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How to Charge Any USB Device with AA Batteries – Make Your Own Battery Pack!!!

Posted by gregd1024 on December 23, 2007

I recently had this weird idea to take apart a USB cable, solder the +VCD and ground wires to a “AA” battery holder, slap in some batteries, and see if the contraption would power/charge my cell phone. Well I just tried this, and it worked! 🙂 Check it out:

AA_Batteries_Powering_USB_Device

Fully_Assembled_USB_Battery_Pack 

And since it takes four 1.5V “AA” batteries outputting six volts total instead of the standard 5V from the phone’s AC adapter, this homemade battery pack charges the phone faster!

I want to tell you how to make your own. It’s really simple. First, you’ll need these supplies (all from Radio Shack):

Supplies_for_Building_AA_USB_Battery_Pack

  1. Wire cutter/stripper.
  2. Four lithium ion AA batteries (Nickel Metal Hydride’s [NiMH] should work good too).
  3. Battery holder.
  4. Battery holder connector plug (looks exactly like a 9V battery connector).
  5. Any cable with a female “4 Pin Mini-USB” or “5 Pin Mini-USB” connector on one end.
  6. Solder and soldering-iron (not shown).

The battery holder needs to carry four “AA” size batteries. Make sure you get a USB cable that you don’t care about because you’ll be destroying it. The wire strippers must do really small gauges (24 – 26 AWG). I would highly recommend using the thickest USB cable you can find or else the internal wires might be too small to strip.

Now you’re ready for the assembly. Here are the steps:

  • Cut the USB cable in half starting from at least one-inch underneath the mini-USB connector’s head. You’ll be working with the side that the mini-connector is attached; discard the other half.
  • Strip off some of the black outer insulation exposing the shielding and wires inside.
  • Cut off the outer shielding, or bend it away making the inner wires easy to access.
  • Now you should see a few little wires each with a different color – strip the red and black wires only (the others aren’t needed).
  • Take the red wire you just stripped and solder it to the battery connector plug’s red wire.
  • Take the black wire you just stripped and solder it to the battery connector plug’s black wire.
  • So far, things should look like this:

Closeup_of_Solder_Joints_in_USB_Battery_Pack

  • Wrap some insulation around the exposed metal to prevent a short.
  • IMPORTANT: IF YOU DON’T PUT INSULATION AROUND THE EXPOSED METAL AND THEY MAKE CONTACT, YOU’LL SHORT-CIRCUIT THE BATTERIES!! THIS CAN CAUSE THEM TO EXPLODE AND KILL YOU!!!
  • Take the four “AA” batteries and insert them into the battery holder.
  • Plug the 9V connector to the battery holder.
  • You’re done! 😉 Now you can plug the whole thing into any device that would normally feed power from your computer’s USB port. (If you have a device that does not take power from your computer’s USB and instead plugs into a wall AC adapter, check the input voltage required for that device. If it is around five volts and requires less than 3,000 mAh, then this homemade battery pack should work on it.)

Not only did my battery pack work on my phone, I also tried it on an “APC USB Backup Battery Pack” (funny – the commercial version of my contraption) and sure enough, the APC pack started charging!

Charge_Other_Devices_with_USB_Battery_Pack

OK, I know this is totally redundant, but it’s the only other device I have which takes a mini-USB connector. I need to get a converter cable and try it on my iPod! That’ll be for a future post.

Speaking of future posts, the whole idea of this circuit being 6V instead of 5V makes me a little nervous. For USB devices, it really should be 5V max. For my next post on this subject I’ll slap two resistors across the battery input leads to make a voltage divider and force a 5V output.

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-Greg Dolley

Posted in Cool Stuff | 46 Comments »