Programmable Solar Charger




Introduction: Programmable Solar Charger

About: I'm currently a chemical research associate. My interests go as far as electronics, mechanics, gardening, sewing, woodwork, 3D printing, CNC, boardgames, music, ... I love to learn new things and make stuff!
I had a solar charger, but wit the years the complex electronics supporting it gave up. But when I took it apart I noticed that the panels them selfs were still working. Wanting to reuse them I came up with this. A programmable solar charger.

by a simple shorting block and headers you can 'program' it so the output is:
  • only from a single panel (left or right)
  • the solar cells are in series
  • the solar cells are in parallel.
I will try to explain here how you can make this yourself.

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Step 1: What You Will Need.

  • A wooden plank (or a project box) to put it in.
  • A soldering iron (and solder of course)
  • Wires in different colors (just one color will work just as well, but can be very confusing)
  • A shorting block and headers (or something else you see fit for the job, if you have enough switches, they should do the job just as well)
  • The most important: solar cells.
  • Triangular piece of wood (optional: it only serves to make the protecting case)
  • Some way to make a variable outfit. I got a gadget key chain at a festival which should charge your phone. It had a cable where you could fit multiple outfit plugs in. but multiple cables should work as well.
  • A hot glue gun
  • A saw
  • A drill
  • Sanding paper

Step 2: Step 1: Thinking It All Through

plan out your lay-out, the scheme, the way you're making the box.
I did a bit of thinking here, but you're free to add or leave certain things as you like.

Step 3: Step2: Cutting the Wooden Plank

This must be precise, the solar cells should fit tightly in there, so rather cut the holes to small than to large.

The sawing method in the pictures below, is how I taught myself to saw rectangles with sharp corners. There are probably many more methods, and far better ways to do it, but I like this one.
Make sure that there is enough wood between the holes so you don't weaken the wood to much.

Make sure that the cells fit tight. Check the size by fitting the cells in the holes, if needed trim a little bit more and fit again (better to small than to large). When your finished with the saw, sand everything smooth with some sanding paper.

The size of the board depends on the size of your solar cells so I can't help you with the dimensions.

When the cells fit, hot glue them into place (gently).

Step 4: Step3: Soldering the Wires.

Solder according to the scheme I made in step one. Or you can think out your own if you want to add more 'programs' or don't need to use one.

Once soldered it's actually a working device, so you can check if it's working. Place it in the sun and connect your phone (or something else if you're afraid to fry your phone).
After soldering and checking make sure the wires won't budge anymore. I went a little too crazy with the hot glue, but at least it's sturdy.

Step 5: Step4: Build a Box Around It.

This step should just make it look more attractive, and protect the wires at the back of your board.
  • Measure the board of your solar cells and saw one of the same size out of your box-wood.
  • Saw the sides (you can decide the hight yourself), but make sure 2 sides are twice longer the thickness of the wood, so they will overlap the other sides.
  • (The total hight of the sides) minus (the thickness of the wood) minus (the thickness of the board with the solar cells on) equals (the hight of the triangular corner blocks). Measure, and cut to the right length.
  • Glue everything together with wood glue. (I used hot glue because I like hot glue, and the wood glue mysteriously vanished and I was too lazy to buy some more)
  • Then hopefully everything fits, now glue in the board with the cells. But don't use to much glue, you have to be able to get it back out of the box again, in case one of the wires disconnects or something else. (Murphy's law)

Step 6: Step5: Use It and Enjoy Free Electricity.

Look on your charger to see what voltage and what current your phone needs to charge, then set in the 'program' accordingly.
My solar cells produce 5,5V and 155mA each, my phone needs 5V and 300mA so I need the parallel program to charge, and it works!

for the scheme below, the programming 'code' is this:
only cell 1 = A(1) B(0) C(1) D(0) E(0)
only cell 2 = A(0) B(1) C(0) D(1) E(0)
parallel     = A(1) B(1) C(1) D(1) E(0)
series        = A(0) B(1) C(1) D(0) E(1)

with (1) = connected; and (0) is not connected.

Have fun with it!

ps: I'm not responsible if you fry your phone, check the voltages and the currents on you standard charger for the right settings!

EDIT: It works perfectly my phone even said it was fully charged, so that's awesome.
But one hot summer day I was forced to move my little power box indoors. The solar panels had expanded due to the heat created in them while laying in the sun. The wooden box however didn't so the solar panels bended out so far I thought they were going to break. So on hindsight you might want to build the box out of something that will expand almost the same as the panels... or cool the panels down. Anyway the circuit still works fine, I just thought this was worth mentioning.

I excuse myself for any spelling mistake that might occurred, English is not my native language. But please correct me if I typed something wrong, we're all here to learn.
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    9 Discussions


    7 years ago on Introduction

    ok i like this very much and have u thought anout using lighter wood or even plastic that looks like wood i like ur project voted for


    Reply 7 years ago on Introduction

    this instructable is originally an entry in the green contest, but now only the hurricane laser contest is in the header :(
    thank you very much for your vote!


    Reply 7 years ago on Introduction

    Thank you very much!
    I have considered other materials, but I really like working with wood. Only the board where the electronics are glued on is a quite dense wood (from a wine case) the protective box is much thinner and lighter. The box parts came from left overs from making a house model. I try to reuse as much as possible.
    plastic for the cover could work, but plastics ain't green ;-)


    Reply 7 years ago on Introduction

    As soon as I posted this a few of my friends wanted that I made one for them, so I'm searching for some panels as well.
    Just google "buy solar cell" or "buy solar panel" that brought me to this:
    but I'm going to the local electronics store to ask their opinion where I could buy solar panels.

    ps: The panels in this project are actually barely strong enough to charge my phone but they cant charge iPods or smart phones so you might want to take this into account when buying new ones ;)


    Reply 7 years ago on Introduction

    No problem at all. ;)
    If I don't do something productive in vacations I go nuts, so this is really fun to do for me.