DESIGN AND CONSTRUCTION OF A UNIVERSAL TRANSFORMERLESS BATTERY CHARGER

KOMMEY OBLITEY NIIANDOH RICHMOND

ASIEDU OTENG BRIGHT

SUBMITTED IN PARTIAL FULFILMENT FOR THE AWARD OF HIGHER NATIONAL DIPLOMA IN ELECTRICAL/ELECTRONICS

ENGINEERING

DEPARTMENT OF ELECRICAL/ELECTRONICS ENGINEERING ACCRA POLYTECHNIC

SEPTEMBER 2008

CERTIFICATION BY SUPERVISOR

I hereby certify that this project work was carried out under my

supervision. I therefore approve that the work is adequate in scope

and quality for the partial fulfillment of the requirement for the award

of a Higher National Diploma (HND) in Electrical/Electronics

Engineering.

SUPERVISOR: F. E. YEBOAH

SIGN…………………………….

DATE……………………………

I

DEDICATION

This project is dedicated to our beloved parents: Mr. and Mrs.

Kommey, Asiedu, Andoh for their untiring love and support

throughout our educational life. Also, our sincere thanks and

dedication goes to all those who supported us through advices and

finances.

II

DECLARATION

I Kommey, Andoh, Asiedu. Declares that the work was undertaken

whilst in Accra Polytechnic.

I further affirm that, this work so far as I know has not been

submitted to any institution for the award of any certificate and the

source of information has been fully acknowledged

NAME: SIGN:

Kommey Oblitey Nii …………………….

Andoh Richmond …………………….

Asiedu Oteng Bright ………………………

III

ACKNOWLEDGEMENT

To GOD be the glory for HIS grace, wisdom, guidance and counsel

which enabled us to produce this work. Our second appreciation

and gratitude goes to our supervisor Mr. F.E. Yeboah the H.O.D. of

Electrical/Electronics Engineering Department whose guidance

enabled us to complete this project

Our profound thanks also goes to Sylvester Delali Dordzi who

through his timeless efforts helped us to build this circuit. Also, to

Calculus, Mrs. Gladys and Mrs. Comfort6 for their financial support

offered us. May the ALMIGHTY GOD bless them.

IV

ABSTRACT

The project in question is a Universal Transformerless Battery

Charger. The charger charges any type of battery irrespective of the

voltage of the battery or the ampage needed by the battery for

charging.

The charger comes with an amp meter which indicated the amount

of current drawn from it as well as a cooling system to maintain less

power loss and ensure maximum performance.

The battery charger charges all kinds of batteries from normal Lead

acid batteries to Gelled maintenance free batteries.

The charger also comes with a volt meter to indicate whether the

battery is fully charged or not.

V

TABLE OF CONTENTS

CONTENT PAGE

CHAPTER ONE

1.1 INTRODUCTION 1

1.2 BACKGROUND 2

1.3 DEFINATION 3

1.4 OBJECTIVES 4

1.5 SIGNIFICANCE OF STUDY 5

1.6 METHOLOGY 6

CHAPTER TWO

2.1 STAGES OF OPERATION 7

2.2 SWITCHING 7

2.3 PULSE GENERATION/ENERGY STORAGE 17

2.4 RECTIFICATION 30

2.5 SMOOTHING 35

2.6 OVERLOAD PROTECTION 38

CHAPTER THREE

3.1 BLOCK DIAGRAM/SCHEMATIC DIAGRAM 44

VI

3.2 COMPONENT LIST 45

3.3 CABLE SELECTION 47

3.4 RECORMENDERED LOAD 48

3.5 LIMITATIONS 49

CHAPTER FOUR

VII

CHAPTER ONE

1.1 INTRODUCTION

Over the years charging of automobile batteries has been very

challenging considering the variety of batteries and their charging

requirement. For example Flooded Lead acid batteries and Deep

Cycle maintenance free batteries are totally different. This is

because the flooded Lead acid battery needs more hash power than

the maintenance free batteries. The common method mostly used is

the transformer – Rectifier Charger which is not designed to suit a

particular Battery. The transformer or diode would burn instead of

just releasing what ever is available at that time, it would force to

charge the battery and so ending up burning.

But for this project, Universal Transformerless Multi purpose

charge, no matter the number of batteries there’s no fears, because

if takes it time to release power for charging according to the type of

batteries connection and the sum up voltage of the Batteries.

1

1.2 BACKGROUND

Over the last two decades decade, the conversional transformer

charger has been the main system for charging Automobile

batteries.

This charger came with a lot of limitations like

1. Overheating: this was as a result of mismatch between the

rating of the charger and the current drawn by the battery for

charging.

2. High Power loss: this was due to the overheating of the

transformer and the rectifier.

3. Limited Voltage Rating: this is because the output voltage

rating was already determined by the transformer and couldn’t

be extended to suit a different voltage rating.

