How do electric cars and hybrids work?

HOW DO ELECTRIC CARS and HYBRIDS
WORK?
Prepared: Hamdi TOSUN
Source: Explainthatstuff

Sr. Wire Harness Design /
Electrical System Design
/hamditosun
Design & Development
Professional in vehicle electrical distribution systems
Process Studies and Improvements
Systems Design and Integration
Material Cost Reductions for vehicle electric systems
Research & Analysis
Process Studies and Improvements
hamdi.tosun@qq.com
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Contents
• Electric cars
• What is an electric car?
• Hybrid cars
• How does a plug-in hybrid work?
• Hydrogen fuel-cell cars
• Key components of an electric car
• Electric motor
• Batteries
• Advantages and disadvantages of electric cars
• A brief history of electric cars
HAMDİ TOSUN
Sr. Wire Harness Design / Electrical System
Design Engineer

Electric cars
Electric cars use older technology than gasoline cars and, in their late-19th-century
infancy, looked set to rule the world. The first electric car was built in 1834 and by
1900 some 38 percent of all cars were electric But oil was cheap and abundant and, in
many ways, offered a better method of powering fast cars over long distances. Henry
Ford's mass-production of affordable gas-powered cars soon put paid to electric
dreams. Fortunately, as people finally woke up to the environmental and economic
drawbacks of petroleum in the late 20th century, technology turned full circle and cars
powered by the zap of electricity started to return to our streets. But is it really
inevitable that all cars will go electric? How long will it take? Before we can consider
that question, it helps to ask something much more fundamental: how exactly do
electric cars work? What's so good about them anyway and what are the drawbacks?
Can you really go to work powered by a few buzzing electrons? Let's take a closer
look!
HAMDİ TOSUN
Design Engineer

HAMDİ TOSUN
Design Engineer

What is an electric car?
Electric cars are child's-play; I know that, for a fact, because I built my first one at the
age of eight. Now, admittedly, it wasn't a Tesla Roadster or a Chevrolet Volt, but it had
all the key features of any electric car. It was a toy I'd made with a construction set
using a battery, electric motor, four little rubber-tired wheels, and a simple
transmission built from ready-made gears. Real electric cars aren't much more than
this, though building one is certainly more of a technical challenge than snapping
together a toy.
HAMDİ TOSUN
Design Engineer

What is an electric car?
All cars gas, electric, hydrogen, or using any other "fuel" are essentially energy
conversion devices: they turn potential (stored) energy into kinetic (movement)
energy. In a conventional car, the energy is stored in chemical form, locked inside the
gas you've pumped in your tank; you release it through a chemical reaction happening
inside the engine in which the hydrocarbon molecules in gasoline burn with oxygen in
the air to release heat, which pushes the pistons that turn the wheels. Electric cars
also use stored chemical energy, though they release it electrochemically, without any
kind of combustion, as electrons ping from their slowly discharging batteries; there's
no burning of fuel, no air pollution spewing from the tailpipe, and no emissions of any
kind are produced by the car itself.
HAMDİ TOSUN
Design Engineer

HAMDİ TOSUN
Design Engineer
2016

Hybrid cars
So.... electric car or gasoline? Both have their advantages; both have their drawbacks.
That's why many of the electric cars on the road today are actually hybrids that
incorporate both technologies side by side: they have a smaller than usual gasoline
engine suited to nippy highway driving and an electric motor for all that stopping and
starting in the city.
HAMDİ TOSUN
Design Engineer

Hybrid cars
Hybrids come in various different flavors. In parallel hybrids, the engine and the motor
both send power to the wheels; in series hybrids, only the motor powers the wheels,
while the engine simply drives the motor like a generator, recharging the
batteries. Full hybrids have powerful enough electric motors and batteries to drive the
engine independently, while in mild hybrids, the motor is too puny to power the car
by itself and simply assists the engine (or allows it to switch off when the car is idle in
traffic). Ordinary hybrids charge up their batteries using power from the engine and
energy recovered from the regenerative brakes (which we'll come onto in a
moment); plugin hybrids can also be "refueled" from a charging station or domestic
power supply, have much bigger batteries, and can be driven by the motor and
batteries alone, so work more like conventional electric cars.
HAMDİ TOSUN
Design Engineer

