Solar USB Charger for Smartphones (including an IPhone)

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Introduction: Solar USB Charger for Smartphones (including an IPhone)

About: Everything seems interesting to me! I teach Nutrition at the University of Colorado, make stuff for a small company called Kitables, advocate for sustainability and play the occasional game of soccer.

We are in constant need for power these days... why not harness the sun! I've seen a few of these on here, so my take is to offer some clear wiring if you want to give it a go... and some drawings for your own box if you have access to a laser cutter. I also give you an alternative to ditch the solar panels if you just want to straight up wall charger your thing.

Step 1: Parts

Things you'll need:

  • A container or in this case a laser cut (birch plywood 3mm) finger joint box.
  • micro USB charging module - like this
  • Standard USB size battery converter step up module --- this is key as these can varyin their output! you need one that will output enough watts for the fancy smartphones - like this
  • Battery - you need enough juice to boost the USB - I have here a rechargeable LiPo 3.7V 2000mah, it gets it done. buy here
  • 2 pin Rocker switch - this
  • Solar Panel... you could put small ones together or have 1 large one - like this
  • rectifying diode, this allows your electrons to flow into your battery but they can't glow back out
  • wires to connect your parts
  • hot glue to insulate wiring and hold box together

Here are my box files, I loaded svg and plt files since the plt works well on our local laser cutter.

(If you want to get all your parts from one source (and pay less), you can check out Kitables, they sell 2 versions of this kit.

Step 2: Wiring Diagram

Here's how I wired my charger with these components

Step 3: Glue Your Box, Mostly

Glue up 5 of your 6 sides to work with...

Step 4: Insert Switch

Put the switch in before wiring.

Step 5: Solder Solar Panel

Start by soldering wires to the positive and negative terminals of your panel. Then slip the wires through the small holes on the unglued part of the box.

Step 6: Diode

Solder rectifying diode to the red panel wire (+) with the black line furthest away from panel.

Step 7: Solder Panel Wires

  • Solder the diode (from the solar panel/red wire) to the IN+ hole on the charger module.
  • Solder the black panel wire to the IN- on the charger module.

Step 8: Solder Some Wires

  • Solder a couple of black wires together and a couple of red wires (color doesn't matter, I just like to use the same ones to keep things clear).
  • Solder black wire set to the BAT- terminal on the charging module and the red wire set to the BAT+ terminal
  • Solder one of the black wires (from the set on the BAT-) to the black wire (negative) on your LiPo battery.
  • Solder one of the red wires (from the set on the BAT+) to the red wire (positive) on your LiPo battery

Step 9: Solder to USB Booster

  • Solder one wire from the switch to the USB Booster (IN-)
  • Solder a red wire from the charging module to the USB Booster (IN+)
  • Solder remaining black wire form charging module (BAT-) to the other switch pin.

Step 10: Charging

  • Plug a mini USB cable into the charging module port (the small one).
  • Takes ~2hours to fully charge Lipo from empty. Or set panel in sunlight, takes ~ 14hours to fully charge.
  • To charge your device, plug your charging into the standard USB port, turn on switch to direct charge from battery to device.

Step 11: No Solar? No Problem.

If you want to ditch the solar panel here's the new wiring diagram.

And here are the new box files, the size is notably smaller because you're no longer trying to fit a panel.

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11 Discussions

Of note, if you don't have a large enough single solar panel, but 2 small ones, you can run them together in series like this picture. You will effectively add up your output voltage while maintaining the same amps (in parallel you'll maintain volts and add up Amps).

Screen Shot 2016-09-06 at 11.48.51 AM.png

Can you please give me a link to which diode to get, thanks!

2 replies

Here's the bundle (100) I had bought on Amazon... it's not available, but you can use the specs to find something similar. https://www.amazon.com/gp/product/B00CGWRPEY/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

Nice!
I've been making a similar solar charger but it charges extremely slow. Approximately, how many h would you say that it takes to charge your phone with this charger?

2 replies

I found a bunch of different calculators/calculations online when I was trying to answer this same question. To charge the charger battery fully from the solar panel, I estimated about 14hrs to go from zero juice to 100%. Then testing out the standard USB to smartphone it was about 2 hours for both an iPhone 6 and Samsung Edge 7 -- neither were completely drained, but the Samsung was at about 15%. It comes down to that USB booster... you need to send out enough Watts (5W) to hit the threshold to charge most current smartphones. You have to take into account the equation [Power = Current x Volts] That's why I chose such a high amp battery. If your battery starts to drop to low, then it might not have enough to boost in the USB to hit that threshold. I tried some other USB boosters which might charge up a kindle or a digital camera, but didn't give that nice lightening bolt ding on the phone. You can this USB booster on Amazon for just under $6 (https://www.amazon.com/gp/product/B00C93Z8JY/ref=oh_aui_detailpage_o09_s00?ie=UTF8&psc=1) and I know it will charge a phone. Or the one available in the kitables kit obviously works too. Hope that helps!

That's so funny... the need arose as folks in our coworking space were killing their batteries running around town! I don't play, but I know there are teams? I think it would be cool to color the wood your team color...or deco with stickers etc.