1 s2.0-s2095756420300647-main (1)

h I G H L I G H T S
● Basic concepts and
challenges were explained
for electric vehicles (EVs).
● Introduce the techniques
and classification of
electrochemical energy
storage system for EVs.
● Introduce the hybrid
source combination
models and charging
schemes for EVs.
● Introduce the operation
method, control strategies,
testing methods and
battery package designing
of EVs.
A B S T R A C T
This review article describes the basic concepts of electric vehicles (EVs) and explains
the developments made from ancient times to till date leading to performance
improvement of the electric vehicles. It also presents the thorough review of
various components and energy storage system (ESS) used in electric vehicles.
The main focus of the paper is on batteries as it is the key component in making
electric vehicles more environment-friendly, cost-effective and drives the EVs into
use in day to day life. Various ESS topologies including hybrid combination
technologies such as hybrid electric vehicle (HEV), plug-in HEV (PHEV) and many
more have been discussed. These technologies are based on different
combinations of energy storage systems such as batteries, ultracapacitors and fuel
cells. The hybrid combination may be the perspective technologies to support the
growth of EVs in modern transportation. The advanced charging systems may also
play a major role in the roll-out of electric vehicles in the future. The general
strategies of advanced charging systems are explained to highlight the importance of
fast charging time with high amount of power and its cost-effectiveness for electric
vehicles. Furthermore, the battery pack designing calculation is briefly explained
along with all mechanical, electrical and environmental battery tests, which helps
in the evaluation of batteries. Moreover, this paper also has a brief summarizing
with the help of a flow chart, which clearly demonstrates all the parts of electric
vehicles in a much simpler way.
© 2020 Periodical Offices of Chang'an University. Publishing services by Elsevier B.V. on
behalf of KeAi Communications Co. Ltd. This is an open access article under the CC BY-
NC- ND license (http://creativecommons.org/licenses/by -nc-
nd/4.0/).

341
J. Traffic Transp. Eng. (Engl. Ed.) 2020; 7 (3): 340e361
1. Introduction
In modern times, the alarming state of reduction of fossil fuels
and increasing awareness about deteriorating climatic condi-
tions has led to the adoption of alternative energy technologies.
Among various developed technology, one such alternative
technology is an electric vehicle (EV) which is rapidly becoming
a part of the modern transportation system. According to Chan
(1999), an energy and environment issue have led to the
development of EVs where the integration of automobile and
electrical engineering is done to achieve high-performance
electric vehicle. In the future, EVs are going to play an
important role in road transportation, and they may also
assist in reducing environmental pollution. Additionally, EVs
may provide power to the electric grid whenever needed.
EV is the summation of diversified technologies, which
include multiple engineering fields such as mechanical engi-
neering, electrical engineering, electronics engineering, auto-
motive engineering, and chemical engineering (Chan, 1993).
By combining different technologies, the overall efficiency of
the EVs can be improved and fuel consumption is reduced.
EVs consists of three major systems, i.e., electric motor,
power converter, and energy source. EVs are using electric
motors to drive and utilize electrical energy deposited in
batteries (Chan, 2002). Unlike fuel-based conventional
vehicles, EVs never exhaust pollution during operation
which alone makes EVs more eco-friendly vehicles (Chan
and Chau, 1997). However, for charging the EV, electrical
energy is required that may be produced from renewable
sources, e.g., from hydroelectric, wind, solar or biogas power
plants (Kiehne, 2003). EVs are not only a road vehicle but
also a new technology of electric equipment for our society,
thus providing clean and efficient road transportation.
The system architecture of EV includes mechanical struc-
ture, electrical and electronic transmission which supplies
energy and information system to control the vehicle. The
specific EV design considerations are listed below.
i. Identifying the environment and market trend for EV.
ii. Determining all the technical specifications and esti-
mation of load requirement s for EV.
iii. Assessing the infrastructure required for designing and
also including the recycling of batteries.
iv. Defining the system requirements according to its
configuration for various applications such as hybrid
EV, battery EV, and fuel cell EV.
v. Defining its energy supply for different cases such as
generation or storage, single or hybrid.
vi. Identifying the primary essential component of EV
propulsion system consisting of a single or multiple
motor, converter, transmission types and mounting
methods.
vii. Determining its driving range and calculating specific
parameters named as speed, torque energy, and power
density, etc.
EVs were invented in the 19th century, the first vehicle was
launched in 1834. EVs were very popular and were used at a
reasonable price, till 1918. In 1918, 4200 automobiles were on
the road, out of which 38% were electric, 40% were steam-
driven and 22% gasoline-powered (Rajashekara, 2013). Since
1930, EVs started vanishing and became irregular in use. The
primary issue of the downfall was insufficient driving
power. By 1933, the numbers of EVs were reduced to nearly
zero because they were slower in driving range as well as
speed and more expensive than the internal combustion
engine. EVs faced an energy crisis in the early 1970s.
Due to the advancement in the field of power electronics
and microelectronics, the USA started research for the
development of hybrid electric vehicles to overcome the above
issues (Koniak and Czerepicki, 2017; Pinsky et al., 2000). In
October 1990 the California air resources board mandated the
use of zero-emission vehicles (Iclodean et al., 2017).
Researchers presented a comparison between conventional
vehicles and electric vehicles and estimated the future
development trend of EVs (Zhang et al., 2017). Wang (2007)
proposed the EVs miniaturization for the development of
low-performance EVs and presented the feasibility of micro
EVs, its power consumption, and technology cost estimation
(Frieske et al., 2013). Some studies analyzed all the
commercial energy vehicles such as hybrid EVs, pure EVs
and fuel cell vehicles with a focus on pure EVs (Frieske et al.,
2013; Zhang et al., 2017). More than 350 EVs were
manufactured by different enterprises in the automotive
industry between the years 2002e2012. During the last ten
years, the demand for EVs has increased due to dramatically
lower oil use, less carbon emission, a decrease in air
pollution and economic development. Also, there is an
improvement in terms of range, performance, safety and
emission of EVs. To increase the penetration of EVs in road
transport, two main areas, i.e., range, and cost need to be
focused on betterment. Therefore, to reduce the cost of EVs,
many efforts have been made by introducing new and
simplified technologies for speed controllers, battery
charging, motors, power electronics and different types of
cells. To cover the longer range, EVs require high energy
density batteries. Presently, EVs required 62 kWh on an
average to accelerate the vehicle for 10 s with 95.6 km/h
(Zhang et al., 2017). Nevertheless, it is realistic to have
31 kWh to achieve a 100-mile range even based on current
technologies (Frieske et al., 2013). The development of
advanced batteries with different materials such as NiMH, Ni-
Zn, Li-ion, Li-polymer, sodium/Nickel chloride is going on to
meet the power requirement of EVs.
This paper presents the historical development of EVs in
chronological order. The reasons for the failure and success of
EVs are outlined along with the most important factors for the
high penetration of EVs on roads. The new technologies
required for decreasing the cost of EVs are also outlined. The
paper presents a comprehensive review of the various aspects
of EV development resulting in new outcomes.
Further, this paper is summarized as follows. Section 1
discusses the factors affecting the EVs performance. A
description of components for EVs is presented. The existing
system that's having different types of propulsion
phenomenon are analyzed and described. The aim is to
develop an efficient and well-structured vehicle with a
reasonable range and good performance. Further in next
section 2, the types of EVs are discussed. The aim is to