To eliminate this problem, the need for a charging system which is

void of this entire problem was invented. The new charging system

(Universal Transformerless Battery Charger) was invented to

increase the voltage rating range and also help reduce the amount

of power needed to charge an automobile battery.

2

1.3 DEFINITION

The Universal Transformerless Battery Charger is a lightweight,

efficient, transformerless battery-charging system especially for use

with electric vehicles and the charging of automobile batteries

wherein a switching regulator (ac capacitor) stores only a fraction of

the energy in each charging pulse, and much of the charging energy

is supplied directly from that power line and never stored in the

charger but is then rectified by a bridge diode to change it from the

AC(alternating current) pulse to DC(direct current) for usage.

3

1.4 OBJECTIVES

This project is designed to reduce the casualty of Battery Charger

burning because more current was demanded by a battery. If also

seeks to make battery charging easy by making it charge battery

bank arrangements from 12V DC to 220V DC without altering any

change operational wise or replace any component before achieving

the desired output voltage rating needed for charging any battery. It

also seeks to reduce cost and weight of battery charger making it

mobile and cheap.

4

1.5 SIGNIFICANCE OF STUDY

The significance of studying this project is to eliminate the major

problems of the old conversional AC to DC battery charger which

comprises of a transformer, diode and a capacitor. This OLD system

is gradually failing because of the numerous problems it brings to its

users.

It is to this effect that this study would help bring out a charging

system which is free of

1. Overloading

2. Overheating

3. Burning

4. High Power Loss Due to Eddy Current

5. Limited Output Voltage Rating

It is our believe that at the end of this study all this problems

associated with the old conversional charging system would be

eliminated.

5

1.6 METHODOLOGY

220 volts AC is connected in series to a capacitor making the AC

tire which passes through the capacitor to make behave like a pulse

which created when a capacitor charges but are discharge. Since

power cannot pass through the charger but only store electrical

power. The output from the capacitor is series to the rectifier,

changes the power to zero Hz making it conductive for battery

charge. The diode only used power stored in the capacitor. This

procedure continues until capacitor charges to full charge.

All important information needed for this project to takeoff was

acquired form two main source namely primary and secondary

sources.

Primary source were sources were the personal interactions with my

supervisor and workers of a well equipped and well knowledgeable

on this project.

Secondary sources were the research at the library and the internet.

6

CHAPTER TWO

2.1 STAGES OF OPERATION

In the manufacturing of this project, three main processes

are involved. The processes are

(a) Switching

(b) Pulse Generation/Energy Storage

(c) Rectification

(d) Smoothing

(e) Overload Protection

2.2 (a) Switching

Since the output of the charger is regulated by the battery it

can be very dangerous when the power probes are not

connected to the battery before switching it on.

To avoid this problem relays are placed in to switch the

system when a battery is connected or is sensed by the

charger.

For this switching system DC powered relays best

recommended.

7

RELAYS

A relay is an electrical switch that opens and closes under the

control of another electrical circuit. In the original form, the switch is

operated by an electromagnet to open or close one or many sets of

contacts. It was invented by Joseph Henry in 1835. Because a relay

is able to control an output circuit of higher power than the input

circuit, it can be considered to be, in a broad sense, a form of an

electrical amplifier.

8

OPERATION

When a current flows through the coil, the resulting magnetic field

attracts an armature that is mechanically linked to a moving contact.

The movement either makes or breaks a connection with a fixed

contact. When the current to the coil is switched off, the armature is

returned by a force approximately half as strong as the magnetic

force to its relaxed position. Usually this is a spring, but gravity is

also used commonly in industrial motor starters. Most relays are

manufactured to operate quickly. In a low voltage application, this is

to reduce noise. In a high voltage or high current application, this is

to reduce arcing.

If the coil is energized with DC, a diode is frequently installed across

the coil, to dissipate the energy from the collapsing magnetic field at

deactivation, which would otherwise generate a spike of voltage and

might cause damage to circuit components. Some automotive relays

already include that diode inside the relay case. Alternatively a

contact protection network, consisting of a capacitor and resistor in

series, may absorb the surge. If the coil is designed to be energized

with AC, a small copper ring can be crimped to the end of the

solenoid. This "shading ring" creates a small out-of-phase current,

which increases the minimum pull on the armature during the AC

cycle

9

By analogy with the functions of the original electromagnetic device,

a solid-state relay is made with a thyristor or other solid-state

switching device. To achieve electrical isolation an optocoupler can

be used which is a light-emitting diode (LED) coupled with a photo

transistor.

TYPES OF RELAY

1. Latching relay: A latching relay has two relaxed states

(bistable). These are also called 'keep' or 'stay' relays.

2. Reed relay: A reed relay has a set of contacts inside a

vacuum or inert gas filled glass tube, which protects the

contacts against atmospheric corrosion.

3. Mercury-wetted relay: A reed relay has a set of contacts

inside a vacuum or inert gas filled glass tube, which

protects the contacts against atmospheric corrosion. Such

relays are used to switch low-voltage signals (one volt or

less) because of its low contact resistance, or for high-

speed counting and timing applications where the mercury

eliminates contact bounce.

