CHAPTER NO. 2
Literature Review
2.1 Batteries in Electrical Vehicles
2.1.1 Fundamentals of battery technology
2.1.2 Battery Chemistry
2.1.3 Review on Electrical Vehicles and its Batteries
2.1.4 Battery models
2.1.4.1 Simple battery model
2.1.4.2 Modified battery model
2.1.4.3 Simplified Lead acid battery model
2.1.4.4 Thevenin battery model
2.1.4.5 Linear battery model
2.1.4.6 Battery equivalent Circuit
2.1.5 Comparison of different battery models
2.2 Electrical Vehicle Performance Parameters
2.3 Review on Modeling and Simulation of Battery
2.4 Review on Hardware in the Loop
Bibliography
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2.1 Batteries in Electrical Vehicles
The purpose of this chapter is to undertake a review of literature on battery technolo-
gy and battery powered electrical vehicles, hybrid electric vehicles and advances in
the hardware in loop. The nature of research carried out by earlier researcher and
scientist has helped to set up direction for further research work in this area. Under-
standing the significance of the battery in automobile field, an overview of battery
technology and battery management systems has been studied. In this chapter, an
account of various topics of battery i.e. battery chemistry, batteries for electrical car,
power backup calculations, etc. has been taken. The literature review has provided a
foundation for secondary data to validate the results obtained during the initial
experimentation. The major challenges in the electrical vehicles are also studied with
special reference to battery performance parameters. A recent trend of Electrical
Vehicles and Hybrid Electric Vehicles are also studied and undertaken survey. This
chapter also describes various battery models like electrochemical model, equivalent
circuit model, simple battery model, superior simple model etc. for better manage-
ment of performance parameters. This chapter provides sound background for
studying battery performance parameters, its management for optimum utilization
and batteries used for electrical vehicles.
2.1.1 Fundamentals of Battery Technology
A cell is an electrochemical unit, while a battery is consists of two or more cells
connected in series or parallel combination to accomplish particular operating
ratings. For example, the BP5-12 battery has a nominal voltage of 12 volts, consist-
ing of 6 cells connected in series. Since this configuration does not provide access to
the internal anode and cathode terminals of each cell in the series string, it is difficult
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to determine much about the electrochemical status of individual cells from the
available battery terminal measurements of voltage and current.
An electrochemical cell contains the basic components: anode, cathode, electrolyte,
and separator. In the electrochemical processes of the cell, an anode is the electrode
where the oxidation reaction occurs, meaning that it releases electrons to the external
circuit. A cathode is correspondingly the location where the reduction occurs, collect-
ing the electrons from the anode through the external circuit. For a battery cell, the
positive electrode becomes cathode during discharge and behaves as anode during
charge, while the negative electrode becomes an anode during discharge and behaves
as cathode during charge [1]. In the common literature, however, the convention is to
adopt the terminal name designations that are appropriate during discharge operation.
The electrolyte is the medium that conducts the ions between the cathode and anode
of a cell. The separator is a nonconductive layer that is permeable to ions, yet capable
of preventing a galvanic short circuit between the cathode and anode terminals.
The accepting of battery technology and knowing battery parameter performance is
an important sector for battery powered instrumentation or devices. However, in
almost all belongings the battery behaves as key component with highest cost, weight
and volume. Some of the electrical specifications of electronic instrument are also
decided by the battery.
A battery is a device which converts chemical energy in to electrical energy. It is
nothing but collection of cells. The cell consists of two different electrodes i.e.
copper and zinc and electrolyte i.e. citric acid. The electrodes are immersed in an
electrolyte as shown in figure 2.1. There are two types of cells which are used
frequently used in different applications i.e. Primary cells and Secondary cells.
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Fig. 2.1: Construction of Electrochemical Cell
The primary cells are designed for single time use and can be disposed with some
industrial process. Common applications of primary cells are cameras, torches, wrist
watches, etc. The secondary cells are used for multi-time and are rechargeable.
Secondary cells are uninterrupted power supply, automobile, standalone instruments,
mobile phone battery, etc. In case of rechargeable batteries, the chemical reactions
are reversed to return charged state of the battery. The output voltage and energy
depends on numbers and types of the cell. Battery uses different materials like lead,
nickel, acid, lithium and alkaline. A battery comes with different sizes and shapes
from compact electrochemical cells to big size battery. Even after the removal of
these materials from consumer batteries many of these substances inside a battery are
toxic to some extent and some are very toxic. Electrochemical cell consisting of two
different plates i.e. zinc and copper and citric acid as an electrolyte as shown in
electrochemical cell figure 2.2.
In order to produce the voltage in the electrochemical cell, first it has to receive a
charge voltage of 2.1 volts per cell from a cell charger. The Lead acid (LA) batteries
or any types of batteries don‟t generate voltage by their own. They only store a
Positive Electrode
Negative Electrode
Electrolyte
Separator
(Insulating Material)
Battery Case
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charge hence LA batteries are sometimes called as storage batteries. The size of the
electrodes or plates and quantity of electrolyte decides storage of amount of charge.
Fig. 2.2: Fundamentals of Electrochemical Cell
The storage capacity of the battery is referred as the Amp Hour (AH) ratings. A
typical 12-volt battery with rating 125 AH, which considers as battery can supply 1 A
current for 125 hours or 10 A current for 12.5 hours or 20-A of current for a period of
6.25 hours. Lead acid batteries can be connected in parallel to increase the total AH
capacity.
Working Principle and Construction:
The battery comprises of two or more than two electrochemical cells combined
together. For lead acid battery, electrochemical cell consisting of two different lead
plates. These plates are positive and negative plates. The positive plate of the elec-
trode covered with a paste of lead dioxide whereas the negative plate made from
sponge lead, along with an insulating material. This insulating material between
plates are called as separator as shown in figure 2.3. These positive and negative
plates are enclosed in a plastic battery case. This plastic case is then submersed into
an electrolyte of the battery. The electrolyte consists of sulfuric acid and water. One
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of the electrodes i.e. lead dioxide loses electrons and it becomes positive electrode
whereas other electrode i.e. sponge lead gains the electron becomes negative elec-
trode [1].
Fig. 2.3: Current flow diagram of Electrochemical Cell
The electrodes do not touch each other but are electrically connected by the electro-
lyte. During electrolysis process the positively charged ions are gets attracted
towards negative electrode and negatively charged ions gets attracted towards
positive electrode and chemical reaction occurs. The chemical reaction between
positive and negative electrodes along with battery electrolyte generates DC electrici-
ty.
2.1.2 Battery Chemistry
Knowing battery electrochemistry is extremely much significant because chemistry is
the driving force behind the science of the batteries. A battery is a package of one or
more electrochemical units or galvanic cells which are used in production and
Electron Flow
Spongy Lead Lead dioxide
Negative Electrode
Positive Electrode
Electrolyte
Separator
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storage of electric energy in the form of chemical way. An electrochemical cell
consists of two half cells, known as a reduction cell and an oxidation cell it is shown
in figure 2.3. Chemical reactions of these two half cells provides the energy for the
electrochemical cell. Each of the half cells consists of an electrode and an electrolyte
solution. Faraday‟s law gives quantitative relationships and based on electrochemical
reactions occurred within the cell.