Hybrid cars
Whatever the coupling of engine and motor, the basic idea is to combine the best of
both worlds to boost fuel economy. The big drawback of a hybrid is that its around 20–
30 percent more expensive than a comparable gasoline model. It's likely to be 10
percent heavier (despite is lighter engine, it has an electric motor, batteries,
regenerative brakes, and all the rest) and have more sluggish performance. But
hybrids score far better on both safety and fuel economy than gasoline cars, which
makes them popular with eco-conscious families who prize their green credentials
HAMDİ TOSUN
Design Engineer

How does a plug-in hybrid work?
A hybrid car is like two cars in one: it has a conventional gasoline (petrol) engine for
fast freeway driving and an electric motor for more economic, pollution-free travel (or
idling). In different designs, the wheels are driven by the engine, the motor, or both
together.
HAMDİ TOSUN
Design Engineer

Hydrogen fuel-cell cars
Cars powered by fuel cells are also electric, though they use tanks of hydrogen to
generate electricity and power an electric motor instead of banks of batteries. You can
read more about them in our separate article on fuel cell cars.
HAMDİ TOSUN
Design Engineer

Key components of an electric car
Gas-powered cars and electric ones have a great deal in common and the key
differences are the stored energy they use (gasoline versus electricity), the machine
they use to convert it into kinetic energy (an engine or an electric motor), and the way
the stored energy powers that machine (through a gearbox and transmission, in the
case of an ordinary car, but often more directly in an electric car). Let's examine the
two key components of electric cars the motor and the batteries in a bit more detail
and compare them with what we have in a conventional car.
HAMDİ TOSUN
Design Engineer

Electric motor
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 (usually thousands
of times a minute), but a 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 you're moving off from a cold start, or a traffic signal,
you need the engine to produce a great deal of force (torque as it's called) at a
relatively low speed, whereas if you're overtaking on a speedy highway, you'll need
the opposite: more speed and less torque.
HAMDİ TOSUN
Design Engineer

Electric motor
Instant torque
There's not a great deal you can do to control the output from a car engine because
it's a chemical machine, driven by an essentially simple chemical reaction between
fuel and oxygen that produces useful mechanical power. In that respect, an internal
combustion engine is just like the external combustion engine you'll find on something
like a steam engine. If you want more power, you need to burn more fuel more quickly
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 makes more power and ultimately delivers more speed. Apart from the
accelerator (supplying more or less fuel), the other two key controls of a conventional
car engine are the gears (transforming the power coming from the engine so the
wheels turn quickly with low force or slowly with high force) and the clutch (briefly
engaging or disengaging the engine's power from the gearbox altogether). And we
need the gears and the clutch because of basic limitations in how an engine works as a
machine that enjoys spinning around thousands of times a minute, however fast
you're driving (the engine keeps turning, burning fuel and costing money, even if
you're stopped at a traffic signal).
HAMDİ TOSUN
Design Engineer

Electric motor
The motor in an electric car is very
different: up to a point, it has no
"preference" whether it spins fast or
slow—it's pretty good at delivering the
same torque at any moderate speed. If
you had an electric train set when you
were young, you probably controlled the
engine with a transformer that had a dial
you could turn up or down. Starting off,
you'd have the dial turned down low to
make the train move slowly (by feeding a
relatively small electric current to the
motor inside it); you could go faster
simply by turning up the current to make
the motor spin more quickly. There's no
clutch in a toy train and (usually) no
gearbox either: the electric motor drives
the train wheels directly, and does so
equally well whether the train is going
fast or slow.
HAMDİ TOSUN
Design Engineer

Electric motor
Transmission
In theory, an electric motor can drive a full-sized electric car just as simply as a toy
train, without the clumsy old gearbox and transmission you'd use in a conventional
gasoline engined car. In practice, electric cars are clearly more complex. Toys are small
and move fairly slowly, while real cars are much bigger and go 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 slightly
faster. (The same is true of toy cars, but the effect is too small to notice.) That's 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.
HAMDİ TOSUN
Design Engineer

Electric motor
The same happens in an electric car when it goes around a corner, and
that rules out any kind of simple transmission. One solution is to have a
front-located electric motor driving the same kind of transmission as an
ordinary gasoline car, using a driveshaft and differential in the usual way.
Another is to do away with the driveshaft and have a motor, gearbox, and
differential unit between two of the wheels and driving them both. A third
option is to have two front or rear motors, each driving one wheel
independently. The final option is to use two or four hub motors,which
are motors built into the wheels themselves. That raises a different
technical issue: how to build a motor that's lightweight, compact, and still
powerful enough to drive a car.
HAMDİ TOSUN
Design Engineer

