DIY USB Travel Charger

A couple of days ago engadget featured this airline USB travel charger that charges your device really slowly from the aircraft audio jack. I wanted something cheaper better so i could use my ipod, phone and camera during my international flight. So I made this AA battery powered USB charger form parts I had lying around.


What you will need:

  • Short USB Extension lead
  • 4xAA Battery Holder with On/Off Switch (cost about a dollar from Jaycar Electronics )
  • 5V Regulator (L7805 – Rated to 1 Amp)
  • Soldering Iron and Solder
  • Wire cutters
  • A multimeter
  • A glue gun OR glue OR blue tack OR gum…
  • 20 Minutes to put it together

So construction is pretty simple:

NOTE: Check your polarity (+ve’s and -ve’s) and voltages with the multimeter after each step.

UPDATE NOTE (21/10/2007): Originally I used a voltage regulator however the 5-6v from the battery pack was not enough for it to sustaion 5v so I had to remove it to get it to charge properly. The max output voltage with 4 AA batteries is 6V so it is unlikely to hurt any usb things.

  1. Chop the usb extension cable about 15cm from the socket end.
  2. Expose the 4 wires in the usb cable, and identify the two which are for power (They should be thicker, mine were red for +ve and black for -ve).
  3. Make or enlarge a hole in your battery holder so that the usb extension cord fits in tightly.
  4. Find a place in your battery holder to fit the L7805 and solder the battery holder leads to it.
  5. Feed the usb cord into the hole we made in the battery holder. so that the 4 wires are dangling on the inside and only full shielded usb cord is on the outside of the battery holder.
  6. Solder the +ve and -ve from the usb cable to the L7805 the battery holder to the +ve and the -ve of the usb cable.
  7. Tuck the L7805 and any wires neatly into the inside of the battery holder.
  8. Check the polarity and voltage on the usb socket using the multimeter.
  9. Glue any parts that may come lose in on the inside if the battery holder.
  10. All Done.

Happy Charging!

NOTE: This setup will not charge all things (it works with my ipod, but not my motorola phone). This is because in the usb spec devices are supposed to contact the host (pc or usb hub) and request high power mode. As this setup has nothing to request high power mode from, the device will never try to charge (as it will assume high power mode is unavailable).
The Minty Boost Kit has the electronics required for most usb devices to work.