research and design module for diagnosis and management of lead acid batteries

Figure 3.10: NTC Thermistor 39 Figure 3.11: Plot for the thermistor 41 Figure 3.12: Peltier chips TEC1-12710 43 Figure 3.13: Principle of Super-tech semiconductor panels 44 Figure 3.15:

MINISTRY OF EDUCATION AND TRAINING

HO CHI MINH CITY UNIVERSITY OF TECHNOLOGY AND EDUCATION

FACULTY FOR HIGH QUALITY TRAINING

RESEARCH AND DESIGN MODULE FOR DIAGNOSIS AND

MANAGEMENT OF LEAD-ACID BATTERIES

LECTURER: PhD NGUYEN MANH CUONG STUDENT: NGUYEN THANH LUAN

PHAN PHU HIEU

GRADUATION PROJECT AUTOMOTIVE ENGINEERNG

S K L 0 1 2 5 4 8

HO CHI MINH CITY UNIVERSITY OF TECHNOLOGY AND EDUCATION

FALCUTY OF INTERNATIONAL EDUCATION

Ho Chi Minh City, January 2024

RESEARCH AND DESIGN MODULE FOR DIAGNOSIS AND MANAGEMENT OF LEAD-ACID

Student ID: 19145146 Major: AUTOMOTIVE ENGINEERING Supervisor: NGUYEN MANH CUONG, PhD

THE SOCIALIST REPUBLIC OF VIETNAM

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Ho Chi Minh City, January 08, 2024

GRADUATION PROJECT ASSIGNMENT

Student name: NGUYEN THANH LUAN Student ID: 19145152

Student name: PHAN PHU HIEU Student ID: 19145146

Major: Automotive Engineering Technology Class: 19145CLA

Supervisor: NGUYEN MANH CUONG, Ph.D Phone number: 0366288115

Date of assignment: _ Date of submission: _

1 Project title: RESEARCH AND DESIGN MODULE FOR DIAGNOSIS AND

MANAGEMENT OF LEAD-ACID BATTERIES

2 Initial materials provided by supervisor: _

3 Content of the project: _

4 Final product:

CHAIR OF THE PROGRAM

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SUPERVISOR’S EVALUATION SHEET

Student name: Nguyen Thanh Luan Student ID: 19145152

Student name: Phan Phu Hieu Student ID: 19145146

Major: Automotive Engineering Technology

Project title: RESEARCH AND DESIGN MODULE FOR DIAGNOSIS AND

MANAGEMENT OF LEAD-ACID BATTERIES

Supervisor: Nguyen Manh Cuong, Ph.D

EVALUATION

1 Content of the project:

2 Strengths:

3 Weaknesses:

4 Approval for oral defense? (Approved or denied)

THE SOCIALIST REPUBLIC OF VIETNAM

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-PRE-DEFENSE EVALUATION SHEET Student name: Nguyen Thanh Luan Student ID: 19145152 Student name: Phan Phu Hieu Student ID: 19145146 Major: Automotive Engineering Technology Project title: RESEARCH AND DESIGN MODULE FOR DIAGNOSIS AND MANAGEMENT OF LEAD-ACID BATTERIES Name of Examiner: Tran Dinh Quy, M.Sc EVALUATION 1 Content and workload of the project

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Ho Chi Minh City, January 08, 2024

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-EVALUATION SHEET OF DEFENSE COMMITTEE MEMBER Student name: Nguyen Thanh Luan Student ID: 19145152 Student name: Phan Phu Hieu Student ID: 19145146 Major: Automotive Engineering Technology Project title: RESEARCH AND DESIGN MODULE FOR DIAGNOSIS AND MANAGEMENT OF LEAD-ACID BATTERIES Name of Defense Committee Member:

EVALUATION 1 Content and workload of the project

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3 Weaknesses:

4 Overall evaluation: (Excellent, Good, Fair, Poor)

5 Mark: ……… (in words: .)

Ho Chi Minh City, January , 2024

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ACKNOWLEGEMENT

Currently, across all car models worldwide, the main component that cannot

be overlooked is the lead-acid battery It serves as the foundation for more advanced energy storage sources like Li-Thium or Li-Ion batteries, gradually replacing traditional sources of electrical energy storage like lead-acid batteries With the knowledge we have acquired over the past four years at university, we have decided

to choose Lead-Acid batteries as the subject of our graduation thesis, titled

"RESEARCH AND DESIGN MODULE FOR DIAGNOSIS AND MANAGEMENT OF LEAD-ACID BATTERIES." We are truly delighted and

proud to have the opportunity to delve into more research and complete our project