Faraday’s First Law:
“The mass of the substance altered at the electrode during electrolysis directly
proportional to the quantity of electricity transferred at that electrode”
Equation of Faraday‟s first Law [2]
𝑚 =1
96485(𝐶.𝑚𝑜𝑙−1)×𝑄𝑀
𝑛 (1)
Where,
‘m’ is the mass of the substance produced at the electrode i.e.in grams
‘n’ is the valence number of the substance as an ion in solution i.e. electrons per
ion
‘Q’ is the total electric charge that passed through the solution i.e. in coulombs
‘M’ is the molar mass of the substance i.e.in grams per mole.
Faraday’s Second Law:
“For a given quantity of DC electricity the mass of an element material altered at an
electrode is directly proportional to the elements equivalent weight” [2, 3]. The
quantity of electricity required to produce one equivalent of chemical action is
known as one faraday i.e. 1 Faraday = 96494 ampere sec or coulomb.
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In a cell, reactions essentially take place at two areas or sites in the device. These
reactions sites are the electrode interfaces. In generalized terms, the reaction at one
electrode (reduction in forward direction) can be represented by
𝑎𝐴 + 𝑛𝑒 ⇋ 𝑐𝐶 (2)
where a molecules of A take up n electrons e to form c molecules of C. At the other
electrode, the reaction (oxidation in forward direction) can be represented by
𝑏𝐵 − 𝑛𝑒 ⇋ 𝑑𝐷 (3)
The overall reaction in the cell is given by addition of these two half-cell reactions
𝑎𝐴 + 𝑏𝐵 ⇋ 𝑐𝐶 + 𝑑𝐷 (4)
The change in the standard free energy ∆G0
of this reaction is expressed as
∆G0 = − 𝑛𝐹𝐸0 (5)
Where F is constant known as the Faraday (96,487 coulombs) and E0 is standard
electromotive force [1]
When conditions are other than in the standard state, the voltage E of a cell is given
by the Nernst equation [3],
𝐸 = 𝐸0 −𝑅𝑇
𝑛𝐹𝐿𝑛
𝑎𝐶𝑐
𝑎𝐴𝑎
𝑎𝐷𝑑
𝑎𝐵𝑏 (6)
Where, R is gas constant, T is the absolute temperature and ai is the activity of
relevant species. The change in the standard free energy ∆G0 of a cell reaction is the
driving force which enables a battery to deliver electrical energy to an external
circuit. The measurement of emf of the battery depends on free energy, entropies and
enthalpies along with activity coefficients, constants and solubility. Generally
solution contains ions which are derived from the electrode using oxidation and
reduction. These spontaneous reactions gives energy there combination of two half
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cell and electrolyte form an electrolytic cell [3]. Loss of the electrons called as
oxidation whereas gain of electrons called as reduction. They have to appear simulta-
neously in the chemical reaction therefore oxidation and reduction cannot be carried
out separately [1]. Thus oxidation and reduction reactions are called as redox reac-
tions. In redox reactions, a reducing agent and an oxidizing agent form a redox
couple and prone to undergo the chemical reaction. An oxidant is an oxidizing
reagent, and a reluctant is a reducing agent. Following are the some chemical reac-
tion given for different batteries i.e. Lead Acid, Nickel Cadmium, and Nickel Zinc
etc.
1. Lead Acid (Pb & H2SO4): Pb+PbO2+2H2SO4 ↔2PbSO4+2H2O
2. Nickel Cadmium (Ni-Cd): Cd+2NiO (OH) +2H2O ↔Cd (OH)2+2Ni
(OH)2
3. Nickel Zinc (Ni-Zn): Zn+2NiO (OH) +2H2O ↔Zn (OH)2+2Ni(OH)2
4. Nickel Metal Hydride (Ni-MH): MH+ NiO (OH) ↔M+Ni (OH)2
5. Sodium Sulphur (Na & S): 2Na+ XS ↔Na2Sx
6. Sodium Nickel Chloride (Na & NiCl2): 2Na+ NiCl2 ↔Ni+2NaCl
7. Lithium Ion (Li-Ion): LixC+ LizMyOz ↔C+LiMyOz
From the manufacturer part the battery can be considered as an unknown black box
which has range of performance characteristics. These characteristics may consisting
of energy density, specific power, typical voltages, specific energy, amp-hour
efficiency, operating temperature, self discharge rate, cost, availability, number of
life cycles and recharge rate [4]. However, basic understanding of the battery chemi-
stry is important, or else the performance and maintenance requirement of the
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different types, life cycle, self discharge, and efficiency will find difficult to under-
stand [2,4]
The most common material used for electrodes in batteries is lead, nickel and li-
thium. Each battery system requires its own charging algorithm. Most of the lead-
acid batteries are prepared using positive electrode i.e. anode .This positive electrode
is made from a lead-antimony alloy with lead (IV) oxide pressed into it, although
batteries designed for maximum life use a lead-calcium alloy[6]. The negative
electrode i.e. cathode is made from pure lead and both electrodes are immersed in
sulfuric acid. When battery starts charging, Lead oxide is deposited or formed at the
anode, pure lead is formed at the cathode and sulfuric acid is liberated into the
electrolyte causing the specific gravity to increase [5,6]. When the battery is dis-
charged, the amount of water is produced, prone to dilute the acid and therefore
specific gravity reduces. On charging of the battery the amount of sulfuric acid is
formed and specific gravity increases in the electrolyte.
The change of specific gravity can be measured using an acidic hydrometer. The
value of specific gravity is about 1.250 for a fully charged cell and 1.170 for a fully
discharged cell [6].
These mentioned values of specific gravity will vary and also depending on the
manufacturer and capacity of the battery. The chemical reaction that occurs in the
battery during charging and discharging are shown in figures 2.4 and figure 2.5
respectively.
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Fig. 2.4: Battery charging chemistry
When lead acid battery starts discharging with some external load then Lead sulfate
is formed at positive and negative electrodes and sulfuric acid is removed from the
electrolyte. This chemical process causes reduction of specific gravity in electrolyte.
The specific gravity of the electrolyte also depends on the electrolyte temperature or
battery temperature.
Specific gravity is defined as:
Specific Gravity =Mass of a specific volume of electrolyte
Mass of the same volume of pure water (7)
If lead-acid batteries are discharged beyond its limit or left for prolonged periods
leads to harden the lead sulfate coats on electrodes then lead sulfate will not be
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removed during recharging. Such build-ups process reduces the efficiency of the
battery and life of batteries. Over charging of battery may cause electrolyte to escape
as explosive gases. Different chemical reactions are occurring at positive and nega-
tive electrode of the battery during charging and discharging of the battery.
