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 QuangGROUP 1

TABLE OF CONTENTS

Table of ContentsList of FiguresAbstract

Chapter 1: Introduction1 Overview

1.1 Introduction to the topic1.2 Battery Charger

1.3 SCR operating modes and Application2 Market Research

3 Electrical CharacteristicsChapter 2: Methodology

1 Type of methodology2 Our MethodologyChapter 3: System Design

1 Block Diagram2 Circuit Diagram

2.1 Transformer2.2 SCR

3 Working ExplanationChapter 4: Calculation

Chapter 5: Conclusion and RecommendationReferences

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 variousportable electronic devices With the increasing dependence on technology, the demandfor efficient and reliable battery chargers has grown significantly This abstract providesan overview of battery chargers, their working principles, and the advancements incharging technology.

Battery chargers are devices designed to recharge the batteries of electronic devicessuch as smartphones, laptops, tablets, and cameras, They convert alternating current(AC) from a power outlet into direct current (DC) to charge the batteries The chargingprocess involves several stages, including bulk charging, absorption charging, and floatcharging, 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 andmore efficient chargers Smart chargers utilize microprocessors and advanced algorithmsto monitor and control the charging process 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 an SCR that is periodically gated on for aduration corresponding to the state of charge of the battery, being gated on for a durationcorresponding to the state of charge on the battery being the gated for only a short intervalwhen the battery is essentially fully charged to keep it charged The conduction angle isdetermined from the open circuited battery potential and the previous charging history ofthe battery obtained from potential sensing circuits A pedestal and cosine modified rampcircuit triggers the SCR's through capacitors with a resistor inter coupling the SCR gateand cathode electrodes Circuitry prevents the unipolar junction transistor in the lattercircuit from remaining latched on A potential circuit for determining the rate of chargeincludes a resistor connected to the output terminal that is bypassed when the averagevalue of the signal connected on the collector of the transistor having the base connectedto the output terminal has a predetermined value Diodes inter-couple the SC R's and theemitter of the latter transistor for providing operating potential to the circuits and thestarting charging current to the output terminal when a connected battery is fullydischarged.

Furthermore, fast charging technology has emerged as a significant trend in batterychargers Fast chargers are capable of delivering higher current levels to rechargebatteries at a much faster rate than traditional chargers This technology is particularlybeneficial for users who require quick battery top-ups, reducing downtime and improvingproductivity Another notable innovation in battery charger technology is the integrationof wireless charging capabilities Wireless chargers use induction or resonant technologyto 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 ACsource is given to the step down transformer which converts the large AC source into alimited AC source, filters the AC voltage and removes the noise and gives that voltage tothe SCR where it rectifies the AC and gives the resulting voltage to the battery forcharging.

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 currentdepends 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 boostercharger is meant to boost the battery When it is first commissioned, when the battery isdischarged completely Float Charger is meant for feeding regulated 220v DC supply toDC 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 Floatcharger 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 overvoltage 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 theanode current Even if we remove the gate voltage also it will be in conduction The onlyway to make the SCR turn off is to make the voltage to zero or make the current less thanthe 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 thegate and compensating the power supply to the break over voltage And the second way isto supply the voltage to operate the SCR with less than break over voltage and apply thesmall 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 theleakage current To turn off the SCR from one state also has only one way Normallypeople 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 voltageto zero.

SCR as Switch: SCR can be used as switch, because SCR has two states ON andOFF states We know that to turn on the SCR we need to increase the supply voltageequal to break over voltage or by giving the small voltage to the gate for triggering, bythis we can turn on the SCR; we can turn off the SCR by decreasing the current to lessthan holding current, or we have another method called force communication in this wedischarge a capacitor in parallel with SCR to make it turn off; by this we can use SCR astypical 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, powercontrol 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 Hereis 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

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 transformerto break the Voltage down to 15V, and a combination of 4 diodes to transform it to DC sothat 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

2.2 SCR

The term SCR stands for silicon controlled rectifier which is one of the most importantmembers 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 SCRinterchangeably So next time when someone says just “Thyristor” in general, then theyare referring to the SCR.