342 J. Traffic Transp. Eng. (Engl. Ed.) 2020; 7 (3): 340e361
Fig. 1 e Key component of an electric vehicle (Diamond, 2009).
analyze the range, price and charging time of vehicles. It could
help us to improve the features of the vehicle and analyze the
improving field. Then in section 3, the design of the battery
pack for EVs is discussed. The aim is to develop a battery for
EV with high energy density and focusing on lightweight,
high energy efficiency, practical usability, and excellent
performance. In sections 4, various tests are discussed
regarding the driving range of battery and various
mechanical, electrical and environment battery tests for
vehicles. Lastly in section 5, paper summarizes with the help
of concluding flow charts and remarks given with some
future development of EVs.
1.1. Factors affecting the EV
There are two types of factors that affect the adoption of EVs,
i.e., internal factors and external factor (Young et al., 2013).
1.1.1. Internal factors
There are certain characteristics of an electric vehicle such as
their driving range, charging time and cost which makes them
less convenient in today's world. EVs are more expensive than
conventional engine vehicles (Coffman et al., 2017). Carley
et al. (2013) found that the cost of the EVs is more dominant
as compared to another traditional vehicle. Graham-Rowe
et al. (2012) also concluded that people were not willing to
pay the high cost as demanded by EVs. As an industrial
survey reviewed by Tran et al. (2013) shows that more than
63% of buyers refused to adopt the EVs because of the high
price. The purchase costs of EVs should decline rapidly and
quickly render the studies regarding the purchase price of
the EVs (Hawkins et al., 2013). Wu et al. (2015) found that
plug-in hybrid EV (PHEV) and battery operated EV (BEV) may
be competitive with internal combustion engine vehicles
(ICEV) in Germany by 2025. The rapid downfall in the price
of EVs suggests the on-going studies on various parameters
such as driving cost, purchase price and ownership costs on
EV (Wu et al., 2015; Young et al., 2013; Zhang et al., 2017). No
valid explanation is found that's why the purchase price fell
more rapidly than the other EV models. More investigat ion
needs to be done to relate the cost of the vehicle's
performance. One of the main obstacles in the way of EVs is
their driving range which is less than other vehicles. Egbue
and Long (2012) proposed that 33% of the consumers
identified that battery range was the most prominent
concern with EVs. Axsen and Kurani (2013) suggested that
consumers most often switch to PHEV because BEVs were
the least favorite, even though it could drive up to 149 miles
approximately in the range at no additional cost. Tamor
et al. (2013) concluded that PHEVs may be more acceptable
than BEVs. On the other hand, Tran et al. (2013) support that
BEVs are more preferred over PHEVs because of their
enhancing charging infrastructure. Now, the other major
issue in the adaptation of EV's is charging time. Although, it
is potentially less severe in comparison to the driving range.
Carley et al. (2013), noted that a majority of consumers
conclude that it was a disadvantage, but they all were
willing to pay for immediate charging. Hidrue et al. (2011)
suggest that most of the consumers are willing to pay nearly
$30 to $70 for the added driving range (Axsen and Kurani,
2013; Tamor et al., 2013).
1.1.2. External factors
Certain external factors may also affect the adoption of EVs
like consumer characteristics, fuel prices and the availability
of charging stations. The hikes in fuel prices are caused due to
the burning of fossil fuel in the combustion engine of vehicles.
According to Tseng et al. (2013) and Wu et al. (2014, 2015), the
petroleum-fuel prices depend directly on the EVs adoption.
Sierzchula et al. (2014) studied vehicles survey of 30
countries and found that fuel price is not a significant
analyzer of EV market share, fuel prices are very important
factor of HEV adoption (Diamond, 2009; Gallagher and
Muehlegger, 2011; Li et al., 2011). As consumers have
different types of interest and the adoption of an EV
depends on different consumer characteristics such as
education, income, level of environmentalism, number and/
or type of car owned and love for technology (Kettles, 2015).
Several studies found that consumers having higher
education are more likely to consider the adoption of

343
Fig. 2 e Classification of motors (Alavije and Akhbari, 2011).
electrical vehicle found that there is no evidence that higher
income makes the consumer-oriented towards using EVs
(Carley et al., 2013; Hackbarth and Madlener, 2013; Hidrue
et al., 2011). In fact, it reduces consumer likelihood and also
makes the EV adoption less due to the driving range and
other factors (Wu and Niu, 2017). It was also observed that
while the reduction of pollution is the most valuable
parameter of EVs, it is evaluated considerably less than
performance indicators. The author reported that most of
the people appreciated the reduction of gasoline vehicle
(Tseng et al., 2013). Sierzchula et al. (2014) reported
education or environmentalism are not the factors in
determining EV market share within a country. Moreover,
studies also suggest that the technology of electric vehicles
needs to be improved for better adaptability of EVs.
According to the consumer's adoption of EVs, the presence
of charging stations plays an important role as the limited
availability of charging stations may discourage the adoption
of EVs. Tran et al. (2013) observed a simulation model that the
presence of an extensive charging network is critical to
support the mass adoption of EVs.
1.2. Components of EVs
EVs are based on propulsion systems; no internal combustion
engine is used. It is based on electric power, so the main
components of electric vehicle are motors, power electronic
driver, energy storage system, charging system, and DC-DC
converter. Fig. 1 shows the critical configuration of an electric
vehicle (Diamond, 2009).
1.2.1. Motors
Each motor has its characteristics and advantages. There are
specific requirements of EVs motor, such as high power den-
sity, fast torque response, high efficiency over full speed and
torque ranges, High robustness and good reliability for many
vehicles operating conditions and at a reasonable cost. In
1993, all the EVs were derived using direct current (DC) Vari-
able drives. DC drives have a commutator due to which
maintenance cost is less as compared to conventional drives
(Chan, 1993). But we all know that DC motor is used for low
power level up to 4 kW, needed support and had a shorter
lifetime. However, it is suitable for small power applications
such as an electric wheelchair, micro-car, etc. So, with the
advent of the alternating current (AC) drives which are more
advantageous, we move towards AC motors. Now, a new era
has pushed towards commutator fewer motors which led to
various benefits like optimum efficiency and high-power
density with low operating cost, more reliability and lower
maintenance of DC motor. Hence, AC motors of different
types that are classified as induction motor, DC brushless
motor, permanent magnet synchronous motor, and
switched reluctance motor (Diamond, 2009). As we know,
the motor is the most essential component of EV, so it is
essential to select a suitable type of motor with a suitable
rating (Gallagher and Muehlegger, 2011). Induction motor
(IM) is used as a commutator motor type for EVs because of
high reliability and free from maintenance (Burridge and
Alahakoon, 2016). Fig. 2 shows the classification of motors
used in EVs (Alavije and Akhbari, 2011).
It is a very popular AC motor and has a variable speed drive
application such as air-conditioning, elevator or escalator, and
many higher power EVs, for more than that of 5 kW energy
(Chan, 1999). Classically, IM and Synchronous motor are used to
feed a sinusoidal supply and produce constant instantaneous
torque without using an electronic controller (Chan, 1999).
Immediately replacing a field winding with a permanent
magnet (PM) then the synchronous motor will turn into PM
synchronous motor (PMSM). PM rotor has been selected by its
high kW rating and current ratings providing superior torque-
speed combined with lightweight commercial availability and
compact dimension (Burridge and Alahakoon, 2016). PM rotor
is further classified into two types, surface-mounted and
interior mounted. Surface-mounted has the magnets outside

the motor whereas the interior model has the magnets inside
the magnetic structure of the rotor. Preference should be given
to the internal model because of its high operating speed.
Now, modern motor, i.e., PM brushless moto, is used to
overcome the IM for EVs because of its advantages like
increasing the speed range and improve efficiency. As in this,
there is no rotor due to which rotor copper losses are absent.
However, motor efficiency is inherently higher, and its
acceleration is also improved (Chan, 2003).
According to Rajashekara (2013), switched reluctance
motor (SRM) is a synchronous device that operates on
inverter-driven square wave unipolar current. It is a variable
reluctance machine, and it has a fault tolerance capability
because of the absence of PM and its reliability also
improves. Some researchers used an SR motor in vehicle
traction that could make the system cheaper and also
improves the performance of the system. Several other
researchers and companies are also in the process of using
SR motor in the electric propulsion system.
1.2.2. Power electronic driver
Power devices are the most crucial element in the electric
propulsion system. This system consists of a power switching
device, with its closed-loop control and switching strategy for
making our system efficient. According to the literature re-
view, in the past 25 years, power semiconductor devices are
used in EVs. In the 1970s, thyristors are used as a power
semiconductor switch in EV controllers. But now a day's re-
searchers replaced a thyristor with new power devices such as
bipolar junction transistor (BJT), metal oxide semiconductor
field effect transistor (MOSFET), gate turn-off thyristor (GTO),
insulated gate bipolar transistor (IGBT) and many more (Chan,
1999). However, selecting a proper power device must be
necessary and selection may depend upon the requirement
of EVs and the parameters of semiconductor devices. Mostly,
three types of semiconductor devices are used for electric
propulsion vehicles. The comparison of related methods is
described in Table 1 (Chan, 1999).
After reviewing the characteristics of all power devices,
IGBT is getting more attention for EVs applications. IGBT has
certain advantages over the other devices such as excellent
conductivity as BJT and high-power density, high efficiency,
compact and costs useful power device. It has six thyristors in
every module, and its drive circuit is integrated into the single
package.
1.2.3. Electrochemical energy storage system (EESS)
In EV, the prime importance is given to the energy storage
system that controls and regulates the flow of energy. At
Table 1 e Comparison of devices (Chan, 1999).
Devices IGBT Transistor Mosfet
Voltage drop Mediu m Low High
Control power Low High Low
Control mode Voltage Current Voltage
Switch speed Fast Mediu m Very fast
Voltage rating Mediu m Mediu m Low
Cost Low Low High
present, the primary emphasis is on energy storage and its
essential characteristics such as storage capacity, energy
storage density and many more. The necessary type of energy
conversion process that is used for primary battery, secondary
battery, supercapacitor, fuel cell, and hybrid energy storage
system.
This type of classifications can be rendered in various
fields, and analysis can be abstract according to applications
(Gallagher and Muehlegger, 2011). According to electric
vehicles applications, the electrochemical ESS is of high
priority such as batteries, supercapacitors, and fuel cells. An
electro-chemical system deals with electrochemistry, i.e.,
shifting of electrons with the help of chemical reactions at
the interface of electrode and the electrolyte (Elliott and
Cook, 2018; Wu and Niu, 2017; Xia et al., 2015). Many other
energy stored devices based on electrochemistry have been
fabricated which are named as primary and secondary
batteries, supercapacitors, fuel cells, electrolyzers and many
more (Xia et al., 2015).
1.2.3.1. Primary battery. The first primary battery was intro-
duced more than 100 years ago, zinc-carbon was the only
battery used in 1940 (Conway, 2013). After that, many
advancements take place in primary cells regarding its
capacity, operating temperature, life cycle, etc., hence, there
are many primary cells designed using various anode-
cathode combinations some of them are discussed in the
following subsections (Elliott and Cook, 2018; Shen et al., 2016;
Xia et al., 2015). There are a variety of batteries explained
below and summarized in Table 2.
● Zinc-Carbon and alkaline manganese dioxide batteries
Zinc-Carbon (Zn-C or Zn-MnO2) batteries were the most
popular battery for more than 100 years (Xia et al., 2015). It is
also known as “dry battery”. In this, Zn is anode material
while the carbon and MnO2 are used as a cathode material
(Jom et al., 1981). The cathode material is based on
electrolytic MnO2, which gives high power and long life. The
theoretical capacity of the primary battery, i.e., Zn-C is
225 A$h/kg, synthesized on both types of cathode material and
this value is based on simplified cells (Xia et al., 2015). As on a
practical basis, the obtained specific capacity of the battery is
97 A$h/kg, and till now, this is the optimum specific capacity
for a cell (Xia et al., 2015). The operating voltage/current of
the primary battery is in the range of 0.16e44 A in prismatic
battery design and button cells 25e60 mA. These batteries
are having a low-temperature range, i.e., 10 ◦C (Bockris,
1981; Wendt and Kreysa, 2013).
● Zinc-air battery
The zinc-air battery consists mainly of three components:
a catalytic cathode, aqueous alkaline electrolyte, and zinc
powder anode (Xia et al., 2015). In this, O2 is utilized from the
air as an active cathode, and due to this, the capacity of Zn-air
is double than that of primary batteries. The gravimetric and
volumetric size of a cell is very high. In the construction of
the button cell, the capacity range is 40e600 mA$h (Xia
et al., 2015). It has an advantage over another cell that its