Fig. 2.5: Battery discharging chemistry
2.1.3 Review on Electrical Vehicles and its Batteries
Environmental issues are the major deciding factor in the adoption of electric vehi-
cles in town and cities. Leaded petrol is already banned in different countries because
of its ability to pollute air and generates toxic material. Therefore, there have been
attempts in some cities to force zero emission vehicles. The fairly complex nature of
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the regulations in the country may increase to interesting development in the fuel
cell, battery based vehicles and hybrid electric vehicles [4].
The electric vehicle has entered in to the twenty first century as a commercially
available product and it has been very successful, outlasting many other technical
ideas that have come and gone. However electric vehicles that normally have much
longer range and are very easy to refuel. Today‟s concern about the environment ,
particularly noise and exhaust emission, coupled to new development in batteries and
fuel cells may swing the balance back in favor of electric vehicles, the relevant
technological and environmental issues are thoroughly understood.
First electric vehicle with non-rechargeable batteries was demonstrated in the 1830.
The first commercial electric car was appeared in the year of 1880. The Electric
vehicles were admired in the end of 19th
century and beginning of 20th
century [7].
The commercial vehicles used large rechargeable batteries and hence electrical
vehicles became fairly worldwide. The first electric car was to exceed „mile a
minute‟ or speed 60 mph. Then after development in performance of the car and
battery, the speed and many other parameters of the car changed gradually. In 1920s
many electric vehicles had been produced by different car manufacturers and used as
cars, vans, taxis, delivery vehicles and buses. An electric car is propelled by electric
motor, using electrical energy. This electrical energy is given to the motor by high
density battery. The electrical energy is stored in batteries or another energy storage
device. Electric motor gives instant torque, creating strong and smooth acceleration
to the electric car. Different electric vehicle examples are given to understand the
name of vehicle and when such vehicles are commercially available in the market.
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The examples of electric vehicles are given along with manufacturing year for classic
electric car and electric powered wheel chair.
First commercial electrical was available at New York, U.S.A. was the taxi cab and
using Lead acid battery in 1991. This vehicle had limited mileage hence not popular
that time and also less number of vehicles sold in the market. Then in the year of
1999, the commercial market was seen fuel cell based Necar 4 fuel cell car. Mahin-
dra Reva (2001),Toyota prius, Honda FCX (2002), Citario fuel cell powered bus
(2003), Smart Electric Drive(2007), Mitsubishi I MiEV (2009), Mercedes-Benz SLS
AMG coupe Electric Drive(2010), Ford Focus EV(2011), Renault Twizy (2012),
Tesla Model S (2012), Mahindra e2o (2013), Chevrolet Spark EV (2013), BMW
i3(2013), Nissan Leaf (2013) and Honda Fit EV(2014) seen in the succeeding years
with advanced battery technology [11].These electric vehicles use different capacity
of the battery and different types of batteries to propel the electric motor. The BMW
i3 was considered as the first complete electric car from BMW Company built
electric from the ground up. This car is a part of BMW‟s “born electric” i series. Its
cost put it somewhat in the center of the Nissan Leaf and the Tesla Model electric
cars. Despite of looking a bit bulky, the BMW i3 is the lightest electric car available
in the world‟s car market. While the selection of hybrid power train is growing every
year, it is seen that Toyota Prius as has top priority because of its low price as
compare to other electric vehicles in the market. The redesigned the Fusion Hybrid is
slightly larger, sportier and more upscale-looking with advance facility than previous
version. This luxurious car has a well-furnished cabin, features and high tech loads
[12]. Second low price category of hybrid electric car is the Chevrolet Volt, this
hybrid car offers an all-electric range of 60km and then fires up its four-cylinder gas
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engine [13]. The Nissan Leaf vehicle proves to be a highly refined and affordable all-
electric car as compare to others. Nissan promises a range of 150 km in city per
210km on highway, but EPA tests put the real-world range at 110km, depending on
conditions and driving style [13].
The Ford C-Max Energi is another outstanding gas sipper to consider. This plug-in
electric hybrid wagon, the first from Ford, delivers an impressive 750km of driving
range between fill-ups, plus lively handling [13]. The lithium-ion battery pack
recharges from a standard 120 volt electric outlet. In 2013, Tesla Model S EV came
in the market with its aluminum body, five passengers interior and powerful battery
pack. The electric drive system, the Tesla simply has no competition at that time
[13]. It‟s only down side is that as a battery-electric car it has limited range, although
it goes a lot farther per charge than other EVs. Tesla also offers two upsized battery
options with estimated range of 240 km to an EPA-certified 390km [13]. In Euro-
peans country, one of the best top end scales model is the Mercedes-Benz S400
Hybrid with its matchless interior design, plenty of safety and technology features,
and sleek sedan body [13].
In India 2013, Mahindra Company has launched e2o electric vehicle and which is
advanced versions than earlier vehicles. This company has launched Reva i in 2001
and considered as first electric car on road in India. The rising prices of petrol, diesel
and gases increased awareness to protest environmental issues and stress on maneu-
verability have made many people seriously considering this option. Even this car is
not that much comparable with earlier vehicle with range, facility and battery tech-
nology.
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It has been observed that use of lithium ion battery pack extends range of the vehicle
because energy densities of the lithium ion batteries are higher than lead acid battery.
Mahindra company used Lead acid battery as well as lithium ion battery pack in their
different versions of electrical cars.
Table 2.1 shows name of Electrical Vehicles and its batteries. Some of the typical
batteries are specially designed for the particular electrical vehicle and hybrid electric
vehicles [11, 14].
