Electric Vehicles

Growing concerns over the limited supply of fossil-based fuels are motivating intense activity
in the search for alternative road transportation propulsion systems. In addition, regulatory
pressures to reduce urban pollution, CO2 emissions and city noise have made electric vehicles,
a very attractive choice as the alternative to the internal combustion engine.
Electric Vehicle (EV)
An electric vehicle is a vehicle that is fully or partially propelled by electric motors, using energy
stored in rechargeable batteries.
The first practical electric cars were produced in the 1880s. Electric cars were popular in the late 19th
century and early 20th century
Types of Electric Vehicle
There are 4 (four) types of electric vehicles namely
 Battery Electric Vehicle (BEV)
 Hybrid Electric Vehicle (HEV)
 Plug-in Hybrid Electric Vehicle (PHEV)
 Fuel Cell Electric Vehicle (FCEV)
Battery Electric Vehicle (BEV)
A Battery Electric Vehicle (BEV), also called All-Electric Vehicle (AEV), runs entirely on a
battery and electric drive train. This types of electric cars do not have an ICE. Electricity is
stored in a large battery pack that is charged by plugging into the electricity grid. The battery
pack, in turn, provides power to one or more electric motors to run the electric car.
Hybrid Electric Vehicle (HEV)
This type of hybrid cars is often called as standard hybrid or parallel hybrid. HEV has both an
ICE and an electric motor. In this types of electric cars, internal combustion engine gets
energy from fuel (gasoline and others type of fuels), while the motor gets electricity from
batteries. The gasoline engine and electric motor simultaneously rotate the transmission,
which drives the wheels
Plug-in Hybrid Electric Vehicle (PHEV)
PHEV is a type of hybrid vehicle that both an ICE and a motor, often called as series hybrid.
This types of electric cars offers a choice of fuels. This type of electric cars is powered by a
conventional fuel (such as gasoline) or an alternative fuel (such bio-diesel) and by a
rechargeable battery pack. The battery can be charged up with electricity by plugging into an
electrical outlet or Electric Vehicle Charging Station (EVCS).
Fuel Cell Electric Vehicle (FCEV)
Fuel Cell Electric Vehicles (FCEVs), also known as fuel cell vehicles (FCVs) or Zero Emission
Vehicle, are types of electric cars that employ ‘fuel cell technology’ to generate the electricity
required to run the vehicle. In this type of vehicles, the chemical energy of the fuel is converted
directly into electric energy.
Components of electric vehicle
The main components of electric vehicle includes Battery, Charger, Drives, Transmission,
Motor and Power Devices. Fig 1 shows the Components of Electric Vehicle

Fig 1 Components of Electric Vehicle

1. Battery

The nature of an EV is governed by the characteristics of a traction battery. The essential nature
of EV batteries is that, packaged in a car, they weigh 300-600 kg and require 200-300 liters
adjoining volume. The battery will contain between 12 and 30 kWhr of usable energy, to
produce 50-150 kW of power and require around eight hours to recharge. An EV will not be
commercially successful unless it is designed to accommodate these fundamental
characteristics of traction batteries.

Some of these batteries are already being used in the few EVs commercially available in the
market, while others are being tested in prototype EVs. Lead/acid batteries are typically used
as the power source for EVs, although other promising battery technologies are also emerging.

Criteria for choosing the battery are

 Power Density
 Energy Density
 Battery Efficiency
 Cost
 Battery Life
2. Chargers

An important consideration in the design of an EV is establishing a safe and convenient system

for recharging of the batteries. The primary purpose of bringing power to the vehicle is to
replenish the vehicle's storage battery. Electric power supply systems have the following
common characteristics.

 All are based on alternating current operating at 50 or 60 Hz.

 All provide electric power at a nominal voltage.
 All are capable of delivering single-phase or three-phase power depending on the size
and nature of the load.

EV power systems have following common characteristics:

 The primary EV electrical system is defined by the main or traction battery that is on
DC.
 The DC system voltage varies with the Battery State of Charge (SOC) and the rate at
which power is flowing into or out of battery.
  Secondary EV electrical system (12 V DC) is normally sourced from the traction battery
system.

