This guide will walk you through building a battery powered charger for any device that charges via a standard USB connection, for example cell phones, iPods, etc.
1. 9V Battery
2. +5V (.7285) Fixed Voltage Regulator
3. Project Case (4x2x1")
4. USB Male A to Female A Cable
5. 22-Gauge Hookup wire
6. 60/40 Rosin Core Solder
7. 9V Battery Snap
8. 9V Battery Clip
All Items can be found at RadioShack
2. Soldering Iron (with a fine point)
3. Soldering Iron Stand
4. Dremel Rotary Tool (with appropriate cutting disc)
5. Wire Strippers
6. Wire Cutter
8. Safety Glasses
9. Screwdriver (Phillips)
And now, a few safety precautions:
1. Wear safety goggles while operating Dremel, pieces of plastic or dremel disc may hit your eyes
2. Choose a well-ventilated space to work, as fumes from soldering are hazardous to your health
3. Do not touch metal parts of the soldering iron while working, it will be very hot
4. Place the soldering iron securely on a stand, do not touch your table, clothing, countertops, or other things you do not want burnt or melted with the tip.
5. Do not touch the voltage regulator, it operates at near 150 C (302 F), it will burn you if you touch it.
As soldering skills are required for this project, if you don't already know how, this link from Make Magazine provides a good tutorial on soldering:
Total Cost: about $25
Time to Complete: approximately an hour
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Step 1: Preparing USB Cable
Cut the USB cable down to size, leaving approximately 1 inch of cable outside the plug.
Strip the insulation from the outside of the usb cable to expose the red, black, green, and white wires inside
Strip the insulation from the red and black wires, red will be our (+) and black will be the (–) connection to the regulator.
Step 2: Case Preparation
Cut a hole in the side of the project case that approximately matches the size of your USB plug.
• Outline the usb plug with pencil on the outside of the case.
• Cut away the plastic using a Dremel or similar rotary tool.
• If your USB plug is rather large, like the one we used, you may need to cut away some of the lid, do this in the same fashion as above.
Note: If you have the means to do so, it may be easier if you clamp the project case to a work surface to hold it steady while you cut.
Step 3: Battery Snap Wire Preparation
Strip the wires from the battery snap to expose a greater soldering surface
Step 4: Battery Clip Mounting
Place the battery clip in the case using glue.
For our case size, we chose to mount it on one side of the case.
Depending on your case size (if you choose to use a different one), you may choose a more fitting location.
Step 5: Prepare the USB Power Wire
Cut two lengths of 22 gauge wire (in our case, just over an inch each).
Strip the insulation from both ends of each wire to expose enough for soldering.
Step 6: Soldering the Battery Snap
Solder the red battery snap lead wire to the (+) end of the voltage regulator and the black lead wire of the battery snap to the (-) end of the voltage regulator.
Ensure you do not cross wires during the soldering process as it will short the connection.
Do not hold the soldering iron to the voltage regulator for extended periods of time, as prolonged temperatures of 150+ degrees C will damage the regulator.
The tutorial mentioned in the introduction page about soldering can be found at this link:
Step 7: Solder the USB Power Wires
Judge how your wire will sit inside the case, and bend the wire in the direction it will need to go to connect with the USB cable.
Solder the first length of wire, one end to the (+) terminal of the voltage regulator and the other to the (+) (red) USB wire.
Solder the second length of wire, one end to the (-) terminal of the voltage regulator and the other to the (-) (black) USB wire.
[Helpful Hint] – forceps may be helpful in holding the wire while soldering
Step 8: Assembly
Place everything into the box
(it may take some effort to get everything in the box at first, keep rearranging as necessary)
Place the lid on the box and screw it down using the four included screws.
Note: it is recommended that you do not leave the battery connected when not in use as the regulator will get extremely hot. To counteract this, you may install a heatsink on the regulator, which should reduce the temperature.
Charge Your USB Device!