Maybe, they finally are getting serious about hybrids. Who are they? Green Car Congress reports that BMW has joined as an equal partner with DCX and GM.
No member of this new, HEV triumvirate has been an advocate of hybrid technology in the past. With the success of Honda and Toyota HEVs, it is a different ballgame. Changes in the oil market, along with recent consumer acceptance, has shortened the timetables in plans by the major automobile manufacturers. Globally, transportation planners are hoping to transition to fuel cells sooner.
Note: Rather than ICE generating electric power, a fuel cell provides the electric power. A hybrid electric vehicle is an intermediary step.
GCC previously reported on a dual mode system developed by General Motors. “The first mode is for low-speed, stop-and-start, in-city driving. The second is for highway driving? “an area in which other single-mode hybrids have not performed as well as expected.”
This system will reduce fuel consumption at highway speeds much more effectively than available single-mode systems and achieve at least a 25% improvement in composite fuel economy in full-size truck applications. — Tom Stephens, Group Vice President, GM Powertrain
The system relies on two electric motors coupled to two gearsets rather than a single motor. This, in essence, is an electrically variable transmission that provides a more flexible range of operating power, control and efficiency than can be obtained using a single electric motor. For low-speed and light loads, one electric motor acts as a generator, while the other electric motor provides propulsion. In the second mode, “both motors selectively operate in motoring or generating modes depending upon the vehicle speed.”
The GCC article notes that “this approach increases the mechanical complexity of the system and the accompanying requirements for sophisticated engine control software.” On the other hand, the dual mode system uses smaller motors, inverters and batteries, thus reducing mass and cost.
What the article fails to mention is whether the ICE provides propulsion or whether it only drives the generators. And, does one of the electric motors also serve as a starter for the ICE? It would seem that this design is consistent with the maxim of Andy Frank, for more efficiency use a bigger electric motor and a smaller ICE, except that GM has divided the electric motor into two.
This design also could support a plug. The GCC article suggests that one possible reason Daimler-Chrysler joined with GM was that Mercedes found during road-testing that their diesel hybrid prototype (F500 MIND) “delivered worse fuel economy in highway driving than the conventional diesel.” A German auto magazine also found a Mercedes diesel to be more efficient than a Lexus hybrid. Daimler-Chrysler also has road-tested (and currently is road-testing in the United States) PHEVs.
A PHEV may have an advantage over the dual mode system, as proposed by General Motors, since a PHEV can go longer running strictly on stored electric power without running the ICE. If the ICE starts and accelerates rapidly to an efficiently operating, constant RPM only for electric power generation, then the potential advantage of the PHEV is reduced since both vehicles are using electric drive for low-speed, stop-and-start, in-city driving and the advantage of more efficient power generation by an electric utility over the on board ICE generation would be offset by the additional battery cost. Furthermore, the dual mode system is efficient because it essentially utilizes a specialized CVT (Constantly Variable Transmission).
It might prove an interesting experiment if DCX places the dual mode hybrid system is some of Sprinter vans similar to the PHEVs now being tested. Besides seeing this new hybrid system in a Chevrolet Tahoe, GMC Yukon or Dodge Durango, you also may see it soon in a Mercedes SUV.
It also is interesting to speculate on why BMW joined this advanced hybrid consortium. If you look at the above graphic and imagine the one electric motor is a starter / generator and the vehicle having not one additional electric motor for propulsion, but four in-wheel electric motors, then you may be envisioning what Mercedes or Mitsubishi will have in the near future. Is BMW also experimenting with in-wheel motors that not only drive the vehicle and provide for regenerative braking, but also use these same capabilities to improve traction control and prevent skidding? Or, is BMW only interested in adding “supercaps” to their version of a dual mode hybrid system?
What’s next? Fuel cell Hummers with in-wheel Symetron motors and ultracaps?
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[...] The challenge to these battery manufacturers is whether fuel cells will quickly “leap frog” this new technology. The major automobile manufacturers in the United States and worldwide have invested heavily in fuel cell development. Nonetheless, the timetable has changed. Automobile manufacturers are introducing, or scrambling to introduce, HEVs on the market and seeking intermediary measures, e.g., better batteries, better motors, etc., while “ramping up” fuel cell development. [...]
[...] Two Electric Motors Another approach is to use two electric motors in line. An example is the GM dual mode hybrid. Another example is the e-CVT, which has two electric motors in the transmission. On the evlist, Lawrence Rhodes provided some url’s of two motor EV’s: [...]