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Tuesday, December 06, 2005

Mitsubishi Continues Work on MIEV Electrics and Hybrids - Plug-ins Possible

Mitsubishi Motors will feature a new MIEV (Mitsubishi In-wheel motor Electric Vehicle) concept car at the upcoming 2006 North American International Auto Show (the Detroit Motor Show, scheduled for Jan 8-22nd), according to a press release issued yesterday. The MITSUBISHI Concept-CT MIEV is a four-door, four-passenger series-parallel hybrid that uses a gasoline generator and a bank of high energy-density lithium-ion batteries that power the in-wheel motors and drive each of its four wheels.

The Concept-CT is ment to showcase technology that, according to the Chicago Tribune, will be featured in a Mitsubishi mini-car to be introduced to the U.S. market "after 2008." The car will likely be based on the Colt currently being sold in Japan and will compete with Toyota's Yaris, Honda's Fit and Nissan's Versa all due out in the U.S. this coming Spring. While Mitsubishi will be late to the game, their offering will be a hybrid electric MIEV (the other three are all gas-only) and there is even talk that Mitsubishi will offer it as a plug-in.

[Update: here's a pic of the Concept-CT from the Detroit Auto Show - It doesn't look like a four-door from the picture through...]

Wayne Killan, vice president of marketing for Mitsubishi, is quoted in the Tribune article discussing charging the vehicle. "We would expect the car to be used in electric-only mode only in cities, where you could have access to a quick charge," he said. He also reportedly said that the estimated recharging time would be a scant 10 minutes although he couldn't definitively answer whether that would be a partial charge to give you enough juice to get to a socket for a full charge or whether it would be a full charge. This suggests the use of a quick-charge battery of the type being developed by Toshiba

Graphic: Possible applications of in-wheel motors: Hybrids, Electrics and Fuel Cell Vehicles

Development of their MIEV technology was first announced this May when Mitsubishi unvieled their The Colt version is a rear-wheel drive all-electric vehicle fitted Colt MIEV test-bed. with two 20 kW in-wheel motors that deliver 600 Nm (443 lb-ft) torque each to the rear wheels. The Colt MIEV has a top speed of 150 km/h (93 mph) and a cruising range of 150 km (93 miles) on a single charge.

Mitsubishi used the Colt testbed to perform on-road testing to identify and resolve any problems unique to the in-wheel motor vehicle, including any deterioration in road holding and ride comfort due to increases in un-sprung weight, as well as reliability and durability issues in the in-wheel motor system and its peripheral components (suspension, wheels, tires). They simultaneously worked on developing a more powerful version of the in wheel motors for 4WD applications.

These made their debut in the Lancer Evolution MIEV announced in August. This new version of the motor uses a hollow doughnut construction that locates the rotor outside the stator as opposed to a common electric motor where the rotor turns inside the stator [see graphic a bit below]. The Lancer used four motors, one in each wheel, to deliver 4WD capability. Each motor, manufactured by Toyo Denki Seizo K.K., produces a maximum output of 50 kW with 518 Nm of torque. A 355V lithium-ion battery system comprising 24 modules fits under the floor between the front and rear wheels to provide power. The Lancer Evolution MIEV has a top speed of 180 km/h (112 mph) and a cruising range of 250 km (155 miles) [Note the improvement over the Colt released just a few months earlier].

Mitsubishi is using the Lancer MIEV to evaluate the outer-rotor motor under a range of driving conditions. They have acquired vehicle type certification for the Lancer that allows the car to leave the proving ground and be tested under normal driving conditions on public roads. The Lancer was also entered in the Shikoku EV Rally 2005, held August 27-28 on the island of Shikoku, Japan [I'm not sure how it did... anyone know?].

The new Concept-CT MIEV seems to use the same in-wheel motors as the Lancer except they are used here in a series hybrid application. A gasoline engine will work as the genset for the car with the lithium-ion battery pack to provide power for the in-wheel electric motors. This would presumably be the same set-up as for the mini-car for retail release with the possible addition of plug-in capabilities.