345
Table 2 e Comparison of primary batteries (Xia et al., 2015).
Primary battery Cathode
material
Anode
material
Electrolyte/reaction Nominal
voltage
/current
Practical
capacity
Zinc-carbon and MnO2 Zn Aqueous KOH/NH4 Cl
Zn þ 2MnO2 þ 2H2O / 2MnOOH þ Zn (OH)2
Zn þ 2MnO2 / ZnO þ Mn2O3
Alkaline electrolyte
Zn þ 2OH— / Zn (OH)2 þ 2e— (anode)
O2 þ 2H2O þ 4e— / 4OH— (cathod e)
1
Zn þ
2
O2 / ZnO (overall reaction )
KOH or NaOH aqueous electrolyte
Zn þ Ag2O / ZnO þ 2Ag (overall reaction )
2Li þ 2SO2 / Li2S2O4 (overall reaction )
4Li þ 2SOCl2 / 4LiCl þ S þ SO2
(overall reaction)
Ion conductin g organics
Li / Liþ þ e— (anode)
2MnO2 þ Liþþ e— / MnO—
2 (Liþ) (cathod e)
MnO2 þ Li / MnO—
2 (Liþ) (overall reaction )
xLi þ CFx / xLiF þ xC (overall reaction )
0.16e44 A 75e35 A$h/kg
alkaline manganese
Zinc-ai r O2 Zn 0.4e2 mA 40e600 mA$h
Silver-o xid e Zn Ag2O 1.5e1.6 V 165 mA$h
Lithium-s ul fu r dioxide Teflo n -b on d ed Li 2.7e2.9 V ~260 W$h/kg
acetylen e black
Lithium-t hio ny l chloride Porous carbon Li 450e600 W$h/kg
Lithium-m an g an es e dioxide MnO2 Li 3.60 V 200 W$h/kg
Lithium-carb on mono fl u ori d e Polycarbo n fluoride Li 2.8 V 200e600 W$h/kg
excellent retention even at 0 ◦C with its flats discharges
curves. But the main problem with this battery is its life
cycle as after 1e3 months the cells come into contact with
the atmosphere. Therefore, these batteries are used in
continuous-drain applications (Xia et al., 2015).
● Silver-oxide battery
Silver-oxide battery was first synthesized in the early 1960s
for various applications such as a pocket calculator, watches,
etc., as this battery offers certain advantages over other bat-
teries named as high capacity, excellent storage capacity
retention and a constant discharge voltage (Xia et al., 2015).
The theoretical energy storage capacity of Zn-Ag2O is
231 A$h/kg, and it shows a steady discharge voltage profile
between 1.5 and 1.6 V at low and high discharge rates (Xia
et al., 2015). Its main advantage is long storage life up to one
year at room temperature, and its performance deteriorates
at low temperatures (—20 ◦C) up to 35% at standard capacity
(Xia et al., 2015).
● Magnesium/manganese dioxide battery
As in other batteries, now magnesium is considered as an
anode material. It has a low atomic weight and a high stan-
dard of potential. The main advantage of Mg battery over the
other is its low operating temperature, i.e., —20 ◦C and below
(Xia et al., 2015). However, the low-temperat ure affects the
performance of heat generation during discharge and is
dependent on the discharge rate, battery configurations,
battery size and many other factors (Xia et al., 2015).
● Lithium primary battery
For high energy density batteries in the 1960s, when the
researchers focused on lithium as an anode (Xia et al., 2015).
The first lithium battery was implemented in the 1970s for
military appliances. The lithium battery has proved
themselves to the best battery till then because of long
operational time, extreme temperature or high power (Xia
et al., 2015). Therefore, the primary lithium batteries can
be classified into several other categories, based on the
type of anode and cathode material discussed below (Xia
et al., 2015).
● Lithium-sulfur dioxide battery
The first lithium commercialized cell was introduced in the
1970s, i.e., lithium-sulfur dioxide (Li-SO2) cells (Broussely and
Pistoia, 2007). In this cell, carbon is placed as a cathode and
lithium used as an anode. Teflon-bonded acetylene black
supported on Al screen also serves as a cathode due to
which cell provides high values of surface area, conductivity,
and porosity (Xia et al., 2015). This has high conduct ivity
even at —50 ◦ C (2.2 × 10—2
U—1
$cm—1
), and working voltage
are 2.7e2.9 V (Zhang, 2012). As the tubular construction also
provides a good energy density of z260 W$h/kg and its
storing capacity is 34 A$h (Xia et al., 2015). However, the
primary concern of this battery is its passivating film, which
starts reducing its capacity when the concentration of SO2 is
below 5% (Xia et al., 2015).
● Lithium-thionyl chloride battery
These batteries were used because of their efficient energy
density of 440e610 W$h/kg and the long-life span of 14e21
years (Xia et al., 2015). Moreover, certain batteries can be
operated at an extensive temperature range —80 ◦Ce150 ◦C
(Xia et al., 2015). As similar to a Li-SO2 battery, Li-SOCl2 also
has porous carbon as a cathode, the solvent for the
electrolyte salt and SOCl2 acts as an anode. In this, the main
component to form the passivating film on the anode is LiCl.