Through this, we want to extend our sincere gratitude to all the professors at the Faculty of International Training of Ho Chi Minh City University of Technology and Education, especially Mr Duong Tuan Tung - Head of the Faculty of International Education and Mr Vu Dinh Huan - Head of Automotive Engineering Technology for providing us with valuable specialized knowledge, creating favorable conditions for us to complete this graduation project Once again, we thank all our esteemed professors and wish them continued success in their endeavors to nurture future talents

ABSTRACT

Electric vehicles are rapidly becoming a significant trend in the automotive industry, driving a surge in research on electric vehicle battery technology Despite these advancements, internal combustion engine vehicles predominantly rely on Lead-Acid batteries for their starting mechanism, a component whose importance remains unrivaled by any alternative Thus, developing diagnostic and management systems for Lead-Acid batteries is crucial

Understanding the characteristics, operational principles, and structure of Lead-Acid batteries is vital for the progress of internal combustion engine vehicles Yet, the focus on management systems for these batteries is relatively scarce, often overshadowed by systems designed for Lithium-based batteries Our objective is to initiate and encourage research into diagnostic and management systems specifically for Lead-Acid batteries

Our team is embarking on a project titled "RESEARCH AND DESIGN MODULE FOR DIAGNOSIS AND MANAGEMENT OF LEAD-ACID BATTERIES." This project aims to create a module capable of assessing battery life

and monitoring its condition As the automobile industry evolves and the need to optimize fossil fuel usage intensifies, our research seeks to innovate in the realm of

"RESEARCH AND DESIGN MODULE FOR DIAGNOSIS AND MANAGEMENT OF LEAD-ACID BATTERIES” contributing to the sustainability and efficiency of automotive technologies

1.6 Domestic and international research on the topic 3

2.1.3 Classification of Lead-Acid Batteries 9 2.1.4 The Operating Principle of Lead-Acid Batteries 11 2.1.4.1 The Discharge Principle of the Lead-Acid Battery 11 2.1.4.2 The Charging Principle of the Lead-Acid Battery 12 2.1.5 Characteristics of Lead-Acid Batteries 13 2.1.5.1 The electromotive force of Lead-Acid batteries 13 2.1.5.2 Capacity of Lead-Acid batteries 14 2.1.5.3 Discharge Characteristics of Lead-Acid batteries 14 2.1.5.4 Charge Characteristics of Lead-Acid batteries 16 2.2 Simulate the charging and discharging process of lead-acid batteries

2.2.1 Build a simulation program 17

2.2.3 Build a diagram of simulation blocks 17 2.2.3.1 Annotate the meaning of used blocks 17

CHAPTER 3: MODULE BUILDING AND BATTERY MANAGEMENT AND

3.1.1 Components included in the module 29

3.2 Design battery diagnostic and management module software 48

3.2.2 Calculate State of Charge of battery 51 3.2.3 Calculate and predict battery life 53 3.2.4 Transmit and receive data from the HMI display screen 54 3.3 Design interface of battery diagnostic and management module 55 3.3.1 Programming and interface design software for display screens 55

4.3 Evaluate the data collection ability of sensors 63

4.4 Evaluate all the systems 64 CHAPTER 5: CONCLUSION AND FUTURE DEVELOPMENT 69

LIST OF FIGURES

Figure 1.1: The Sealed Lead-Acid Battery (12V – 75Ah) 1 Figure 2.1: Structure of Lead-Acid Battery 5 Figure 2.2: Layers of plates inside the battery 6 Figure 2.3: Structure of vent caps 9 Figure 2.4: Sealed Lead-Acid batteries with H2SO4 acid in gel form 10 Figure 2.5: Flooded Lead-Acid batteries with a liquid solution 11 Figure 2.6: Discharge Principle of the Lead-Acid Battery 12 Figure 2.7: Charging Principle of the Lead-Acid Battery 13 Figure 2.8: Discharge Characteristics of Lead-Acid batteries 15 Figure 2.9: Charge Characteristics of Lead-Acid batteries 16 Figure 2.10: Select battery parameters for simulate 17 Figure 2.11: The program simulates the battery in a charging state 18 Figure 2.12: The program simulates the battery in a discharged state 19 Figure 2.13: The program controls the charging and discharging process of the

Figure 2.15: Current value 21 Figure 2.16: Battery voltage value 22 Figure 2.17: Operation of CANBus 24 Figure 2.18: UART Communication 26 Figure 2.19: Frame Formats of UART communication 27 Figure 3.1: Arduino Mega 2650 29 Figure 3.2: Arduino Mega 2650 Pinout Diagram 30 Figure 3.3: HMI UART TJC display screen 31 Figure 3.4: WCS1700 Hall current sensor 33 Figure 3.5: Function block of WCS1700 34 Figure 3.6: 25VDC Voltage Sensor 35 Figure 3.7: Structure of Voltage Sensor 36 Figure 3.8: Two-channel 5V relay module 37 Figure 3.9: Structural diagram of relay 38

