Solar Battery Charger Circuit
In this post
let us see the circuit for recharging Lead-Acid battery using Solar panel.
Solar concept is not new for us. As non-renewable energy
sources are decreasing, usage of solar energy is increased. This solar energy
is not only used on the Earth but also used in space stations where no
electrical power is available.
Here is the simple circuit to charge 12V, 1.3Ah rechargeable
Lead-acid battery from the solar panel. This solar charger has current and
voltage regulation and also has over voltage cut off facilities. This circuit
may also be used to charge any battery at constant voltage because output
voltage is adjustable.
Table of Contents :-
1. Specifications
of the Charging Circuit
2.a Solar
Battery Charger Circuit Design
2.b For Charging
12V Battery
3.c Output
voltage
4.d Charging
current
5.e Time taken
for charging
6. How to
Operate this Solar Battery Charger Circuit?
7. Solar
Battery Charger Circuit Advantages:
8. Solar
Battery Charger Circuit Applications:
9. Limitations
of this Circuit
Specifications of the Charging
Circuit :-
Solar panel
rating – 5W /17V
Output
Voltage –Variable (5V – 14V).
Maximum
output current – 0.29 Amps.
Drop out
voltage- 2- 2.75V.
Voltage
regulation: +/- 100mV
Solar Battery Charger Circuit
Principle:-
Solar Battery Charger Circuit
Diagram:-
solar battery charging diagram.
Circuit Components:-
Solar panel
– 17V
LM317
voltage regulator
DC battery
Diode –
1n4007
Capacitor –
0.1uF
Schottky
diode – 3A, 50V
Resistors –
220, 680 ohms
Pot – 2K
Connecting
wires
Solar Battery Charger Circuit Design:-
Circuit must have adjustable voltage regulator , so Variable voltage regulator
LM317 is selected. Here LM317 can produce a voltage from 1.25 to 37 volts
maximum and maximum current of 1.5 Amps.
Adjustable Voltage regulator has typical voltage drop of 2
V-2.5V .So Solar panel is selected such that it has more voltage than the load.
Here I am selecting 17v/5w solar panel.
Lead acid battery which is used here has specification of
12v/1.3Ah. In order to charge this battery
following are required.Schottky diode is used
to protect the LM317 and panel from reverse voltage generated by the battery
when it is not charging. Any 3 A diode
can be used here.
For Charging 12V Battery:-
Output
voltage
Set the
output voltage to 14.5 volts(This voltage is specified on the battery as cycle
use.)
Charging current:-
Charging current = Solar panel wattage/Solar Panel Voltage =
5 / 17 = 0.29A.
Here LM317 can provide current upto 1.5A .So it is
recommended to use high wattage panels if more current is required for your
application.(But here my battery requires initial current less than 0.39Amps.
This initial current is also mentioned on the battery).
If the battery requires initial current more than 1.5A,it is
not recommended to use LM317.
Time taken for charging:-
Time taken
for charging = 1.3Ah/0.29A = 4.44hours.
Power dissipation:-
Here solar
panel has 5Watts
Power going
into battery = 14.5*0.29 =4 watts
Thus 1 watt
of power
going into regulator.
All
the above mentioned parameters have to be taken into account before charging a
battery.
For 6V
Application
Set the
output voltage to 7.5-8 volts as specified on the battery.
calculate
the charging current ,power dissipation as shown above.
Power Dissipation:-
In this project, power is limited because of the thermal
resistance of LM317 voltage regulator and the heat sink. To keep the
temperature below 125 degree Celsius, the power must be limited to 10W. LM317
voltage regulator internally has temperature limiting circuit so that if it
gets too hot, it shuts down automatically.
When battery is charging, heat sink becomes warm. When
completing the charging at maximum voltage, heat sink runs hot. This heat is
because of excess power that not needed in the process of charging a battery.
Solar Charger Protection:-In this
circuit, capacitor C1 protects from the static discharge. Diode D1 protects
from the reverse polarity. And voltage regulator IC provides voltage and
current regulation.
Solar Charger Specifications:-
Solar panel
rating: 20W (12V) or 10W (6V)
Vout range:
5 to 14V
Maximum
power dissipation: 10W (includes power dissipation of schottky diode)
Typical drop
out value: 2 to 2.75V (depends on load current)
Max current:
1.5A (internally it limited to 2.2A)
Voltage
regulation: +/- 100mV
How to Operate this Solar Battery
Charger Circuit?
1.Give the
connections according to the circuit diagram.
2.Place the
solar panel in sunlight.
3.Now set the
output voltage by adjusting pot RV1
4.Check the
battery voltage using digital multi meter.
Solar Battery Charger Circuit
Advantages:-
Adjustable
output voltage
Circuit is
simple and inexpensive.
Circuit uses
commonly available components.
Zero battery discharge when no sunlight on the
solar panel
Limitations of this Circuit:-
In this project current is limited to 1.5A.
The circuit requires high drop-out voltage.
Solar batteries are one of the power tools to make the device
function efficiently. As the non-renewable energy sources are decreasing there
is a need to increase the usage of solar power. Solar batteries play crucial
role to make it happen within no time.
But the thing is when you get the solar batteries you need to
have the electronic device that supports the solar batteries. My best
suggestion is to purchase the Solar Lights Kits that can affix to home gardens,
walkways and on the walls.
They come at very affordable prices and make the
outdoor look more beautiful and romantic especially at night times. You can
spend some time with your beloved ones in the presence of bright white light
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