International Journal of Engineering Trends and Technology (IJETT) – Volume 35 Number 3- May 2016
Wireless Battery Charger
Shilpa S1, Manasa. H.M1, Sadaf shahana Mariam, Mr. Keerthi Kumar M2
Student, 3rd year Telecommunication Engineering, GSSSIETW, Mysore.
2
Assistant professor, Dept of Telecommunication Engineering, GSSSIETW, Mysore.
1
Abstract: Nowadays, mobile phones have become
an integral part of everyone’s life and hence we
require frequent charging of battery owing to longer
duration usage. With mobile phones being a basic
part of our life, the recharging of mobile phone
batteries has always been a problem. The mobile
phones vary in their talk time and battery standby
according to their manufacturer and batteries. All
these phones irrespective of their manufacturer and
batteries have to be put to recharge after the battery
has drained out. The main objective of this current
proposal is to make the recharging of the mobile
phones independent of their manufacturer and
battery make.
Mobile battery charger circuit is a device that can
automatically recharge a mobile phone’s battery
when the power in it gets low. A battery charger
or recharger is a device used to put energy into a
secondary cell or rechargeable battery by forcing
an electric current through it. Battery charger comes
as simple, trickle, timer based, intelligent, universal
battery charger- analyzers, fast, pulse, inductive,
USB based, solar charges and motion powered
charges.
It consists of three sub projects – Auto turn off
battery
charger,
Solar
Power
Charge,
Microcontroller based photovoltaic MPPT charge
controller.
The aim of auto turn off battery charger is to
automatically disconnect a battery from the mains
when the battery gets fully charged. This system can
be used to charge partially discharged cells as well.
Solar power charger is to charge a battery by using
solar panels. This project deals with the mechanisms
charge controlling that will also do over charge,
deep discharge and under voltage protection of the
battery.
The aim of the project is to design charger
controller with maximum power point tracking based
on microcontrollers.
1. INTRODUCTION
Wireless charging uses an electromagnetic field to
transfer energy between two objects. This is usually
ISSN: 2231-5381
done with a charging station. Energy is sent through
an inductive coupling to an electrical device, which
can then use that energy to charge batteries or run the
device.
Induction chargers use an induction coil to create an
alternating electromagnetic field from within a
charging base, and a second induction coil in the
portable device takes power from the electromagnetic
field and converts it back into electric current to
charge the battery. The two induction coils in
proximity combine to form an electrical transformer.
Greater distances between sender and receiver coils
can be achieved when the inductive charging system
uses
resonant
inductive
coupling.
Recent
improvements to this resonant system include using a
movable transmission coil (i.e. mounted on an
elevating platform or arm) and the use of other
materials
for
the
receiver
coil
made
of silver plated copper or
sometimes aluminum to
minimize weight and decrease resistance due to
the skin effect.
The major advantages are – Protected connections,
low infection risk, durability, increased convenience
and aesthetic quality.
Charging methods are classified into two categories:
fast charge method and slow charge method. Fast
charge is a system used to recharge a battery in about
two hours or less than this, and the slow charge is a
system used to recharge a battery throughout the
night.
Slow charging is advantageous as it does not require
any charge detection circuit. Moreover, it is cheap as
well.
The only drawback of this charging system is that it
takes maximum time to recharge a battery.
There are inductive and conductive wirelesses
charging. Inductive charging involves the use of an
induction coil which produces an electromagnetic
field via a charging station where energy is
transferred to an electronic
device which is also equipped with a corresponding
induction coil.
Conductive charging requires a physical connection
between the electronic device's battery and the power
supply. The need for a metal-to-metal connection
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International Journal of Engineering Trends and Technology (IJETT) – Volume 35 Number 3- May 2016
between the charger and the device requiring
charging is one of the main drawbacks of this
method. To accomplish this without the use of
physical cords connected to wall outlets, special
attachments are made from electronic devices which
are fitted with technology that can detect when the
device makes connection with the power source,
often a charging base. Conduction based wireless
accessories may include changeable backs for
cellular phones, special sleeves and attachable clips.
The aim of this project is to automatically disconnect
a battery from the mains when the battery gets fully
charged. This system can be used to charge partially
discharged cells as well. The circuit is simple and
consists of AC-DC converter, relay drivers and
charge stations.
Solar cell phone chargers use solar panels to
charge cell phone batteries.. They are an alternative
to conventional electrical phone chargers and in some
cases can be plugged into an electrical outlet.
There are also public solar chargers for mobile
phones which can be installed permanently in public
places such as streets, park and squares. Solar cell
phone chargers come in different shapes and
configurations including folding (Goal Zero, Endless
Sun Solar) and rotating types (Solio). They also come
in the form of straps, with solar cells on the outer
surface and a nickel metal hydride battery within.
Current solar cell technology limits the effectiveness
and practicality of phone solar chargers for everyday
use. The fold-out design has proven to allow for
higher charge current while maintaining a compact
size and current designs are capable of charging a
modern Smartphone in 3 hours.
Fig1. Solar cell Phone charger
2. WORKING PRINCIPLE
Wireless charging mainly involves three sub projects.
2.1 Auto turn off battery charger
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Fig2. Auto turn off battery charger
In an AC-DC converter section, the transformer stepdowns the available AC supply to 9v AC which is
rectified by using a full wave rectifier, and then
filtered by the capacitor. When the
switch S1 is pressed, the charger starts working and
the power on LED glows to indicate the charger is
„on‟.
The relay driver section consists of PNP transistors to
energize the electromagnetic relay.
This relay is connected to the collector of first
transistor and it is driven by a second PNP
transistor which in turn is driven by the PNP
transistor.
In the charging section, regulator. A D6 diode is
connected between the output of the IC and a limiting
output voltage of the battery up to 6.7V is used for
charging the battery.
