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Electric Vehicles

Challenges Still Exist

Engineers still struggle with energy density. Average energy density in today's EV batteries is about 70W-hr/kg (one W-hr/kg is roughly one mile of range in a four-passenger sedan). In order to increase driving ranges, battery makers must find new alloys for cathodes and anodes. Merely placing more batteries per vehicle is not sufficient.

Cost remains a challenge, particularly battery costs. Automakers say they need to offer their customers $100-per-kilowatt-hour batteries. Today, the best long-term EV batteries cost $10,000–20,000 per kilowatt-hour.



Question 349. Science and Technology Desk Reference. 2nd ed. Carnegie Library of Pittsburgh Science and Technology Department, 1996.


"The Case for Electric Vehicles." Scientific American (November 1996).

"Out of Juice." Design News (October 5, 1998).

"Waiting for the Supercar." Scientific American (April 1999).


Electric Vehicle Association of the Americas. <http://www.evaa.org>.


Office of Transportation Technologies. Hybrid Electric Vehicle Program. (2003). <http://www.newscientist.com/ns/970705/ndope.html>.

Laurie Toupin


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—A battery is a container, or group of containers, holding electrodes and an electrolyte for producing electric current by chemical reaction and storing energy. The individual containers are called "cells." Batteries produce direct current (DC).


—Basic unit used to store energy in a battery. A cell consists of an anode, cathode and the electrolyte.


—Device managing electricity flow from batteries to motor(s), from "on-off" function to vehicle throttle control.

Direct current (DC)

—Electrical current that always flows in the same direction.


—The medium of ion transfer between anode and cathode within the cell. Usually liquid or paste that is either acidic or basic.


—Rapidly spinning wheel-like rotors or disks that store kinetic energy.

Hybrid vehicle

—Vehicles having two or more sources of energy. There are two types of hybrid electric vehicles (HEVs), series and parallel. In a series hybrid, all of the vehicle power is provided from one source. For example, with an IC/electric series hybrid, the electric motor drives the vehicle from the battery pack and the internal combustion engine powers a generator that charges the battery. In a parallel hybrid, power is delivered through both paths. In an IC/electric parallel hybrid, both the electric motor and the internal combustion engine power the vehicle.


—Electromechanical device that provides power (expressed as horsepower and torque) to driveline and wheels of vehicle.

Regenerative braking

—A means of recharging batteries using energy created by braking the vehicle. With normal friction brakes, a certain amount of energy is lost in the form of heat created by friction from braking. With regenerative braking, the motors act as generators. They reduce the energy lost by feeding it back into the batteries resulting in improved range.


—These are higher specific energy and power versions of electrolytic capacitors—devices that store energy as an electrostatic charge. They are electrochemical systems that store energy in a polarized liquid layer at the interface between an ionically conducting electrolyte and a conducting electrode.


—The basic unit of electrical power equal to 1 joule per second.

Additional topics

Science EncyclopediaScience & Philosophy: Dysprosium to Electrophoresis - Electrophoretic TheoryElectric Vehicles - Batteries, Advantages, Hybrids, Challenges Still Exist