How Does Electric Cars Work?
Electric cars are something that show
up in the news all the time. Actually, there are many reasons for the non-stopping
interest in these kind of automobiles:
All cars—electric, hydrogen, gas, or using any other type
fuel”—are essentially energy conversion devices: they change stored potential
energy (P.E) into kinetic energy (K.E). In a conventional car, the energy is kept
or in other words is stored in chemical form, locked inside the gas we have pumped
in our tank; We release it through a chemical exothermic reaction happening
inside the engine in which the hydrocarbon molecules in gasoline
burn with oxygen in the air to produce heat and power, which pushes the pistons
that turn the wheels. In fact, this all happens inside the engine’s cylinders,
so that is the reason it is internal combustion.
Electric cars also use stored chemical energy, however
they release it electrochemically, without any type of combustion, as electrons ping from their slowly discharging batteries;
there is no burning of fuel therefore no air pollution spewing from the tailpipe (exhaust), and no
emissions of any kind are produced by the car.
(A) Electric cause less pollution than gasoline-powered cars, so that is why they are named as
environmentally friendly compared to gasoline-powered vehicles.
regarding hybrid cars usually talks about electric cars as well.
Note: A vehicle is a hybrid if it uses more than one form of
onboard energy to achieve propulsion. In practice, that means a hybrid will
have a normal internal-combustion engine and a fuel tank, as well as one or
more electric motors plus a battery pack.
powered by fuel cells are electric cars, and fuel cells are getting a
lot of eyes or attention right now in the news all over the world.
electric car is a car powered by an electric motor rather than a gasoline
The importance of electric vehicles:
Gas is a scarce,
natural resource, electricity is cheaper than gas. , electricity can come from
renewable resources such as wind power and solar, electric cars pollute less
than gas-powered cars, electric cars are much more reliable-accurate and
require less maintenance as mentioned in more than one article according to
several statistics than gas-powered cars, we do not even need to get our oil
changed every 3,000miles= 4828.032 Kms, cheapness in amount of fuel consumed,
produce 27 percent less CO2 (carbon dioxide) than petrol cars, help to reduce
greenhouse gas emissions.
components of an electric car
not a great deal we can do to control the output from a car engine because it is
a chemical machine, driven by an important simple chemical reaction between
oxygen and fuel that produces useful mechanical power. As a matter of fact, an
internal combustion engine is just like the external combustion engine we will find
on something such a steam
engine. In fact, if we want more power, we need to burn more fuel
more quickly. Actually, a basic law of physics called the “law of
conservation of energy” tells
us that—which is why operating a car’s accelerator is informally called
“stepping on the gas”: burning gas faster gives more power and basically
delivers more speed (RPM). Apart from the accelerator, supplying more or less
fuel, the other two key controls of a conventional car engine are the gears (Function
of gears: to transform the power coming from the engine, so the wheels turn
quickly with low force or slowly with high force) and the clutch (Function: it
is briefly engaging or disengaging the engine’s power from the gearbox
altogether). In addition to this, we need the gears and the clutch because of
basic limitations in how an engine works and functions—as a machine that enjoys
spinning around thousands of times a minute, however fast we are driving (the
engine keeps turning, burning fuel and costing money, even if we stopped at a
motor in an electric car is completely different and unique in its own way. It
has no preference whether it spins slow or fast. Plus, it is amazing at
delivering the same torque at any speed.
motors are quite different from gasoline engines—and not just in the fuel they
burn. An engine needs to spin round relatively quickly to work efficiently/perfectly
(normally thousands of times a minute), but the car’s wheels seldom need to go
anything like that fast. The power an engine can produce at any given moment
may be very different from what the driver needs. For example, if we are moving
off from a cold start, or in a traffic signal, we need the engine to produce a
great deal of force which is known as Torque at a relatively low speed, whereas
if we are overtaking on a speedy highway, we will need the opposite: less
torque and more speed.
an electric motor can drive a full-sized electric car just as simply as a toy
train, without the clumsy old gearbox and transmission we would use in a
conventional gasoline-engine car. In practice, electric cars are quite more
complex. Toys are small and move at a slow pace while real cars are much bigger
and go much faster. When a real car corners, its two outside wheels are
traveling around a curve of bigger radius than its two inside wheels, but in
exactly the same time, which means they have to spin somehow faster. In fact, the
same is true of toy cars, but the effect is too small to notice or realize.