Figure 3.10: NTC Thermistor 39 Figure 3.11: Plot for the thermistor 41 Figure 3.12: Peltier chips TEC1-12710 43 Figure 3.13: Principle of Super-tech semiconductor panels 44

Figure 3.15: Low voltage DC module DC-DC 46 Figure 3.16: Hardware structure diagram 47 Figure 3.17: Circuit diagram of the module 47 Figure 3.18: Diagram of voltage divider circuit 48 Figure 3.19: UART communication port on HMI screen 55 Figure 3.20: UART communication port on Arduino Mega 2560 56 Figure 3.21: USART HMI software logo 57 Figure 3.22: Working interface of USART HMI software 57 Figure 3.23: The 3D shape of the cooling box is designed using Solidworks

Figure 4.1: Lead-Acid battery diagnostic and management module box 60 Figure 4.2: Cooling box for Lead-Acid batteries 60 Figure 4.3: Electrical system inside the module box 61 Figure 4.4: Electrical system of the cooling box 62 Figure 4.5: Actual image of the cooling box installed on the vehicle 63 Figure 4.6: Data is collected from sensors 64 Figure 4.7: First page of the module interface 65 Figure 4.8: Second page of the module interface 66 Figure 4.9: Danger warning about low battery voltage 67 Figure 4.10: Temperature and cooling warnings for batteries 68

LIST OF TABLES

Table 2.1: The physical and chemical properties of the electrolyte 8 Table 3.1: The relation between the battery capacity and open circuit voltage 52 Table 4.1 Statistics of hardware and software of the module system 59

Chapter 1: INTRODUCTION 1.1 Reason for choosing the topic

Globally, with a particular emphasis on Vietnam, electric vehicles (EVs) are witnessing substantial growth While the future landscape of the automotive industry will likely be dominated by EVs, it's undeniable that the Lead-Acid Batteries used in internal combustion engines have not yet been fully optimized and can't be immediately replaced with an alternative type Our market research and analysis have pinpointed several significant issues associated with these batteries, leading to startup failures or disruptions in the vehicle's primary electrical systems Surprisingly, no dedicated system exists to alert drivers to these battery-related challenges This identified gap serves as the primary impetus for our research project Furthermore,

we aim to delve deeper into simulating battery functionalities using the Matlab software

1.2 Subject and scope of research

1.2.1 Subject of research:

Sealed Lead-Acid Battery.

Figure 1.1: The Sealed Lead-Acid Battery (12V – 75Ah)

- Simulate the lead-acid battery system on a car using Matlab/Simulink

- Build modules and design diagnostic and battery management software

1.5 Research Methods

- Theoretical research methods: Applying learned knowledge, collecting and gathering relevant documents, analyzing and researching to build a theoretical standard, that theory is the foundation for the research rescue

- The method of analyzing the Lead-Acid Batteries system model on Matlab/Simulink software and using the technical parameters of the battery to analyze some results

1.6 Domestic and international research on the topic

a) Domestic Research on the topic

Research in the country on the design of diagnostic and management modules for lead-acid batteries is still quite limited Most topics focus on the management of lithium batteries and automatic battery charging systems, but not many specifically address lead-acid batteries Although lead-acid batteries are widely used in cars to start internal combustion engines, domestic research primarily targets batteries for electric vehicles This indicates a significant gap in the development of technology and solutions for diagnosing and managing this type of battery

b) International Research on the topic

In contrast to the domestic scene, research on lead-acid batteries abroad has progressed much further There are a number of studies related to diagnosing and predicting the lifespan of batteries, requiring the collection and analysis of large amounts of complex data However, most of these studies are conducted in laboratories and lack practical application solutions that are easily accessible to consumers This creates a significant challenge in transitioning from theory to practice, as well as in making diagnostic and management technology for batteries widespread and accessible to end-users

Chapter 2: THEORETICAL BASIS 2.1 Lead-Acid Batteries

Essentially, a car battery is considered a secondary power source, operating on the basis of converting energy into electrical power and supplying it to the devices in the vehicle When the alternator is not working (engine off) or lacks the capacity to meet the demands of the electrical devices in the car, the battery will serve the purpose

of providing a steady current during that time

2.1.1 History of Lead-Acid Battery

In 1836, British chemist John F Daniell introduced an improved version of the battery, capable of producing a more stable current than previous versions By

1859, French physician Gaston Planté had invented the first rechargeable battery based on lead-acid technology, a technology that is still in use today Prior to this, all batteries were non-rechargeable