Table 3 e Comparison of secondary batteries (Xia et al., 2015).
Secondary
batteries
Cathode
material
Anode material Electrolyte/reaction Nominal voltage (V) Practical capacity (W$h/kg)
Lead-aci d PbO2 Pb H2SO4 aqueous solution
2— —
Pb þ SO4 4 PbSO4 þ 2e (anode)
PbO2 þ 4Hþ þ SO2— þ 2e— 4 PbSO4 þ 2H2O (cathode)
4
PbO2 þ 2PbSO4 þ Pb 4 PbSO4 þ 2H2O (total reaction)
KOH aqueous solution
Cd þ 2OH— 4 Cd(OH)2 þ 2e— (anode)
2NiOOH þ 2H2O þ 2e— 4 2Ni(OH)2 þ 2OH— (cathode)
2NiOOH þ Cd þ 2H2O 4 Ni(OH)2 þ Cd (OH)2 (total reaction)
KOH aqueous solution
H2 þ 2OH— 4 2H2O þ 2e— (anode)
2NiOOH þ 2H2O þ 2e— 4 2Ni(OH)2 þ 2OH— (cathode)
2NiOOH þ H2 4 2Ni(OH)2 (total reaction)
Organic electrolyt e with lithium salt
Li (C) 4 Li(1-x)(C) þ xLiþ þ xe—(anode)
xLiþ þ xe— þ Li (1-x)CoO2 4 LiCoO2 (cathode)
Li (C) þ Li (1-x)CoO2 4 LiCoO2 (total reaction)
Liquid electrolyt e
Li2S8 þ 2e— þ 2Liþ 4 2Li2S4
Li2S4 þ 2e— þ 2Liþ 4 2Li2S2
Li2S2þ 2e— þ 2Liþ 4 2Li2S
Liquid or gel electrolyt e
2Li þ O2 4 Li2O2
4Li þ 6H2O þ O2 4 4(LiOH$H2O)
2 30e50
Nickel-cad mi u m NiOOH Cd 1.2 50
Nickel-met al hydride NiOOH Hydrogen 1.2 100
adsorbed alloy
Lithium-i on LiCoO2 C þ Li/Li 3.6 150e200
Lithium-s ul fu r S Li 2.15 2600e2800
Lithium-ai r LiCoO2 C 3.1 3620e5200
346
J.
Traffic
Transp.
Eng.
(Engl.
Ed.)
2020;
7
(3):
340e361

347
Hence, to increase the capacity of cell AlCl3 is adding in excess
to the electrolyte (Xia et al., 2015).
● Lithium-manganese dioxide battery
Li-MnO2 was introduced in 1975 and also known as solid-
cathode primary batteries (Broussely and Pistoia, 2007). These
are widely used due to certain advantages followed as
relatively high energy density, high working voltage,
nominal operating temperature range (350 ◦C e400 ◦C), long
lifespan, and low cost (Xia et al., 2015). The most widely
used electrolyte is LiClO4-P C-D ME. Li-MnO2 can be
constructed in various forms according to its applications
such as cylindrical, cover coin and prismatic structures (Xia
et al., 2015).
● Lithium-carbon monofluoride battery
Another solid-cathode primary battery is made with Li-C
monofluoride (Li-CFx) battery, in which polycarbonate fluo-
ride is used as a cathode (Xia et al., 2015). In this, Carbon
enhances the electronic conductivity of the cathode
material. Hence, the CFx system has advanced features and
shows the flat operating voltage profile (2.8 V), energy
density (200e600 W$h/kg), high capacity and full
temperature range (—40 ◦Ce85 ◦C and reached up to 125 ◦C
depends upon design) (Xia et al., 2015). Also, Li-CFx also
shows the self-discharge rate among all lithium batteries.
Although there are many more lithium primary batteries,
which are designed for various types of applications such as
cell phones, notebooks, etc.
1.2.3.2. Secondary battery. A rechargeable battery acts as en-
ergy storage as well as an energy source system. The initial
formation of the lead-acid battery in 1858 by Plante (Broussely
and Pistoia, 2007; Wendt and Kreysa, 2013). Later, the nickel-
iron alkaline battery was introduced as a power source for the
electric automobile by Edison in 1908 (Shen et al., 2016;
Thomas, 2010; Zoski, 2006). Similarly, other critical commer-
cialized batteries are explained in detail and summarized in
Table 3 (Xia et al., 2015).
● Lead-acid battery
The lead-acid battery was the very commercialize battery
in the early era, as this battery was introduced in 1859 (Xia
et al., 2015). As compared with other battery it shows
certain advantages such as low-price, a high voltage of the
cell (2 V), high electrochemical activity, excellent reliability,
and long-life span (Xia et al., 2015). The main components
of the lead-acid battery are electrodes, separator, and
electrolyte. In this, the dioxide serves as a cathode and
lead serves as an anode, which is immersed in an
electrolyte solution of sulfuric acid (Bullock, 1994). These
batteries have different types of construction due to which
their characteristics vary such as tubular construction,
bipolar construction and prismatic construction with grid
or tubular plates. As we know lead is more substantial in
weight, so its specific energy is low 30e50 W$h/kg (Xia
et al., 2015).
● Nickel-cadmium battery
Nickel batteries were introduced in 1908e1909 by Edison as
a power source for various applications. There are five
rechargeable batteries, which belong to nickel groups named
as Ni-Cd, Ni-H2, Ni-MH, Ni-Zn and Ni-Fe batteries (Xia et al.,
2015). Presently, Ni-Cd batteries have two significant struc-
tures, vented and sealed type. In all types of battery, b-NiOOH
is used as the positive electrode material and Cd is used as a
negative electrode. The KOH aqueous solution acts as an
electrolyte for LiOH, which helps in improving cycle life as
well as its temperature performance (Xia et al., 2015). The
advantages of Ni-Cd over other types of batteries are high
rate capability and excellent lifespan up to ten years in an
optimum temperature range (—30 ◦Ce80 ◦C) (Pistoia, 2008). On
the other hand, these batteries rapidly lose their capacity at
ambient temperature and excellent self-discharge (Pistoia,
2008).
● Nickel-metal hydride battery
Ni-MH battery was introduced in the 1960s as a replace-
ment for both Ni-Cd and Ni-H2 batteries because of its ad-
vantages such as lower pressure, high energy, and low cost as
compare to Ni-Cd. It was commercialized in 1989 as a
rechargeable battery for multiple applications such as
portable computers, electronic devices, and hybrid vehicle
propulsion systems (Huggins, 2010). In the Ni-MH battery, the
hydrogen alloy is a negative side and b-NiOOH is a positive
alloy and there is no electrode reaction involving H2O due to
which concentration and conductivity remain the same
during the charge and discharge process (Xia et al., 2015).
During overcharge process, both H2 and O2 evolve from the
positive electrode and recombine to form H2O. The energy
density of the cell can approach 100 W$h/kg and 300 W$h/L
(Xia et al., 2015). However, there are significant issues with
Ni-MH, which is yet to be solved such as limited high rate
capability, poor low-temperature capability and also high
self-discharge (Xia et al., 2015).
● Lithium-ion battery
Among all other secondary batteries, lithium-ion has high
specific energy and energy density (Xia et al., 2015). In the
1970s, the development of lithium-ion batteries was started
(Sadoway and Mayes, 2002; Shukla et al., 2001). An earlier
lithium-ion battery cathode material contains different
layered structures explained as Li-cobalt oxide (LiCoO2) or a
tunneled structure named as Li-manganese oxide (LiMnO2)
(Zimmerman, 2009). There are some other metal oxide
materials that act as a cathode such as LiMn2O4, LiFePO4,
and LiNi1-xMnxCoyO2 and many more (Xia et al., 2015). The
first commercialized lithium-ion battery was explained, for a

