project report electronics 2 topic automatic battery charger

They can detect the battery type, condition,and charge level, allowing for optimized charging cycles and preventing overcharging orundercharging.A circuit for battery charging includes a

HANOI UNIVERSITY OF SCIENCE AND TECHNOLOGY

SCHOOL OF ELECTRICAL AND ELECTRONIC ENGINEERING

PROJECT REPORT

ELECTRONICS 2 TOPIC: AUTOMATIC BATTERY CHARGER

Instructor: Dr Nguyen Canh Quang

GROUP 1

Hanoi, 07/2023

TABLE OF CONTENTS

Table of Contents

List of Figures

Abstract

Chapter 1: Introduction

1 Overview

1.1 Introduction to the topic

1.2 Battery Charger

1.3 SCR operating modes and Application

2 Market Research

3 Electrical Characteristics

Chapter 2: Methodology

1 Type of methodology

2 Our Methodology

Chapter 3: System Design

1 Block Diagram

2 Circuit Diagram

2.1 Transformer

2.2 SCR

3 Working Explanation

Chapter 4: Calculation

Chapter 5: Conclusion and Recommendation

References

LIST OF FIGURES

Figure 1 Battery Charger – LiFePO4, Li-ion, Ni-MH, Ni-C ………7

Figure 2 Enecharger Battery Charger 4x AA/AAA/C/D ……… 7

Figure 3 Panasonic AA/AAA Charger With 4 Eneloop AA Batteries ……….7

Figure 4 Fast Battery Charger AA/AAA ……… 8

Figure 5 Methodology ……… ……… 9

Figure 6 Block Diagram ……….10

Figure 7 Circuit diagram ……….10

Figure 8 Current to SCR1 Gate ……… 13

Figure 9 Uncharged Current ……… 13

Figure 10 Complete diagram……….14

Figure 11 First mesh……… 14

Figure 12 3 meshes………15

Battery chargers are essential devices that play a crucial role in powering various portable electronic devices With the increasing dependence on technology, the demand for efficient and reliable battery chargers has grown significantly This abstract provides

an overview of battery chargers, their working principles, and the advancements in charging technology

Battery chargers are devices designed to recharge the batteries of electronic devices such as smartphones, laptops, tablets, and cameras, They convert alternating current (AC) from a power outlet into direct current (DC) to charge the batteries The charging process involves several stages, including bulk charging, absorption charging, and float charging, which vary depending on the battery type and charger design In recent years, advancements in battery charger technology have led to the development of smarter and more efficient chargers Smart chargers utilize microprocessors and advanced algorithms

to monitor and control the charging process They can detect the battery type, condition, and charge level, allowing for optimized charging cycles and preventing overcharging or undercharging

A circuit for battery charging includes an SCR that is periodically gated on for a duration corresponding to the state of charge of the battery, being gated on for a duration corresponding to the state of charge on the battery being the gated for only a short interval when the battery is essentially fully charged to keep it charged The conduction angle is determined from the open circuited battery potential and the previous charging history of the battery obtained from potential sensing circuits A pedestal and cosine modified ramp circuit triggers the SCR's through capacitors with a resistor inter coupling the SCR gate and cathode electrodes Circuitry prevents the unipolar junction transistor in the latter circuit from remaining latched on A potential circuit for determining the rate of charge includes a resistor connected to the output terminal that is bypassed when the average value of the signal connected on the collector of the transistor having the base connected

to the output terminal has a predetermined value Diodes inter-couple the SC R's and the emitter of the latter transistor for providing operating potential to the circuits and the starting charging current to the output terminal when a connected battery is fully discharged

Furthermore, fast charging technology has emerged as a significant trend in battery chargers Fast chargers are capable of delivering higher current levels to recharge batteries at a much faster rate than traditional chargers This technology is particularly beneficial for users who require quick battery top-ups, reducing downtime and improving productivity Another notable innovation in battery charger technology is the integration

of wireless charging capabilities Wireless chargers use induction or resonant technology

to transfer power to compatible devices without the need for physical connections

CHAPTER 1: INTRODUCTION

1 Overview

1.1 Introduction to the topic

The battery is charged with a small amount of AC voltage or DC voltage The AC source is given to the step down transformer which converts the large AC source into a limited AC source, filters the AC voltage and removes the noise and gives that voltage to the SCR where it rectifies the AC and gives the resulting voltage to the battery for charging

1.2 Battery charger

A battery charger is a device used to put energy into a secondary cell or (rechargeable) battery by forcing an electric current through it The charge current depends upon the technology and capacity of the battery being charged