In 1899, Swedish inventor Waldmar Jungner invented the nickel-cadmium (NiCd) battery, using nickel and cadmium as the electrodes However, the high cost

of these materials limited their popularity In 1901, Thomas Edison replaced cadmium with iron, creating the nickel-iron (NiFe) battery, but this type of battery was not successful due to low efficiency and high self-discharge It was not until

1932, thanks to improvements made by Schlecht and Ackermann, that the NiCd battery achieved higher current load and improved lifespan In 1947, Georg Neumann further improved the technology by sealing the cells

For many years thereafter, NiCd became the primary rechargeable battery for portable devices However, environmental concerns in Europe in the 1990s led to restrictions on the use of NiCd batteries under the European Union Directive 2006/66/EC, except for special industrial applications A replacement was the nickel-metal hydride (NiMH) battery, which is more environmentally friendly

Currently, most research focuses on improving lithium-based systems, first commercialized by Sony in 1991 Li-ion batteries not only power mobile phones, laptops, and medical devices but are also used in electric vehicles and satellites The main benefits of Li-ion batteries include high energy density, simple charging process, low maintenance, and environmental friendliness

2.1.2 Structure of Lead-Acid batteries

Based on the information in [1], [2] and [3] we have information about the structure of Lead-Acid batteries

Figure 2.1: Structure of Lead-Acid Battery

a) Case of batteries

Currently, acid battery casings are commonly manufactured from materials such as Ebonite, Polypropylene plastic, or rigid plastic rubber To enhance their acid resistance and durability, during the production process, a layer of acid-resistant Polyclovinyl lining is applied inside the casing, with a thickness of approximately 0.6

mm Thanks to this lining, the lifespan of the battery can increase by two to three times

Inside the battery enclosure, depending on the specified voltage of the battery, they are divided into separate compartments, with partitions separating them and providing electrical isolation Each compartment is referred to as a single battery cell

At the bottom of each compartment, support ribs are designed to create a gap between the bottom of the casing and the underside of the ribbing This design creates

a useful empty space to prevent short circuits between the terminals due to the effects

of the preserving compound On the external surface of the battery casing, ribbing is cast in a structural pattern, enhancing rigidity and facilitating handling, and can also

be equipped with handles for ease of transport and use

b) Plates and plates distribution in batteries

The negative plates consist of lead (Pb) and an alloy of lead-antimony (Sb), typically containing 87% to 95% Pb and 5% to 13% Sb The addition of antimony enhances hardness, corrosion resistance, and casting properties of the plates

These plates serve to separate the active material and facilitate the flow of current across the surface of the plates This is crucial, especially for the positive plates, as the electrical conductivity of the active material (lead dioxide, PbO2) is significantly higher compared to pure lead, making the thickness of positive plates instrumental in enhancing battery performance

The plates are cast in a frame-like structure, encompassing both sides of the separators and featuring two tabs for connection to the cell's lead straps at the bottom

of the battery The negative plate columns, being less electrically conductive, are also less prone to corrosion, making them thicker than the positive plate columns Notably, the two sides of the negative plate separators are thicker, as they only interact with the positive plate columns

Figure 2.2: Layers of plates inside the battery The active material is manufactured from lead oxide, concentrated sulfuric acid, and approximately 3% of the organic salts of sulfuric acid for the negative plates, while for the positive plates, it is made from lead oxides Pb3O4, PbO, and concentrated sulfuric acid solution The addition of organic salts of sulfuric acid in the negative plates serves to increase charge acceptance and the durability of the

active material, thereby improving the depth of discharge of the electrolyte into the plate's interior, and participating in the electrochemical reaction

After being filled with active material, the plates are pressed, dried, and undergo the formation process, where they are immersed in diluted sulfuric acid solution and charged with direct current at a controlled rate Following this formation process, the active material in the plates is fully converted into PbO2 (dark brown in color) Subsequently, the plates are rinsed, dried, and assembled

Identically named plate groups within a single battery are welded together to form plate sets, and are connected through lead cones to exit the battery cell towards the terminals It is noteworthy that to increase the capacity of the battery, one should increase the number of plate sets connected in parallel within a single battery Typically, 5 to 8 sets are used To increase the nominal voltage of the battery, one should increase the number of plate sets connected in series

Currently, these partitions are typically made from polyvinyl chloride (PVC) with a thickness ranging from 0.8 to 1.2 mm One side of the partition faces the negative plates, while the other side may have a wave or groove pattern to facilitate the movement of electrolysis current towards the positive plates and to allow for efficient circulation of the solution

d) Electrolyte

The electroplating solution in the battery cell is sulfuric acid (H2SO4) prepared from pure acid and distilled water according to specified ratios, depending on climate conditions and the material used for the separator The density of sulfuric acid solution ranges from (1.1 ÷ 1.3) g/cm3. The strength of the electroplating solution significantly affects the electrical conductivity of the battery

