How To Build A Solar Powered Battery Charger For Under $25.00 (25 bucks)

I finally got my solar powered battery charger assembled. There was a delay when I had to do the soldering because its very difficult to solder when your soldering iron won't melt anything. Word to the wise. If you have any soldering to do, don't buy the cheap Radio Shack brand. Spend a few bucks more and get a name brand like "Weller." I learned that lesson the hard way. I picked up a Weller soldering iron at Lowes. So, the design of the solar powered battery charger (which I will refer to as the SPBC from now on) was pretty simple. I used the following items to assemble my project.

  1. Three small solar panels that I bought at Sundance Solar online (each panel was under 6 bucks each). Here is a link to the exact panels I bought. ($5.75 each)

  2. Some wire (you can get it at Radioshack-I used both 18 solid and 22 stranded gauge).($5.99)

  3. A Rectifier Diode (also bought at Sundance Solar but can also be purchased at RadioShack)($.50)

  4. a battery holder (purchased at Sundance Solar)($1.95)

    (Optional Accessories)

  5. super glue

  6. electrical tape

  7. alligator clips (purchased at RadioShack)

  8. a clip board (purchased at Office Max)

  9. Suction cups (purchased at Office Max)

And I used the following tools when assembling:

  1. A multimeter (you must have a multimeter if you want to know if things are working or not!). They are cheap and easy to find. I bought one online directly from Hong Kong and found a killer deal! Here is an awesome multimeter for VERY cheap compared to store prices. If you need to learn how to use a multimeter, go here.

  2. A soldering iron

  3. solder

  4. wire cutter/stripper

  5. needle nose pliers

  6. a cordless drill

The basic premise is this. You use the solar panels to generate electricity, which is then transferred through the wires to the rechargeable batteries being held in the battery holder. I won't get into the details about electricity, voltage, amps, or any of that because that would be way too much information and you would get bored reading it all. You can learn about those things at this website. If you want to make your own SPBC, here is how you do it.

  1. Connect your solar panels in series. Make sure you are running each wire from the negative part of one panel to the positive part of the next panel. This creates a higher voltage than one panel can produce alone. [I am charging 4 AA batteries, so I needed a voltage higher than 6 volts. The panels are each rated to produce 3 volts a piece, so I decided to use 3 panels for a total of 9 volts). You can connect your panels with wire, using alligator clips, soldering, or some other method that will conduct electricity.You can see in the picture below that I connected my panels using wire and soldering. I was nervous about this method, but it turned out to be perfect. You MUST burn off the plastic coating protecting the copper contacts at each end. If you don't do that before you solder, you won't get a good contact and current will not flow. If you want to learn how to solder, its fun and easy. Here is a website that will teach you.

  2. Install a diode at the positive end of the solar panels. This prevents electricity from running out of the batteries back into your panels when there is no sunlight. If you buy your diode from sundance solar, they send you a handy little piece of paper explaining the correct way to install it. If you don't install it in the right direction, its bad.


    3. Connect the positive cable coming from the diode, and the negative cable from the negative end of the solar panels, to the battery holder.

    Thats it!

    I know, you are probably thinking its a lot more complicated than that, but it really isn't. I went a little beyond that because I glued my solar panels to a clipboard, and then drilled holes so I could hang it on the window using suction cups, but the basic steps are easy to achieve. Anyone can put a solar powered battery charger together if they really want to. All you need are supplies and a little bravery to give it a try. If you are worried about electrocuting yourself, then you probably need to read up on how electricity works. At this small voltage, you are in no danger of getting electrocuted.

    Here is a picture of the solar panels powering an LED light that I hooked up temporarily to test if the solar panels were working. As you can see, the blue light is working perfectly.

    Here is what it looks like when mounted to the clip board. I used superglue on the back of the panels to adhere them to the clipboard. (This method of adhering was recommended on the solar panel website).


    This is a picture of the back side with the battery holder and diode taped down with electrical tape. I tried to use superglue to make the diode stick to the board, but it got too warm and melted the glue. Electrical tape works just fine.As you can see, I am using alligator clips to attach my wires to the wires of the battery holder. I did this so I can play with the solar panels instead of making it a permanent battery charging station. The alligator clips allow me to disconnect the battery charger if I ever want to try something else.


    I was pleased to find out that the combined voltage of all of the panels wired in series actually turned out to be much more than advertised. I got 11.5 volts from them on a cloudy day when placed in the window at a tilt to face the sky in mid day. 

    One other thing to note is that these panels are getting high voltage, but that does not speed up the recharging time. These solar panels are rated at 50mA. (That's 50 milliamps), so it will take several hours to charge my batteries since they hold roughly 2000 milliamps each. In hindsight, I wish I would have gotten some solar panels that were capable of more amps, but that's okay. This is my first project, and I enjoyed it thoroughly.***It will take DAYS to charge 4 AA batteries so if you do this project on your own, I highly recommend you get a 1 battery holder or 2 battery holder rather than a 4 battery holder like I did.

    Another side note is that the manufacturer that produces these solar panels also produces some panels that are flexible and weather resistant, meaning they could be installed on clothing or bags. It would be very easy to make a back pack with solar panels that can charge an IPOD or something similar. Here is a link to their website if you are interested. They are a bit more expensive which is why I didn't use them for this project.

    Feel free to email me if you have any questions! Go Solar!!!


Dallan said...

You are so amazing! Great job on the tutorial. I think interested people will be trickling in to see, and benefit from, your pictures and text on this for a long time to come.

Eddie the Girl said...

oh my heck. I am totally sending this post to my husband and my dad.

Halvorsen Family said...

What a great project for my boys! I love the idea of the backpack mount for recharging ipods and such. Terrific idea! Thanks for sharing your experiments.

Anonymous said...

Hi, where can i find smaller panels?

javieth said...

Solar energy is the best natural resource that we have this time even more that fuel is too expensive. In fact i want to approach costa rica investment opportunities and look all the alternative this country can have because it climate. We must to find the way to save our planet and to use solar energy could be the first step.