Solar Backpack Ipod/usb Charger

Jason sent me his solar ipod charger how-to. The regulator may not be neccesary – but there are so many models, I don’t know if the new Nano’s hold up to the old power input standard. He put a 7805 regulator on a 6v 100ma flexible panel that he mounted on his backpack. I’ve seen this sort of thing on a shuffle before, but this one should work for most iPods. USB power management sometimes shoots itself in the foot, but iPods are willing to pull power if it’s not present. It’s nice, clean and simple. I’d consider adding some high temp hot glue (or epoxy)to keep the soldered connections from breaking.

24 thoughts on “Solar Backpack Ipod/usb Charger

  1. To protect it from wind/rain/branches you could try and place a transparent film/sheet of plastic on each side , seal the edges with tape and at the wire exit hole add some epoxy.
    First post btw :P.

  2. I did something like this, although it was a bit simpler.

    I was doing a week long backpack to Mt. Wittney, and wanted to bring a th55 and gps so that I could have tunes/games/gps location and all that.

    So I made a panel that gave out .2a/4v (8×0.5v cells) and just plugged it into a 1a/hr lithium battery I had laying arround. It hung it off my pack and charged the battery the battery during the day, then at night I used them to charge my th55 and little gps that i had been using.

    I figured that at 200ma I couldn’t kill the battery, and to this day that battery still works great ;)

  3. @3 While it is an easy and safe method of charging something up it is also rather inefficient as you loose some energy during the electric>chemic>electric conversion due to a part of the energy getting converted into heat and the general efficiency of the intermidiary battery.

  4. Err, Not the best circuit, the 78M05 is not the best for this circuit – it requires about 2V more to regulate – e.g. at least 7V to give 5V out….

    What is required is a LDO (Low Drop Out) regulator also a few caps on the circuit would make it more stable e.g. 10uf 16V, and 10nf on the input, and the same on the output (Yes, 2 Caps for each, 10uf smooths the supply, and the 10nf remove the High frequency instability)

    Nice idea…

  5. I am quite afraid by what I’m reading here.

    1) NEVER EVER charge a Lithium battery without the proper charging circuitry. Li-ion and Li-po batteries are extremely susceptible and they _WILL_ protest if you charge them incorrectly, sometimes by catching fire at an unexpected moment.

    2) Using a 7805 off a 6V panel is stupid as common 7805 have a drouput voltage larger than 1.5V, which means that you’d need a stable 6.5V (min) at the 7805 for it to deliver a proper, regulated, 5V output. To do things professionnally you’d need a flyback/SEPIC switching power supply that generates a 5V only when the light is sufficient.

    3) Feeding your iPod or [insert your favorite MP3 player model here] by some unregulated voltage may harm it, especially if the voltage gets higher than the rated power supply nominal voltage.

  6. C’mon guys! Ok… So I am a total newbie, but I thought this project was great! I actually was able to understand something out of it – and is giving me interest into all of this!

    I think the article is good and that more of these “SIMPLE” projects are welcomed! Then, we can share ideas and improvements!

    And please! keep it always very cheap, very understandable (as this article is!), and positive!!


  7. I like this concept. The thought of being able to listen to my motorola V360 iTunes (1000 song hacked version) or play a game or video if I want while in the bush makes me want to make one.
    If the voltage is stable who cares usb is usb. The right voltage regulator would make all the difference for me. Mybe he could use laminating film to seal it instead of packing tape.Good hack

  8. This is my first visit to this site. Pretty cool. anyone know of a version of this that uses a hand crank like those wind up flashlights to charge a usb device. The solar panels are great but I need an option for use at night.


  9. I bought the solar panel, the usb female adapter and the voltage regulator, precise as he listed… I built the device. It doesn’t work. I’m a new, for sure, in soldering and building this stuff, but this is a pretty simple project and based on a friend’s recommendation, I tried it. It just doesn’t work.
    Worst, I can’t figure out how to email the author for advice as to why it might not. I’m sure I must have done something wrong.

  10. Welllll…. I figured out the problem. The picture he uses is ambiguous as to where the leads to the regulator go (or the panel is backwards from his and the manufacturer’s instructions). I ended up just having to switch the input and output wires and it all worked out, after I bought it outside for a full sunlight. It works. Sorry for the panic.

  11. This circuit will not charge an Ipod. Perhaps a nano or shuffle, but not a bigger ipod.

    As was stated by comment 9, you need to get a lvdo regulator and probably 1uF caps between Vin and ground and Vout and ground.

    Now you have a steady 5V supply for your USB, but your ipod will still not charge from this circuit, you need a voltage divider. I don’t know how to post it here, but if you take apart any USB ipod charger, the voltage divider is there.

    This being said, it’s probably much easier to buy a higher voltage panel, regulate down to 9V (anything from 9V-12V is fine) and charge directly through USB or firewire, as the ipod’s charging circuitry will automatically begin charging from this voltage without any handshake/voltage divider. However, you won’t be able to charge any other USB devices from this charger.

  12. Thanks for all the input. As I tried to make clear, i am no electronics guy, I just want an ultralight iPod charger to go with me backpacking and I really appreciate the feedback. Now, how do I do that voltage divider business?

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