Temperature and environmental conditions also greatly affect the concentration of the electroplating solution with materials in the equatorial region, the specified concentration should not exceed 1.1 g/cm3 For materials in cold

environments (polar regions), the electroplating solution can have a maximum concentration of up to 1.3 g/cm3 In cold climates, it is advisable to choose a solution density in the range of (1.25 ÷ 1.26) g/cm3, while in winter, a density of about 1.27 g/cm3 is recommended It should be noted that excessively high concentration can damage the separator and the electrodes, and can also lead to sulfate formation within the electrodes, resulting in a rapid reduction in the battery's lifespan Excessively low concentration will reduce the capacitance and rated voltage of the battery, especially for materials in cold environments, the solution may freeze in winter

Notes when preparing the electroplating solution for the battery:

- Avoid using acids with high impurity content, such as typical technical-grade acids, and avoid using distilled water, as such a solution would enhance the battery's discharge process

- The utensils used for preparation must be made of glass, porcelain, or resistant plastic They must be clean and free from mineral salts, oils, or other impurities

acid To ensure safety during preparation, never pour distilled water into concentrated acid Instead, pour the acid slowly into the distilled water and stir evenly with a glass rod

Based on the information in table 2.1 in [4], we have more information about the physical and chemical properties of the electrolyte inside the Lead-Acid battery:

Properties Listed Below are for Electrolyte:

Boiling Point: 210 - 245° F Specific Gravity (H2O

= 1):

1.215 to 1.350

Melting Point: N/A Vapor Pressure (mm

Evaporation Rate:

(Butyl Acetate = 1)

Less than 1 % Volatile by Weight: N/A

pH: ~1 to 2 Flash Point: Below room

temperature (as

hydrogen gas)

LEL (Lower Explosive

a clear liquid with a sharp, penetrating, pungent odor

Table 2.1: The physical and chemical properties of the electrolyte

e) Cover, vent caps and cells connectors

The cover of the battery is made from either ebonite or bakelite On top of the cover, there are specially designed openings to facilitate the pouring of the electrolyte into each compartment This is also where the concentration and temperature of the solution inside the battery are monitored and adjusted, creating optimal conditions for its operation The cover is engineered for maximum sealing, ensuring that no solution spills out and preventing foreign substances from entering Additionally, a vent caps is integrated to allow for flexible pressure adjustments within the battery

According to [5], the structure of vent caps is as follows:

Figure 2.3: Structure of vent caps For batteries with porcelain tops, in addition to the aforementioned features, a separate vent hole is integrated next to the pouring hole, providing utmost convenience for concentration adjustments

Different compartments of the battery are connected by a lead cells connectors

2.1.3 Classification of Lead-Acid Batteries

There are two main types of lead-acid batteries, namely sealed and flooded Each type has its own characteristics, advantages, and disadvantages Depending on the usage needs, users can consider choosing between these two types In this research, we have selected Flooded Lead-Acid batteries as the subject of our study

a) Sealed Lead-Acid batteries

Sealed Lead-Acid batteries are a type of battery with a sealed structure that does not require regular addition of water Essentially, the inside of a dry battery is not completely dry but still contains H2SO4 acid in gel form

Figure 2.4: Sealed Lead-Acid batteries with H2SO4 acid in gel form Advantages:

- Convenient, no need for frequent water additions

- High durability, long lifespan

- Ability to quickly recover voltage after providing a strong electric current

- Safe, does not cause corrosion to surrounding metal parts

Disadvantages:

- The battery can suddenly run out of power Therefore, users need to have a contingency plan

- Higher cost compared to Flooded Lead-Acid batteries

b) Flooded Lead-Acid batteries

This is a type of battery that utilizes a liquid solution (appropriate concentration of H2SO4), combined with lead plates and alternating metal layers

Advantages:

- It provides a stronger current compared to dry batteries, and can still be recharged after prolonged periods of non-use

- Simple construction, easy to remove for use in other electrical devices

- Lower cost compared to dry batteries

Disadvantages:

- Requires regular recharging

- H2SO4 acid has a high corrosive nature, leading to potential rusting and an unpleasant odor

- Shorter lifespan compared to dry battery types.

