Build a Battery Powered USB Charger

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.

Parts Needed:

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

Necessary Tools:

1. Glue
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
7. Forceps
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.


Note:
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:
http://blog.makezine.com/archive/2007/01/soldering-tutorial-make-v.html



Total Cost: about $25

Time to Complete: approximately an hour

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.

Comments

[buteman]

dwoods-1 is correct you WILL damage anything which requires 5 volts with these connections as you WILL be supplying 9 volts directly.
I cannot find any reference to a .7285 regulator but a 7805 would be fine.

Looking at the diagram you provide you need to connect both black wires to the centre pin. Connect the red wire from the battery clip to the top pin and the red wire of the usb cable to the bottom one.

See this diagram: http://www.talkingelectronics.com/projects/LogicDesigner/images/7805.gif

[Robot Lover]

Scrap the earlier comment. Follow this schematic:

[domints]

This is configuration for sources, which can give you 1A. If you're not sure if it can acheve this, it's safer to use this schematic: http://www.ladyada.net/images/mintyboost/usb4res500mA.gif
because it limits current draw to 500mA, which is safer to regulator and lowers its temperature. I hope you understand what I mean :)

[Robot Lover]

I forgot to mention that the above schematic is what is inside the Apple USB chargers. I figured since Apple uses it in their charger, then it would probably work for a lot of the newer apple devices. Although, this schematic is a few years old, so Apple might have changed the schematic around a little bit. Also, since it is line powered, it can draw the single amp that it needs. And for the heating problem, the common output current is up to 1 amp (I'm sure there are higher current regulators). Because 1 amp is the highest current output, and that is what the above schematic uses, there would be heat. A simple heat sink would suffice. I will agree that my schematic is obviously not suitable for a portable charger. Although, if it were powered by some "D" type batteries it is possible. Anyway, to anyone still reading this, use the circuit in domints comment.

[dwoods-1]

http://www.raphnet.net/electronique/gc_n64_usb/lm317rev1g.pdf

The chip in your picture and sorry but as you point out there you basically hooking the usb power straight to USB @9v !!

would it not be better to use a 7805 5v roltage regulator in this configuration ?

http://forum.allaboutcircuits.com/image_cache/httpwww.sminntech.comimages7805datasheet.gif

[srhadaham]

you could add a switch between the battery and the regulator, it would save the trouble of actually removing the battery, but would accomplish the same thing.

[mreinhard]

Hi there, these kind of voltage regulators are not efficient at all. If you regulate from 9V down to 5V then you are burning 4V through a resistor, which is almost have of what the battery gives. It is better to use a switching voltage regulator such as the TL497. You can even make a design to keep charging even after you have less than 5V of potential differential in your battery.

[Ejji]

Okay Ive seen this so many times before and have made this 2 different ways i understand the use of a resistor but have you tested it with and without one?? i'm curious about charge time as well as battery life both with and without the resistor.

[Robot Lover]

I agree with domints. The way it's soldered would just supply 9 volts to the USB port. Regarding the pullup resistor, you will only need these if you want to charge newer apple products. A 10k-50k resistor is needed between ground and pin4(data line) of the USB port and a 10k-50k resistor between a 3 volt power source and pin3(data line) of the USB port. I am not 100% on this but I am pretty sure that it will work. Good ible!

[domints]

Hey. Nice 'ible, but there's one think that you should change in this project. You should use some pullup resistors on data lines, 'cause this won't load Apple devices. You can read about this here:
http://www.ladyada.net/make/mintyboost/icharge.html

And what is full name for your voltage regulator? Even Google doesn't know much about 7285/.7285 . I think 7805 / LM7805 is more popular. With 7805 you can use even 2.8 pullups, because you can get 1A from 7805, but I'd use heatsink for regulator. With pullups for 0.5A it shouldn't be neccesary to use haetsink.

[domints]

And connection to voltage regulator is a bit weird. Are you sure, you get out of this devide 5V? I think it isn't possible to achieve this, because you are just soldering battery clips to USB plug, with something connected in parallell to USB. I'd like to see how fast you'll bake your phone or iPod.

[randofo]

Hello Group2. Nice project. Is this for a school assignment?