The battery charger consists of a separate boost charger and separate float charger The boost charger is of silicon diode type and float is of thyristor type The booster charger is meant to boost the battery When it is first commissioned, when the battery is discharged completely Float Charger is meant for feeding regulated 220v DC supply to

DC loads like breakers, coils, memory circuits, emergency lights, pump sets Etc Operating on DC voltage and also to trickle charge the 220v battery both boost and Float charger work on 3-phase, 415v, 50 Hz, 4-wire AC input supply

1.3 SCR operating modes and Application

To turn on the SCR the small amount of voltage or voltage equal to break over voltage is required to the gate which will trigger the SCR and when the SCR is turned on,

it will have very low resistance and allow the power to conduct and also increase the anode current Even if we remove the gate voltage also it will be in conduction The only way to make the SCR turn off is to make the voltage to zero or make the current less than the handling current between the anode and cathode

There are two ways to turn on the SCR The first way is to turn on by opening the gate and compensating the power supply to the break over voltage And the second way is

to supply the voltage to operate the SCR with less than break over voltage and apply the small amount of about 1.5V applied to the gate which will trigger the SCR

When the SCR is turned off it will have high resistance and restrict the current to the leakage current To turn off the SCR from one state also has only one way Normally people think that if we stop the gate current the SCR will turn off, but it will not this state

is called “loss of control”, the only way to turn off the SCR is reducing the supply voltage

to zero

SCR as Switch: SCR can be used as switch, because SCR has two states ON and OFF states We know that to turn on the SCR we need to increase the supply voltage equal to break over voltage or by giving the small voltage to the gate for triggering, by this we can turn on the SCR; we can turn off the SCR by decreasing the current to less than holding current, or we have another method called force communication in this we discharge a capacitor in parallel with SCR to make it turn off; by this we can use SCR as typical SWITCH There are a lot of advantages using SCR as a switch, like

- Switching speed of SCR is very high, like switching operation per second

- It allows huge current up to 100 m through the load just by triggering the gate with very low voltage to turn it on

- Small in size and has low noise which gives high efficiency and reliability SCR can be used in half wave rectifiers, full wave rectifiers, inverter circuits, power control circuits, static contactor, over light detector, speed control circuit, crowbar circuit, automobile ignition circuits, etc

2 Market Research

Different Types of Battery Chargers

As technology has advanced, so too have the various types of battery chargers Here

is a look at some of the different types of battery chargers on the market:

Figure 1 Battery Charger – LiFePO4, Li-ion, Ni-MH, Ni-Cd

Figure 3 Panasonic AA/AAA Charger With 4 Eneloop AA Batteries

Figure 4 Fast Battery Charger AA/AAA

3 Electrical Characteristics

Table 1 Electrical Characteristics

CHAPTER 2: METHODOLOGY

1.Type of methodology

1.1 Classified according to research function

- Descriptive research

- Explanatory research

- Solution research

- Forecasting research

1.2 Classified according to the stages of the study

- Fundamental research

- Applied research

- Technological Experimental research

2.Our methodology

Figure 5 Methodology

CHAPTER 3: SYSTEM DESIGN

1 Block diagram

Figure 6 Block Diagram

This whole circuit consists of a 220V AC source, which will require a transformer

to break the Voltage down to 15V, and a combination of 4 diodes to transform it to DC so that the battery can make use of it

The SCR is for the automatic stopping function whenever the battery is full

2 Circuit diagram

Figure 7 Circuit diagram

This circuit consist of :

- 220V/50hz AC source

- 1 transformer 15V-3A

- 1 combination of 4 diodes

- 2 SCR to control how this circuit will stop the charging of battery

- 1 conductor to filter the current

- Some LEDs to indicate some important timelines of the charging process

- Many resistor to protect the diodes

- 1 12V battery

There are many methods to make a charging circuit for a battery But if the requirement is using direct voltage from the plug, we have to use a transformer 2.1 Transformer

Most important transformer has 2 parameters: how much voltage and current capacity For this circuit purpose we will use a 15V 3A transformer The transformer has primary and secondary coils The primary side is to supply 220VAC (mains power, i.e taken from the household's electrical outlet), and the secondary side is often left out The primary side: Connects to the 220VAC source by wire-electricity -with a plug (for power supply, of course), here it should be noted that the second side (small voltage) touching it will not die (unless there is a power leak), but the 220VAC secondary side - touching it will die short, so after wiring we need to insulate the terminals to ensure safety