Figure 2.5: Flooded Lead-Acid batteries with a liquid solution

2.1.4 The Operating Principle of Lead-Acid Batteries

a) The Discharge Principle of the Lead-Acid Battery

During discharging, which means the battery is providing current to the load, the reaction in the battery compartment can be summarized as follows:

Figure 2.6: Discharge Principle of the Lead-Acid Battery Electrical energy is released as sulfuric acid in the electrolyte reacts with lead, transforming into water At this point, sulfuric acid combines with the positive and negative electrodes, converting into lead sulfate

At the positive electrode, the reaction proceeds as follows:

PbO2 + 3H+ + H2SO4 − + 2e– → PbSO4 + 2H2O

At the negative electrode, the reaction occurs as follows:

Pb + H2SO4 → PbSO4 + 2e + 2H+

The discharging process leads to an increase in the amount of water, while reducing the concentration of sulfuric acid Consequently, the electrolyte's concentration decreases, and the electrodes, essentially composed of PbSO4, cause the potential difference between them to gradually decrease

The strength or weakness of the reactions, as well as the quantity of reactants involved, depends on the dissociation and diffusion abilities of SO4(2-) and H(+) Therefore, factors such as electrolyte concentration, porosity of the electrodes (larger PbSO4 particles result in less porous electrodes), voltage, and charging current intensity are influencing factors on the extent of reactions at the electrodes

b) The Charging Principle of the Lead-Acid Battery

When charging, sulfuric acid is released from the electrodes, and the electrolyte transforms back into sulfuric acid, increasing the concentration of the electrolyte The positive electrodes convert into lead dioxide, and the negative electrodes convert into lead The direction of the charging current is opposite to that during discharging During the charging process, water in the electrolyte solution is electrolyzed into hydrogen and oxygen

Figure 2.7: Charging Principle of the Lead-Acid Battery

At the positive electrode, the reaction occurs as follows:

2.1.5 Characteristics of Lead-Acid Batteries

Each compartment of the battery serves as an independent individual battery, designed with specific attributes tailored for the entire unit The amalgamation of multiple compartments within the battery is executed to augment its rated voltage Consequently, when conducting research on the battery's characteristics, studying one compartment of the individual battery is sufficient for assessment

2.1.5.1 The electromotive force of Lead-Acid batteries

The electromotive force of the lead-acid battery primarily depends on the voltage across the battery cells, meaning it is contingent on the chemical properties

of the materials composing the plates and the electrolyte solution, rather than the dimensions of the plates This electrical capacity also relies on the concentration of the electrolyte solution and can be accurately determined through the following empirical formula:

𝐸0 = 0.85 + 𝛾 (𝑉) Where:

E0: Electromotive force of each lead-acid battery, measured in Volts

𝛾: Concentration of the electrolyte solution, not in units of g/cm3, but measured in Volts adjusted to +15°C

Furthermore, the electromotive force is also affected by the temperature of the electrolyte solution

During the discharging process, the electromotive force of the lead-acid battery is calculated using the formula:

𝐸𝑝 = 𝑈𝑝 + 𝐼𝑝 𝑟𝑎𝑞Where:

Ip: Discharge current (A)

Up: Voltage measured across the battery cells during discharge (A)

raq: Internal resistance of the battery during discharge When fully discharged, raq = 0.02Ω

During the charging process, the electromotive force of the lead-acid battery

is calculated using the formula:

𝐸𝑛 = 𝑈𝑛− 𝐼𝑛 𝑟𝑎𝑞Where:

In: Charging current (A)

Un: Voltage measured across the battery cells during charging (V)

raq: Internal resistance of the battery during charging When fully charged, raq = (0.0015 ÷ 0.001)Ω

2.1.5.2 Capacity of Lead-Acid batteries

The discharge capacity of a battery measures its ability to supply energy over

a specific period and is calculated using the formula:

𝐶𝑝 = 𝐼𝑝 𝑡𝑝 (𝐴ℎ) Where:

Cp: Capacity obtained during the discharge process (Ah)

Ip: Steady discharge current (A) over the discharge period tp (h)

The charge capacity of a battery measures its energy storage capability and is calculated using the formula:

𝐶𝑛 = 𝐼𝑛 𝑡𝑛 (𝐴ℎ) Where:

Cn: Capacity obtained during the charging process (Ah)

In: Steady charging current (A) over the charging period tn (h)

2.1.5.3 Discharge Characteristics of Lead-Acid batteries

The discharging characteristics of a battery can be depicted through a graph, illustrating the relationship between electromotive force, battery voltage, and the concentration of the electrolytic solution throughout the discharge process with a stable current

Observing the graph, we can note:

Figure 2.8: Discharge Characteristics of Lead-Acid batteries

In the period from tP = 0 to tP = tgh, values like electromotive force, voltage, and solution concentration decrease gradually, but not too steeply This is referred to

as the steady phase of discharge or the permissible duration based on the battery's discharge mode

At the point tgh, there's a significant shift in the graph Continuing to discharge beyond this point will rapidly reduce the electromotive force and voltage Concurrently, the lead sulfate (PbSO4) crystals formed during the reaction become coarse and are hard to dissolve during the subsequent charging phase The point tgh defines the discharge limitation