4. Polarized relay: A Polarized Relay placed the armature

between the poles of a permanent magnet to increase

sensitivity

10

5. Machine tool relay: A machine tool relay is a type

standardized for industrial control of machine tools, transfer

machines, and other sequential control.

6. Contactor relay: A contactor is a very heavy-duty relay

used for switching electric motors and lighting loads. With

high current, the contacts are made with pure silver. The

unavoidable arcing causes the contacts to oxidize and

silver oxide is still a good conductor.

7. Solid state contactor relay: A solid state contactor is a

very heavy-duty solid state relay, including the necessary

heat sink, used for switching electric heaters, small electric

motors and lighting loads; where frequent on/off cycles are

required.

8. Buchholz relay: A Buchholz relay is a safety device

sensing the accumulation of gas in large oil-filled

transformers, which will alarm on slow accumulation of gas

or shut down the transformer if gas is produced rapidly in

the transformer oil.

9. Forced-guided contacts relay: A forced-guided

contacts relay has relay contacts that are mechanically

linked together, so that when the relay coil is energized or

de-energized, all of the linked contacts move together.

11

10. Solid-state relay: A solid state relay (SSR) is a solid state

electronic component that provides a similar function to an

electromechanical relay but does not have any moving

components, increasing long-term reliability. With early

SSR's, the tradeoff came from the fact that every transistor

has a small voltage drop across it

11. Overload protection relay: One type of electric motor

overload protection relay is operated by a heating element

in series with the electric motor . The heat generated by the

motor current operates a bi-metal strip or melts solder,

releasing a spring to operate contacts. Where the overload

relay is exposed to the same environment as the motor, a

useful though crude compensation for motor ambient

temperature is provided

12

APPLICATIONS

Relays are used:

to control a high-voltage circuit with a low-voltage signal, as in

some types of modems or audio amplifiers,

to control a high-current circuit with a low-current signal, as in

the starter solenoid of an automobile,

to detect and isolate faults on transmission and distribution

lines by opening and closing circuit breakers (protection

relays),

to isolate the controlling circuit from the controlled circuit when

the two are at different potentials, for example when

controlling a mains-powered device from a low-voltage switch.

The latter is often applied to control office lighting as the low

voltage wires are easily installed in partitions, which may be

often moved as needs change. They may also be controlled

by room occupancy detectors in an effort to conserve energy,

to perform logic functions. For example, the Boolean AND

function is realized by connecting NO relay contacts in series,

the OR function by connecting NO contacts in parallel. The

change-over or Form C contacts perform the XOR (exclusive

or) function. Similar functions for NAND and NOR are

accomplished using NC contacts. The Ladder programming

language is often used for designing relay logic networks

13

o Early computing. Before vacuum tubes and transistors,

relays were used as logical elements in digital

computers. See ARRA (computer), Harvard Mark II,

Zuse Z2, and Zuse Z3.

o Safety-critical logic. Because relays are much more

resistant than semiconductors to nuclear radiation, they

are widely used in safety-critical logic, such as the

control panels of radioactive waste-handling machinery.

to perform time delay functions. Relays can be modified to

delay opening or delay closing a set of contacts. A very short

(a fraction of a second) delay would use a copper disk

between the armature and moving blade assembly. Current

flowing in the disk maintains magnetic field for a short time,

lengthening release time. For a slightly longer (up to a minute)

delay, a dashpot is used. A dashpot is a piston filled with fluid

that is allowed to escape slowly. The time period can be varied

by increasing or decreasing the flow rate. For longer time

periods, a mechanical clockwork timer is installed.

Relay application considerations

Selection of an appropriate relay for a particular application requires

evaluation of many different factors:

14

Number and type of contacts - normally open, normally closed,

(double-throw)

There are two types. This style of relay can be manufactured

two different ways. "Make before Break" and "Break before

Make". The old style telephone switch required Make-before-

break so that the connection didn't get dropped while dialing

the number. The railroad still uses them to control railroad

crossings.

Rating of contacts - small relays switch a few amperes, large

contactors are rated for up to 3000 amperes, alternating or

direct current

Voltage rating of contacts - typical control relays rated 300

VAC or 600 VAC, automotive types to 50 VDC, special high-

voltage relays to about 15,000 V

Coil voltage - machine-tool relays usually 24 VAC or 120 VAC,

relays for switchgear may have 125 V or 250 VDC coils,

"sensitive" relays operate on a few milliamperes

Package/enclosure - open, touch-safe, double-voltage for

isolation between circuits, explosion proof, outdoor, oil-splash

resistant

Mounting - sockets, plug board, rail mount, panel mount,

through-panel mount, enclosure for mounting on walls or

equipment

15

Switching time - where high speed is required

"Dry" contacts - when switching very low level signals, special

contact materials may be needed such as gold-plated contacts

Contact protection - suppress arcing in very inductive circuits

Coil protection - suppress the surge voltage produced when

switching the coil current

Isolation between coil circuit and contacts

Aerospace or radiation-resistant testing, special quality

assurance

Expected mechanical loads due to acceleration - some relays

used in aerospace applications are designed to function in

shock loads of 50 g or more

Accessories such as timers, auxiliary contacts, pilot lamps,

test buttons

Regulatory approvals

Stray magnetic linkage between coils of adjacent relays on a

printed circuit board.

