lot of news in this space. But I think this is a super interesting cleantech solution with a lot of potential. Reposted from Electric Love, here’s a company betting its money (and tens of millions of dollars from investors) on in-wheel electric drive:

Electric vehicles are very different from gasoline-powered vehicles, as we all know. But one unique thing about electric cars that might not have crossed your mind is that the wheels of an EV could potentially receive their power directly from electric motors.

Protean Electric, which has received tens of millions of dollars from Chinese and US investors, is reportedly working on building a manufacturing facility in China for such a technology.

Notably, Protean Electric’s CEO is a certain Bob Purcell, the “father” of the EV-1 (the world’s first modern electric vehicle) at his former employer, General Motors (GM).

“The Protean Drive™ system can improve vehicle fuel economy, add torque, increase power and enable improved vehicle handling to both new and existing vehicles,” Protean writes.

“The direct-drive configuration reduces part count, complexity and cost, so there is no need to integrate traditional drivetrain components such as external gearing, transmissions, driveshafts, axles and differentials.

“Direct-drive, in-wheel motors require no gearboxes, driveshafts or differentials thus giving far greater flexibility to vehicle designers while substantially reducing drivetrain losses. The reduced drivetrain losses mean less energy is wasted (during both acceleration and regenerative braking), resulting in more of the energy from the battery pack being available to propel the vehicle.”

Sounds pretty darn tasty.

With such a system, each individual wheel can actually be controlled separately, with better performance being the result.

Since an announcement of $84 million in venture funding back in July 2012, Protean hasn’t released any big news. However, its site states: “Prototype manufacturing will begin in early 2013 with volume production in 2014, out of Protean’s new manufacturing facility in Liyang, China”

Here’s a video for more on the technology, followed by the company’s full statement on the technology’s benefits:


Protean’s system can increase fuel economy by over 30 percent depending on the battery size and driving cycle. It is also powerful enough to be the only source for traction on a variety of vehicles. Its ease of integration can simplify the adoption of hybrid and electrified powertrains across a broad range of vehicles.

Protean’s in-wheel motors have the highest torque and power density of any of today’s leading electric propulsion systems. Each Protean Drive™ in-wheel motor can deliver 81 kW (110 hp) and 800 Nm (590 lb-ft), yet weighs only 31 kg (68 lbs.) and is sized to fit within the space of a conventional 18- to 24-inch road wheel.

Protean Drive™ also has superior regenerative braking capabilities, which allow up to 85 percent of the available kinetic energy to be recovered during braking. This can increase driving range up to 30 percent and contribute to the reduction of battery size and cost.

Other benefits include:

  • Can deliver hybrid and electric vehicle technology faster and with fewer new parts, less complexity, and at a lower total cost than other leading electric drive systems
  • Can be developed as a retrofit application for existing fleets as well as for new vehicles
  • Does not require external gearing, drive shafts or differentials
  • Each motor has a built-in inverter, control electronics and software
  • Does not require a separate motor power electronics module to be fitted to the vehicle
  • Can be added to FWD, RWD or AWD platforms regardless of the fuel type
  • Avoids costs of unique hybrid drive tooling changes to chassis, bodies and transmissions
  • Can help create a hybrid vehicle with fewer changes to the base engine systems and components and is less disruptive in the assembly plant
  • Can be a common system for HEV, PHEV and EV vehicles on the same platform

Check out our new 93-page EV report, based on over 2,000 surveys collected from EV drivers in 49 of 50 US states, 26 European countries, and 9 Canadian provinces.

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About the Author

is tryin' to help society help itself (and other species) with the power of the typed word. He spends most of his time here on CleanTechnica as its director and chief editor, but he's also the president of Important Media and the director/founder of EV Obsession, Solar Love, and Bikocity. Zach is recognized globally as a solar energy, electric car, and energy storage expert. Zach has long-term investments in TSLA, FSLR, SPWR, SEDG, & ABB — after years of covering solar and EVs, he simply has a lot of faith in these particular companies and feels like they are good cleantech companies to invest in.

  • Pingback: Protean's In-Wheel Electric Motors Coming To Market In 2014 | CleanTechnica()

  • Zach, this is great stuff! The simplification/weight reduction arguments carry the day. What I haven’t yet seen from any EV manufacturer is a quantification of these benefits, other than the relatively vague “30% more range” statement. If the manufacturers could come up with a car that had 200+ miles of range, and contrast the average cost of ownership /mile with ICE cars, I think they’d sell a heck of a lot more vehicles.

