Electronica Automotriz

4
Electric Vehicles
Ramesh C. Bansal
Birla Institute of Technology and Science, Pilani, India

4.1

INTRODUCTION

An electric vehicle (EV) is a vehicle powered by an electric motor, instead of an internal combustion engine (ICE), and the motor is run using the power stored in the batteries. The batteries have to be charged frequently by plugging into any main (120 V or 240 V) supply. EVhas a much longer history than most people realize. EVs were seen soon after Joseph Henry introduced the first DC-powered motor in 1830. The first known electric car was a small model built by Professor Stratingh in the Dutch town of Groningen in 1835. The first EV was built by in 1834 by Thomas Davenport in the U.S., followed by Moses Farmer, who built the first two-passenger EV in 1847. Therewere no rechargeable electric cells (batteries) at that time. An EV did not become a viable option until the Frenchmen Gaston Plante and Camille Faure respectively invented (1865) and improved (1881) the storage battery. EVs are known as zero emissions vehicles (ZEVs) and are much environment friendly than gasoline- or LPG-powered vehicles. As EVs have fewer moving parts, maintenance is alsominimal. With no engine there are no oil changes, tune-ups, or timing and there is no exhaust. EVs are also far more energy efficient than gasoline engines and they are very quiet in operation. EVs have been in continual use since the 1900s in various applications. Today these quiet vehicles with no tailpipe emissions are no longer limited to golf carts. New advances in battery technology, systemintegration, aerodynamics, and research and development by major vehicle manufacturers has led to the producing of electric vehicles that will play a practical role on city streets. EVs don’t have ICEs in them. Instead, electrical energy is stored in a storage battery or ultracapacitor, converted from chemical energy in a fuel cell, or converted from mechanical energy in a flywheel. This electricalenergy is used to power an electric motor, which then turns the wheels and provides propulsion. Since no fuel is

© 2005 by Taylor & Francis Group, LLC

burned in an EV, they don’t produce the pollution that ICE vehicles do. EVs are not new: The first automobiles to be built were all EVs, using energy stored in rudimentary leadacid batteries to drive DC electric motors. Only in the 1910s didgasoline-powered vehicles begin to make serious inroads in the automobile market. Unfortunately, EVs have a serious disadvantage that played a large role in the takeover by ICE vehicles: limited range. By limited range we mean that EVs could only travel on the order of 50 miles or so on a single charge, and that only under good conditions (lead-acid batteries lose energy capacity when they become cold,so in cold weather the range of a vehicle could be reduced by as much as 50% or even more). Also, recharging takes hours. ICE vehicles can go much farther on a tankful of gas and could be quickly refueled. Now, urban air quality issues, coupled with a rising awareness of the problems associated with the world’s (and particularly America’s) appetite for oil, have created interest in EVs. Powerelectronics have revolutionized motor drives, bringing within the realm of possibility electric drivetrains with extremely high performance, and the motors themselves have been improved, offering higher reliability and better performance with reduced cost. Unfortunately, the weak link in the chain remains — electrochemical batteries. There are some new battery chemistries floating around that offergood promise in terms of range, but none has the desired combination of three features: fast charging/discharging (high power density), large storage capacity (high energy density), and low cost. Traditional lead-acid batteries have been improved some over the years, but their energy and power densities remain disappointingly low, particularly when compared with gasoline. This chapter contains...