negative electrode as a coke-based material and after that in
the mid-90s era; graphite-based anode materials were
utilized (Xia et al., 2015). The capacity of the graphitic
content is higher (350 A$h/kg) as compared to the original
coke material (180 A$h/kg) (Xia et al., 2015). The other
advantages are good energy density (150e210 W$h/kg), the
top voltage level of graphitic material (4 V in fully charged
state and 3 V in discharged rate) and relatively good cycle
life with acceptable low self-discharge (<10% per month).
However, for a lithium-ion battery, the significant
disadvantage is a very high cost and overcharging or heating
above 100 ◦C causes the decomposition of the positive
electrode and the electrolyte with the liberation of gas (Xia
et al., 2015).
● Lithium-sulfur and lithium-air batteries
Li-S holds unique advantages to achieve the demand for
renewable energy. Since, sulfur as a cathode is considered for
the battery which leads to specific advantages like optimum
cost, good specific energy and eco-friendly (Fu et al., 2013).
However, both lithium and sulfur are light in weight and
good in exerting multielectron conversion electrochemistry
which has a high specific energy (Xia et al., 2015). In 1962,
sulfur type battery had been introduced, but there are
particular issues that are still not solved such as the
solubility of intermediately formed polysulfide in general
liquid organic electrolyte and electronically insulating
nature (Goodenough, 2012). Lithium-sulfur battery also
shows low coulombic efficiency due to its shuttling effect
and its capacity fades rapidly (Goodenough and Kim, 2009).
When based on overall reaction S8 þ 16Li ¼ 8Li2S, shows the
voltage of 2.16 V with a theoretical calculated specific
capacity of 1676 mA$h/g and energy density of 2600 W$h/kg
(2800 W$h/L) which is five times greater than other batteries
(Whittingham, 2004; Yuan et al., 2016; Zhao et al., 2015).
Moreover, the modern advancement in Li-sulfur batteries
has been done because of the increasing demands of high
storage energy system, and it also gives many opportunities
to solve their issues related to bulk material's conductivity
(Amine et al., 2014; Barchasz et al., 2012; Bruce et al., 2011;
Peng et al., 2017; Su and Manthiram, 2012).
The other most developing Li batteries regarding energy
density are lithium-air system since the cathode active mass
material is not included in these batteries. The excellent
advantage of the lithium-air battery is its energy density of
3621 W$h/kg (when discharged to Li2O2 at 3.2 V) or 5210 W$h/
kg (when discharged to Li2O at 3.2 V). Therefore, Li-air gives
competition with liquid fuels. Visco and Abraham were the
first to describe the aqueous and non-aqueous Li-air batteries
in 1996. Although both cells involve O2 reduction, both have
significant differences according to their merits (Bruce et al.,
2011; Xia et al., 2015).
In a non-aqueous Li-air battery, the primary focus is its
pore volume for higher conductivity and low cost. During
discharging, Li2O2 gets accumulates in the pores and creates
fast discharging. So, for blocking the Li2O2, a porous carbon
material is used as a cathode. This material has small pores
size, and carbon pores may easily block Li2O2 before filled,
thus limits the discharge capacity (Xia et al., 2015). Although,
solid pores size material may compromise rechargeability
and rate because of their low surface area. Hence pores size
should be optimal, i.e., 10e200 nm (Xia et al., 2015).
For the aqueous Li-air battery, the solid electrolyte is only
functioned in the system, which behaves like an ionic
conductor that covers the Li anode and then Li violently reacts
with water (Bruce et al., 2011; Xia et al., 2015). This invention
by Visco had made a Li cell real. Although, on the other hand,
the aqueous system suffers from corrosion, which leads to
high impedance. Therefore, both types of Li-air batteries face
many challenges for practical implementation (Xia et al.,
2015).
1.2.3.3. Supercapacitor. Electrochemical supercapacitors (ES)
or ultracapacitors have high demand, because of their high-
power density and long lifetime (Chen et al., 2013; Xia et al.,
2015). The earliest supercapacitor was invented in 1957. After
the 1990s supercapacitor starts achieving attention in the field
of HEVs. The primary purpose of a supercapacitor in the
hybrid electric vehicle is to boost the battery/fuel cell for
providing the necessary power for acceleration. For further
development, the US Department of Energy has analyzed ES to
be as important as the battery in the future of energy storage
applications (Xia et al., 2015).
The electrochemical supercapacitor is divided into two
types, namely faradaic supercapacitor (FS) electrostatic or
electrical double-layer supercapacitors (EDLS) (Xia et al., 2015).
● Electric-double layer capacitance
EDLC produces a non-faradic process featuring ion
adsorption between the electrode and electrolyte (Seh et al.,
2013; Yu et al., 2013). They have an unlimited degree of
cyclability in theory (Adler et al., 1998; Li et al., 2011). In this,
every layer is conductive and has more power density (Li et al.,
2011). In this supercapacitor, no ion evolves in exchange
between the electrode and electrolyte.
● Pseudocapacitance
It evolves a faradic process, intercalation on the surface or
redox reactions electrosorption of the electrode achieved by
adsorbed ions that gives reversible faradaic charge-transfer
on the electrode (Subrahmanyam et al., 2012). The pseudo-
capacitors constitute electrode materials of electronically
conducting polymers. There are three different types of
faradaic processes explained as redox reactions reversible
electrochemical doping, reversible adsorption and de-doping
process (Xia et al., 2015). Three components can be
categorized into electrode materials of supercapacitors:
conducting polymer, carbon material with the high specific
surface area and metal oxides (Li et al., 2012; Ma et al., 2013;
Sobha and Narayanankutty, 2014).
1.2.3.4. Fuel cell. An electrochemical device made to transfer
the electrical energy from chemical reactions is known as a
fuel cell (Xia et al., 2015). The difference between the fuel cell
and other storage device are: 1) fuel cell uses liquid reactants
or supply of gaseous for the reactions (Ahmer and Hameed,
2015); 2) it is easy to eliminate the reaction products and

349
keep the operation longer (Bagotsky, 2012; Revankar and
Majumdar, 2014; Wang et al., 2012; Wang and Xia, 2013;
Zhang and Zhao, 2009). There are many advantages of the
fuel cell such as no combustion reaction, pollution-free
electrical energy, excellent energy efficiency, lightweight,
silent operation, and vibration-free operation. The fuel cell
experiment was performed by Sir William Grove (Grove,
1839; Hoogers, 2002; Srinivasan, 2006). After more than 100
years, a fuel cell was developed by Francis Thomas Bacon in
1959 (Dincer and Bicer, 2018). NASA used it as an auxiliary
power source for space vehicles. The fuel cell working
voltage is less than 1 V, but to have more voltage like 6, 12,
or 24 V then individual cells are connected to form the
stacks for real-time applications (Xia et al., 2015). Depending
upon fuel and electrode, fuel cell may be different types
reactions such as PEM fuel cells (low temperature), alkaline
fuel cells (low temperature), molten carbonate fuel cells
(high temperature), phosphoric acid, fuel cells (intermediate
temperature), direct methanol fuel cells (low temperature)
and solid oxides fuel cells (high temperature) (Xia et al.,
2015). Among all these, phosphoric fuel cells and methanol
fuel cells are used in hybrid electric vehicles because they
are easily connected in parallel with lead-acid/NieCd battery
to supply peak power and to have a good advantage in
regenerative braking (Dincer and Bicer, 2018).
1.2.3.5. Hybrid energy storage system (HESS). The energy
storage system (ESS) is essential for EVs. EVs need a lot of
various features to drive a vehicle such as high energy density,
power density, good life cycle, and many others but these
features can't be fulfilled by an individual energy storage
system. So, ESS is required to become a hybrid energy storage
system (HESS) and it helps to optimize the balanced energy
storage system after combining the complementary charac-
teristics of two or more ESS. Hence, HESS has been developed
and helps to combine the output power of two or more energy
storage systems (Demir-Cakan et al., 2013). In HESS, there is a
combination of two or more features such as high energy
density or fast response of ESS, high power density and high
cost or low cost which may be considered in power
electronic configurations to deliver a suitable power during
operation (Zhang et al., 2010).
Nowadays, lithium-ion battery is most widely used due to
its surplus demands of EVs in today's market. The current
demand for EVs goes on increasing day by day due to which
requirement of lithium-ion battery is on the boom and the
automobile market demands surplus energy from Li-ion bat-
1.3. Charging schemes
The essential component of BEV is a charger to charge a battery.
Charging is not merely to charge a battery, but it needs an
advancedcontrolsystemtoregulatethecurrentandvoltage. The
charger can be build-in-charge or a standalone charger at a
charging station. For any battery, the charging and discharging
process help to determine its safety, durability, and perfor-
mance. For EVs, there are different charging methods such as
constant current, constant voltage, combination of constant
voltage andconstantcurrent(Ahmadian etal., 2015). For EVs, the
random charging of batteries is essential due to regenerative
braking. So, there are different levels of charging an EVs such
as shown in Table 4 explained below (Dost et al., 2015).
i. Slow charging
Level 1 is suitable for a residential outlet (120 V-AC). All EVs
are equipped with an on-board charger that can be considered
as the average power of 2 kW. It is the most available form for
battery charging and can typically charge a vehicle's batteries
overnight, as an outcome recharging of the battery will pro-
vide four miles of travel per hour (Ahmadian et al., 2015).
ii. Semi-fast charging
Charging power at Level 2 charging stations can be five-time
higher than that of Level 1. As, it will supply up to 16 miles of
travel for one hour of charging with a 3.4-kW on-board charger,
or 35 miles of travel for one hour of charging with a 6.7-kWh on-
board charge (Ahmadian et al., 2015). These chargers are
especially depleted for PEV batteries that can be charged
entirely within seven hours (Rahman et al., 2016).
iii. Fast charging
Level 3 is for DC fast charging (DCFC), which provides
350 km range in half an hour charging (Rahman et al., 2016). In
this level, the charger has to be off-board because its charging
power exceeds 100 kW, which is significantly higher than
other levels (Perry and Fuller, 2002). As in general, DCFC
recharging will provide 85e105 miles of travel within
25e30 min. In DCFC charger, high power DC is directly fed to
the EV's traction batteries through the charging inlet on the
vehicles (Grove, 1839, 1843; Perry and Fuller, 2002). The most
tery, i.e., 2000 W/kg in terms of power density but the current
status of power density is 500 W/kg (Zhang and Read, 2012).
Hence, to fulfill this demand we combine the battery with
ultracapacitor because it provides high power density
(1170 W/kg) to the EVs. But this option is only suitable for
significant increase in power density with a small decrease
in energy density. So, we have a look at other hybrid
systems that are classified in various types such as fuel cell
and battery hybrids, flywheel and battery hybrids or many
more, that depend on types of applications (Aurbach et al.,
2009; Zhang and Read, 2012).
Table 4 e Comparison of levels for charging an EV (Dost
et al., 2015).
Quantity Level 1 Level 2 Level 3
Voltage (V) 120 208/240 200e450
Current (A) 15 40 125
Useful power (kW) 1.4 7.2 50
Maxi mu m output (kW) 1.9 19.2 150
Chargin g time (h) 12.00 3.00 0.33
Connect o r J1772 J1772 J1772 combo

