This month's Toyota e-bulletin has some timely "information" (some might call it propoganda) regarding hybrid technologies - now and in the future.  You'll notice in the article that the only technologies with negatives are ones that Toyota does not currently employ (Mild Hybrids, Series Hybrids, Plug-Ins, and Li-ion batteries).  It does provide mostly good and accurate, though biased, information.  You can check out the whole Toyota eBulletin here (caution:  pdf link). 

Curre­nt And Future Hybrid Technology:

What's In It For Consumers?

As the mainstreaming of hybrid technology accelerates, and the price of oil hits record highs, Toyota factories churn out hybrids in an array of vehicle segments. And at the same time, Toyota engineers aggressively research near- and long-term solutions, from plugin hybrids to advanced batteries to fuel cells.

In the not-too-distant-future, a large portion of vehicles will employ a hybrid powertrain of some description. In this fast-changing landscape, here's a quick overview of current and near-future hybrid technologies, along with their advantages and disadvantages to consumers.

• Parallel hybrids have both an electric motor and an internal combustion engine, which both power the vehicle, sometimes separately or in combination. Most hybrids currently sold in North America are parallel, including all Toyota and Lexus hybrids.

• Advantages for consumers: As illustrated by the more than 1 million Toyota hybrids on the road worldwide, parallel hybrids are proven, reliable, easy to use and widely accepted by consumers. Operation is nearly indistinguishable from current conventional vehicles, with the bonus of substantially better fuel mileage and lower emissions.
  

• Disadvantages for consumers: Extra purchase price offset by excellent fuel economy and low emissions.

• Full Hybrids are a subset of Parallel hybrids. All Toyota hybrids are full hybrids, and have sufficient electric motor power and battery capacity to propel the vehicle solely under electric power in certain conditions.

• Advantages for consumers: Quiet, emission-free stop-and-go electric operation in some conditions. Because both electric motor and engine can simultaneously contribute power, acceleration to merge into fast-flowing freeway traffic or pass 18-wheelers on two-lane roads equals that of conventional vehicles.
  

• Disadvantages for consumers: Extra purchase price offset by excellent fuel economy (particularly in stop-and-go driving) and good power.
  

• Mild Hybrids/Very Mild Hybrids are another subset of parallel hybrids.

Mild hybrids like some GM vehicles use the electric motor as an assist for the gasoline engine, and never use only the electric motor to motivate the vehicle. “Very mild” hybrids do not have an electric propulsion engine at all. Instead they switch the engine off when coasting, braking or stopped in traffic. A combination electric motor and generator charges the batteries while coasting and braking and uses the power to restart

the engine.

• Advantages for consumers: Mild hybrids offer less fuel economy advantage than comparable full hybrids. Fuel mileage for “very mild” hybrids is increased by about 10 percent.
  

• Disadvantages for consumers: Extra cost and complexity for modest fuel economy gain.
  

• Series hybrids are propelled only by an electric motor. An on-board internal combustion engine (turning at an efficient constant rpm) recharges batteries, but never drives the wheels directly. This technology is currently employed by locomotives and some buses, but no series hybrid cars or light trucks are currently mass produced.

• Advantages for consumers: Potential for better mileage and lower emissions than parallel hybrids, especially if plug-in technology is used. Efficient diesel engines, tiny turbines, fuel cells, or other powerplants could replace piston engines.
  

• Disadvantages for consumers: Because the gasoline engine is not available to propel the car, the electric motors and batteries must potentially be much bigger and costlier those of a parallel hybrid to provide acceptable acceleration. Also, while comparatively long range on EV power alone is promising, the engine, generator and gas tank in those situations would be extra weight and cost that would be underutilized.

• Plug-in hybrid technology now under development by Toyota and others would add the ability to use low-cost, household electricity to recharge the batteries of a parallel or series hybrid.

• Advantages for consumers: The cost to go a given distance on household electricity alone would be significantly lower than current hybrids.
  

• Disadvantages for consumers: Many consumers do not have electric outlets where they park. Additional coal-fired powerplants may be needed to meet extra electricity demand. Additional batteries may drive up purchase price and reduce overall mileage if the plug-in feature is not employed.
  

• Nickel-metal hydride (NiMH) batteries are the most common type used in hybrids.

• Advantages for consumers: Proven technology offers long life and reasonable cost. NiMH are warrantied for up to 150,000 miles or 10 years and some Prius taxis have racked up a quarter-million miles.
  

• Disadvantages for consumers: Electric-only range is limited.

• Lithium-ion (Li-ion) batteries are common in personal electronics and are used by low-volume vehicle makers and modifiers. Toyota and others are currently conducting experiments with this promising technology.

• Advantages for consumers: Potential for longer electric-only operation. Li-ion should weigh less than NiMH.
  

• Disadvantages for consumers: Has yet to show life-of-the-vehicle reliability. Li-ion batteries for vehicles must overcome thermal runaway issues found in computer batteries. Li-ion batteries are more difficult to recycle than NiMH batteries.
  

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