16

2.3 (b)Pulse Generation/Energy Storage

In the charging process after the relay have sensed a

battery and has competed the switching process, the mains

is connected in series with a capacitor to the diode for

rectification.

Because the power can not pass through the capacitor

directly, it is released in bits thus not releasing power until it

is fully charge and will stay in that mode until all the power

has been used before it would allow another power to enter

for storage. The routine continuous, creating a waveform in

pulses.

Since high voltage like 220vac is connected in series to the

capacitor it is important to use only AC capacitor with

minimum rating of 300volts and a charge capacitance of

50uf for good frequency of pulses.

Electrolytic capacitors can not be used for this system

because it has polarity and can only be used for a DC

(Direct Current) application.

17

CAPACITOR

A capacitor is an electrical/electronic device that can store energy

in the electric field between a pair of conductors (called "plates").

The process of storing energy in the capacitor is known as

"charging", and involves electric charges of equal magnitude, but

opposite polarity, building up on each plate.

Capacitors are often used in electric and electronic circuits as

energy-storage devices. They can also be used to differentiate

between high-frequency and low-frequency signals. This property

makes them useful in electronic filters.

Capacitors are occasionally referred to as condensers. This term is

considered archaic in English, but most other languages use a

cognate of condenser to refer to a capacitor.

Capacitor types

Practical capacitors are available commercially in many different

forms. The type of internal dielectric, the structure of the plates and

the device packaging all strongly affect the characteristics of the

capacitor, and its applications.

18

AC CAPACITOR

Capacitors do not behave the same as resistors. Whereas resistors

allow a flow of electrons through them directly proportional to the

voltage drop, capacitors oppose changes in voltage by drawing or

supplying current as they charge or discharge to the new voltage

level. The flow of electrons “through” a capacitor is directly

proportional to the rate of change of voltage across the capacitor.

This opposition to voltage change is another form of reactance, but

one that is precisely opposite to the kind exhibited by inductors.

Expressed mathematically, the relationship between the current

“through” the capacitor and rate of voltage change across the

capacitor is as such:

The expression de/dt is one from calculus, meaning the rate of

change of instantaneous voltage (e) over time, in volts per second.

The capacitance (C) is in Farads, and the instantaneous current (i),

of course, is in amps. Sometimes you will find the rate of

instantaneous voltage change over time expressed as dv/dt instead

of de/dt: using the lower-case letter “v” instead or “e” to represent

voltage, but it means the exact same thing.

19

To show what happens with alternating current, let's analyze a

simple capacitor circuit: (Figure below)

Pure capacitive circuit: capacitor voltage lags capacitor current by 90o

If we were to plot the current and voltage for this very simple circuit,

it would look something like this: (Figure below)

Pure capacitive circuit waveforms.

Remember, the current through a capacitor is a reaction against the

change in voltage across it. Therefore, the instantaneous current is

zero whenever the instantaneous

20

voltage is at a peak (zero change, or level slope, on the voltage sine

wave), and the instantaneous current is at a peak wherever the

instantaneous voltage is at maximum change (the points of steepest

slope on the voltage wave, where it crosses the zero line). This

results in a voltage wave that is -90o out of phase with the current

wave. Looking at the graph, the current wave seems to have a

“head start” on the voltage wave; the current “leads” the voltage,

and the voltage “lags” behind the current. (Figure below)

Voltage lags current by 90o in a pure capacitive circuit.

21

As you might have guessed, the same unusual power wave that we

saw with the simple inductor circuit is present in the simple capacitor

circuit, too: (Figure below)

In a pure capacitive circuit, the instantaneous power may be positive

or negative.

As with the simple inductor circuit, the 90 degree phase shift

between voltage and current results in a power wave that alternates

equally between positive and negative. This means that a capacitor

does not dissipate power as it reacts against changes in voltage; it

merely absorbs and releases power, alternately.

A capacitor's opposition to change in voltage translates to an

opposition to alternating voltage in general, which is by definition

always changing in instantaneous magnitude and direction. For any

given magnitude of AC voltage at a given frequency, a capacitor of

given size will “conduct” a certain magnitude of AC current.

22

Just as the current through a resistor is a function of the voltage

across the resistor and the resistance offered by the resistor, the AC

current through a capacitor is a function of the AC voltage across it,

and the reactance offered by the capacitor. As with inductors, the

reactance of a capacitor is expressed in ohms and symbolized by

the letter X (or XC to be more specific).

