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Solar Battery Charging
Make a solar charger for NiCd and NiMH rechargeable AA, AAA etc batteries
One of the simplest DIY solar projects is to make your own solar battery charger using a small Photovoltaic (PV) solar panel (1).
Only a few readily available components are necessary for this project:
Rechargeable batteries - AA or AAA sized. £1-2 each.
Plastic battery holder with leads. £0.20-£0.50.
One diode. £0.05-£0.10.
Solar panel. £depends on size.
NEW - REUK.co.uk are now selling suitable solar panels in the REUK shop (2). The panels on offer are 3 Volt 100 milliamp (3) PV Solar Panels (for charging 1 or 2 batteries), and 6 Volt 250 milliamp (4) (for charging 4 batteries).
If you are interested in putting together a solar battery charger feel free to email neil@reuk.co.uk (5) with details of your exact requirements and we'll see if we can put together a suitable package for you including all of the necessary parts.
Building a Solar Battery Charger
Pictured above is a battery holder for one AA battery. These battery holders are available in a range of sizes from 1 AAA to 4 AA batteries. Use the one which is suitable for your needs. The size of the solar panel required depends on the number of batteries you intend to charge and on their capacities. Note that all batteries charged at the same time should have the same capacity.Each rechargeable AA or AAA battery is rated at 1.2 volts and needs a charging voltage of around 1.3-1.4 volts to reach full capacity. Therefore if you want to charge 4 x AA batteries you would need a 6 or 9 volt solar panel.
Select a Suitable Solar Panel
Ideally you should not charge a battery with more than 10% of its capacity as current - for example, charge a 2,000mah capacity battery with a current of 200ma or lower. This is particularly important when the batteries are nearing full charge and far less important when they are fully discharged. If you break the 10% rule then overcharging can occur damaging the battery potentially beyond repair and generating heat.A diode (6) is used to prevent the batteries' charge being dissipated back through the solar panel when it is dark. A 1N5817 diode is perfect for the job as it only 0.2 volts is lost as the generated electricity passes through it. If you have a Germanium Diode (7) these are also excellent.
Putting Your Solar Battery Charger Together
Detailed instructions on putting together a simple solar charger like this are now available in our article Basic 4 AA Solar Battery Charger Plans (8). These plans can be used for all solar battery chargers whether you are making a 1 AAA battery charger or a 4 AA battery charger.
Solar Battery Charger Enhancements
This very basic solar charger can be improved by adding a current limiting circuit. Click here to find out how to Make a Solar Battery Charger with an LM317T (9). The LM317T is a cheap electronic component (cost under £1) which can be used to regulate current. Therefore you can safely charge batteries with a larger solar panel without the batteries overcharging or overheating.Web Link References
(1) http://www.reuk.co.uk/How-Do-PV-Solar-Panels-Work.htm(2) http://www.reuk.co.uk/REUK-Products-For-Sale.htm
(3) http://www.reuk.co.uk/buy-SOLAR-PANEL.htm
(4) http://www.reuk.co.uk/buy-6V-250MA-SOLAR-PANEL.htm
(5) Email address: neil@reuk.co.uk
(6) http://www.reuk.co.uk/Diodes-and-Solar-Panels.htm
(7) http://www.reuk.co.uk/Germanium-Diodes.htm
(8) http://www.reuk.co.uk/Basic-4-AA-Solar-Battery-Charger-Plans....
(9) http://www.reuk.co.uk/Solar-Battery-Charger-With-LM317T.htm
Article from REUK.co.uk:
http://www.reuk.co.uk/Solar-Battery-Charging.htm
Published: 30th July 2007
© REUK 2010