Introduction: Battery Powered Emergency USB Charger

In this, my first ever, Instructable, I will show you how to make a USB charger powered by 4 AA batteries. This is similar to the USB Solar Charger Instructables, except it runs off batteries. It costs about 25 dollars for the parts and that is a lot less than brand name chargers. Please don't over criticize my Instructable, as it is my first one.

Step 1: Purchasing and Collecting Parts

For this Instructable, I used the following materials, all purchased at RadioShack.

1. ABS Plastic Project Enclosure (6x4x2 inches) ($4.99)
2. Red and Black 18 Gauge hookup wire ($6.99) Product # 278-1226
3. 4 AA Battery holder with snap connectors ($1.79) Product # 270-383
4. 9 Volt heavy duty snap connectors ($2.69) Product # 270-324
5. DPDT Toggle Switch ($2.99) Product # 275-666
6. 5 Volt Regulator ($1.59) Product # 276-1770
7. TO-220/TO-202 Aluminum Heat Sink ($1.99) Product # 276-1368
8. Green LED Power Indicator ($1.99) Product # 276-271
9. A screw to hold the 5 Volt Regulator to the Heatsink (can be found anywhere, just find one that fits.)
10. A cable with a connector compatible with your device.

Tools Needed:
1. Phillips screwdriver
2. Drill and bits to drill switch and LED holes, and wire hole
3. Soldering iron and solder
4. Wire cutter and stripper
5. Pliers
6. Digital Multimeter

Lets get building!

Step 2: Constructing the Circuitry

Step 1: Drill 2 holes about an inch apart on the cover of the enclosure for the switch and LED of appropriate sizes.

Step 2: Screw the switch and LED onto the top of the project enclosure

Step 3: Take one of the snap connectors and solder it to the center 2 legs of the switch. They are labeled 2(red wire) and 5(black wire).

Step 4: Cut and Strip 4 inches of red and black wire.

Step 5: Twist the red wire you just cut and stripped to the red wire of the LED indicator. Solder this to the #3 leg on the switch.

Step 6: Twist the black wire you just cut and stripped to the black wire of the LED indicator. Solder this to the #6 leg of the switch.

WARNING: The next few steps are extremely polarity-sensitive. If you connect the wrong way, you will fry the 5 Volt Regulator.

Step 7: Solder the other end of the 4 inch red wire to the first leg of the regulator (# 1 in my schematic)

Step 8: Cut and strip 2 more pieces of black wire, about 4 inches long.

Step 9: Solder one of the new black wires to the middle (# 2 leg) of the regulator.

Step 10: Solder the black wire from the switch to the black wire from the regulator and the 3rd black wire.

Step 11: Check your work: Are you left with a snap plug? Do you have 1 red and 1 black wire with free ends? Make sure everything is connected correctly.

Step 12: Take a break and find 4 new AA batteries.

Step 13: Put the 4 AA batteries into the holder and hook it up to the snap connector feeding the switch. Get your digital multimeter and turn it to DC 20 Volts (or something close if you don't have 20).

Step 14: Connect the red and black leads of the multimeter to the the red and black free leads off of the regulator.

Step 15: Turn the power switch on. The green LED should glow. Your multimeter should read about 5 Volts.

Step 16: Drill a hole for the device cable to exit the enclosure through. Put the wire through it. It should fit snugly.

Step 17: Solder the red and black wires of your device cable to the free red and black regulated leads.

Step 18. Screw the heat sink to the 5 volt regulator.

Step 19: Cover all wire solder joints with electrical tape.

Step 20: Test the charger with your device. If it works, proceed to step 21. If it does not work, then check all connections with the schematic and test everything with the multimeter. Once you get it working, proceed to step 21.

Step 21: Screw the enclosure closed with the four included screws. You are now done!!!!!!

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