Since capacitors “conduct” current in proportion to the rate of

voltage change, they will pass more current for faster-changing

voltages (as they charge and discharge to the same voltage peaks

in less time), and less current for slower-changing voltages. What

this means is that reactance in ohms for any capacitor is inversely

proportional to the frequency of the alternating current. (Table

below)

Reactance of a 100 uF capacitor:

Frequency (Hertz) Reactance (Ohms)

60 26.5258

120 13.2629

2500 0.6366

23

Please note that the relationship of capacitive reactance to

frequency is exactly opposite from that of inductive reactance.

Capacitive reactance (in ohms) decreases with increasing AC

frequency. Conversely, inductive reactance (in ohms) increases with

increasing AC frequency. Inductors oppose faster changing currents

by producing greater voltage drops; capacitors oppose faster

changing voltage drops by allowing greater currents

As with inductors, the reactance equation's 2πf term may be

replaced by the lower-case Greek letter Omega (ω), which is

referred to as the angular velocity of the AC circuit. Thus, the

equation XC = 1/(2πfC) could also be written as XC = 1/(ωC), with ω

cast in units of radians per second.

Alternating current in a simple capacitive circuit is equal to the

voltage (in volts) divided by the capacitive reactance (in ohms), just

as either alternating or direct current in a simple resistive circuit is

equal to the voltage (in volts) divided by the resistance (in ohms).

The following circuit illustrates this mathematical relationship by

example: (Figure below)

Capacitive reactance.

24

However, we need to keep in mind that voltage and current are not

in phase here. As was shown earlier, the current has a phase shift

of +90o with respect to the voltage. If we represent these phase

angles of voltage and current mathematically, we can calculate the

phase angle of the capacitor's reactive opposition to current.

25

Voltage lags current by 90o in an inductor.

Mathematically, we say that the phase angle of a capacitor's

opposition to current is -90o, meaning that a capacitor's opposition to

current is a negative imaginary quantity. (Figure above) This phase

angle of reactive opposition to current becomes critically important in

circuit analysis, especially for complex AC circuits where reactance

and resistance interact. It will prove beneficial to represent any

component's opposition to current in terms of complex numbers, and

not just scalar quantities of resistance and reactance.

26

HAZARDS AND SAFETY

Capacitors may retain a charge long after power is removed from a

circuit; this charge can cause shocks (sometimes fatal) or damage

to connected equipment. For example, even a seemingly innocuous

device such as a disposable camera flash unit powered by a 1.5 volt

AA battery contains a capacitor which may be charged to over 300

volts. This is easily capable of delivering an extremely painful (and

possibly deadly) shock.

Care must be taken to ensure that any large or high-voltage

capacitor is properly discharged before servicing the containing

equipment. For board-level capacitors, this is done by placing a

bleeder resistor across the terminals, whose resistance is large

enough that the leakage current will not affect the circuit, but small

enough to discharge the capacitor shortly after power is removed.

High-voltage capacitors should be stored with the terminals shorted,

since temporarily discharged capacitors can develop potentially

dangerous voltages when the terminals are left open-circuited, due

to ambient static electricity and dielectric absorption.

Large oil-filled old capacitors must be disposed of properly as some

contain polychlorinated biphenyls (PCBs). It is known that waste

PCBs can leak into groundwater under landfills.

27

If consumed by drinking contaminated water, PCBs are

carcinogenic, even in very tiny amounts. If the capacitor is physically

large it is more likely to be dangerous and may require precautions

in addition to those described above. New electrical components are

no longer produced with PCBs. ("PCB" in electronics usually means

printed circuit board, but the above usage is an exception.)

Capacitors containing PCB were labeled as containing "Askarel" and

several other trade names.

Aging Capacitor

The capacitance of certain capacitors decreases as the component

ages. In ceramic capacitors, this is caused by degradation of the

dielectric. The type of dielectric and the ambient operating and

storage temperatures are the most significant aging factors, while

the operating voltage has a smaller effect. The aging process may

be reversed by heating the component above the Curie point. Aging

is fastest near the beginning of life of the component, and the device

stabilizes over time.[2] Electrolytic capacitors age as the electrolyte

evaporates. In contrast with ceramic capacitors, this occurs towards

the end of life of the component.

28

REVIEW:

Capacitive reactance is the opposition that a capacitor

offers to alternating current due to its phase-shifted storage

and release of energy in its electric field. Reactance is

symbolized by the capital letter “X” and is measured in ohms

just like resistance (R).

Capacitive reactance can be calculated using this formula:

XC = 1/(2πfC)

Capacitive reactance decreases with increasing frequency.

In other words, the higher the frequency, the less it opposes

(the more it “conducts”) the AC flow of electrons.

29

2.4 (c)Rectification

After the capacitor had stored the power it now necessary to rectify

the out put from AC to DC for easy acceptance by the battery for

charging.

Rectification

The purpose of the rectifier section is to convert the incoming

ac power source via the capacitor to change it to some kind of

pulsating dc. That is, it takes current that flows alternately in

both directions as shown in the first figure to the right, and

modifies it so that the output current flows only in one direction,

as shown in the second and third figures below.