When the Switch is pushed, it latches relay and starts
charging the battery. As the voltage per cell
increases, the voltage drop starts decreasing at R4.
When the voltage falls, then the T3 transistor cuts off
and drives to T2 transistor and in turn cuts off
transistor T3. As a result, relay RL1 gets deenergized to cut off the charger and red LED1 is
turned off.
Currently 700mAH cells, which can be charged at 70
mA for ten hours, are available in the market. The
voltage of the open circuit is about 1.3V.
The shut-off voltage point is determined by charging
the four cells fully (at 70 mA for fourteen hours) and
adding the diode drop (up to 0.65V) after measuring
the voltage and bias LM317 accordingly. In addition
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International Journal of Engineering Trends and Technology (IJETT) – Volume 35 Number 3- May 2016
to the above simple circuit, the real time
implementation of this circuit based on the solar
power projects are discussed below.
The project below describes the design for maximum
power point tracking in mobile phones using
microcontroller.
2.2 Solar power charge controller
2.3 Microcontroller based photovoltaic MPPT
mobile charger.
Fig 3 Solar power charge controller
The main objective of this solar power charge
controller project is to charge a battery by using solar
panels. This project deals with a mechanism
of charge controlling that will also do over charge,
deep discharge and under voltage protection of the
battery. In this system, by using photo voltaic cells,
solar energy is converted into electrical energy.
This project comprises of solar panel, Op-amps,
MOSFET, diodes, LEDs, potentiometer, charging
switch and battery. Solar panels are used to convert
sun light energy into electrical energy. This energy is
stored in a battery during day time and makes use of
it during night time. A set of OP-AMPS are used as
comparators for monitoring of panel voltage and lead
current continuously.
LEDS are used as indicators and by glowing green,
indicates the battery as fully charged. Similarly, if the
battery is under charged or over loaded, they glow
red LED. The Charge controller makes use of
MOSFET – a power semiconductor switch to cutoff
the load when the battery is low or in overload
condition. A transistor is used to bypass the solar
energy into a dummy load when the battery is fully
charged and it protects the battery from getting over
charged.
For maximum power point tracking, microcontrollers
are used.
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Fig 4 Microcontroller based photovoltaic MPPT mobile
charger.
The major components used in this project are solar
panel, battery, inverter, wireless transceiver, LCD,
current sensor, light sensor and temperature sensor.
The power from the solar panels is fed to the charge
controller which is then given as output into battery
and is allowed for energy storage.

Sensors
The sensors are the devices that are going to
be in charge of monitoring and communicating
everything that was happening in the system to the
microcontroller.

DC-DC Converter
A DC-to-DC regulator is needed to
increase or decrease the input panel voltage to the
required battery level.
Boost converter- is power converter which DC input
voltage is less than DC output voltage. That means
PV input voltage is less than the battery voltage in
system.
Buck converter is power converter which DC input
voltage is greater than DC output voltage. That
means PV input voltage is greater than the battery
voltage in system.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 35 Number 3- May 2016
 Microcontroller
The microcontroller is responsible for all input and
output processing of the entire photovoltaic system.
The tasks included reading sensor values, controlling
battery-charging circuitry, monitoring system
performance and anomalies, along with transmitting
data.
 Battery
The batteries used in photovoltaic MPPT charge
controller served as a way to store energy so that
devices can be powered in the event that the sun is
not shining and when more power is needed than can
be provided by the solar arrays at a given time.
 Inverter
The inverter is the final stage of the system. It is
through the inverter that the user has the opportunity
to access the power stored in the batteries that was
originally generated in the solar panel. The main
functionality of the inverter is to take the DC voltage
stored in the batteries and transform it into AC
voltage.
 RS485 Interface
The RS485 interface
is responsible
for
communicating the sensor and performance values to
a remote computer over cables. The advantage of
RS485 is that it supports long distance
communication and multiple receivers may be
connected to such a network in a linear, multi-drop
configuration.
The solar panel, battery and inverter are bought as the
off shell parts while the MPPT charge controller is
designed and built by solar knights. A LCD screen is
provided for displaying storage power and other alert
messages. The output voltage is varied by pulse
width modulation from the microcontroller to
MOSFET drivers.
Added cost.
Reduced efficiency.
5. CONCLUSION
This is how one can make one‟s own battery charger
for the mobile phones. The two examples mentioned
here can make the process easier for you. Mobile
phones have become the most important part of one‟s
life. We almost keep every important detail in our
mobiles. Therefore battery backup is the most
important criteria. Hence, wireless mobile charges
help us keep the mobiles charged always or when the
battery goes down. Not only this they also prevent
overcharging of cells and keeps us connected.. This
method provides great advantage to the mobile phone
users to carry their phones anywhere even if the place
is devoid of facilities for charging. Wireless charging
has now become a mainstream technology. Initially it
was a novelty, but with its applications and
advantages becoming recognized, it has now become
a mainstream application. It is anticipated that
wireless battery charging will become very
widespread, if not the most common method.
With standardized interfaces and techniques, only a
single wireless battery charger will be required to
charge a variety of items. No longer will a whole
myriad of chargers be required. Also reliability and
convenience will be improved as it is far easier to
place the item to be charged on the charging mat,
rather than having to use a small connector. Although
the efficiency of wireless battery charging is less than
that using direct connections, the added intelligence
could reduce the end of charge current, thereby
reducing the overall power consumption as many
normal chargers are left connected even when they
are not charging.
REFERENCES
The way to track a maximum power point by using
MPPT algorithm implementation in controller
ensures that the battery is charged at maximum
power from the solar panel.
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3. Advantages.
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Reduced wear of plugs and sockets.
Resilience from dirt.
Application in medical environment.
[2].
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4. Disadvantages.
Added complexity.
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