The following are the main three functions of the charging system:

 To change/rectify alternating current to DC.

 To maintain supply voltage at higher voltage level than the primary EV electrical
system voltage.
 To physically couple/connect the power source to the EV.
3. Drives

EV drives depends on important parameters like load requirement, performance specifications,

and operating environment which are as listed below.

 Usually require frequent start/stop, high rate of acceleration/deceleration, high torque

low speed hill climbing, low-torque high-speed cruising, and a very wide-speed range
of operation.
 Need to offer four to five times the maximum torque for temporary acceleration and
climbing.
 Need to achieve four to five times the base speed for highway cruising.
 Should be designed according to the vehicle driving profiles and drivers habit.
 Demand both high-power density and a good efficiency map.
 Desire high controllability, high steady-state accuracy and good dynamic performance
for multiple-motor coordination.
 Need to be installed in mobile vehicles that run in harsh operating conditions such as
temperature, bad weather, and frequent vibration.
4. Transmission

The desired power rating of the electric motor can be calculated from the equations based on
the system constraints of initial acceleration, vehicle-rated velocity, and vehicle maximum
velocity. An electrically driven propulsion system does not need multiple gears to match the
vehicle speed and the engine speed. The wide speed range operation of electric motors enabled
by power electronics control makes it possible to use a single-gear ratio transmission for
instantaneous matching of the available motor torque with the desired tractive torque. The gear
ratio and the size depend on the maximum motor speed, the maximum vehicle speed, and the
wheel radius. A higher motor speed relative to the vehicle speed indicates a higher gear ratio,
larger size, and higher cost. A higher motor speed is also desired in order to increase the power
density of the motor.

5. Motors

The electric motor of the vehicle must overcome the road load, which is established by the
vehicle mass, roadway gradient, rolling resistance and aerodynamic drag coefficients and
vehicle velocity and acceleration. The motor is desired to have a high starting torque for initial
acceleration, high power density, and high efficiency to extend the battery range, and a wide
operating speed range to facilitate single gear transmission.

Types of electric motors used are

 DC Motor
 Induction Motor
 Permanent Magnet(PM) Synchronous Motor
 Permanent Magnet(PM) Brushless DC Motor
 Switched Reluctance Motor(SRM)
6. Power Devices

Existing power devices for EV drive include thyristor, gate turn-off thyristor (GTO), power
bipolar junction transistor (BJT), power metal-oxide field-effect transistor (MOSFET),
insulated-gate bipolar transistor (IGBT), static-induction transistor (SIT), static-induction
thyristor (SITH), MOS-controlled thyristor (MCT) and turn-off thyristor (MTO). IGBT is
almost exclusively used for modern EVS. The power MOSFET has also been accepted for
those low-voltage low-power EVs

Electric Vehicle Scenario in India

The Ministry of Non-conventional Energy Sources (MNES), Government of India has set up a
committee on exploring high-energy density batteries for EVs had recommended the following
measures for accelerated commercialization in India:

 Development of appropriate type of batteries for EVs, including advanced lead acid
batteries as a short-term strategy, nickel metal hydride batteries as a medium-term
strategy, and lithium batteries as a long-term strategy.
  Development of efficient and reliable electronic drives (for example, development of
transistorized or IGBT pulse width modulated controller using three-phase AC motor
and switched reluctance motor as a drive train for EVs).
 Development and use of innovative, quick-charging methods and devices for charging
of batteries.

Based on these and other recommendations, R&D projects for the development of efficient,
reliable, and durable EVs and their components are being supported by the Government. The
use of lightweight materials such as aluminum for the body and chassis of EVs is necessary in
order to reduce the overall weight of the vehicle. Aluminum can be recycled after disposal of
the EVS. Efforts are being made to improve fuel economy of EVs by improving efficiency of
battery charger, batteries used, electric motors and the controllers, besides reducing the overall
weight of the vehicle as well as the aerodynamic and rolling resistance.