    • Thanks. Yeah, would always be nice if they shared more numbers with us. 😀
      There does seem to be a lot of potential here. Just wonder if it will end up competing with the more common systems or not.

      We Will See 😀

  • wattleberry

    Bob, I wonder if Michelin’s reticence on this may be the unsprung weight issue. Possible solutions could be making the motor very light or, perhaps more feasible, incorporating some elasticity into the link between motor and wheel rim?

    • Bob_Wallace

      I’ve seen the unsprung weight argument a number of times. Last time I looked around on the web and found this…

      “*A stock 2007 Ford Focus was compared with an identical vehicle modified with 66 lb (30 kg) of ballast fitted to each wheel. The weight was distributed between rotating and nonrotating unsprung masses as to broadly replicate Protean Electric’s PD18 (18-in diameter) wheel-hub-motor unit. The project plan included three phases of analysis and testing.

      Phase 1 focused on modeling of different modifications, including suspension spring, bushing, and damper rates, and different tires and pressures, and their effects on the IWM-equipped vehicle. It was determined that simply fitting a standard Focus ST suspension (an upgrade on the stock base car) would be a good practical solution.

      In phase 2, the stock vehicle was modified with the Focus ST suspension. This setup included revisions to the front and rear spring rates, dampers, and the rear antiroll bar. In phase 3, the Focus with the modified ST suspension was retested. The process included a subjective vehicle assessment, objective ride and handling tests, on-road shake measurements, and two-post shaker rig measurements.

      The studies concluded, and the presenters argue, that while the vehicle carrying the greater unsprung mass at each wheel did display perceptible differences compared with the stock vehicle, those differences were minor and can be mitigated using “normal engineering processes within a product development cycle.”

      By fitting the upgraded ST-level suspension to the car replicating one equipped with Protean PD18 in-wheel motors, the vehicle’s handling and on-center tracking were improved back to reference. Overall, the effort conducted by Protean Electric, Lotus Engineering, and Dunamos may help convince skeptics that the addition of 30 kg of unsprung mass per corner will not adversely impact overall vehicle dynamics and can be addressed fairly easily with cost-effective countermeasures.”*


      Furthermore, it seems to me if you’re using electric motor to control the vehicle height rather than liquid/air shocks then the unsprung weight wouldn’t matter. Feed a bit more power to the motor as the wheel travels downward in order to maintain the same amount of force between vehicle and wheel, capture that power back as the wheel comes back up.

      You’d loose a bit of energy in the transaction but it’s like more than offset by eliminating drive train power loss and by overall weight reduction.

    • Bob Wallace

      Here’s something I had stored away on the Michelin wheel…

      “Hub or wheel motors have been used in prototype electric cars and trucks, though none are yet in volume production. They are quite common in electrically assisted bicycles and other personal transportation vehicles.
      Now, Michelin has taken the hub motor idea one step further with its Active Wheel. Besides the electric drive motor found in all hub motors, the Active Motor also includes the vehicle’s suspension and brake components.

      Along with a small but powerful main drive motor, a second motor powers the active suspension system that’s fitted vertically across the diameter of the wheel. The suspension, which is now electrically controlled, can automatically and very rapidly correct for pitching and rolling. Response times of just 3/1000ths of a second are claimed. Finally, a ventilated brake disc is fitted inside the rim. Because it’s larger in diameter than a conventional brake disc, the disc depth is smaller, allowing more compact packaging.

      According to Michelin, the Active Wheel greatly simplifies vehicle design because an engine gearbox, clutch, transmission shaft, differential, and shock absorbers are no longer needed. Besides being simpler, the vehicle can be substantially lighter and thus more energy efficient. Packaging propulsion and suspension components in the wheel frees up space at the front of the car, which could be used to improve the absorption of impact energy.

      Other advantages include the potential for a flat floor and more efficient interior packaging.”

  • Bob_Wallace

    Michelin did build a prototype in-hub EV a few years back, but they’ve been pretty quite since then.

    In-hub is very interesting to me. Should make it easy to market 4wd versions and with electronic suspensions should allow for vehicles to rise up on rough roads for clearance and then lower themselves on smooth roads for better mileage and handling.

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