The circuit required to do this may be nothing more than a

single diode, or it may be considerably more complex.

However, all rectifier circuits may be classified into one of two

categories, as follows:

30

Half-Wave Rectifiers: An easy way to convert ac to pulsating dc is

to simply allow half of the ac cycle to pass, while blocking current to

prevent it from flowing during the other half cycle. The figure to the

right shows the resulting output. Such circuits are known as half-

wave rectifiers because they only work on half of the incoming ac

wave. 

Full-Wave Rectifiers.

The more common approach is to manipulate the incoming ac wave

so that both halves are used to cause output current to flow in the

same direction. The resulting waveform is shown to the right.

Because these circuits operate on the entire incoming ac wave, they

are known as full-wave rectifiers.

Rectifier circuits may also be further classified according to

their configuration, as we will see below.

31

Bridge Diode

A bridge diode or bridge rectifier is an arrangement of four diodes

connected in a bridge circuit that provides the same polarity of

output voltage for any polarity of the input voltage. When used in its

most common application, for conversion of alternating current (AC)

input into direct current (DC) output, it is known as a bridge rectifier.

The bridge rectifier provides full wave rectification from a two wire

AC input (saving the cost of a center tapped transformer) but has

two diode drops rather than one reducing efficiency over a center

tap based design for the same output voltage.

The essential feature of this arrangement is that for both polarities of the voltage at the bridge input, the polarity of the output is constant.

The diode bridge circuit is also known as the Graetz circuit after its inventor, the physicist Leo Graetz.

32

Full-wave Rectifier

The half-wave rectifier chopped off half our signal. A full-wave

rectifier does more clever trick: it flips the - half of the signal up into

the + range. When used in a power supply, the full-wave rectifier

allows us to convert almost all the incoming AC power to DC. The

full-wave rectifier is also the heart of the circuitry that allows sensors

to attach to the RCX in either polarity.

A full-wave rectifier uses a diode bridge, made of four diodes, like

this:

At first, this may look just as confusing as the one-way streets of

Boston. The thing to realize is that the diodes work in pairs. As the

voltage of the signal flips back and forth, the diodes shepard the

current to always flow in the same direction for the output.

Here's what the circuit looks like to the signal as it alternates:

33

 

So, if we feed our AC signal into a full wave rectifier, we'll see both

halves of the wave above 0 Volts. Since the signal passes through

two diodes, the voltage out will be lower by two diode drops, or 1.2

Volts.

AC Wave In:

AC Wave Out (Full-Wave Rectified):

If we're interested in using the full-wave rectifier as a DC power

supply, we'll add a smoothing capacitor to the output of the diode

bridge.

34

2.5 (d)Smoothing

Most circuits will require 'smoothing' of the DC output of a rectifier,

and this is a simple matter since it involves only one capacitor, as

shown below

The output waveform in figure 2 shows how smoothing works. 

During the first half of the voltage peaks from the rectifier, when

the voltage increases, the capacitor charges up.  Then, while the

voltage decreases to zero in the second half of the peaks, the

capacitor releases its stored energy to keep the output voltage as

constant as possible.  Such a capacitor is called a 'smoothing' or

'reservoir' capacitor when it is used in this application.

35

Ripple

If the voltage peaks from the rectifier were not continually charging

up the capacitor, it would eventually discharge and the output

voltage would decrease all the way down to 0V.  The discharging

that does occur between peaks gives rise to a small 'ripple' voltage. 

The amount of ripple is affected by a combination of three factors:

36

The value of the capacitor.  The larger the capacitor value,

the more charge it can store, and the slower it will discharge. 

Therefore, smoothing capacitors are normally electrolytic

capacitors with values over 470μF.

The amount of current used by the circuit.  If the circuit

connected to the power supply takes a lot of current, the capacitor

will discharge more quickly and there will be a higher ripple voltage.

The frequency of the peaks.  The more frequent the voltage

peaks from the rectifier, the more often the capacitor will be

charged, and the lower the ripple voltage will be.

If you want to calculate the ripple voltage, you can use this

formula...

Where Vr is the ripple voltage in Volts, I is the current taken by the

circuit in Amps, C is the value of the smoothing capacitor in

Farads, and F is the frequency of the peaks from the full-wave

rectifier, in Hertz.  This frequency will be double the normal mains

frequency, i.e. 100Hz in the case of the UK mains supply, or

120Hz in the case of the US mains supply.The ripple voltage

should not be more than 10% of Vs - if it is, increase the value of

the smoothing capacitor.

37

2.6 (e) Overload Protection

Since the output power of the charger for charging has limitations, it

is important to protect the out put against overloading.

The input of the charger is protected with an appropriate circuit

breaker to prevent the charger from drawing more than 10 Amps.

When the charger draws 220V at 10A the maximum output power

would be

Voltage x Current = P

220V X 10A =2200Watts

The circuit breaker is also to prevent short circuiting.

