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Hiccups on the Road to Hybrid Acceptance
4 November 2005
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Although hybrids have been generally well-received in the US since their introduction here over five years ago, service and repair information has been slow to trickle down to the independent auto repair industry, even though many hybrids are now coming out of warranty.
A recent trade magazine article inadvertently highlighted this problem when it set out to explain basic hybrid powertrain configurations to professional auto repair technicians—and got the definitions wrong.
The October 2005 issue of Motor Age, a leading monthly auto repair industry magazine with a readership of over 380,000, focuses on hybrid technology. However, the magazine’s cover article, Don't Be Puzzled by Hybrid Repairs, incorrectly describes Honda hybrids as series hybrids and Ford, Lexus, and Toyota hybrids as parallel hybrids.
Honda’s hybrid vehicles are of a parallel configuration, while hybrids sold in North America by Ford, Lexus, and Toyota are equipped with series-parallel hybrid powertrains.
Toyota has produced a series hybrid, the 25-passenger Coaster bus, and its subsidiary Daihatsu now builds a parallel hybrid version of its HiJet Cargo microvan (earlier post); however, those vehicles are sold exclusively in Japan.
Today’s series hybrids use an internal-combustion engine to turn a generator, which in turn supplies current to an electric motor, which then rotates the vehicle’s drive wheels. A battery pack can be used as a buffer of sorts to store excess charge. Examples of series hybrids include DaimlerChrysler’s hybrid Orion bus (earlier post), as well as many diesel-electric locomotives.
Parallel hybrids, such as Honda’s Insight, Civic, and Accord hybrids, can simultaneously transmit power to their drive wheels from two distinct sources—for example, an internal-combustion engine and a battery-powered electric drive.
A series-parallel hybrid has the flexibility to operate in either series or parallel mode. Toyota’s powertrain, which some refer to as “series-parallel with power-split,” can operate in both series and parallel mode at the same time.
Although automakers have developed training programs for repair technicians employed by dealerships, such training is generally closed to the rest of the industry. Toyota and Lexus training is usually rated as very good by those who have completed their courses, while Ford’s and Honda’s training has been less than satisfactory to many of their technicians. Several independent training companies have addressed the industry’s need with seminars of their own.
Independent automotive technicians have historically played a significant part in the public’s acceptance of new automotive technologies, and consumers often look to the family mechanic for frank appraisals of new vehicles being considered for purchase.
Recent US legislation has forced automakers to launch public pay-to-play repair information websites, but no multimedia presentation can equal hands-on training in a workshop setting. Consumers overwhelmingly migrate to independent repair facilities when a vehicle’s warranty has expired, and a wider access to training will encourage those facilities to support hybrid technology and help to preserve the resale value of used hybrids.
November 4, 2005 in Hybrids | Permalink | Comments (6) | TrackBack (0)
Comments
Posted by: Ash | November 05, 2005 at 07:55 AM
It's about the power path; the Hondas run engine power to the wheels through a path parallel to the motor, not through the motor. Toyota's HSD has both series and parallel paths.
Posted by: Engineer-Poet | November 05, 2005 at 10:12 AM
Ash, hybrid powertrains are defined by the path(s) of energy through the powertrain. In a series hybrid, energy from one source is used to directly drive another source, which then drives the vehicle's drive wheels. There is only one path of energy, just like in a series electrical circuit.
In a parallel hybrid, such as those made by Honda, there are two distinct paths of energy: engine to drive wheels, and battery to electric motor to drive wheels. The two separate paths of energy converge to a single point, just like in a parallel electrical circuit.
Honda's hybrids can indeed run the engine without running the electric motor, if need be, although the electric motor can run by itself only in the 2006 Civic hybrid.
Furthermore, series-parallel hybrids, such as the Prius, can by definition run in either series OR parallel mode. If the electric traction motor is being powered by the battery to turn the drive wheels, and the engine is also contributing power to the drive wheels, then at that moment, the powertrain is operating as a parallel hybrid. If, on the other hand, the engine is used to directly turn the electric motor, which then turns the vehicle's drive wheels, then - again, at that moment - the vehicle is a series hybrid.
And yes, the Prius (and others) can switch back and forth between modes, or even combine the two, thanks to the set of planetary gears that Toyota calls a power-split device, or PSD.
Hybrid powertrain classifications were established decades ago. For more information on hybrid powertrains, you may want to check out the hybrid articles in the Bosch Automotive Handbook, 6th Edition, which is widely considered to be the "bible" of the industry.
Posted by: Jack Rosebro | November 05, 2005 at 10:41 AM
Doesn't Honda's ICE directly drive the Electric motor? Since the IMA motor is integtrated with the flywheel/flexplate?
Sure the electric motor can be turned on/off/generate ... but it still spins whenever the ICE spins.
Posted by: Ash | November 06, 2005 at 08:11 AM
Exactly, Ash. Now think of the path the power takes: both engine power and motor power go straight to the same shaft (parallel). A series configuration would run the engine power through the motor.
Posted by: Engineer-Poet | November 06, 2005 at 02:40 PM
Actually, this is where it gets sticky. Although the engine crankshaft and electric motor are on a parallel axis (actually, they are on the same axis), the fact that they are physically parallel does NOT make the system a parallel system. Rather, it is the fact that there are two paths, or "legs", of energy that eventually converge to drive the wheels.
An electrical parallel circuit, for example, is not so named because the circuit's two (or more) paths are physically parallel in the real world. It got its name from the fact that we draw them as parallel in wiring diagrams and schematics to make it easier on the eyes. Hybrid classifications have borrowed the nomenclature.
Again, a hybrid does not need to have the axis of the electric motor physically parallel to the engine's crankshaft to qualify as a parallel hybrid.
Technical classifications of hybrid powertrains is relatively easy, once you get them. On the other hand, the cultural classifications - full hybrid, mild hybrid, muscle hybrid, micro-hybrid - are a mess, and one which I won't touch publicly.
Posted by: Jack Rosebro | November 06, 2005 at 03:56 PM
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This naming scheme seems entirely backwards.
Honda's motors can't run the ICE and Electric motor seperatly, they have to run TOGETHER, to me that makes them series. (Like light bulbs in a series, they have to run together)
Toyota's Prius can run either the electric OR the gasoline, OR both... to me that makes them parallel.
The "correct" definitions seem counter-intuitive.