Table 2.1.: Electrical vehicles and its battery
Sr. No. Year Name of Electric Vehicle Name of Batteries
1. 1901 New York taxi cab Lead-Acid Batteries
2. 1966 Electrovair II (General Motors) Silver-Zinc Batteries
3. 1999 Necar 4 fuel cell car Fuel Cell
4. 2001 Reva i [13] Lead-Acid Batteries
5. 2002 Honda FCX Lithium-ion Batteries
6. 2003 Citario fuel cell powered bus Fuel Cell
7. 2005 Volvo 3CC (Volvo) Lithium-ion Batteries
8. 2007 Chevy Volt (General Motors) Lithium-ion Batteries
9. 2007 Nissan Mixim (Nissan) Lithium-ion Batteries
10. 2007 Smart Electric Drive Sodium nickel chloride
and Zebra battery
11. 2007 Truck,Van,Bus,
Taxicab and Trailers
Zebra battery
12. 2008 Continental DC
(Bentley Motors)
Lead-Acid Batteries
13. 2008 Subaru Stella (Subaru) Lithium-ion Batteries
14. 2008 Nissan Denki Cube (Nissan) Lithium-ion Batteries
15. 2008 Tesla Roaster [11] Lithium-ion Batteries
16. 2009 Reva NXR/NXG Lithium-ion Batteries
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Sr. No. Year Name of Electric Vehicle Name of Batteries
17. 2009 Mitsubishi I MiEV Lithium-ion Batteries
18. 2010 Mira EV Lithium-ion Batteries
19. 2010 Mercedes-Benz
SLS AMG coupe
Electric Drive
liquid-cooled 400 V
Lithium-ion battery
20. 2011 Ford Focus EV liquid-cooled
Lithium-ion battery pack
21. 2011 Chevrolet Volt [11] Lithium-ion Batteries
22. 2011 Reva L-ion [13] Lithium-ion Batteries
23. 2012 Renault Twizy Lithium-ion Batteries
24. 2012 Tesla Model S Lithium-ion Batteries
25. 2013 Chevrolet Spark EV Lithium-ion Batteries
26. 2013 Nissan Leaf Nissan LEAF®
Lithium-ion Batteries
27. 2013 Mahindra e2o Lithium-ion Batteries
28. 2013 BMW i3 Lithium-ion Batteries
29. 2014 Honda Fit EV Lithium-ion Batteries
Lithium-ion batteries are commonly used rechargeable batteries for EV/HEV,
because of high energy density, more cell voltages and lower weight to volume
ratios. Therefore Lithium-ion batteries are also preferred in industrial, transportation
and power-storage applications. Hence uses of such batteries are helping in im-
provement of electrical vehicle performance in terms of mileage, weight and vehicle
weight.
An electric car is propelled by electric motor, using batteries or another energy
storage device. Electric motor gives instant torque and smooth acceleration to the
electric vehicles. Portable devices or instruments are often relying on battery for its
operation.
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The electric vehicles or hybrid electric vehicles are propelled by the battery pack.
Hence understanding technology of battery is necessary. Mileage of the EV/ HEV
majorly depends upon capacity of the battery pack. The energy stored in battery pack
is also limited. So, it is important to use this energy as efficiently as possible, to
extend the battery lifetime. Generally the batteries are classified into two categories.
Primary batteries are non-rechargeable and are commonly found in different con-
sumer electronic products all over the world. Commonly primary batteries are zinc-
carbon, zinc-alkaline-MnO2, zinc-air, and lithium batteries. Secondary batteries are
distinguished by their ability to recharge. The Examples of secondary batteries
include Nickel-Cadmium (Ni-Cd), Lead-acid, Nickel-Metal Hydride (Ni-MH), and
Lithium-ion (Li-ion). For electric vehicle or vehicular applications, secondary
batteries are the preferred candidates for power source or load-leveling devices.
There are other possible options for the batteries include fuel cells and ultra capaci-
tors. The energy density and power density of secondary battery along with cost are
major factors for suitability for a particular application [4] [8]. Many commercial
secondary batteries are manufactured with a series of cells packaged in a container.
In general, a battery manufacturer provides the rated capacity of the battery in their
datasheet or sometimes written on the body of battery. The rated capacity, expressed
in Amp-Hours (AHs), is specified for discharging under a stated set of operating
conditions. A common discharging condition is to discharge at the rate 𝐶
20 A, where C
is the rated capacity in Ahs until the specified cut-off voltage is reached.
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Fig. 2.6: Energy density ranges of different batteries
Meanwhile, the energy density of a battery is often expressed in Watt-hours per liter
Wh
l and the power density in Watts per liter
W
l. Figure 2.6 shows relation between
different types of batteries and energy density. The energy density of the battery is
the amount of energy stored per unit volume or mass. Later on energy density term
more accurately called as specific energy. The above graph figure2.6 shows that
capacitor type of batteries have very low energy density as compare to other batteries
but this battery has very short recharge time hence it can be used for specific applica-
tions. So recharge time of the battery is also important parameter to decide refuel
time of the battery.
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The pictorial comparisons of the batteries are given for high power and high capacity
Ni-MH batteries. In many applications these batteries are used according to the
application need and specification. As far as the electric vehicles and hybrid electric
vehicles are concerned higher energy density and short energy recharge time batteries
is the requirement hence scientist and researcher are working on new Li-ion Batte-
ries.
The physical design of the batteries heavily influences their battery performance
capabilities.
In addition to the components for the electrochemical processes, nonreactive compo-
nents such as the current collectors, separator, and electrolyte are needed to comprise
a functional cell. These components add to the weight of the battery without adding
to the energy density.
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Fig. 2.7: Applications wise energy density and batteries
The figure 2.7 shows the range of energy density and energy recharge time for
various applications of battery in vehicular sector. Transportation and some hybrid
electrical vehicles smaller energy density moderated energy recharge time is pre-
ferred.
Whereas electrical vehicles of e bike needs higher energy density and longer energy
recharge time. Inverters, Electric vehicles and electric bicycle vehicles or e-bikes
uses different type of batteries according to their specifications, cost, weight and
expected mileage. Hence for high end applications in electrical car or hybrid car high
energy density and lower energy recharge time is needed in future hence need to be
work on this range of application batteries. The different batteries along with their
applications are given in the following table 2.2.
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Table 2. 2: Comparison of batteries according to applications [7, 11, 14]
Sr. No. Battery Types Applications
1. Flooded lead acid Battery Automobiles, Forklifts and UPS
2. Unflooded or Sealed lead
acid battery (SLA)
UPS, Biomedical instruments, Wheelchairs
and emergency lights
3. Valve regulated lead acid
battery (VRLA)
Cellular repeater towers, internet hub, banks,
hospitals, airport and military installments
4. Absorbed Glass Mat (AGM)
Battery
This battery withstands severe shock and
vibration. Cells will not leak even if the case is
cracked. So it can be used in Military applica-
tions
5. Lead Antimony Batteries Electrical Vehicles and deep discharge applica-
tions
6. Lead Calcium Batteries Higher Cold Cranking Amp ratings applica-
tions
7. SLI Batteries
(Lead Acid Battery)
Starting , Lightning and ignition applications
i.e. Cars, trucks, buses, lawn mowers, wheel
chairs, robots
8. Lithium Ion Laptop, Mobile phones, EV, HEV
9. Zinc mercury oxide Hearing aids
10. Silver Zinc , Zink air Aeronautical application
11. Alkaline Batteries Digital cameras, CD players, MP3 players,
pagers, toys, lights, and radios
12. Ni-Cd Digital cameras, CD players, MP3 players,
pagers, toys, lights, and radios
13. LiFePO4 E-Bike (36V/10AH)
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Sr. No. Battery Types Applications
14. Nickel Metal Hydride
(Ni-MH )
EVs, HEVs, PHEVs, fork lift trucks, milk
floats, locomotives (Ni-MH and Lithium) Ni-
MH RAV4EVs (Vehicle traction Batteries)
15. Sodium or Zebra batteries
molten chloroaluminate
(NaAlCl4) sodium
Electric Vehicles ( EV) and Hybrid Electric
Vehicles( HEV)
2.1.4 Battery models
Battery modeling is useful for understanding behavior of the battery system for its
dependence on various parameters. In case of battery model, the effect on viscosity
of electrolyte used in battery can be predicted to understand battery performance
parameters. Such models could be used in battery operated vehicles to predict its
performance. There are different kinds of batteries used for electrical vehicles and
many factors affect on battery performance parameters. For the estimation of battery
performance various mathematical models plays a significant role. The battery
performance parameters are state of charge (SOC), battery storage capacity, rate of
charge or rate of discharge, temperature, battery age or shelf life etc [5,15]. The
battery performance depends on the measurable quantities like temperature and
performance characteristics. However, battery performance also depends on parame-
ter such as battery age, the way battery handling, manufacturing defects or tolerances
and variations of cells within the battery. The lead-acid battery represents a funda-
mental and main element in the renewable energy systems and in the hybrid vehicles.