That is why real cars need complex transmissions with speed-adjusting gears
called differentials that
allow one pair of wheels to go at a slightly different speed—faster on the
outside of a curve, slower on the inside than the other.
happens in an electric car when it goes around a corner, and that rules out any
kind of simple transmission (for example, a single electric motor driving the
two back wheels from a common axle). One solution is to have a front-located
electric motor driving the same kind of transmission as a normal gasoline car,
using a driveshaft in other words propeller shaft and differential in the usual
way. Another solution is to do away with the driveshaft and have a motor,
gearbox, and differential unit between two of the wheels (either front or rear)
and driving them both. A third option is to have two front or rear motors (with
or without gearboxes), each driving one wheel independently. The final option
is to use two or four hub motors (in-wheel
motors), which are motors built into the wheels themselves. That shows a
different technical issue: how to build a motor that’s lightweight, compact,
and still powerful enough to drive a car (although if there are four hub
motors, we need to generate only a quarter of the total power with each one).
Every car is an electric car inasmuch
it uses a battery to get the engine spinning when we first start off. Basically,
cars were the pioneers of rechargeable batteries. Cars were showing the
possibility of using batteries over and over again. The only problem was, car
engines used big-sized and heavy lead-acid batteries that were not well enough
to power automobiles at high speeds, over long distances, for long durations of
Today’s electric cars mostly use lithium-ion batteries,
exactly the same technology we find in our E-book
reader or laptop. They are relatively light, fairly nice at
storing useful amounts of power for their weight, last several years and
hundreds of charges, and perform reasonably well
at the varied range of temperatures most car drivers routinely encounter around
the world. Well, that does not mean they are extremely perfect. The main
problem with car batteries is that they still cannot carry as much energy compared
to gasoline car per unit of mass. In other words, they have a lower energy density. In fact, Lithium-ion
batteries are likely to stay the popular choice for electric cars for the predicted
future, though alternatives such as nickel metal hydride (NiMH), which are cheaper
and safer, and other lithium-based technologies (including
lithium-nickel-manganese-cobalt, lithium-phosphate, lithium-manganese, and lithium-cobalt)
are also waiting in the wings. Super capacitors also
known as ultra-capacitors are another promising alternative/choice.
When we drive an electric car, often the only
thing that clues us in to its true nature is the fact that it is almost silent.
Under the bonnet of the car, there are a lot
of differences between electric and gasoline cars:
The engine is replaced by the electric motor.
The electric motor receives its power from
The controller receives its power from an
array of rechargeable batteries.
A gasoline engine, with its fuel lines,
exhaust pipes, coolant hoses and intake manifold, tends to look like a plumbing
project and complicated. An electric car is definitely a wiring project. In order to get
a feeling for how electric cars work in general, let us start by looking at a
typical electric car to see how it comes together.
The gasoline engine, along with the muffler, catalytic converter,
tailpipe and gas tank, they were all removed.
The clutch assembly was also removed. The
existing manual transmission was
left in place, and it was pinned in second gear.
A new AC electric motor was bolted to the
transmission with an adapter plate.
An electric controller was added to control
the AC motor.
A battery tray was installed in the floor of
Fifty 12-volt lead-acid batteries were placed
in the battery tray (two sets of 25 to create 300 volts DC).
Electric motors were provided to power things
that used to get their power from the engine: the air conditioner, water pump,
power steering pump.
A vacuum pump was added for the power brakes (which
used engine vacuum when the car had an engine).
The shifter for the manual transmission was
replaced with a switch, disguised as an automatic transmission shifter,
to control reverse and forward.
An automatic transmission
shifter is used to select forward and reverse. It contains a small switch,
which sends a signal to the controller.
A small electric water heater was added to provide
A charger was added, so that the batteries can
be recharged. This particular car actually has two charging systems — one from
a normal 120-volt or 240-volt wall outlet, and the other from a magna-charge
inductive charging paddle.
The Magna-Charge inductive
paddle charging system
Well, the gas gauge was replaced with a
Everything else about the car is stock-is the
same. When we get in to drive the car, we put the key in the ignition and turn
it to the “start on” position to turn the car on. We shift into “drive”
with the shifter, push on the accelerator pedal and go. It works like a normal
some interesting statistics written below:
The range of this car is about 50 miles (80
The 0-to-60 mph time is about 15 seconds
varies from a car to car.