A number of EVs are already plying on the roads today. BHEL developed and commercialized
a 16-seater EV bus more than a decade ago. Several improvements in the control system,
vehicle design, and performance based on operational experience of this bus have been made.
Three-wheeler EVS are also commercially available in the country. Scooter India Limited has
developed and demonstrated electric three wheelers, which are now in the advanced stage of
commercialization. Other major players for electric three wheelers include Mahindra Eco
Mobiles, which has come up with a three-wheeler EV called "Bijli". The Government has been
supporting demonstration programme for electric three wheelers in Agra and other citics. Bajaj
Auto and Eicher are also entering the three-wheeler EV marked. Ashok Leyland has developed
a hybrid EV bus has been developed with the support by DSIR which is in the demonstration
stage. The Government has also supported a demonstration program for 20 battery-operated
cycle rickshaws at Nimbkar Agricultural Research Institute, Phaltan, Maharashtra. Based on
the experience of this demonstration program, it is proposed to deploy commercial models of
electric cycle rickshaws, which are expected to make a major contribution in controlling
pollution and improving the air quality. Passenger EVs are also commercially available in the
country. Reva, Bengaluru, has developed battery-operated passenger cars.

With further technical performance improvement, cost reduction, and increasing awareness,
EVs are expected to find greater acceptance and market penetration. The main targeted users
of EVs would be public transport systems, urban services industries, service sectors and the
central and state governments. The Government is launching a major operational program on
battery-operated four wheelers, three wheelers, and two wheelers. Its objective is to carry out
extensive field-testing and obtain feedback on it. It also encourages making further
improvements and creating awareness of eco-friendly vehicles among the people and rapid
commercialization of EVs in the country. Exide Industries Ltd, Kolkata, and other
manufacturers are producing lead acid traction batteries for EV applications. Lucas TVS,
Mahendra, Tata are also entering the EV area.

Advantages of EVs

 Zero emissions: EVs produce zero emissions at the point of use. An EV produces only
5% 10% of the emissions of an ICE per mile traveled. All the EVs emissions occur at
a power plant, which runs 400%-500% more efficiently than an ICE.
 High efficiency: EVs are very efficient. An electric motor is 400% -600% more
efficient than an ICE
 Quick torque generation: Torque generation of electric motor is quick and accurate.
An electric motor's torque response several milliseconds, which is 10-100 times as fast
as that of the internal combustion engine or hydraulic braking system.
 Easy measurement of motor torque: There exists much smaller uncertainty in driving
or braking torques generated by an electric motor than that of an IC engine or hydraulic
brake Motor torque can be easily known from the motor current.
 Electric cars are high performance and low maintenance: All-electric vehicles are
also high performance vehicles whose motors are not only quiet and smooth but require
less maintenance than internal combustion engines.

Disadvantages of EVs

 The batteries now used in EV limit the average vehicle's driving range to between 100
and 200 km depending on the battery type.
 Most batteries must be replaced after 400-500 charges, which is an expensive
proposition.
 Recharge Points -Electric fuelling stations are still in the development stages. Not a lot
of places you go to on a daily basis will have electric fuelling stations for your vehicle,
meaning that if you’re on a long trip or decide to visit family in a rural or suburban area
and run out of charge, it may be harder to find a charging station. You may be stuck
where you are.
  High initial investment
 Electricity is not free -Electric cars can also be a hassle on your energy bill if you’re

not considering the options carefully.

 Silence as a Disadvantage - Silence can be a bit disadvantage as people like to hear

the noise if they are coming from behind them. An electric car is, however, silent and
can lead to accidents in some cases
 Not Suitable for Cities, Facing Shortage of Power- As electric cars need the power
to charge up, the cities that already facing acute power shortages are not suitable for
electric cars. The consumption of more power would hamper their daily power needs.
 Lower Amount of Choices-The market today for electric cars is expanding, with no
signs of slowing down. However, the truth is that there are fewer options to customize
and choose the aesthetics of your EV.