Therefore, it is necessary to study the modeling and simulation of lead acid battery.
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Modeling & Simulation of BPP for Efficient Electrical Vehicles ……. Page 33
The many underwater vehicles are driven by lead acid batteries because of its lower
cost of production, diversity, easy to charging and discharging operation and effi-
ciency [9]. The lead acid batteries have an appropriate cell voltage i.e. 2V per cell
and correspondingly high energy efficiency. These batteries are charged and dis-
charged with high current [9]. Lead acid battery technology has been successfully
serving for different energy needs that vary from the requirements from traditional
automobile applications tom the modern plug in hybrid electric vehicles. The lead
acid battery generally used in starting, lightning and ignition in automobile indus-
tries. Hence these batteries are called as SLI batteries [10].
For the modeling of the battery, a modified model explained in figure 2.9 is used. In
most of the research work modeling of the battery were done using variable voltage
source and fixed resistance. The experimental results and manufacturing data are
presented and shown that battery resistance is not constant but the change in battery
resistance is small and it can be assumed as a constant [9]. Literature surveys of
different battery models are undertaken and some of them are studied and described.
The described models consider battery storage capacity, self-discharge, over and
under voltage, battery internal resistance and ambient temperature. Described battery
models have advantages and disadvantage over each other. A comparison between
the model and experimental results are reported in the battery evaluation test system
is used for verification. These battery models can be used to study accurately to
evaluate battery performance in different electrical systems.
\
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Rbat
Vbat ~Voc Ein
2.1.4.1 Simple battery model
The simplest electrical battery-model is shown in figure 2.8. This battery model
consists of an ideal voltage source i.e. Ein, constant internal resistance i.e. Rbat and the
terminal voltage i.e. Vbat. This model consists of an ideal battery with open-circuit
voltage Ein and a constant internal resistance Rbat or Equivalent Series Resistance.
Fig. 2.8: Simple battery model
This model consists of an ideal battery with open-circuit voltage Ein and a constant
internal resistance i.e. Rbat or Equivalent Series Resistance (ESR). The terminal
voltage is given by Vbat which can be determined from open-circuit measurement.
The equivalent series resistance can be determined from open-circuit measurements
and extra measurement with load connected [12]. The simple battery model has
several drawback and disadvantage for modeling the battery. This simple model does
not take into account of varying internal resistance because of varying state of
charge, electrolyte concentration and sulfate formation [5]. The basic assumption of
this model is limitless battery and model does not depend on state of charge of
battery. It means that dynamic behaviors of the battery parameters are not consi-
dered. This information clearly indicates that it is approximate model and cannot be
considered for battery monitoring in Hybrid Electric Vehicles (HEV).
𝐼𝑏𝑎𝑡𝑡 =𝑑𝑞
𝑑𝑡 (8)
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𝑆𝑂𝐶 = 100𝑞
𝑄 (9)
𝐸𝑖𝑛 = 𝐸0 − 𝐾 𝑄
𝑄−𝑞 + 𝐴𝑒−𝐵𝑞 (10)
In these above equations E0, K, Q, A and B are constants depends on the types of
battery. „q‟ be the static battery voltage and battery current is Ibatt. Ein and Vbat are
internal battery voltage and Terminal voltage respectively. The integral of current
determines the charges with the number between lower limit zero and upper limit
determined by the battery capacitance (Q) [9].
The terminal voltage equation of the simple model is
𝑉𝑏𝑎𝑡 = 𝐸𝑖𝑛 − 𝑅𝑏𝑎𝑡𝑡 × 𝐼𝑏𝑎𝑡𝑡 (11)
However, the internal resistance of the battery is different under discharge and charge
conditions. This model does not consider the internal dynamics of the battery, in
particular the effect of the diffusion of the electrolytic chemicals between the battery
plates [16, 17].
2.1.4.2 Modified battery model
The modified battery model is written from the simplest battery model. It is neces-
sary to modify the simplest battery model into advanced model which will consider
the dynamic behavior of the battery like state of charge and internal resistance of the
battery [19]. The simplest circuit of battery model is modified and given in figure
2.9.This model gives non linear effects due to diodes in the charging and discharging
paths [5]. This modified battery model consists of different charging and discharging
resistances along with capacitance. The different resistance values are considered in
this modified model of battery under charge and discharge conditions i.e. Rc and Rd.
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Rb
Rd
Rc
Vo Ein C
I4
I3
I1
I I2 I2 Ri
Cs
R1
Vo Rsd Cb
The diodes are also shown in figure2.9 has no physical significance in the battery so
these diodes are included only because of modeling purposes.
Fig. 2.9: Battery model with charging and discharging resistance and polarization
capacitance
In order to model the cell diffusion of the electrolytic through the battery and its
resultant effect of causing transient currents in the battery, a capacitor C is added to
the model [18].
2.1.4.3 Simplified Lead Acid Battery Model
Now a day‟s lead acid batteries are also used in electrical vehicles and power backup
applications rigorously due its availability of any ampere hour rating range. Hence
dynamic model of lead acid battery is presented in the figure 2.10, which is simpli-
fied proposed equivalent circuit. [12,20]
Fig. 2.10: Simplified equivalent circuit of a lead acid battery
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This modified model of lead acid battery consists of surface capacitor and polarized
resistance connected in parallel and in series with internal resistance or lumped
resistance. This model is also called as third order lead acid battery model [5].
The cell voltage is represented by VO, and Rint is a lumped internal resistance due to
cell interconnections. The double layer of capacitance Cs surface-capacitor is shown
in parallel with the charge transfer polarization represented by Rt. This double layer
capacitor is the results of charge separation at the electrolyte/electrode interface.
