Battery cost a big question for hybrids


I’ve been reading everything I can find on hybrid vehicles. I’m seriously considering purchasing one but am still torn as to whether the long-term payoff justifies the higher price. What’s your take on hybrids? Are they reliable? – Susan Tedesco, Santa Clara, Calif.

I’ve been intrigued by this topic ever since trying out a right-hand-drive Japanese-market Toyota Prius in 1999. I learned about regenerative braking, complex powertrain management, and the complementary blending of gasoline and electric drive. While impressed with the creative and diligent engineering, I couldn’t help but wonder about the added complexity of maintaining two powertrains, battery replacement cost, return on investment and other issues.

Fixing broken cars for a living does that to you, especially after seeing great ideas fizzle miserably, such as the Cadillac 8-6-4 cylinder-deactivation system of 1981. Fast forward to 2006 and hybrids are selling like hotcakes, their powertrain, batteries and control systems are well-proven, and my initial skepticism has turned to admiration.

Hybrid propulsion systems have been around in one form or another – in automobiles, submarines and locomotives – for a very long time. Ferdinand Porsche was a hybrid pioneer, combining electric and diesel power to maximize performance in 1899.

An electric motor generates the most torque as it is just beginning to turn, while an internal-combustion engine needs to spin up to become efficient. Coupling the two together provides more consistent torque through all ranges of operation. In addition to providing supplemental or stand-alone power, modern hybrid vehicles use the electric motor to generate electricity during braking, recapturing energy that would have been lost to heat. A modest battery pack, about the size of a suitcase, stores the energy for electric-only operation, for starting the gasoline engine, or for combined use.

How efficient is a hybrid? A typical gasoline-powered automobile is only about 16 percent efficient in delivering raw energy to the wheels. Much is lost to heat – about 70 percent goes out the tailpipe and radiator – and friction, wind resistance and occasional braking grab the rest.

A Toyota Prius puts about 32 percent of the fuel’s energy to the pavement. It also reduces carbon-dioxide emissions, which are an unfortunate product of even the most efficient internal combustion engine. The more time the gas engine is unused, the better!

Are hybrids worth the extra purchase price? It depends on your driving habits, how long you’ll keep the vehicle and a bunch of intangibles. Besides fuel economy, the equation also includes the merits of carbon-dioxide reduction, possible HOV lane usage, potentially higher maintenance costs and even image.

My primary concern is the cost of battery pack replacement. In spite of proven durability and generous warranty coverage, this will be an issue someday for a high-mileage hybrid owner. Depending on the vehicle, this can run around $2,000.

For more information on hybrids, check out this great Web site:

Brad Bergholdt is an automotive technology instructor at Evergreen Valley College in San Jose.