Step 1: The Supplies
. Dollar store solar garden lights ($1.50 for small solar cells or $3 for large solar cells) You may chose how many of these you use, I would recomend using four small if you have those or two large. If you plan on using more or you need to reduce the voltage, you may have to use a resistor or a voltage regulator.
. Electrical wire (Positive and negative wire)
. Batteries that are rechargeable (AA or AAA)
. Heat shrinker
. Electrical tape
. Soldering iron
. Solder rosin 60/40 core
. Wire cutters
. (You might need other tools for the solar light disassembly ie screwdrivers or pliers)
Step 2: Solar Garden Light Disassembly
Step 3: The Circuit
A diode will be used to prevent the current from flowing backwards when the sun is out of view. Once we check our output of the cells, we may need to implement a resistor or voltage regulator, in my case I didn't. If you plan on adding a charge controller to the circuit then you won't have to check on the batteries every so often, which can be convenient.
I will use a voltmeter to check on the condition of my batteries and their charging rate, this will allow me to make sure they won't overcharge and are fully charged. If some of the materials in the circuit you might be using are bit different from mine, so if you use different batteries, solar cells, resistors, etc expect different results.
Step 4: Plan Before Soldering
Let your soldering iron heat up and have your rosin core ready. Make sure the area your working in is well ventilated and try not breath in the fumes. Some advise would be to use a fan and have the windows open in your work space to allow air flow. Allow the fan to blow towards the were you are soldering and in the direction of an open window or door.
Step 5: Soldering
Once your ready to go begin to solder the connections from wire to wire. Make sure your soldering technique is good or you may not get the best connection from the circuit. Once everything is soldered use your volt meter to check the connect of the circuit, current and voltage. If it looks like the batteries will need protection add a voltage regulator or resistor to the circuit.
Step 6: Mounting the Charger (Optional)
Step 7: Test Results
It may take a few days to charge your batteries depending on how many solar cells are in your circuit or the conditions of the sun brightness. You will need to check the status of your batteries by using a voltmeter. I got a reading of about 3.0 volts and an output of about 10 mah (I might be wrong but about the output since I tested it under a lamp at night). Since the batteries are 1.5 volts I had to use a resistor to slow down the voltage. The output depends on the brightness of the sun.
Thank you for reading my Instructable, if you have any questions or ideas on how to improve this project please let me know in the comments, I look forward to from hearing you. If you enjoyed it please favorite it and vote for me in the solar contest, every ballot counts. :)
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Step 8: Improvements to the Circuit
Here are some possible mods or improvements that I have come up with, if someone wanted to improve the circuit:
. Charge controller (To limit and control the output of the cells and not keep having to check on them with a voltmeter)
. More battery holders (Able to charge more batteries)
. More solar cells (would need a charge controller or voltage regulator)