Graphic: Exploded view of Mitsubishi's in-wheel motor

Mitsubishi's latest in-wheel motor (i.e. the one showcased in the Lancer) uses a hollow doughnut construction that locates the rotor outside the stator as opposed to a common electric motor where the rotor turns inside the stator. Mitsubishi points to several benefits from this design for the motor:

  • Greater ease of raising power output and torque.

  • Higher torque allows the speed reducer unit to be eliminated, meaning less weight and improved power transmission efficiency.

  • Better space efficiency with the brake assembly fitting inside the motor which itself fits neatly within the wheel house.

  • The outer-rotor arrangement also surmounts the difficulties presented to date by the steering system, making it suitable for fitting to and driving the front wheels—and facilitating 4WD in-wheel motor vehicles.

  • According to the press release on the Colt:
    the in-wheel motor makes it possible to regulate drive torque and braking force independently at each wheel without the need for any transmission, drive shaft or other complex mechanical components. For this reason, MIEV offers highly promising potential in the ongoing evolution of Mitsubishi's all-wheel control technology ... The fact that the drive system is housed inside the wheel itself offers significantly greater design freedom and also makes it easier to locate such space-consuming components as the battery system, fuel cell stacks and hydrogen tanks used in hybrid and fuel cell vehicles.

    The MIEV concept seems to be a versatile one with potential applications in hybrids, all electrics and fuel cell vehicles. Most importantly though, Mitsubishi's development of this system may well breath new life into the potential of the electric vehicle at a time when other major manufacturers have turned away from straight EVs and are even reluctant to discuss plug-ins. Mitsubishi is not only developing full EVs but even hybrids that only use the electric drive train and use the gasoline engine only as a generator and their Vice President for Marketing is even openly talking about plug-ins.

    I will certainly be watching the development of their MIEVs. Who knows, maybe one will be on the market by the time I need to buy my next car...

    [A hat tip to Jim at the Energy Blog and of course, Green Car Congress]

  • Mitsubishi press release on the Colt MIEV - May 11, 2005.

  • Green Car Congress on the Colt MIEV

  • Green Car Congress on the Lancer Evolution MIEV

  • Green Car Congress on the Concept-CT MIEV

  • Mitsubishi press release on the Concept-CT - December 05, 2005

  • The Chicago Tribune: Mitsubishi ponders joining mini derby despite late start - December 5, 2005

  • The Energy Blog on the Concept-CT and plug-in possibilites


    Jesse Jenkins said...

    Thanks for the ideas, Lucas. I've seen them posted elsewhere before so I know you've been talking about this kind of in-wheel motor long before Mitsubishi revealed their development of the concept.

    I agree that plug-in series hybrids (i.e. where the internal combustion engine runs a generator and does not directly provide traction) like the one you discuss, capable of running on biofuels as well (i.e. a flex-fuel plug-in hybrid of 'trybrid'), seems like the best approach to reducing use of oil and making our transport fleet significantly more efficient. I've gone through the numbers for a series plug-in hybrid as well as full EVs here.

    Jesse Jenkins said...

    Green Car Congress has more on the Concept CT, which was unveiled this week, as promised, at the Detroit Auto Show.

    Anonymous said...

    I like this statement: i-minicar targets the aging baby-boomers. Hey! They are not the only ones who demand cleaner cars. Me too! :)

    Jesse Jenkins said...

    Gizmag's got an article on the MIEV Concept-CT here if you're looking for more reading on the vehicle.

    Anonymous said...

    Along with the additional un-sprung weight and reliability problems mentioned, there's also wicked torque steer if one motor should fail. In a 4WD the system can immediately shutdown the opposing wheel and get to safety on the remaining two, but a 2WD might become almost undriveable.

    Anonymous said...

    Just to let people know an electric bike won the rally. You can get the official results here, but its a japanese pdf. If someone is willing to translate, I think a lot of people would be happy.