Electric motor
Artwork: Transmissions: How does power
get from the motor to the wheels? Four
example arrangements of the electric
motor (green), gearbox (orange),
differential (scarlet), driveshafts (light
blue), and hub motors (red) in an electric
car.
1) In this arrangement, the electric motor
powers the car much like a traditional
engine through a gearbox and
driveshaft.
2) A central motor powers both wheels
through one or two gearboxes.
3) Two separate motors power two wheels
through separate gearboxes.
4) Hub motors power two (or sometimes
all four) wheels with no other gearboxes,
driveshafts, or other transmission parts.
HAMDİ TOSUN
Design Engineer

Batteries
Every car is an electric car inasmuch it uses a battery to get the engine spinning when
you first start off. Historically, cars were the pioneers of rechargeable batteries. Long
before we had laptops and cellphones, windup torches and all the rest, back when
most of us routinely used batteries one minute and threw them away the next, cars
were demonstrating the possibility of using batteries over and over again. The only
trouble was, car engines used big and heavy lead-acid batteries that weren't good
enough to power vehicles at high speeds, over long distances, for long periods of time.
HAMDİ TOSUN
Design Engineer

Batteries
Today's electric cars mostly use lithium-ion batteries, exactly the same technology
you'll find in your laptop or ebook reader. They're relatively light, fairly good 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 round the world (though not always that well in the extremes you
can find even in hotter and colder US states). That doesn't mean they're perfect. The
main problem with car batteries is that they still can't carry as much energy as
gasoline per unit of mass; in other words, they have a lower energy density. Lithium-
ion batteries are likely to remain the popular choice for electric cars for the
foreseeable future, though alternatives such as nickel metal hydride (NiMH), which are
safer and cheaper, and other lithium-based technologies (including lithium-nickel-
manganese-cobalt, lithium-phosphate, lithium-manganese, and lithium-cobalt) are
also waiting in the wings. Supercapacitors (also called ultracapacitors) are another
promising alternative. A bit like a cross between batteries and capacitors, they offer
much faster charging times.
HAMDİ TOSUN
Design Engineer

Advantages and disadvantages of electric cars
What's good?
Emissions
At first sight, electric cars are green cars: sometimes they're even referred to as ZEVs
(zero-emission vehicles) and the official fueleconomy.gov website actually quotes zero
grams of CO2 emissions per mile for most electric cars. Now while it's true that the
car itself makes no pollution and produces no CO2 emissions in the place where you
drive it, it's also misleading: unless your electricity comes from a wind turbine or
a solar panel, some emissions are still produced in the process of electricity generation
in a distant power plant somewhere). Even with that qualification, electric cars are no
worse than the greenest fossil fueled cars and that comparison will only get more
favorable as electricity generation becomes greener.
HAMDİ TOSUN
Design Engineer

How much better are electric cars? This chart compares mpge (mpg equivalent) or
mpg ratings for 18 cars with 2015 specifications: six electrics (green), six hybrids
(yellow), and six gasoline cars (red).
HAMDİ TOSUN
Design Engineer

Performance
Even in performance, electric cars sometimes outclass gasoline ones. As we've already
seen, electric motors can produce high torque even at low speeds, which means they
can accelerate more quickly than gasoline cars that don't produce their peak torque
until they reach relatively high engine speeds. They're also quieter and smoother. As
Tesla have demonstrated, there's no reason whatsoever why electric motors and
batteries once thought of as dull, worthy, and rather plodding can't power racy,
exciting sports cars. A Tesla Model S can accelerate from 0–60mph (100km/h) in just
3.9 seconds, comparable to a high-performance gasoline powered BMW M5
Size is no obstacle for electric power either. Diesel-electric trains (in which diesel
engines power electric motors that provide the traction) have been around for years.
In November 2014, truck manufacturer BelAZ announced a super powerful new 500
tonne diesel electric mining truck in which four giant AC motors are powered by two
16 cylinder diesel engines.
HAMDİ TOSUN
Design Engineer

Maintenance
Maintenance is also less of a chore, because electric cars are generally simpler than
gasoline ones. According to a 2012 report by the Institute of Automobile Economics,
electric vehicles cost about a third less to maintain than equivalent gas or diesel cars.
Why? An electric motor is an inherently simpler bit of kit than a gasoline engine with
far fewer moving parts to wear out; if it uses no transmission or gearbox, that makes
the entire car simpler still. Even the brakes last longer, since regenerative braking
means you need to use the conventional (frictional) brake pads much less than in an
ordinary car. On the other hand, some of the technology used in electric cars is
relatively untested, which means it could be more prone to early failure even if it is,
paradoxically, simpler and theoretically more reliable in the long run.
HAMDİ TOSUN
Design Engineer