It takes about 12 kilowatt-hours of
electricity to charge the car after a 50-mile trip (80 km).
The batteries weigh approximately 1,100
pounds (500 kg).
The batteries last three to four years
To compare the
cost per mile of gasoline cars to this electric car, here’s an easy example.
Electricity in North Carolina is about 8 cents per kilowatt-hour right now (4
cents if we use time-of-use billing and recharge at night). That means that for
a full recharge, it costs $1 (or 50 cents with time-of-use billing). The cost
per mile is therefore 2 cents per mile, or 1 cent with time-of-use. If gasoline
costs $1.20 per gallon and a car gets 30 miles to the gallon, then the cost per
mile is 4 cents per mile for gasoline.
Clearly, the “fuel” for electric
vehicles costs a lot less per mile than it does for gasoline vehicles. And for
many, the 50-mile range is not a limitation — the average person living in a
city or suburb seldom drives more than 30 or 40 miles per day.
To be completely fair, however, we should
also include the cost of battery replacement. Batteries are the weak link in
electric cars at the moment. Basically, battery replacement for this car runs
about $2,000. The batteries will last 20,000 miles or so, for about 10 cents
Well, the heart of any electric car consists of
The electric motor
The motor’s controller
The controller takes the power from
the batteries and then
passes it to the motor. The accelerator pedal connects to a pair of potentiometers (variable resistors),
and these potentiometers provide the signal that tells the controller how much
power it is required to deliver. The controller can deliver zero power when the
car is not moving and full power when the driver presses the accelerator pedal,
or any power level in between. Well, in this car, the controller takes
in 300 volts DC from the battery pack. It changes it into a maximum of 240
volts AC, three-phase, to send to the motor. It actually make this using very
large transistors that quickly
turn the batteries’ voltage on and off to create a sine wave.
When we push on the gas pedal, a cable from the pedal
connects to these two potentiometers:
The signal from the potentiometers tells the controller
how much power to deliver to the electric car’s motor. There are two potentiometers
for safety. The controller reads both potentiometers and ensures that their
signals are equal. However, if they are not, then the controller does not function.
This arrangement guards against a situation where a potentiometer fails in the
controller’s job in a DC electric car is quite simple to understand. Let us
assume that the battery pack contains 12 12-volt batteries, wired in series to
create 144 volts. The controller takes in 144 volts DC, and passes it to the
motor in a controlled manner. The very simplest DC controller would be a big
on/off switch wired to the accelerator pedal. When we push the pedal, it would turn
the switch on, and when we take our foot off the pedal, it would turn it off.
As the driver, we would have to push and release the accelerator to pulse the
motor on and off to maintain a given speed.
Obviously, that sort of on/off approach would work but
it would be a pain to drive, so the controller does the sensing/pulsing for the driver.
The controller reads the setting of the accelerator pedal from the
potentiometers and regulates the power accordingly. Let us say that the driver
have the accelerator pressed halfway down. The controller reads that setting
from the potentiometer and quickly switches the power to the motor on and off, so
that it is on half the time and off half the time. If the driver have the
accelerator pedal 25 percent of the way down, the controller pulses the power
so it is on 25 percent of the time and off 75 percent of the time.
In fact, most controllers pulse the power more than
15,000 times per second, in order to maintain the pulsation outside the range
of the human hearing. The pulsed current causes the motor housing to
vibrate at that frequency, so by pulsing at more than 15,000 cycles per second,
the controller and motor are silent to the ear of humans
An AC controller connects to an AC motor. By using
six sets of power transistors, the controller takes in 300 volts DC and emits
240 volts AC, 3-phase. The controller additionally provides a charging system
for the batteries, and a DC-to-DC converter to charge again the 12-volt
In an AC controller, the job is a somehow more complex,
however it is the same idea. The controller creates 3 pseudo-sine waves.
Actually, it does this 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. Therefore, we actually need transistors of six sets
in an AC controller, while we need only one set in the DC controller. In the AC
controller, for each phase we need a single set of transistors to pulse/sense
the voltage and another set to reverse the polarity. We replicate that three
times for the three phases — six total sets of transistors.