Fig. 3 e General topology of advanced charging system.
reliable charging technique for fast charging is constant
voltage and constant current (CV-CC).
Furthermore, these charging schemes can also be
explained in the form of on-board and off-board chargers.
Both these chargers can be inductive or conductive and also
described as bi-directional or unidirectional. For low power
level applications, on-board chargers are installed within the
vehicle whereas off-board chargers are installed outside the
vehicle such as malls, hotels, etc. However, both these char-
gers can be single-stage and two-stage systems. In a two-stage
EV charger, an AC-DC converter is connected in cascade with
DC-DC converter as shown in Fig. 3 (Castello et al., 2014).
This two-stage system represents a dual-stage converter,
in which first stage is the AC-DC converter and the second
temperature and high current (Sorrell et al., 2005). Hence,
to allow EVs to be charged quickly without reducing their
performance, it becomes necessary to analyze the main
technical factors, such as (1) the utilization of an adequate
LIB technology with an architecture design optimized for
fast charging and (2) the use of an appropriate fast charging
protocol (Dost et al., 2015). The main factor to achieve high
power performance in LIBs is to decrease the polarization
resistances, so energy can rapidly be extracted (Betz et al.,
2017). Various high-power cell technologies are available in
the market, including LFP and LTO. Therefore, high power
batteries are the best choice for fast charging (Nguyen
et al., 2014).
stage is the DC-DC converter. The first stage is interfaced be-
tween the power grid and the DC link, which is composed of
parallel with two full-bridge voltage source converters
(Castello et al., 2014). The second stage is interfaced between
the DC link and the batteries, which is composed of a bi-
directional three-level asymmetrical voltage source
converter. The two main reasons to employ a two-stage
charger instead of a single-stage are (i) provide galvanic
isolation, and (ii) reduce the second-order harmonic on the
DC side of the charger. The second-order harmonics are a
natural byproduct of a single-phase AC-DC converter
(Castello et al., 2014).
There are two types of topologies in the two-stage system
which can transfer power according to the requirement such
as in unidirectional topology power is transferred from grid
to vehicle (i.e., G2V), whereas in bi-directional topology, there
is an advantage to work in the vehicle to grid (V2G) mode
(Castello et al., 2014). In this, active power is transferred to
the grid according to the requirement. Apart from active
power, it can also provide reactive power either in lagging
or leading phase. Therefore, for maintaining the unity
power factor, reactive power is compensated by using
various techniques such as capacitor banks, static VAR
compensator and many more. In addition to these types of
equipment, the increasing demand for EV owners will have
a frequent effect on electric utilities and consumers
(Castello et al., 2014). Nowadays, all EVs are powered by
lithium-ion battery (LIB) technology, and unfortunately, fast
charging may also affect the LIB's performance by
accelerating its aging/durability. Fast charging gives high
2. Types of electric vehicles
The most emerging transportation system, i.e., EV, is also
described as an automobile vehicle that develops through the
electric propulsion system. Due to this, EVs may include
hybrid electric vehicles (HEVs), battery electric vehicles (BEVs)
and plug-in hybrid electric vehicles (PHEV) (Singh et al., 2006).
The use of batteries in EV has an absolute advantage over
traditional vehicles. EVs are quiet in operation, helps in the
removal of flue gas pollutants which are created from
conventional vehicles and the most crucial factor is
exploitation cost of EV which is three times lower.
Unfortunately, batteries have certain disadvantages also,
like substantial weight, the high cost of batteries, and
volume impose significant range restrictions and
performance of battery changes according to the climatic
conditions (Koniak and Czerepicki, 2017). Hence, we focused
on EVs in brief for more enhancement and future
development.
2.1. Battery electric vehicle (BEV)
BEV runs using a battery and the electric motor, and it oper-
ates solely on the electricity stored in a high-capacity battery.
BEV can also be charged from the grid. According to the
transportation sector mainly in the field of electric vehicles,
one of the leading elements is batteries (Chan and Chau, 1997).
So, the main focusing factors related to batteries are cost,
climatic condition, energy density and power density due to

351
which we differentiate them. According to Nitti et al. (2015),
Batteries are significantly reduced greenhouse gas emission
and used for various power-grid applications that provide
the high quality of energy derive from various renewable
sources like wind, solar, geothermal and other renewable
sources. As first, EV was launched in 1834, i.e., tricycle,
which is powered by a battery (De Luca et al., 2015).
According to Pinsky et al. (2000), Electric vehicles have two
main issues: limited range and cycle life. So, to overcome
these issues anciently, the author used lead-acid batteries
because of its robust design and high charge rate
acceptance. Regarding the cycle life of the battery, the
author discussed the pulsed type algorithm for optimum
lead oxide morphology. Therefore, the range of vehicle
depends upon battery configuration, power density, and
energy density. For EVs, LIB technology is best suited for
vehicular application, hence LTO and LFP cell technologies
are used in the market. There are various BEVs, which run
on the road with different ranges listed in Table 5 (Ansean
et al., 2011).
BEVs have a range of 100e400 km, depending upon the
battery capacity. Charging time varies according to the battery
cell configuration and its capacity. It is also affected by the
ambient temperature. Furthermore, for increasing the range
of EVs, we switched to other technologies such as HEV, PHEV
and many more.
2.2. Hybrid electric vehicle (HEV)
Hybrid means a combination of two or more sources that has
multiple powered sources that could drive the vehicle sepa-
rately to propel the vehicle (Emadi, 2005). There are many
other hybridization configurations designed as fuel cell, gas
turbine, pneumatic, ethanol, electric drive, solar, hydraulic,
and much more developed in recent years. Among these
techniques, the most proven and established procedure is
electric motor and an internal combustion (IC) engine
(Emadi, 2005). The one form of HEV is gasoline with an
engine as a fuel converter, and other is a bi-directional
energy storage system (Kebriaei et al., 2015). Nowadays,
efficiency-improving technologies are used in HEVs named
as regenerative braking, which converts kinetic energy into
electrical energy to charge a battery (Kebriaei et al., 2015).
According to the previous reviews, the conventional IC
engine produces lots of harmful gases, wastage of fuel
during heavy traffic and many more. HEV is used to
overcome all the disadvantages of IC engine by switching to
Table 5 e Comparison study of different BEVs.
Vehicle model Range (km) Price ($) Charge time (h)
Tesla Model S 335e426 82,820e1 20,0 00 5
BMW i3 160 44, 950 6
Mitsubishi IMiEV 100 27,998 7
Ford Focus EV 110 36,199 4
Smart EV 109 26,990 6
power transmission through the motor and shutting off the
engine (Hannan et al., 2014; Shen et al., 2011). Another
advantage of HEVs is that when the fuel tank gets empty
while driving the engine, then the vehicle can be driven on
electric power with its maximum range (Thompson et al.,
2011). The HEV is classified into three types according to its
structure.
i. Series hybrid
A series hybrid system is also known as a range extender.
In this system, as shown in Fig. 4, the combustion engine
drives an electric generator to charge a battery and provide
power to make the electric motor (Shen et al., 2011).
In this system, the electric motor is the only means of
supplying power to the vehicles. The generator gives supply to
both batteries as well as the motor that drives the vehicle.
These vehicles have a large battery pack and a large motor
with a small IC engine (Thompson et al., 2011). In this system,
there is no mechanical connection between the IC engine and
transmission (Shen et al., 2011). Thus, IC can operate at
maximum efficiency to satisfy the required power of the
vehicle (Shen et al., 2011). The only disadvantage of this
connection is the high cost of batteries and its components
(Pollet et al., 2012).
ii. Parallel hybrid
In this system, the parallel connection is connected with
an IC engine and electric motor for mechanical transmission.
Usually, the IC engine operates as a primary means and
electric motor acts as a backup or torque power booster (Pollet
et al., 2012). The advantage of this system is that EV requires
lightweight and smaller batteries. The batteries in the
parallel mode can be recharged during regenerative braking
and during cruising. As shown in Fig. 5, there is a fixed
mechanical link between the EV wheels and the motor (Shen
et al., 2011). Hence, the battery can't be charged when the
car is not moving (Kebriaei et al., 2015).
iii. Combined hybrid
A combination of both series and the parallel hybrid sys-
tem is known as a combined hybrid or series-parallel or
complex/power split system (Kebriaei et al., 2015; Shen et al.,
2011). The principle of this system is the decoupling of the
power supplied by the engine from the energy derived by the
driver. There is a second connection between the engine and
the drive axle: mechanical and electrical (Beresteanu and Li,
2011). This is the most complicated system due to the
interconnection of both mechanical and electrical power,
through which it allows to split power paths as explained
with the help of Fig. 6 (Pollet et al., 2012; Thompson et al.,
2011).
This is the most expensive system for real-time applica-
tions. Hence, the parallel hybrid system is mostly used in
HEVs. Although, HEVs are 8e10 times more costly than BEVs
and it cannot charge the vehicle at home.