CIRCUIT BREAKER

A circuit breaker is an automatically-operated electrical switch

designed to protect an electrical circuit from damage caused by

overload or short circuit. Unlike a fuse, which operates once and

then has to be replaced, a circuit breaker can be reset (either

manually or automatically) to resume normal operation. Circuit

breakers are made in varying sizes, from small devices that protect

an individual household appliance up to large switchgear designed

to protect high voltage circuits feeding an entire city.

38

ORIGINS

An early form of circuit breaker was described by Edison in an 1879

patent application, although his commercial power distribution

system used fuses. Its purpose was to protect lighting circuit wiring

from accidental short-circuits and overloads.

OPERATION

All circuit breakers have common features in their operation,

although details vary substantially depending on the voltage class,

current rating and type of the circuit breaker.

The circuit breaker must detect a fault condition; in low-voltage

circuit breakers this is usually done within the breaker enclosure.

39

Circuit breakers for large currents or high voltages are usually

arranged with pilot devices to sense a fault current and to operate

the trip opening mechanism.

The trip solenoid that releases the latch is usually energized by a

separate battery, although some high-voltage circuit breakers are

self-contained with current transformers, protection relays, and an

internal control power source.

Once a fault is detected, contacts within the circuit breaker must

open to interrupt the circuit; some mechanically stored energy within

the breaker is used to separate the contacts, although some of the

energy required may be obtained from the fault current itself. The

stored energy may be in the form of springs or compressed air.

Small circuit breakers may be manually operated; larger units have

solenoids to trip the mechanism, and electric motors to restore

energy to the springs.

The circuit breaker contacts must carry the load current without

excessive heating, and must also withstand the heat of the arc

produced when interrupting the circuit. Contacts are made of copper

or copper alloys, silver alloys, and other materials. Service life of the

contacts is limited by the erosion due to interrupting the arc.

40

Miniature circuit breakers are usually discarded when the contacts

are worn, but power circuit breakers and high-voltage circuit

breakers have replaceable contacts.

Short circuit current

Circuit breakers are rated both by the normal current that are

expected to carry, and the maximum short-circuit current that they

can safely interrupt.

Under short-circuit conditions, a current many times greater than

normal can exist (see maximum prospective short circuit current).

When electrical contacts open to interrupt a large current, there is a

tendency for an arc to form between the opened contacts, which

would allow the current to continue. Therefore, circuit breakers must

incorporate various features to divide and extinguish the arc.

The maximum short-circuit current that a breaker can interrupt is

determined by testing. Application of a breaker in a circuit with a

prospective short-circuit current higher than the breaker's

interrupting capacity rating may result in failure of the breaker to

safely interrupt a fault. In a worst-case scenario the breaker may

successfully interrupt the fault, only to explode when reset, injuring

the technician.

41

Miniature circuit breakers used to protect control circuits or small

appliances may not have sufficient interrupting capacity to use at a

panel board; these circuit breakers are called "supplemental circuit

protectors" to distinguish them from distribution-type circuit

breakers.

Low voltage circuit breakers

Small circuit breakers are either installed directly in equipment, or

are arranged in a breaker panel.

The 10 ampere DIN rail-mounted thermal-magnetic miniature circuit

breaker is the most common style in modern domestic consumer

units and commercial electrical distribution boards throughout

Europe. The design includes the following components:

42

1. Actuator lever - used to manually trip and reset the circuit

breaker. Also indicates the status of the circuit breaker (On or

Off/tripped). Most breakers are designed so they can still trip

even if the lever is held or locked in the on position. This is

sometimes referred to as "free trip" or "positive trip" operation.

2. Actuator mechanism - forces the contacts together or apart.

3. Contacts - Allow current when touching and break the current

when moved apart.

4. Terminals

5. Bimetallic strip

6. Calibration screw - allows the manufacturer to precisely adjust

the trip current of the device after assembly.

7. Solenoid

8. Arc divider / extinguisher

43

CHAPTER THREE

3.1 Block /Schematic Diagram

S2

S1

F1

+Ve

0V

D2

+

C3

0V

220V IN

C2

C1

D1

RLY1

44

220 Volts AC Source

Pulse Changer Capacitor

RectifierTo Battery

3.2 COMPONENT LIST

PARTS QUANTITY DESCRIPTION

220VAC brushless Fan 1 Force Air Cooling system

AC light 1 Power on indicator

C1,C2 2 450uF 50VAC AC capacitor

C3 1 450V/330UF

S1,S2 2 Single Pole Double Throw

switch with 10A contact

F1 1 32 amps Breaker

For protection against over

current

100amps amp meter 1 Measuring Output Current

D1,D2 2 8811 MEXICO 8278909

Bridge diode converts AC to

DC.