In fact, most DC controllers used in the electric cars usually
come from the electric forklift industry. The Hughes AC controller is the same
sort of AC controller used in the GM/Saturn EV-1 electric vehicle. It can
deliver a maximum of 50 Kilo-Watts to the motor.
Electric cars can use AC or DC motors:
the motor is a DC motor,
then it may run on
anything from 96 to 192 volts. Many of the DC motors used in electric cars usually
got from the electric forklift industry as mentioned earlier.
If it is
an AC motor, then it is
almost certainly a three-phase AC motor running at 240 volts AC with a 300 volt
installations usually tend to be less expensive and simpler. A typical motor
will be in the 20,000-watt to 30,000-watt range. A typical controller will be
in the 40,000-watt to 60,000-watt range. For instance, a 96-volt controller
will deliver a maximum of 400 or 600 amps. DC motors have the wonderful feature
that we can overdrive them
(up to a factor of 10-to-1) for short durations of time. That is, a 20,000-watt
motor will accept 100,000 watts for a short period of time and deliver 5 times
its rated horsepower. Well, this is awesome for short bursts of acceleration.
The only disadvantage or limitation is heat made up in the motor. Too much
overdriving and the motor heats up to the point where it self-damages.
installations allow the use of almost any industrial three-phase AC motor, and
that can make finding a motor with a specific size, shape or power rating
simpler. AC motors and controllers often have a regen-feature. During braking, the motor changes into a generator and delivers power
back to the batteries.
now, the weak link in any electric car is the batteries. There are at least six
huge problems with current lead-acid battery technology:
They are heavy (a
typical lead-acid battery pack weighs 1,000 pounds or more).
(B) They are bulky (big in size)
They have a limited capacity (a typical
lead-acid battery pack might hold 12 to 15 kilowatt-hours of electricity,
giving a car a range of only 50 miles or so).
They take a lot of time to charge (typical
recharge times for a lead-acid pack range between 4 to 10 hours for full
charge, depending on the battery technology and the type of the charger).
They have a short life (three to four years)
They are quite expensive
We can replace lead-acid batteries with NiMH
batteries. The range of the car will double and the batteries will last 10
years (thousands of charge/discharge cycles), but the cost of the batteries
today is about 12 (10 to 15) times greater than lead-acid. In other words, a
NiMH battery pack will cost $20,000 to $30,000 (today) instead of $2,000. In
fact, prices for advanced batteries fall as they become mainstream, so over the
next several years it is likely that NiMH and lithium-ion battery packs will
become very competitive with lead-acid battery prices. Electric cars will have
significantly better range at that point.
When we look at the problems associated with
batteries, we get a different
perspective on gasoline. Two gallons of gasoline,
which weighs about 15 pounds, costs $3.00 and takes about 30 seconds to pour
into the tank, is equivalent to 1,000 pounds of lead-acid batteries that cost
$2,000 and take about four hours to recharge.
problems with battery technology explain why there is so much excitement
around fuel cells today.
Compared to batteries, fuel cells will be smaller, much lighter (not heavy) and
instantly rechargeable. When powered by pure hydrogen,
fuel cells have none of the environmental problems associated with gasoline. It
is very likely that the electric car will be the most used car in the future
that receives its electricity from a fuel cell. There is still a lot of studies,
research and development that will have to occur, however, before inexpensive,
reliable fuel cells can power automobiles.
about any electric car has one other battery on board. This is the normal
12-volt lead-acid battery that every car has. The 12-volt battery provides
power for accessories — things like headlights, radios, fans, computers, air bags, wipers, power windows and instruments
inside the car.
all of these devices are readily available and standardized at 12 volts, it
makes sense from an economic standpoint for an electric car to use them.
an electric car has a normal 12-volt lead-acid battery to power all of the
accessories. To keep the battery charged, an electric car needs a DC-to-DC converter. This converter
takes in the DC power from the main battery array (at, for example, 300 volts
DC) and converts it down to 12 volts to recharge the accessory battery. When
the car is on, the accessories get their power from the DC-to-DC converter.
When the car is off, they get their power from the 12-volt battery as in any
DC-to-DC converter is normally a separate box under the hood, but sometimes
this box is built into the controller.
course, any car that uses batteries needs a way to charge them.