Battery Switch Technology

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Saturday, January 23, 2010

Hybrid Electric & Fuel Cell Vehicles



Hybrid Electric Vehicles


Both technologies come together in hybrid electric vehicles, also known as HEVs or hybrids. Present-day hybrids are equipped with ICEs and electric motors. A hybrid's ICE engine, as in any ICE-powered car, produces power through continuous, controlled explosions that push down pistons connected to a rotating crankshaft. That rotating force (torque) is ultimately transmitted to the vehicle's wheels.

A hybrid's electric motor is energized by a battery, which produces power through a chemical reaction. The battery is continuously recharged by a generator that—like the alternator of a conventional car—is driven by the ICE.

Hybrids can have a parallel design, a series design, or a combination of both:

  • In a parallel design, the energy conversion unit and electric propulsion system are connected directly to the vehicle's wheels. The primary engine is used for highway driving; the electric motor provides added power during hill climbs, acceleration, and other periods of high demand.
  • Series design, the primary engine is connected to a generator that produces electricity. The electricity charges the batteries, which drive an electric motor that powers the wheels. HEVs can also be built to use the series configuration at low speeds and the parallel configuration for highway driving and acceleration.

  • In conventional vehicles, energy from deceleration is wasted as it dissipates. In some hybrid vehicles, regenerative braking systems capture that energy, store it, and convert it to electricity to help propel the vehicle—ultimately increasing overall efficiency. Some hybrids also use ultracapacitors to extend the life of a hybrid vehicle's on-board battery system because they are better suited to capturing high power from regenerative braking and releasing it for initial acceleration.

    Hybrid passenger cars arrived in the United States in model year 2000, following their introduction in Japan a few years earlier. First came the two-seat Honda Insight, followed by the Toyota Prius in model year 2001. Honda then introduced a hybrid version of its Civic sedan, and Toyota offered a second-generation Prius. Ford plans to introduce its first hybrid, a version of the Escape sport utility vehicle, in model year 2005. Several other major automakers now either offer HEVs or plan to do so in the near future. Hybrid systems have also proved effective in buses and heavy trucks. For example, Oshkosh Truck Corporation has demonstrated a diesel-electric system that may significantly improve the fuel economy and driving range of military vehicles. As a bonus, hybrids can be devised to generate alternating current electricity for other applications such as plug-in power tools. General Motors, through its Allison Transmission Division, produces a diesel-electric hybrid drivetrain for transit buses.

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