The bulk capacitor Cb models the cell‟s open circuit voltage, and Rsd is included to
represent the self-discharge of the cell. Voltages and currents are describing the
characteristics of the model shown in figure. 2.10 are given by equations
𝑉𝑜 = 𝑅𝐼 × 𝐼2 + 𝑉𝐶𝑆 + 𝑉𝑐𝑏 = 𝑅𝑠𝑑 × 𝐼1 (12)
𝑉𝑐𝑠 =1
𝐶 𝐼4 𝑑𝑡 = 𝑅𝑡 × 𝐼3 (13)
𝑉𝐶𝑏 =1
𝐶 𝐼2 𝑑𝑡 (14)
𝐼1 = 𝐼1 + 𝐼2 & 𝐼2 = 𝐼3 + 𝐼4 15
Where VCb and VCs denote the voltages across the bulk- and surface-capacitors,
respectively taking as state variables the voltages VO, VCs, VCb and assuming that
𝑑𝐼2
𝑑𝑡≈ 0
The rate of change of terminal current per sampling interval is very small and neglig-
ible when implemented digitally. The complete state variable description i.e. the state
model of battery is obtained:
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𝑉0
𝑉𝑐𝑠𝑉𝑐𝑏
=
−
1
𝑅𝑠𝑑
1
𝐶𝑠+
1
𝐶𝑏 −
1
𝑅𝑡𝐶𝑠 0
−1
𝑅𝑠𝑑𝐶𝑠 −
1
𝑅𝑡𝐶𝑠 0
−1
𝑅𝑠𝑑𝐶𝑠 0 0
× 𝑉0
𝑉𝑐𝑠𝑉𝑐𝑏
=
1
𝐶𝑠+
1
𝐶𝑏
−1
𝐶𝑠
−1
𝐶𝑏
× 𝐼
𝑦 = 𝑉0 = 1 0 0 𝑉0 𝑉𝑐𝑠 𝑉𝑐𝑠 𝑇 (16)
The control strategies of the batteries for hybrid and electric vehicles are based on
SOC knowledge. The batteries dynamic behavior can be modeled with different
electrical circuit structures and different linear or nonlinear mathematical models.
The different estimation methods can be used for the batteries parameters calculation.
The estimated parameters could be battery SOC calculation and this is very much
important in the hybrid and electrical vehicles [18]. SOC calculates the left energy of
the battery and can be used to predict distance that can be covered is possible.
2.1.4.4 Thevenin Battery Model
The battery voltage is related to the sum of the reduction and oxidation potentials.
Electrical energy is produced when the chemicals in the battery react with one
another [19].The rate of the chemical reaction varies with the state of charge, battery
storage capacity, rate of charge and discharge, environmental temperature and age or
shelf life [5]. There have been many proposed lead acid battery models [19]. One of
the proposed models for lead acid battery is Thevenin equivalent circuit, shown in
following figure 2.11, which is a simple way of demonstrating the behavior of battery
voltage i.e. Vth. It contains the electrical values of no-load voltage (VOC), internal
resistance (R1) and overvoltage i.e. parallel combination of C and R2 [18,19].This
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R2 R1
C Ein
Voc ~Vth
Ib
capacitance represents capacitance of parallel plates and R2 means nonlinear resis-
tance contributed by contact resistance of plate to the electrolyte.
Fig. 2.11: Thevenin Battery Model
This model is not accurate because these values are not constants as modeled but in
fact are functions of the various battery conditions stated above [19,21]. The first
order battery model is much closer to the approximation than the zero order models
to true battery voltage response. As we know that, the first order model contained
one resistor and capacitor pair in addition to the elements contained in the zero order
battery models.
𝑉𝑜𝑐 = 𝑉𝑏 − 𝐼𝑅𝐼 (17)
𝑉𝑏 = 𝑓 𝑆𝑜𝐶,𝑇 (18)
𝑅𝐼 = 𝑓 𝑆𝑜𝐶,𝑇, 𝑆𝑖𝑔𝑛 𝐼 (19)
This resistor capacitor pair added two extra parameters to the battery system, a
resistance and a capacitance, and resulted in a much better representation of true
battery voltage response. The added resistance and capacitance were both dependent
on current direction i.e. charging and discharging, SoC, and battery temperature, but
the same assumptions are also made for internal resistance before were applied to
both parameters.
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Voc
nm(t) IP
RP Vb
Ib R2 R3
C3 C1 R1 C2
Cb
Ein
2.1.4.5 Linear Electrical Battery Model
Fig. 2.12: Linear Electrical Battery Model
The added resistor and capacitor pair was responsible for adding first order dynamics
to the system. The main disadvante of this model is all elements asumed in this
model are constant but in actual battery these elements are the functions of battery
conditions [21].An improvement upon the Thevenin model is a linear electrical
battery model, shown in figure 2.12 [19]. This model shows linear components to
account for self discharge (R p ) and various over voltages. This model is assumed as
more accurate than other battery models; however this model does not considers
temperature dependence factor and uses dissimilar sets of element values to model
the battery [5,19]. Therefore a continuous battery evaluation becomes difficult and
robust.
This linear battery model was verified experimentally in the University of Lowell
battery evaluation test system [19]. This second order battery model, describes the
battery with a battery voltage source, internal resistance, and two parallel polarization
circuits as shown in figure 2.12. The battery parameters of this battery model are
estimated and can validate with the aid of them with simulation modeling [16].
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I
R2
C
E
R1 External
Load V
Use of battery with more efficiency, it is important that battery response for various
operating condition has to understood precisely. The energy stored in any battery is a
chemical energy that is translated into electrical energy [19].
2.1.4.6 Battery Equivalent Circuit
The purpose of battery simulation is to predict the battery performance and could be
interpreted for electrical vehicles, in terms of range, acceleration, speed and many
more. Simulation of any electrical system requires its equivalent circuit. This equiva-
lent circuit consists of circuit elements and each one has precisely predictable
behavior. It is necessary to understand that the values of circuit parameters are not
constant i.e. E and R. The open circuit voltage (Voc) changes with state of charge
(SOC). In case of lead acid battery, open circuit voltage is directly proportional to the
state of charge of the battery. Figure 2.13 is highly useful even though it does not
explain dynamic behavior of the battery.
Fig.2. 13: Equivalent Circuit Model of Battery.
The electric charge that a battery can supply is an important parameter. The capacity
of the batteries used in electric vehicles is usually quoted for some hours discharge.
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The electric cells have nominal voltages E, which gives approximate voltage when
cell delivers electrical power. The internal resistance i.e. R1, the current I is flowing
out of the battery.
2.1.5 Comparison of different battery models
Various battery models are studied and explained in the previous section. Each and
every battery model has an advantages and disadvantage over each other. Therefore
these battery models are compared in this section. Brief comparison summary of
battery models along with their merits and demerit has been given systematically in
tabular format as shown in table 2.3. At a glance applications and appropriate type of
battery model is given to understand significance of battery model for various
applications.
Table 2.3: Comparison of different battery models
Sr. No
Battery Model
Advantages Disadvantages
1. Simple Model Battery simple model is an
approximate model.
The basic assumption of this
model is limitless battery.