2.2 SCR

The term SCR stands for silicon controlled rectifier which is one of the most important members of the thyristor family It is more popular than the other Thyristors like TRIAC, SCS, DIAC, etc that some people even use the words Thyristor and SCR interchangeably So next time when someone says just “Thyristor” in general, then they are referring to the SCR

SCRs are constructed from silicon and are most commonly used for converting AC current to DC current (rectification), hence the name Silicon controlled rectifier They are also used in other applications such as regulation of power, inversion, etc The SCRs have

an ability to handle high values of current and voltage hence they are used in most of the industrial applications

The SCR has three main terminals: the anode (A), the cathode (K), and the gate (G)

It also has a fourth terminal called the gate-cathode junction (G-K)

In its normal state, the SCR acts as an open circuit, preventing current flow between the anode and the cathode However, when a positive pulse is applied to the gate terminal with respect to the cathode, it triggers the SCR into conduction

Once triggered, the SCR "latches" into a conducting state even if the gate signal is removed It remains conducting until the current flowing through it drops below a threshold called the holding current or until the anode-cathode voltage drops to zero

To turn off an SCR that is conducting, the anode-cathode current must be reduced below the holding current or the anode-cathode voltage must be reduced to zero This process is known as commutation

SCRs are often used in applications such as motor control, power regulation, and

AC power switching, where they can handle high currents and voltages

It's important to note that the detailed operation and characteristics of an SCR can be more complex, involving concepts such as forward and reverse blocking regions, voltage and current ratings, and different modes of triggering However, the basic principle described above provides a general understanding of how an SCR works

3 Working Explanation

First of all, the source is at a very high voltage, with approximately 220V AC, which is taken directly from the electric mesh If we use this voltage to directly charge the battery, it will break the battery completely That is where the transformer comes into the play With modern transformers, it can effectively transform the 220V AC into the 15V

AC, which is perfect for our battery health

The problem is, it is still AC, and the battery requires DC to work with, that is why

we need a system of 4 diodes to effectively transform the AC source into DC source The AC supply is converted to 15V DC with the help of a transformer and bridge rectifier and the Green LED is turned on The DC output is a pulsating DC as there is no filter after the rectifier The R1 and the green LED is to indicate that the source is connected, and the battery is charging

Let get through some theory quickly, the SCR will not let the current go through it if

it does not receive Gate voltage, not until the current flow through the R2 and D5, and into the SCR1:

Now, the SCR1 is activated and lets the current flow into the battery, and starts charging it

When the charge on the battery is almost full, it opposes the flow of current and the current starts to flow via R5

Now the current is filtered with C1 and when the potential reaches 6.8V, Zener ZD1 starts conducting and supplies enough Gate voltage to SCR2 to turn it on and Red led will

be turned on to indicate that the battery is fully charged

When SCR is turned on all of this mesh will become short circuit and no current flow

in to Gate of SCR1:

Figure 9 Uncharged Current

CHAPTER 4: CALCULATION

Figure 10 Complete diagram

The R1 is to protect the RED LED, and this LED can only take 20mA at maximum

so R1 should be at least: R1min = 15V/20mA = 750 ohm So we choose R1 = 1K Ohm Next, we should calculate R2

For the SCR, we choose the TYN 612 with the spec:

- Irms = 12A

- Igt = 0.2 mA -> 15mA

- Vgt max = 1.5V

We have a function: I*R2 + 0.7 = 15 where 0.2mA < I < 15mA

so 953 < R2 < 71500 => We choose R2 = 1k ohm

We choose The battery to be the Rita 12V9A with the Standby Use Voltage of 13.7

to 13.9V

When the battery is full, the capacitor becomes open circuit cause the source is now become the battery which supplies a voltage of 13.7V

Figure 12 3 meshes

First let’s calculate R5 and R6

As we are using RC firing delay, in theory 1ms <= T <= 10ms and 0.01 uF <= C <=

uF Then we choose C = 1uF We also have an equation: T = (R5 + R6)*C

=> 1ms = (R5 + R6min)*C and R6min = 0 => R5 = 1000 ohm

10ms = (R5 +vR6max)*C => R6 max = 19000 ohm We choose R6 = 20000 ohm

As we only have one capacitor, the minimum delay angle will be 1 * 36° = 36° And the maximum delay angle will be 10*36° = 360°

When the zener is activated, its voltage become 6.8V

For 3 loops, we have these equation:

- I1*(R5 + R6) - I2*R6 = Vbattery

- I2*(R6 + R4) - I3*R4 + 0.7 = -V zener

- I3*R4 - I2*R4 + 0.7 = Vgt max

Then: