Basic 4 AA Solar Battery Charger Plans
Basic 4 AA Solar Battery Charger Plans
Make a simple solar charger for 4 AA rechargeable batteries
solar | educationIn this article you will find out how to make a very simple
solar battery charger for 4 AA rechargeable batteries using a small 6 Volt
solar panel. A labelled photograph of the completed charger is provided at the end of the article.
nb.
An introduction to Solar Battery Charging can be found by clicking here.
This
Solar battery charger is built entirely from parts available in the
REUK Shop. Here is the parts list:
1 of
4 x 2700mah AA Rechargeable Batteries.
1 of
6V 250ma Solar Panel.
2 of
2 AA Battery Holder with Flying Leads.
1 of
Blocking Diode.
Click here to put all of the necessary parts into your REUK Shop basket:
Buy Solar Charger Kit
. (We will throw in some
terminal strip (see later) for
free in case you are not planning on soldering the parts together.)
The Solar Battery Charger Specifications
The long life rechargeable batteries used have a capacity of
2,700mah - therefore a charging current of 10% of this (i.e. 270ma) is safe. The nominal voltage of each battery is 1.2V, so four in series is 4.8V with a fully charged voltage of around 5.2V being normal. Therefore our 6 Volt 250ma
solar panel is perfectly rated to be used as a charger for these batteries.
In order to prevent stored power in the batteries being released through the
solar panel during the night, a
blocking diode is used. Placed in the postive line from the solar panel this only allows electricity to flow from the solar panel to the batteries and
not from the batteries to the solar panel.
Up to 0.7 Volts from the solar panel are lost as heat in the diode as electricity flows from the panel to the battery leaving us with a perfect charging voltage of around 5.30 Volts for the batteries.
Putting the Solar Battery Charger Together
To keep things simple no soldering is required to built this
solar battery charger. Instead
terminal strip is used to make the connections - only a small flat head screwdriver is required to secure each wire/component in place.
First of all the four
batteries are put into the two
battery holders and then the holders are wired together in series. To do this the positive lead from one battery holder is connected to the negative from the other. The remaining free wires - one positive and one negative - are our charging inputs.
The ringed end of the
blocking diode (pictured above) is then connected to the positive battery input (red), and the other end to the positive output from the solar panel (red). The negative output from the solar panel (blue) is connected directly to the negative battery input (black)
.
Pictured above is the completed
Solar Battery Charger. The voltage measured across the points labelled
B and
C is the voltage coming in from the
solar panel. The voltage measured across the points labelled
B and
A is the voltage of the batteries. (Note that during charging the battery voltage measured will be higher than the true voltage of the batteries. Cover the solar panel to measure the true battery voltage.)
A suitable multimeter is required to make these measurements.
Enhanced Solar Battery Charging
In this example the
solar panel and
batteries are perfectly matched; however this is not usually the case. Here are a couple of links to related articles which will explain how to make more advanced solar battery chargers:
1. Make a
current-limited solar battery charger using an LM317T.
2. Find out how to make a
Solar iPod Charger using the LM317T to regulate the voltage.
Article Last Modified: 09:43, 30th Jul 2007Comment on this Article
If you have any comments on this article, please email them to
neil@reuk.co.uk.
Your article about the solar charger can be improved if you suggest the builder to use either an old Germanium diode, or a more modern Schottky low voltage drop diode, instead of the silicon diode. A silicon diode has a voltage drop or around 700 millivolts, while a germanium diode will only drop around 200 millivolts... I do not remember the actual voltage drop
of the typical Schottky device, but it is surely less than 700 millivolts!
My own solar charger was built using two panels from a home power tool charger... each panel produces about 3.3 volts at a current of 110 milliamps, so I put them in series connection, and use a half of an old power germanium transistor as the series reverse current protection diode... The Ni Mh rechargeable batteries take longer to charge because the smaller charging current produced by the solar panels.
Here in Cuba where sunshine is really plentiful the year round it is possible to use solar panels everywhere, but they are very expensive !!!
Prof Arnaldo Coro Antich, Cuba
July 18th 2010 |
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