This model does not consider the
internal dynamic properties of the
battery, in particular the effect of
the diffusion of the electrolytic
chemicals between the battery
plates.
This model does not depend on
state of charge of battery.
This model cannot be considered
for battery monitoring in Hybrid
Electric Vehicles.
2. Modified
battery model
This is modified model of
simple battery model.
This modified battery model
consists of charging and
discharging resistances along
with capacitance.
Effect of causing transient
currents is considered by
This advanced model considers
the dynamic behavior of the
battery like state of charge and
internal resistance of the battery.
The diodes used in model have no
physical significance in the battery
model and these diodes are
included only because of model-
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adding capacitor C in the
model.
ing purposes.
3. Simplified
equivalent
circuit
This is a dynamical lead-acid
battery model.
This is a modified model with
surface capacitor and polarized
resistance.
The double layer capacitor in a
model used for charge separa-
tion at the electrolyte/electrode
interface.
The bulk capacitor Cb models
open circuit voltage of the
battery cell whereas Rsd
represents the self-discharge.
The batteries dynamic beha-
vior can be modeled with
electrical circuit structures and
linear or nonlinear mathemati-
cal models.
This model gives complete
state variable solution for
terminal voltage Vo , Vcb and
Vcs
The SOC estimation can be
done in this battery model.
4. Thevenin
battery Model
This is modified model and
describes dynamic behavior of
the battery for charging and
discharging, battery storage
capacity, temperature and shelf
life.
This model is not considered as an
accurate because parameter values
are not constants as modeled but
in fact are functions of the various
battery conditions stated above.
5. Linear
Electrical
Model
This model is modified version
of Thevenin battery model and
works as linear battery model.
This model is more accurate
than Thevenin model and
which considers self discharge
and over voltages also.
This model does not considers
temperature dependence parame-
ter
2.2 Electrical Vehicle Performance Parameters
For development of any dedicated advanced system for electrical cars, one has to
understand each function of the devices, quality of parts and electrical models. For
these reasons, it has become necessary to devote a lot more time to select right parts
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for electric car. The right parts will ensure that car works as a functional unit and that
do not have misaligned components. An electric car is supposed to bring a lot of
savings to the motorist. In any electrical car, various electric loads are installed and
controlled by controllers or conventional electronics. These loads are of active load
such that they get constant current through battery. If active load consumes more
power then battery will not hold charge long time means it will discharge. Hence
loads and controlling techniques or control strategy algorithm can be though rigo-
rously so that battery will hold charge for long time. Therefore, there is a need to
study battery performance parameters. Modeling and simulation plays important role
in estimating the performance parameters. Developing a hardware setup for verifying
these parameters will give boost to the research in electrical vehicles. Further esti-
mating this parameter in HIL set up for on line monitoring leads to dynamic
measurement of performance parameters.
The CitiCar (1970) was the earliest vehicle and ran on as little as 24 volts and up to
48 volts of lead acid battery. These lead acid batteries supported a three horsepower
electric motor and radio as one of the option in the car. The ComutaCar vehicle was
upgraded to the electric CitiCar as electrical vehicle with a six horsepower motor
with forced air cooling system, easier to open doors with rear flip up rear glass and
three different axle configurations. In the same time Zipper was a three wheeler
electric designed specifically to be towed by recreational vehicles with similar
category electric vehicle. The vehicle performance depends on battery technology
and electric motor and other facilities. The vehicle performance improves with
advance battery technology and low power high torque electric motor. The vehicle
performance is also depends on the driving style, regular maintenance and add-on
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facilities. Lithium-ion batteries are used EV/HEV, due to high energy densities,
relatively high cell voltages etc .hence these batteries are also preferred in industrial,
transportation applications. Hence uses of such batteries are helps in improving EV
performance in terms of mileage and vehicle weight.
The special batteries are designed to allow EV drivers to reach their destination
without unnecessary stops to recharge the electric vehicles. However, this additional
battery capacity pack would affect the vehicle‟s space, weight and cost. In view of
these issues in terms of limitations, integrating EVs with the vision of Intelligent
Transportation Systems (ITS) is explained and proposed predictive intelligent battery
management system. This Predictive Intelligent Battery Management System
(PIBMS), will increase the taken as a whole performance of Electric Vehicles
including energy consumption and emissions using the ITS infrastructure [22]. The
advancement in battery technology and charging technologies has allowed the
Electric Vehicle (EV) to be considered as the next generation of automotive transport
[22].
Apart from the issues of increasing efficiency and reducing cost and wastage, rechar-
geable battery are the key enabling technology for solving energy problems of future.
Finally battery health management will also play important role in electrical vehicles
that will be dependent on an accurate gauge for remaining charge and trade offs in
long term durability.
2.3 Review on Modeling and simulation of battery
In early stages of the design process modeling and simulations tools are used before
the availability of hardware. Iterative modeling and simulation can improve the
quality of the system design, thereby reducing the number of errors in the design
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process. The software components of any model or system driven by mathematical
input and output relationships then that designed model can be simulated under
various conditions to validate the system. The modeling and simulations are impor-
tant in electrical system for capacity determination and optimum component
selection. The life of the battery imposes stringent constraints on its operation with
active loads. During the discharge cycle of battery, the battery voltage decreases up
to certain cutoff voltage. The discharge capacity and delivered energy by battery is
determined with the help of empirical model. Modeling is the process of producing a
model. The one of the purpose of a model is to enable the analyst to predict the effect
of changes to the system. The model should be a close approximation to the real
system and incorporate most of its salient features. It should not be so complex that it
is impossible to understand and experiment with it. A good model is a well judged
tradeoff between realism and simplicity [23].
Battery modeling and simulation makes it possible to analyze operating conditions,
design optimization, design of automatic control, and design parameters for electro-
chemical systems [15, 24]. By developing battery equivalent models and its
performance simulations, helps designer to understand the possible limitations and
battery related information. From the battery manufacturer context, modeling and
simulations improve the design of cells and modules i.e. identifying limitations in the
suggested model helps in next battery design process. With simulated results in the
intuition for a system that is required for making vital improvements. For instance,
the designer can study the influence on battery geometries, electrode materials, pore-
distribution, electrolyte composition, and other fundamental parameters [24].
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Accuracy in battery modeling helps in characterizes its real world performance in
different industrial complex system modeling. Correctness of the battery model
depends on the number of parameters considered which affect the performance of the
battery [25]. Therefore battery parameter identification and its performance is
important and useful in battery modeling technique.
A simple, fast, and effective equivalent circuit battery model structure for lead-acid
batteries was implemented to facilitate the battery model part of the system model
[15]. This developed equivalent circuit model has been described in detail in that
research paper. The additional tools and processes for estimating the battery parame-
ters from laboratory data were implemented in the same work. After estimating
battery parameters from laboratory secondary data, the parameterized battery model
was used for electrical system simulation. This developed battery model is capable of
providing accurate simulation results and very fast simulation speed [15].
