A simple modification will allow you to use a $20 AA Energizer cell phone charger with any USB device to charge your cell phone, iPod etc. *(note in testing it does not have enough juice to charge an iPhone 3G)
It cost about the same as the minty boost ($20) and is about the same size. Almost no assembly is required by compairson. I completed this project with parts I had lying around. Not sold yet? Did I mention it has flashing blue LED's?
Step 1: Parts
Here are some of the parts and tools you will need.
- The energizer AA battery charger for cell phones (found at many drug stores)
- USB extension cable ( Comes with many different USB devices/dongles, you or your friends probably have some in a drawer somewhere)
- Soldering Iron and Solder ( I like the radio shack butane powered ones because they heat up fast and have no power cable to catch on things, also highly portable)
- Wire strippers ( these came from the dollar store and they are 3+ years old! )
Disassemble the usb charger. It is pretty strait forward. The cap with the springs pops off easily to remove the batteries. The remaining cap can be pried off with a screw driver or by pulling the two halves of the casing apart. What we want is to get at the circuit inside the cap.
Step 2: Prep the Circuit
Here is the circuit in all of its' glory. Pretty small and I am guessing similar to the minty boost circuit as it takes the available 3v from the batteries ( 1.5x 2AA ) and up converts it to 5v
Since we don't want to use the silly phono style jack we are going to desolder it from the board. This is fairly simple and easier if you have desoldering braid. If not then heating up one pin till the solder melts then rocking it out with some pliers and repeating for each of the three pins should inch its' way out of the pcb.
Use a multimeter or your eyes to figure out which connection is positive and which is negative. It will be important later when we wire it back up. It can be found easily by looking for which solder connection is grounded, which isnt used, and the remaining one is the power.
Step 3: Prep Your USB Cable
Now that you know where to solder the power and ground connections you need to prep your USB extension cable.
All we care about is the female end as we want to plug other devices into it. In the picture I have cut off all but 3-4" of cable leaving the female end.
Use your wire strippers or a knife to remove the plastic wire shielding almost all the way up to the USB connector.
Open and seperate the wires out. Inside you will typically find, Shielding, ground wires, and 4 insulated wires in standard USB colors Red(+) Black(-) and white+green for USB data
We only care about the red and black wires as we are only using the port for power so we can loose everything else.
In the second picture you can see the shielding cut away and the green and white wires shortened and bent back out of the way and away from each other to not short out.
Then some heat shrink tubing (or electrical tape etc) is added to make everything look nice and keep wires from moving around too much.
RESIST THE URGE TO SOLDER THE USB CONNECTOR TO THE CIRCUIT RIGHT NOW!!!
Step 4: Solder
OK good you made it so far and did not solder the nice looking USB cable you made to the circuit yet. That is because we need to fit the cable through the end cap first!
You will need to play around with the fit a little to get the length of the wires just right so they do not bend too much and everything is snug.
This is a pretty simple solder job but I would recommend some kind of "helping hands" to hold the circuit for you as you go due to not being able to set it down on a flat surface.
Once you are done the circuit board should snap back in place ( it only fits one way) and you can reassemble the charger.
Pop in the batteries and plug in your ipod/cellphone etc and try it out. Sure you can test it out first with a multimeter if you have one but its simple enough that it should just work. A charge light/indicator should come on your device and the blue led's on the top cap's sides should blink indicating it is charging.
This is a great little charger to have in your bag/car for the times that your cell/ipod dies and you are not near an outlet. It also comes with nice Lithium batteries. I have tested it with the iPod nano and my motorola Q and it works great. It does not work on my new iPhone 3G I am guessing this is due to higher amperage requirements by the new iPhone.
Motorola has a resistor in the tips of the Mini-USB cable ends for all phones they make that have a mini-usb port charger. By cutting off this special mini-USB tip infused with the special "I-am-a-legit-motorola-charger" resistor and splicing it with a standard Male USB connector (perhaps the other end of the USB cable you just cut up ;-) you can create a custom motorola USB charger which will work on any USB port and your new USB charger. The included mini-USB charging tip that came with this charger did not have the resistor and therefore did not work.
Also, remember not to set your hand down on your soldering iron like I did. It will hurt and it will take about 3 months to heal.