Basics
All-electric cars, a.k.a. electric vehicles (EV) or battery electric vehicles (BEV), are propelled
purely by means of an electric motor powered by an on-board battery (to be precise, the battery
powers a controller which in turn powers the motor). The battery can be recharged using a
standard electrical outlet or at a charging station.
Motor Types
AC Motors
Virtually all of the EV's and hybrids on the market use AC motors. Alternating-Current
motors are better for continuous power (hills). Starting power is slower, but the motor can
run at high RPMs without overheating. Because they can run at high RPMs they do not
require a transmission. They can also move a heavier vehicle.
AC motors are best suited to the regenerative braking systems featured in both EVs and
hybrids. Regenerative braking, which returns braking power to the battery, combined
with superior efficiency make for better fuel economy. Generally speaking, AC motors
run more smoothly and can be precisely controlled. For these reasons, production model
electric cars and hybrids use AC motors.
AC motors have significant disadvantages, particularly for the DIY hobbyist. They are
more expensive than DC Motors and so are the battery packs. They are also more
complicated to control. Because battery output is DC, they require a converter which
takes up a lot of space.
DC Motors
Though the debate rages on, about the pros and cons of AC vs DC, DC Motors are the
favorite choice of DIYers who convert their gas-powered cars to electric. DC motors are
more affordable and easier to control. They also have greater initial torque and higher
peak power, so they are popular with racers.
A major disadvantage of DC motors is a tendency to overheat. They also become very
large and heavy according to their power output.
AC conversion kits are now available and will become more popular for conversions.
However, there are a wide variety of DC motor designs which may improve for EV
application.
Battery types
Batteries are the greatest obstacle to the proliferation of EVs. Electric cars require a lot of
batteries which must be installed in an array and housed in a battery pack. These batteries are
heavy (the Tesla Roadster's battery pack weighs 1,000 lbs) and take up a lot of cubic centimeters.
Then there is the simple fact that batteries run out of power and must be recharged.
"But regular cars have to be refueled," you might say. True, but if we're going to replace gas
stations with charging stations we're going to have a parking problem because batteries take a
long time to recharge.
Three types of batteries are found in electric cars:
Lead-acid batteries
Oldest type of rechargeable battery. Cheap to produce and compatible with existing
electronics. Messy, toxic and prone to explosion.
Lithium ion batteries [Li-ion]
High energy-to-mass ratio (which means less weight per unit of stored energy). They
retain their stored energy when not in use but lose capacity with age. Considered to have
the most potential for mass-market EVs but the most advanced models are too expensive.
NiMH batteries are toxic and require special handling to recycle.
Nickel metal hydride [NiMH]
Good energy-to-mass ratio (a.k.a. energy density). Non-toxic which makes for easy
recycling. The major disadvantage to nickel metal hydride batteries is that they don't hold
a charge very well when they aren't being used.
The problems with battery technology explain why there is so much excitement around fuel
cells. Compared to batteries, fuel cells will be smaller, much lighter and instantly rechargeable
next page
Electric cars are the great irony of the auto industry. They are widely seen as the wave of the
future, silent, emmissions-free wonder cars that will have us humming about the highways
science-fiction style. History reveals, however, that electric cars are a relic of the past.
"Relic" might be too harsh; I don't mean to suggest that battery-powered cars don't have a future.
Rather, I want to highlight a rather surprising fact: electric cars developed alongside those with
internal combustion engines and at the dawn of the 20th century, electric cars outsold their
explosive relatives.
So when it comes to electric cars, there is a lot to talk about: a rich history and an exciting future.
In these pages, we will try to cover all of it - yesterday's pioneers and tomorrow's innovators.
Enjoy the quiet, smog-free ride!