SCRs are constructed from silicon and are most commonly used for converting ACcurrent to DC current (rectification), hence the name Silicon controlled rectifier They arealso used in other applications such as regulation of power, inversion, etc The SCRs havean ability to handle high values of current and voltage hence they are used in most of theindustrial 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 betweenthe anode and the cathode However, when a positive pulse is applied to the gate terminalwith respect to the cathode, it triggers the SCR into conduction.

Once triggered, the SCR "latches" into a conducting state even if the gate signal isremoved It remains conducting until the current flowing through it drops below athreshold 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 reducedbelow the holding current or the anode-cathode voltage must be reduced to zero Thisprocess is known as commutation.

SCRs are often used in applications such as motor control, power regulation, andAC 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 bemore complex, involving concepts such as forward and reverse blocking regions, voltageand current ratings, and different modes of triggering However, the basic principledescribed 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 thebattery, it will break the battery completely That is where the transformer comes into theplay With modern transformers, it can effectively transform the 220V AC into the 15VAC, which is perfect for our battery health.

The problem is, it is still AC, and the battery requires DC to work with, that is whywe 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 bridgerectifier and the Green LED is turned on The DC output is a pulsating DC as there is nofilter after the rectifier The R1 and the green LED is to indicate that the source isconnected, and the battery is charging.

Let get through some theory quickly, the SCR will not let the current go through it ifit does not receive Gate voltage, not until the current flow through the R2 and D5, andinto the SCR1:

Now, the SCR1 is activated and lets the current flow into the battery, and startscharging it.

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

Now the current is filtered with C1 and when the potential reaches 6.8V, Zener ZD1starts conducting and supplies enough Gate voltage to SCR2 to turn it on and Red led willbe 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 flowin 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 maximumso 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 < 15mAso 953 < R2 < 71500 => We choose R2 = 1k ohm.

We choose The battery to be the Rita 12V9A with the Standby Use Voltage of 13.7to 13.9V.

When the battery is full, the capacitor becomes open circuit cause the source is nowbecome 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 6.8VFor 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 maxThen:

I1 = 0.333 mA

and 52 <= R4 <= 1496.33 So we choose R4 = 1k ohmConclusion:

● R1 = 1000 ohm.● R2 = 1000 ohm.● R5 = 1000 ohm.● R6 = 20000 ohm.● R4 = 1000 ohm.● C = 1uF

CHAPTER 5: CONCLUSION & RECOMMENDATION

In conclusion, the battery charger report project highlighted the importance ofunderstanding the charging process and its impact on battery life Through the analysis ofdifferent charging methods, it was evident that slow and controlled charging resulted inlonger battery lifespan compared to fast charging methods Additionally, the projectrevealed the significance of using the correct charging voltage and current to preventdamage to batteries.

Based on the findings of the project, it is recommended to design and developbattery chargers that incorporate slow and controlled charging methods This approachwill not only extend the battery lifespan but also ensure the safety of the charging process.Furthermore, it is crucial to educate consumers and raise awareness about the negativeeffects of fast charging on battery health.

Manufacturers should consider incorporating intelligent charging algorithms in theirbattery chargers to optimize the charging process and prevent overcharging This can beachieved by implementing features such as automatic cut-off when the battery reaches itsmaximum capacity or monitoring the battery's temperature during the charging process.

It is essential for consumers to be provided with clear instructions and guidelines onproper battery charging and maintenance This will help prevent common mistakes, suchas using incompatible chargers or over the batteries.

Overall, the battery charger report project emphasized the need for a more carefuland informed approach to battery charging By adopting slow and controlled chargingmethods and promoting consumer education, we can ensure the longevity and optimalperformance of batteries in various applications.