Fig. 4 e Series hybrid electric vehicle (Shen et al., 2011).
2.3. Plug-in hybrid electric vehicles (PHEV)
PHEVs are capable of running with electricity or gasoline. They
are hybrids that can be plugged into the power grid for battery
charging. In general mode, the vehicle allows having a me-
dium capacity of the battery (Wirasingha and Emadi, 2009).
This helps to achieve a range of several dozen kilometers,
with excellent rates of acceleration and top speeds as
compared to other gasoline-powered vehicles. There are
different types of PHEVs with different varieties. Some of
them are listed below in Table 6 (Thompson et al., 2011).
PHEVs have a good range as compared to other electric-
powered vehicles but the significant disadvantages are: 1)
costlier than BEVs, 2) not wholly eco-friendly (Thompson
et al., 2011). However, after comparing all the vehicles,
battery electric vehicle (BEVs) are suitable in all aspects
because of their environmental and eco-friendly behavior.
BEV does not produce any emission in the environment,
and the only disadvantage is its battery ranging and
speed (Thompson et al., 2011). So, to overcome these
factors, researchers have to be more concern about
batteries for future development. Henceforth, research
have been focused on the batteries in brief, how their
packaging, testing and ranging are developed (Thompson
et al., 2011).
3. Battery pack design of EV
A battery pack is a combination of cells connected in series
and parallel for the desired operating voltage and current
ratings. These packs having different designs involving
electrochemical, mechanical, control and thermodynamic
principles. For EVs applications, many individual cells
stacked in a specific order for making the interconnection
between battery for power flow (Rajasekhar and Gorre, 2015).
Hence, battery packs are very expensive for EVs applications
due to a high number of cells, different chemistry types
based on lithium and different protection circuits. The
battery pack design consists of many steps, such as (1)
select the battery cell technology and the pack
specifications by battery sizing; (2) battery pack designing
(electrical, control and structural); (3) battery pack safety
and testing (Rajasekhar and Gorre, 2015).
For the battery to be used in EVs, the primary parameter is
the energy density of the cell which decides the EV's driving
range, speed, and accelerations. Hence, the most recognized
material is lithium-ion cells because of its excellent energy to
volume ratio/weight. Currently, the Li-ion cells are used
mostly for energy storage, which is based on the following
compounds: LTO (Li4Ti5O12), LFP (LiFePO4), NMC (LiNiMnCoO2)
Fig. 5 e Parallel hybrid electric vehicle (Shen et al., 2011).

353
¼
Fig. 6 e Combined hybrid electric vehicle (Shen et al., 2011).
Table 6 e Comparison study of different PHEVs
(Thompson et al., 2011).
Vehicle model Range Price
($)
Charge
time (h)
BMW i3 REX 160 km on electric, gasoline 48,950 6
GM Chevy Volt 60 km on electric, 500 km on 36,895 2
gasoline
Ford Cmax 34 km on electric, 557 km on 36,999 2e3
Energe gasoline
and NCA (LiNiCoAlO2) (Koniak and Czerepicki, 2017). Table 7
represents energy density data for four different types of
lithium-ion cells. The lithium nickel manganese cobalt oxide
(NMC) has the highest energy density as compared to other
cells (Koniak and Czerepicki, 2017).
Battery packaging required some calculation which is dis-
cussed stepwise in the following paragraphs.
Step 1: calculation of battery voltage.
The essential requirement of any vehicle is maintaining
the required voltage during the drive. There are multiple cells
connected in series to realize the required voltage. The voltage
can be estimated in Eq. (1).
V ¼ nv (1)
where V is the voltage of the battery, n is the number of cells
and v is the cell voltage.
For example, if the energy density of the LFP cell is
100 W$h/kg and the cell voltage is 73.2 V (Lee et al., 2015).
Hence for designing the battery pack, 100 cells are
connected in series.
Step 2: calculation of battery pack size.
The battery pack size (S) can be estimated by Eq. (2).
S ¼ VA0 (2)
where voltage (V) is obtained in Eq. (1) and A0 denotes the
ampere rating of the cells.
For estimating the weight (W) of a battery, then pack size
(S) can be estimated from the above equation and capacity (C)
of the battery is known in W$h/mile and then weight is esti-
mated by Eq. (3).
W ¼ SC (3)
For example, if the capacity of the battery is 27 kW$h/mile,
then the estimated weight of the battery would be 270 kg for
10 cells (Lee et al., 2015).
Step 3: calculation of battery range.
The battery range (R) is calculated with the help of pack
size (S) and the capacity (C) of the battery using Eq. (4) given
below.
R
S
(4)
C
After calculating the above parameters, an extra 19% is
added to the battery capacity due to the reason that only 81%
of the battery capacity is utilized normally and the efficiency
of battery charging is considered to be 81% only (Ahmer and
Hameed, 2015).
Step 4: calculation of battery power.
The vehicle performance in terms of power delivered and
energy usage is calculated. The force Fx required to move the
vehicle with a certain constant velocity v for energy con-
sumption is calculated using Eq. (5) given below (Ahmer and
Hameed, 2015).
rACdv2
Fx ¼
2
þ mgfrr (5)
where r is air density, A is the frontal area, Cd is aerodynamic
drag coefficient, m is mass of the vehicle including passenger
and cargo, g is gravitational constant and frr is the tyre rolling
resistance coefficient (Ahmer and Hameed, 2015).
Table 7 e Comparison study of lithium cell (Koniak and
Czerepicki, 2017).
Cell type The energy
density per weight
The energy density
per volume
LTO 90 200
LFP 130 247
NMC 150 300
NCA 240 670

d
Furthermore, the required power which is delivered by the
battery for moving a vehicle can be calculated using Eq. (6)
given below.
P
Fx Paux
DC ¼
h
þ
v
(6)
where PDC is the DC energy usage of an electric vehicle, often
expressed in W$h/km, hd is the overall constant efficiency,
Paux is power uses of the auxiliary system independent of the
forward velocity (Besselink et al., 2013).
4. Testing for EVs
Various tests are performed on the batteries to lay down the
operating parameters of the battery so that it can work reliably
and remain resilient against failures. Range testing is per-
formed at a constant speed using test benches ETA-TP004 and
SAE J227. There are certain conditions below that must be
satisfied for range testing (Dhameja, 2001).
i. Battery pack temperature should be within the range of
60 ◦F and 120 ◦F.
ii. Wind speed at the test location recorded during a test
should not exceed ten mph.
iii. EV accessories should not be used during the test
activities.
iv. Range related tests should always commence with
batteries, initially charged to the standard point by
using rapid charging.
The range test is conducted at different driving periods and
spans up to three days. It helps to determine the driving range
achieved maximum during a 12-h period (Dhameja, 2001). For
determining the average miles for each day, the average is
taken from the total miles driven by the EV over the three-
day period. The second type of test is the driving test which
is performed on the EV for safety purposes (Dhameja, 2001).
The following parameters are checked during the driving
test (Dhameja, 2001).
● Average speed of the vehicle.
● Average distance required for charge.
● Average distance traveled between charges.
● Average kWh available per charge.
The third type of test is a safety test that batteries have to
pass through. These tests evaluate the characteristics of the
battery and also determine how the battery will behave in
certain abnormal/severe situations. The safety tests are
divided into the following three stages, mechanical tests,
electrical tests, environment tests.
Tables 8e10 present further details of these tests. In Table
8, mechanical tests for batteries in EVs are explained (Doughty
and Crafts, 2006; Holze and Pistoia, 2012; Ruiz et al., 2017).
There are five different tests such as drop test, penetration
test, immersion test, crush test, and rollover test. In all these
tests mechanical force is applied on the battery and
accidental situation is created to evaluate the battery
capability for practical applications. Similarly, in Tables 9
Table
8
e
Mech
anical
tests
for
batteries
in
electric
vehicle
s
(Zhu
et
al.,
2018).
Test
type
Drop
te
st
Evaluate
battery
for
various
accidental
situations
During
installation
or
rem
oving
a
battery
from
the
vehicle,
it
sudde
nly
drops.
He
nce
to
ove
rcome
this
situa
tion,
this
te
st
is
pe
rform
e
d.
W
he
n
sha
rp
obje
cts
pe
netrate
inside
the
ba
ttery,
a
nd
it
induc
e
d
m
e
c
ha
nic
a
l
a
nd
e
le
c
tric
a
l
da
m
a
ge
.
Parameters
required
S
urface
type
(rigid
flat
or
concret
e),
drop
height
(1e10
m
)
and
state
of
charging
(95%e100
%
).
How
they
are
performed
During
this
te
st,
the
ba
tte
ry
is
fre
e
ly
droppe
d
on
a
rigid
surfa
c
e
.
This
te
st
has
to
pe
rform
several
tim
e
s
a
t
va
ries
he
ights.
During
the
te
st,
the
na
il
inse
rte
d
through
a
c
ell,
a
nd
the
inte
rfa
c
ing
of
the
se
pa
rator
a
nd
e
lec
trode
is
da
m
aged.
Although,
a
short
c
irc
uit
is
m
e
c
hanica
lly
induc
ed
a
nd
c
onse
quently
he
a
t
is
re
le
ase
d.
During
the
te
st,
the
te
ste
d
ba
tte
ry
is
im
m
e
rsed
fully
in
the
lim
e
wa
te
r
for
a
pe
riod
of
a
t
le
a
st
(1e2
h)
until
bubbling
ha
d
stoppe
d.
T
he
re
sult
of
this
te
st
is
a
short
c
irc
uit
with
ha
z
a
rdous
ga
ses
possibly
be
ing
re
leased.
During
the
te
st,
the
ba
tte
ry
e
nc
losure
is
c
om
pressed/
pre
sse
d
down
till
it
re
a
c
he
d
85%
of
its
initia
l
dim
e
nsion
or
till
a
n
a
brupt
volta
ge
drop
wa
s
observed.
During
this
test,
a
battery
m
odule
is
slowly
rotated
(6
◦
$s
—
1
)
for
one
com
plete
revolution
(360
◦
).
The
test
evaluate
s
the
presenc
e
of
any
leakag
e
(electrol
yt
e,
coolant,
liquid)
or
venting.
Pe
ne
tra
tion
te
st
S
harp
steel
rod,
the
diam
eter
of
the
rod
(3
m
m
),
the
speed
of
penetration
(8
cm
$
s
—
1
),
the
m
inim
um
depth
of
penetration
(100
m
m
).
Im
m
ersion
fluid
(saltwater),
tem
perature
((25
±
5%)
◦
C
),
im
m
ersion
tim
e
(>2
h),
S
tate
of
charging
(100%)
Im
m
e
rsion
te
st
When
a
battery
subm
erge
d,
or
a
vehicle
is
partially
flooded.
C
rush
speed
(5e10
m
m
$
m
in
—
1
),
crush
plate
(cylindric
al
),
crush
force
(<1000
tim
es
of
battery
weight),
state
of
charge
(95%e100
%
)
R
otation
speed
(360
◦
$m
in
—
1
),
rotation
steps
(90
h
—
1
),
state
of
charge
(95%e100
%).
Crush
te
st
During
a
n
a
c
c
ide
nt,
when
forc
e
is
a
pplie
d
or
a
ny
oute
r/
e
xte
rna
l
loa
d
forc
e
tha
t
m
ay
dama
ge
a
ba
tte
ry
e
nclosure
a
nd
c
a
use
deformation.
T
his
sim
ula
te
s
a
n
ove
rturn
of
a
ve
hicle
tha
t
might
oc
cur
in
a
n
a
c
c
ide
nt.
R
ollover
test

Table 9 e Electrical tests for batteries in electric vehicles (Abaza et al., 2018; Kellner et al., 2018; Wang et al., 2018; Zhu et al., 2018).
Test type Evaluate battery for various accidental
situations
Parameters required How they are performed
Extern al short circuit Measu re safety perform an ce fro m overcurrent Resistan ce element (5e100 mU), passive short circuit During this test, a resistance is extern all y connect ed to
protection . protection device, state of chargin g (95%e10 0 % ). the battery termin al fro m about 10 min. As a
consequence, current flows across the system and
protection devices are connected to limit the current
such as a fuse, circuit breaker, etc. (Zhu et al., 2018).
Internal short circuit This test is not for consu mer's safety. This repres ent s e e
the imperfection during manufacturing, the
presence of impurities in the battery shows the
dendritic growth of lithium (Zhu et al., 2018).
Overch arg e/ o v erdis ch arg e test Evaluate the function ali ty of battery during charging / Charge rate and discharg e rate (>C/3), end of charge. During the test, the controlled current is applied to the
dischargi ng . battery up to a limited range (Zhu et al., 2018).
Table 10 e Environment tests for batteries in electric vehicle (Knap et al., 2018; Li et al., 2018; Rago et al., 2018; Ren et al., 2018; Zhang et al., 2018).
Test type Evaluate battery for various accidental
situations
Parameters required How they are performed
Thermal stability
Thermal shock and cycling
Evaluates the thermal stability of a battery under the
various condition of temperature. When an accident
scenario involves fire.
Determine changes in the integrity of the device
from various conditions arising from expansion and
contraction of the cell during sudden changes in
temperature.
Heating rate (>5), Heating steps (5 ◦Ce10 ◦C),
termin ati o n (300 ◦C), repetition in case of self-
heating (2 ◦C heating steps-hold for >1 h), state of
charging (95%e10 0 % )
Protection device, Tmax (80 ◦C), Tmin
(—40 ◦C), hold time (>1 h), Repetitions (5 or 10), state
of charging (95%e100 %).
During this test, the battery is placed in a chamber
and temperature goes on increasing slowly and
slowly in different ranges such as 80 ◦C, 85 ◦C till
130 ◦C.
During the test, the device is exposed to different
temperat u re limits for a specifi c period of time.
355
J.
Traffic
Transp.
Eng.
(Engl.
Ed.)
2020;
7
(3):
340e361

Level 3 (450 V)
and 10, electrical and environmental tests for batteries in EVs
are explained and different electrical and thermal inputs are
provided to the batteries for evaluating the battery capacity
for hazardous situations.
5. Conclusions
able to meet their goals. The new approaches such as high
capacity metal oxide cathode materials, high capacity anode
material and new electrolyte with high oxidation potential,
metal-air batteries after replacing the positive electrode with
an air electrode may help the BEV to perform as expected.
New DC fast charging schemes need to be developed to in-
crease the accelerating rate with higher efficiency of
charging.
Among several technologies, EVs would be one of the widely
used technologies in the near future due to the development
of battery design and control techniques. In this paper, a
detailed discussion on all the aspects of EVs is presented
with a focus on the design and development of batteries for
EVs. The paper also outlines the issues coming in the way of
operationalization of EVs at a mass level. The cost, lifespan,
safety, reliability, sustainability, usability and power or en-
ergy of the battery is of the major issue to be solved to make
EVs popular. This paper attempted to highlight the most
important discoveries for designing and development of new
material for batteries to attain improvements. The de-
velopments in new fields such as nanotechnology, recycla-
bility, manufacturing process, battery pack design and
testing may also supplement the battery design process for
EV. Due to advancements in Li-ion and NiMH battery tech-
nology, the transportation system like HEV and PHEV are
Conflict of interest
The authors of this paper do not have any conflict of interest
with any other entities or researchers.
Acknowledgment
Authors are thankful to Lithium-ion Batteries Technology Lab,
Department of Applied Physics, Delhi Technological Univer-
sity, New Delhi for providing support to carry out this research
work.
Appendix
Fig. A1 e Summarization of EVS.
Electric vehicles
Concept History Factors affecting EV Components
Electric propulsion
system
First vehicle
launched in 1834
Motors
Internal External
Main system for
EV
Till 1918, EV on
high demand
Purchase
price and
battery
cost
Fuel price and
environment
Power electronic
driver
EV vanished from
market till 1930
Electric Energy
motor source
In 1976, new EVs
launched
Consumer
characteristics
Energy storage
system
Power
converter
Driving
range (150
miles)
In 1998, EV were
compulsory on
road
Charging
time
Availability of
charging
station
In 2003, technical
comparison with fuel cell
was estimated.
Level 1 (120 V)
Level 2 (240 V)
In 2007, micro EV was
proposed.
During last 10 years, EVs
demand goes on increasing
Charging
schemes

357
Fig. A2 e Summarization of ESS (for EV).
Fig. A3 e Summarization of BEV (manufacturing).

1 s2.0-s2095756420300647-main (1)

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to 1 s2.0-s2095756420300647-main (1)

Similar to 1 s2.0-s2095756420300647-main (1) (20)

Recently uploaded

Recently uploaded (20)

1 s2.0-s2095756420300647-main (1)