After ceasing discharge for a while, metrics such as electromotive force and voltage will recover, termed as the recovery phase or rest period of the battery, depending on its discharge mode

To compare the efficiency of batteries with the same voltage, we consider the discharge capacity over 20 hours This capacity is termed C20

The duration and the discharge limitation values depend on the current For instance, the discharge capacity of a battery with a C20 of 60Ah hinges on its discharge current

2.1.5.4 Charge Characteristics of Lead-Acid batteries

The charging characteristic graph of a battery illustrates the relationship between electromotive force, voltage, and the concentration of the electrolyte solution throughout the charging process, assuming a constant charging current

From this graph, we can observe:

Figure 2.9: Charge Characteristics of Lead-Acid batteries During the period from the start to t = ts, parameters such as electromotive force, voltage, and the concentration of the electrolyte solution tend to increase

Upon reaching time ts, gas bubbles begin to form on the surface of the negative electrode (also known as the boiling phenomenon) At this point, the potential difference between the battery's terminals increases to 2.4V If the charging continues, this value quickly reaches 2.7V and remains steady This phase is referred

to as the full charging stage, facilitating a complete transformation of the active substances inside the electrode, thereby enhancing the battery's discharge capacity

In practice, the full charge phase for the battery lasts about 2 to 3 hours Throughout this duration, the potential difference across the battery terminals and the concentration of the electrolyte solution remain stable As a result, the discharge capacity is often less than the capacity required for a full charge When the charging

is halted, parameters like voltage, electromotive force, and the concentration of the electrolyte solution decrease and stabilize This period is also known as the resting phase after charging The charging current significantly impacts the battery's quality

The standard charging current for the battery is set at 0.05C20

2.2 Simulate the charging and discharging process of lead-acid batteries using Matlab-Simulink software

2.2.1 Build a simulation program:

Use Matlab-Simulink software to simulate the state of a Lead-Acid Battery Based on that, we can better understand the charging and discharging characteristics

of batteries, serving the process of researching and designing battery diagnostic and management modules Helps evaluate the actual condition of Lead-Acid batteries before connecting to the system to ensure safety during use

2.2.2 Select battery parameters

Figure 2.10: Select battery parameters for simulate

2.2.3 Build a diagram of simulation blocks

2.2.3.1 Annotate the meaning of used blocks

- Charging voltage source: DC 14.5V

- Simulate the resistor as a load to discharge the battery (R=1 Ω)

- Use the switch to control the charging and discharging process (Switch is in state 0 - open and 1 - close)

2.2.3.2 Programs used for simulation

a) When the battery is in charging state: The switch is closed (1) and the charging voltage from the DC source (Vcharge = 14.5 V) will be connected to the battery pack At this time, the battery is charged and the load uses voltage from the

DC source as the load voltage (Vload = 14.5 V)

Figure 2.11: The program simulates the battery in a charging state b) When the battery is in commune state: Switch is open (0) and charging voltage from DC source (Vcharge= 42 V) will disconnect the battery pack At this time, the battery provides voltage to the resistive load

Figure 2.12: The program simulates the battery in a discharged state

Figure 2.13: The program controls the charging and discharging process of

the battery

2.2.4 Simulation results

2.2.4.1 Simulation results of the battery Discharging process

Figure 2.14: SOC value The state of charge of a battery explains the distinction between a battery that

is fully charged and one that is in use It has to do with how much electricity the cell still has available It can be defined as the battery's maximum charge delivery capacity divided by the battery's remaining charge Here is how it is expressed as a percentage

𝑆𝑜𝐶/% = 100(𝑄0+ 𝑄)

𝑄𝑚𝑎𝑥 = 𝑆𝑜𝐶0/% + 100

𝑄

𝑄𝑚𝑎𝑥+ Q0/mAh= Initial charge of the battery

+ Q/mAh= The quantity of electricity delivered by or supplied to, the battery It follows the convention of the current: it is negative during the discharge and positive during the charge

+ Qmax/mAh= The maximum charge that can be stored in the battery + SoC0/%= The initial state-of-charge (SoC/%) of the battery

+ If the battery is new: Qmax=Cr and Q0=0.5Qmax generally Cr is the rated capacity of the battery as given by the manufacturer

+ If the battery is fully charged: Q0=Qmax and SoC0=100%

Based on the chart determined by downloading, the person making the regulation after 4 time steps, the battery's state will decrease slightly after the specified time step, then the charging time will come again and the battery's state will gradually decrease achieve 100%

Figure 2.15: Current value Any movement of electric charge carriers, such as ions (atoms that have gained

or lost one or more electrons), holes (electron deficiencies that can be thought of as positive particles), and subatomic charged particles (e.g., electrons having negative charge, protons having positive charge) can be considered as electric current

