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Calculating Standard Cell Potentials

Introduces cell potentials and discusses how to mathematically predict reduction potential of different types of chemical cells.

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Practice Calculating Standard Cell Potentials

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Horsepower and Hybrids

Horsepower and Hybrids

Credit: Kecko
Source: http://www.flickr.com/photos/kecko/8217510887/

Concern about depleting petroleum supplies has stimulated interest in alternate power sources. This stimulus is also fed by a desire on the part of many people to reduce air pollution. One outcome of these concerns is the development of hybrid vehicles powered both by gasoline and electricity.

News You Can Use

• Hybrid vehicles are designed to operate at least part of the time on an electric battery. In order to have a functioning vehicle, there needs to be some idea of how much power will be needed from the battery. If we know the power output (voltage) of an individual cell, we can begin our calculations. By knowing the horsepower demands of the engine, the proper number of cells can be employed to power the vehicle. Consideration must be given to the demands made in terms of top speed, weight of the vehicle, the amount of hill traffic expected, and the desired distance to be traveled before refueling.
• Today, most hybrids use some form of a nickel-metal hydride battery pack for electric power. The positive electrode is nickel oxyhydroxide (NiOOH) while the negative electrode is a hydrogen-absorbing alloy. The vehicle battery is made up of a number of 1.2 volt cells packaged in modules (some are 1.3 volts). Total power output will depend upon the specific battery configuration, but will be in the range of 200 volts or more.
• Credit: Michael Pereckas
Source: http://www.flickr.com/photos/beigephotos/343495739/

Hybrid cars often have multiple batteries to power the various functions of the car [Figure2]

• More recently, a great deal of interest is being shown in lithium ion batteries. These batteries have a higher power output than nickel-metal hydride and tend to be lighter in weight. There are some safety issues that don’t exist with other kinds of batteries, but scientists and engineers are working to resolve these questions.

Show What You Know

1. What is “idle-off”?
2. What is regenerative braking?
3. What do lithium-ion and nickel metal hydride batteries use to store energy?
4. How expensive are lithium-ion batteries?

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