Electric Cars
Andrew D. Bushner
Engineering 223A Electric Circuits Lab
Thesis
One of the greatest engineering marvels
that are becoming more and more
popular today is the electric car, which
has come a long way since they were first
introduced in 1828.
What will be covered
History of the electric car
When electric cars were first introduced History to modern day
How today’s electric cars work
Electric motors and batteries Charging
History
1828
Ányos Jedlik invented an
early type of electric motor that powered a tiny model car
1839
Robert Anderson invented
the first electric vehicle that was powered by
1859
Gaston Planté invented the rechargeable
lead-acid storage battery, improved a few years later by Camille Faure
1891
William Morrison of Des Moines, Iowa built
the first successful electric automobile in the United States
24 battery cells 4-horsepower
Top speed of 20 mph Range of about 50 miles
1897
Electric Vehicle Company introduced
electric taxicabs to New York City that could be driven about 50 miles on one charge
By 1899 the city had more than 60 electric
1900
More than four thousand were cars on the road, electric cars made up about one third of them Electric cars had advantages over the other
cars of its time
Quicker to start up than the steam-powered
cars
Ran cleaner than the internal combustion
engines
1908
Henry Ford introduced the Model T which cost
only $850 compared to the average price of an electric car of about $2000
Model T’s had a better production method and
eventually overtook electric cars
Four years later, Charles Kettering invented the
first practical electric automobile starter, making gasoline-powered cars even more practical
1920
Electric cars ceased to be a viable commercial
product
Roads were more developed
Consumers wanted to travel further Gasoline was inexpensive
Electricity was not as readily available as gasoline
Electric cars became impractical and, by the late
1920s, were nearly gone from the market
From the mid-1920s to the early 1990s, there was
1966
Congress introduced an early bill that
recommended the use of electric vehicles as a means of reducing air pollution
1970s
Concerns over soaring price of oil and the
growing environmental movement resulted in renewed interest in electric cars
1988
Roger Smith, CEO of G.M., funded research
to build a practical consumer electric car
G.M. teamed up with California's
Late 1990s and early 2000s
G.M. unveiled the EV1 in 1996 which
traveled 80 miles per charge
A few thousand all-electric cars from big
car manufacturers were produced, but
most of them were available for lease
only
2003
G.M. announced it would not renew leases
on its EV1 cars saying that they can no longer supply parts to repair the vehicles
By 2005, all the EV1s were collected and
“recycled”
The car was the subject of the 2006 film
"Who Killed the Electric Car?" where
General Motors spokesman stated that the EV1s were to be recycled, not just crushed
2006
Tesla Motors unveiled the Tesla Roadster
which brought luxury to the electric car market
The Tesla Roadster was priced over $100,000 They were meant for a high-income market
and aimed to show off what an electric engine could accomplish
The car had 300 HP, 295 ft-lb of torque, 3-phase 4-pole AC induction motor, and a 53 kWh Lithium-ion battery
Almost 250 mile range
Can accelerate from 0 to 60 mph in 3.7 seconds
2010 to present
Nissan released its new electric car called
the LEAF (Leading, Environmentally friendly, Affordable, Family car)
Maximum speed of 90 mph
Can travel 100 miles on a full charge Capable of being recharged to 80% of
battery capacity in 30 minutes
Several new electric cars, including the
BMW Mini E and Mitsubishi i-MiEV, have been produced and sold with a reported 3.8 million to be on the roads worldwide by 2016
Electric Motors
Electric motors get their power from a
controller, and the controller gets its power from rechargeable batteries
The motor's controller is what takes the power
from the batteries and delivers it to the motor
The accelerator pedal is hooked up to a pair
of potentiometers, which are variable
resistors, and these potentiometers provide the signal that tells the controller how much power it is supposed to deliver
DC controller
connected to
batteries and a DC
motor
• The DC controller reads the
setting of the accelerator pedal from the potentiometers and regulates the power accordingly • If the accelerator is pushed
halfway down, the controller reads that setting from the potentiometer and rapidly
switches the power to the motor on and off so that it is on half the time and off half the time
• If the accelerator is pushed one-fourth of the way down, then the controller pulses the power so it is on one-fourth of the time and off three-fourths of the time
AC controller
connected to AC
motor
• An AC controller creates three pseudo-sine waves by taking the DC voltage from the
batteries and pulsing it on and off
• In an AC controller, there is the additional need to reverse the polarity of the voltage 60 times a second
• AC controllers need six sets of transistors
• For each of the three phases, one set of transistors is needed to pulse the voltage and
another set to reverse the polarity so six transistors are needed
DC vs. AC motors
Electric cars can have two different types of electric motors: a DC
motor or an AC motor
If the motor is a DC motor:
It runs on voltage ranging from 96 to 192 volts They are more affordable and easier to control
They have greater initial torque and higher peak power
However, they have a tendency to overheat and become very
large and heavy according to their power output
If the motor is an AC motor:
They are a three-phase AC motor running at 240 volts AC with a 300
volt battery pack
They are better for continuous power, which helps with climbing hills
but starting power is slower
They run at high RPM without overheating and because of this, they
do not require a transmission
They are best suited for regenerative braking systems, which is a
feature present on many electric vehicles that recovers
approximately 20% of the energy usually lost in the brakes to recharge the battery
They run more smoothly and can be precisely controlled
Conversely, they are more expensive and require a converter, so
Batteries
There are three types of batteries found in electric cars: lead-acid batteries, nickel-metal hydride batteries, and lithium ion batteries
Lead-acid batteries:
Are the cheapest and most common batteries available
Do not last long and typically need replacement every 3 years End up being a significant portion of the final weight of the vehicle
Efficiency and storage capacity decreases with lower temperatures, and diverting power to run a heating coil reduces efficiency and range by up to 40%
Nickel-metal hydride batteries:
Have an energy density higher than lead-acid
Have exceptionally long lives, being known to still operate well after 100,000 miles and over a decade of use
Are less efficient in charging and discharging than lead-acid batteries
Tend to have the poor efficiency, high self-discharge, finicky charge cycles, and poor performance in cold weather
Lithium ion batteries:
Are considered to have the most potential for mass-market electric vehicles Have a very high energy density, good power density, and 80 to 90%
charge/discharge efficiency.
Have short cycle lives, usually few thousand charge cycles, and significant degradation with age
Are somewhat toxic and can pose a fire risk if punctured or charged improperly
Do not accept or supply power in cold conditions so expensive and energy inefficient systems are necessary to warm them up
Charging
Chargers monitor current and make assumptions about average
battery characteristics
The chargers apply maximum current to the batteries up through eighty
percent of their capacity, and drop the current back to a preset level for the final twenty percent to avoid overheating the battery
Normal household 120-volt outlets typically have a 15-amp circuit
breaker, meaning that the maximum amount of energy that the car can consume is approximately 1.5 kilowatt-hours per hour
Most batteries need anywhere from 12 to 18 kilowatt-hours for a full
recharge, so it can take over eight hours to fully charge the vehicle
However, by using a 240-volt circuit, like an outlet for an electric dryer,
the car will receive 240 volts at 30 amps, or 6.6 kilowatt-hours per hour, allowing significantly faster charging with a full recharge in about four to five hours
Problems
Batteries
Heavy and take up a lot of space Need to be recharged
Charging stations are a rarity in most cities Take a long time to recharge
Need to replaced somewhat frequently