What's bad?
Batteries
Electric motors and batteries are the two main points of difference between
conventional and electric cars. Where motors are well understood and highly reliable,
giant battery packs remain the Achilles heel of electric cars. Despite its environmental
and economic drawbacks, kilo for kilo, a tank of gasoline can carry far more energy
than a bunch of batteries (see chart below)—and that will remain the case for the
foreseeable future. You can completely refuel a gas-powered car in a couple of
minutes (as long as it takes to fill up your tank) and drive several hundred kilometers
on the energy you've pumped in without stopping. But electric cars can take anything
from half-an-hour to a whole night to recharge ("fill up") and, even then, probably
won't get you further than a couple of hundred kilometers before the batteries run
flat. Where a gas tank is a relatively compact thing that sits neatly out of sight, the
batteries in an electric car are expensive (about a quarter of the cost of a Tesla, which
still works out at around $20,000), bulky, heavy, and take up room you might use for
other things.
HAMDİ TOSUN
Design Engineer

Why we still drive gasoline cars in a nutshell. Kilo for kilo, gasoline can carry far more
energy than batteries. Hydrogen is a much better energy carrier, but there are
significant problems in making and storing it. Coal scores highly too, but it's dirty and
impractical: steam cars disappeared long ago!
HAMDİ TOSUN
Design Engineer

A brief history of electric cars
• 1800: Italian Alessandro Volta invents the battery (a primitive stack of zinc and
silver discs separated by cardboard soaked in saltwater).
• 1821: English chemist Michael Faraday shows how electricity and magnetism can
work together to make a force—the basic scientific principle of the electric motor.
• 1829: American electricity pioneer Joseph Henry develops a practical motor,
though it's still far from a viable machine.
• 1834: Thomas Davenport develops a viable electric motor and goes on to develop
the first battery-powered electric car running on a track. Unlike in modern electric
cars, the batteries are not rechargeable.
• 1837: Robert Davidson of Scotland develops a battery powered car and later (in
1842) an electric train that whizzes along the Edinburgh to Glasgow Railway at a
breathtaking 6km/h (4mph).
• 1859: Frenchman Gaston Planté invents the lead-acid battery, made from nine
cells connected in parallel, and demonstrates it to the French Academy of Sciences
the following year.
HAMDİ TOSUN
Design Engineer

• 1859: Electricity pioneer and prolific US inventor Thomas Edison develops an
electric car.
• 1881: Siemens constructs the first permanent electric railroad in Lichterfelde,
Germany.
• 1885: Leo Daft uses an electric motor to power a commuter train to 50km/h
(30mph) in New York City.
• 1890: William Morrison develops the first successful American electric car. It can
manage a respectable 23km/h (14mph).
• 1900: German Ferdinand Porsche develops the world's first hybrid, hub-motor
electric car (the Lohner-Porsche).
• 1908: Henry Ford gives his wife Clara a Detroit Electric car as a present after she
complains she couldn't start a gasoline car with a hand crank. Later, he buys
another one for his friend Thomas Edison as a Christmas present.
• 1910s–1960s: Ironically, despite Ford's enthusiasm, his development of cheap,
mass-produced gasoline cars pushes electric car technology to one side.
• 1940s–1970s: Electric vehicles are used for little more than powering delivery
vehicles, such as "milk floats" (widely used to deliver dairy products door-to-door
in the UK before supermarkets take over).
HAMDİ TOSUN
Design Engineer

• 1971: Apollo 15 astronauts David Scott and James Irwin drive the electric Lunar
Roving Vehicle on the Moon for the first time.
• 1976: US Congress passes the Electric and Hybrid Vehicle Research, Development,
and Demonstration Act to encourage the production of electric cars.
• 1990: The California Air Resources Board spurs the development of electric cars
with its zero-emission vehicle program.
• 1996: General Motors begins leasing its pioneering and futuristic looking EV1.
Later, the cars are controversially taken back by GM and crushed.
• 1997: Toyota launches the Prius in Japan—and it soon becomes the world's best-
selling hybrid.
• 2008: The first Tesla Roadster electric car is shipped to customers.
• 2013: Toyota announces it has sold over 5 million hybrids worldwide, including 2
million in the United States alone.
HAMDİ TOSUN
Design Engineer

HAMDİ TOSUN
Design Engineer
Thank You For Your Attention

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