Modeling and simulation also allows for the analysis of an almost unlimited number
of design parameters and operating conditions to a relatively small cost. Experimen-
tal observations of the battery system serve as the necessary verification and
validation of the designed battery model [24]. To understand simulated results
processes in state-of-the-art models, electrodes, electrolyte and battery pack needs to
be notice properly. The different implications of design parameters and operating
conditions have been discussed with respect to experimental observations of battery
performance, ageing, and battery safety in the said research work. The battery
manufacturing company eventually uses these models to optimize the battery design
with respect to these parameters. This paper also comments on electrolyte salt
concentration (mol/m3) profiles at various times during the cycle during the dis-
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charge. The electrolyte the salt concentration increases in the negative electrode and
decreases in the positive electrode. Similarly temperature distribution in a cylindrical
battery during a discharge has been simulated and presented. The temperature
difference between the core and the outer regions increases when the cell is dis-
charged with higher C-rates is also given and explained with simulated graphs. The
life of the battery imposes stringent constraints on its operation with active loads.
During the discharging of battery, the battery voltage decreases up to certain cutoff
voltage level. The discharge capacity and delivered energy by battery is determined
with the help of empirical model. The battery model is a representation of the con-
struction and working of some system of interest. A model is similar to but simpler
than the system it represents. The main purpose of battery model is to enable the
analyst to predict the effect of changes to the system. The model should be a close
approximation to the real system and incorporate most of its salient features [26].
A mathematical model classification includes deterministic, stochastic, static and
dynamic types of models. The input and output variables are fixed values in determi-
nistic model whereas in stochastic at least one of the input or output variables is
probabilistic.
In static model the time term is not taken into account where as in dynamic model
time-varying interactions among variables are taken into account. Typically, simula-
tion models are stochastic and dynamic models. The purpose and scope of the model
has to be properly understood or defined in the research context. In this research
work,it is planned to study the above process of development and application of
model. Herre, different battery models are to be studied and simulate it in MATLAB
and Simplorer software to understand behaviour of the battery. The model
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development consists of formulation of conceptual model,analysis,data acquire and
building detailed model. Whereas in applying model includes simulation, result
analysis, redefining, model optimisation and verification and validation. The
mathematical formulation is needed for the planed system so that dependant and
independent parameters could be identified and used in software system. After
analysis the specific model is represented and used for simulation experimentation,
the simulation is executed and genrerated results are again analysed. In case the
simulated results are not validated with reality system in optimization or redefination
then model mdification is necessary and required otherwise no modification in the
prescribed model. With the help of MATLAB or SIMPLORER researcher can build
mathematical models for forecasting and optimizing the behavior of complex sys-
tems. For model developments following steps are to be considered.
Develop models using data fitting and first principle modeling techniques
Identify parameters that optimize system performance
Simulate models and develop custom post processing routines
Generate reports that document model derivation and simulation results
Share the developed models
2.4 Reviews on Hardware in the Loop
The main initiative of Hardware in Simulation Loop (HIL) is to test the hardware
device on a simulator before implementation on the real system process. Hardware in
the loop is generally used in development and testing of sophisticated and dedicated
real time embedded systems. The real time test bench simulation enables the drive
cycle testing and fault injection capability in the electrical vehicle system through
hardware in the loop platform. In the present time the HIL testing has shown signifi-
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cant contribution for comprehensive rapid prototyping and automated testing plat-
form for advanced electrical systems [18, 27]. In HIL testing physical models of the
systems are replaced by mathematical model that completely describes the important
dynamics of the physical model. Validation of hardware in the loop test platform for
variable speed drive controller of electric vehicle has been described and imple-
mented. This work of HIL enables the testing of closed loop device under test
controllers under realistic operating conditions without need to interface with high
power system HIL tools enables i.e. accelerated testing and validation, testing time
reduction, simulation of all operating points and scenarios which are difficult to
recreate with real system, fault injection capacity and real time access to all signals
[28, 29].
The HIL system comprises of real time platform and electrical emulation of sensors
and actuators to read, process, monitor, control and stores the acquired data for
analysis. This system monitors motor simulated parameters and battery important
parameters.
In recent scenario, HIL simulation becomes an inescapable means of performing real
time experimentation, testing in decisive conditions of the system and validation of
models and prototypes. This HIL simulation technique provides test platform for the
control system. Automotive industries have started using HIL simulation for testing
electronic control units and vehicle performance [26].
HIL is useful to test a controller function with a simulated process before the control-
ler applied to the real process. If the mathematical model used in the simulator then
it might be an accurate representation of the real process, and one can even tune the
controller parameters. This is useful for the process operator and learns to know
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working of the system using hardware-in-the-loop simulation. An additional benefit
of Hardware-In-the-Loop is that testing can be done without damaging electric
equipments. Modelica and Dymola are the object oriented modeling language tools
and used effectively to design hardware in the loop setup for hybrid electrical ve-
hicles using micro hybrid architecture. This HIL work is done for start- stop system
along with brake energy regeneration. This concept is having fuel saving potential
and this has been demonstrated effectively in the research paper of HIL simulation of
hybrid electric vehicle using Modelica and Dymola tools. This paper is elaborated on
the control strategy of brake energy regeneration to charge the battery using sensitivi-
ty function. [30].
The design procedure of HIL for electric vehicle power train system modeling and
simulation has been explained and presented in some of research work. For these
works MATLAB and SIMULINK tools were used for simulation of various compo-
nents of electric vehicle. The battery management system (BMS),Motor control unit
(MCU) and Vehicle management system (VMS) is build on the dSPACE with
MATLAB /SIMULINK along with real time workshop tool box (RTW tool box).
Through this developed system electric vehicle control strategy is simulated and
validated. The offline simulated results and laboratory prototype are presented in the
said work of hardware in the loop [31].
The HIL systems are used to test electrical vehicles before final deployment. The
above electrical vehicle system consists of various electrical sections and devices.
The main component of the system is high voltage battery pack and battery manage-
ment system.
Chapter: 2 Literature Review
Modeling & Simulation of BPP for Efficient Electrical Vehicles ……. Page 52
The offline simulations were used within the early phases of the development process
are often called Model-in-the-Loop simulations. In software development phases
module test and system test are accompanied by MIL or Software-in-the-Loop (SIL)
simulations. These established simulation method increases the overall test coverage.
In the SIL simulation the functional model of an electronic control unit is replaced by
LabVIEW code. But in order to use the HIL simulation, real-time capable simulation
models is needed. After the software tests are successfully passed the calibration of
the ECUs can be done on the test-bench of the vehicle.
Therefore in this Literature review the evaluation of various battery technologies,
battery chemistry, diverse battery models and its comparisons are explained. The
review of the electrical vehicles, its performance with Hardware in the loop is studied
and explained.
Chapter: 2 Literature Review
Modeling & Simulation of BPP for Efficient Electrical Vehicles ……. Page 53
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