When electrons are the charge carriers in a wire, the amount of charge that passes through any given location in the wire in a given amount of time is measured

as electric current The electric charge motion is occasionally reversed in alternating current but not in direct current The direction of current in electric circuits is often interpreted as the flow of positive charge, which is the opposite direction of the real electron drift As stated, the present

The letter I is typically used to represent current Ohm's law, or V = IR, states that the current flowing through a conductor is related to the voltage V and resistance

R I = V/R is an alternate way to express Ohm's law

Based on the chart, we can see a significant change in the input current from positive to negative Accordingly, we can see that during the discharge and charging process, there is a sudden induction current in the shield system The current changes suddenly and gradually increases to positive when in the charging state again

Figure 2.16: Battery voltage value The electric potential difference per unit charge between two places in an electric field is known as voltage (also known as electric potential difference, electromotive force emf, electric pressure, or electric tension) In mathematics, voltage is represented by the symbols "V" or "E" in formulas Go to this section of the article if you're seeking for a more straightforward definition of voltage

The potential energy that exists between two locations in a circuit is known as voltage The potential of one point is greater than the potential of the other points A voltage or potential difference is the difference in charge between a greater and a lower potential The electrons are propelled through the circuit by the voltage or potential difference More electrons will flow across the circuit as a result of a larger force and higher voltage Electrons would travel randomly in free space if there was

no voltage or potential difference Another term for voltage that is occasionally used

is "electric tension." For instance, low tension, high tension, and 33 kV cables are referred to depending on their voltage handling capacity

After observing the chart, we can see the change in voltage during the charging and discharging process of the battery During the discharging process, the battery has about 11.6V and during the charging process, the battery's voltage needs to be equal to 11.6V The charging voltage is about 14.5V

2.3 Lead-acid battery diagnostic and management module

2.3.1 Concepts and composition

a) Concepts:

The Battery Management System (BMS) is an advanced engineering system designed to monitor, protect, and optimize the performance of lead-acid batteries during their charging and operational phases BMS can interface with various sensor

supervise the acid concentration inside the battery, and perform several other functions In applications demanding high reliability and efficiency, such as Uninterruptible Power Supplies, backup power systems, and transportation like electric vehicles, the BMS is crucial as it ensures safety and optimizes energy consumption

b) Composition:

The primary components of the battery management system include: lead-acid batteries, management modules, and sensors that measure temperature, voltage and current intensity

High-Temperature Protection: When the temperature of the lead-acid battery exceeds the limit, the system module will notify on the display screen and activate the thermal management system to cool the battery If it exceeds the maximum temperature, the circuit will instantly cut off the power

Overcurrent Protection: When charging or discharging, if the current of the battery exceeds the set value, the system will immediately alert through the display screen for users to take measures to check and repair

Monitoring the operation of some main electrical systems in the vehicle: Detect and warn about abnormalities in the vehicle's electrical systems for timely inspection and repair

Additionally, the module is integrated with a touch-sensitive display screen that can collect battery information through data input This initial data will be the basis for the module to calculate and more accurately predict the risks of damage to the vehicle's electrical energy system The screen will display all the information, parameters of the battery, and additionally, there are charts about the battery's operating status (temperature, charging voltage, State of Health (SOH), State of Charge (SOC), etc.)

2.3.3 Communications:

2.3.3.1 CANBus communication

a) Overview of CANBus

Definition: CAN Bus, short for Controller Area Network Bus, is a serial communication protocol that allows various devices within a vehicle (such as sensors, engines, control panels) to communicate with each other without the need for a central processor

Development History: Developed by Bosch in the 1980s, CAN Bus has become an ISO international standard and is an essential part of most modern automobiles It was developed to reduce the complexity of electrical wiring systems and to improve reliability in vehicles

b) Structure and Operation

Network Topology: CAN Bus typically uses a bus topology with two main data transmission lines, CAN-High and CAN-Low The ECU of different systems in the car can connect to this network

Figure 2.17: Operation of CANBus Data Frame: Also known as CAN ID, it is a data frame that includes an identification field, control field, data, and CRC field

Transmitting and Receiving Data: Devices on the CAN network can transmit

or receive data Each data frame begins with a unique identifier field, helping to determine the source and target of the data

c) Applications in Automobiles

Communication between Engine Control Unit (ECU) and Transmission, Safety Systems, Entertainment and Information Systems, ABS braking systems, airbags, and cruise control systems, etc

Integration of Sensors and Actuators: CAN Bus allows the integration and control of multiple sensors and actuators in the vehicle

Remote Control Support: This technology supports functions such as remote start, remote control via mobile apps