300Volts Voltmeter 1 Measuring Output voltage

60Amps connectors 1 DC output connection

5” Grill 1 Cover for FAN

Heatsink 1 4” Aluminum Heat sink with

light fins

45

DC cable 1 2yards of 10mm Auto flex

cable

Battery tags 1 Pair of Brass battery tags for

DC output connection

RLY1 1 DPDT Switch

single pole double throw

switch with10Amps contact

NOTE:

R - RESISTOR C - CAPACITOR

T - TRANSFORMER D - DIODE

Q - TRANSISTOR ZD- ZINER DIODE

COMPONENTS SELECTION

For this project the rectifier is to be selected carefully because they

determine the output current and the use of inferable quality would

prevent max output.

46

3.3 CABLE SELECTION

Cables are the main material that connects on component to the

other so it is very important that the right cable is used to deliver the

right amount of power needed at a particular place.

Cables for dc applications should not be less than 6mm in diameter

and colors are also very important because to clearly explain to

someone the type of signal passing through the cable whether it is

positive or negative. For example a Red cable clearly explains that

the power passing through the cable is positive.

47

CHAPTER FOUR

4.1 LIMITATIONS

The difficulties involved in getting the major component from a

reliable source was very difficult because all the companies

who manufactures these components do not sell components in

small quantities and it was very hectic getting all these

components.

48

4.2 CIRCUIT CONSTRUCTION

This circuit was first divided into two parts and each stage was

carefully tested with electronics schematic stimulation software and

then assembled.

This circuit was finally tested after all the two parts were puts

together to check and correct its short falls.

Much consideration was given to meter readings or voltages and

current.

49

4.3 GENERAL MODE OF OPERATION

220 volts AC is connected in series to a capacitor making the AC

tire which passes through the capacitor to release the power in

pulses, which created when a capacitor charges but are discharge.

Since power cannot pass through the charger but only store

electrical power. The output from the capacitor is series to the

rectifier, changes the power to zero Hz making it conducive for

battery charge. The diode only used power stored in the capacitor.

This procedure continues until capacitor charges to full charge.

50

4.4 PRECAUTIONS

In other to arrive at a good and a successful project, the following

precautions were taken into consideration:

1. The circuit was built under supervision to ensure accuracy.

2. Do not put the power switch on until a battery is connected to

avoid electrical shock.

3. Do not open this system whiles it is connected to the mains.

4. The right size of cables was used at high current lines like the

main positive input which is connected from and to the battery.

5. The entire component were thoroughly checked and tested for

consistency and efficiency.

6. The project was well housed before handling, due to the

amount power circulating in the system.

7. Correct soldering techniques were ensured as well as the

usage of a correct solder.

8. The right tools and equipment were used for this project.

9. Suitable equivalent replacement of components was ensured

at places where the original components were not available.

51

4.5 CONCLUSION

The use of this type of charger can be dangerous and also friendly

provided it is used correctly.

This charger can be used to charge any battery no mater the

voltage or current demanded.

The use of this could reduce cost, since it is void of burning as

compared to the chargers which uses transformers.

52

SUMMARY

From the above research it has been proven that transformerless

battery charger can be used to replace transformer charger which

has a lot of problems associated with it.

Further research into this project could enhance this system to a

level that the power can even cut whenever the battery gets fully

charged.

Further investment into this project could help to create jobs.

53

RECOMMENDATIONS

My recommendations were based on research made is that this

system can be repackaged to be used in UPS charging system and

also be made to charge large quantity of batteries and even for

industrial application.

54

REFERENCES

1. Carols Advance Electronics and Training Centre.

2. wikipedia English Article on Battery chargers:

Credits to:

The Great Battery Shootout" by Dave Etchells

AN913: Switch-Mode, Linear, and Pulse Charging

Techniques for Li+ Battery in Mobile Phones and

PDAs" Maxim 2001

A New Pulse Battery Charger" by Jean-Michel Cour

fast pulse battery charger" patent 2003

Battery charger with current pulse regulation"

patented 1981 United States Patent 4355275

Pulse-charge battery charger" patented 1997 United

States Patent 5633574

Pulse Maintenance charging."

The pulse power(tm) battery charging system"

Negative Pulse Charge, or "Burp" Charging: Fact or

Fiction?"

Tech Brief: Negative Pulse Charging Myths and Facts

and Negative Pulse Charging: Myths and Facts

55

http://www.sanyo.co.jp/koho/hypertext4-eng/

0704/0418-1e.html, from Sanyo website, and

http://www.stefanv.com/electronics/usb_charger.html

for those that want to build their own.

http://www.usbcell.com/support/faqsection/5, from a

Moixa Energy website

Our Products - usbcell.com

Mobile phone battery care

Ionhub all-in-one universal multi charger multiple

iPhone iPod Razr Treo Blkberry travel charger more!

Example of solar charger

China to work out national standard for mobile phone

chargers

EV Charger News - Home

Green Car Congress: Fuji Heavy Speeds Up

Recharging Of R1e EV

RUSSCO Safety Electric Vehicle Battery Chargers.

3. Ron J article on transformerless power supply