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Step 1: Parts list

Picture of Parts list

1x Battery box  - $1.99 (I saw it at another Radio Shack for $2.29, but my local one had it for 1.99)
4x AA batteries - $.50 (I went to the dollar store and bought this 8 pack for $1)
Cell phone cord  $1.50 (I found one cheap on Amazon, but make sure you get the one that fits your phone)
1A diode (these are very cheap if you buy them in bulk - probably in the 10 cent range). 

Soldering iron / solder
Heat shrink tubing, or you could use electrical tape I suppose

Step 2:

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1st, cut the cord, leaving about 3-4 inches from the part that attaches to the phone. You need to strip the cord back and you'll notice some insulation, probably some foil, and 4 wires: red (+), black (-), and green and white wires (data). Cut it so that you leave just the red and black wires remaining. The green and white wires are only for transferring data, which you will not be doing. Which leads to an interesting point - this charger cannot be used for an iphone because Apple created phones that draw current from the data cables - I think around 2v each. Even though you could make something to charge an iphone, it would require resistors to drop the voltage on these 2 cables. I don't have an iphone, so I didn't care to do this. 

Cut the black and red wires coming from the battery box leaving about 1.5 inches left. 

Take your diode and cut it leaving about 1/2 - 3/4 inch left on each side. (You'll notice that this is a 3A diode and I mentioned before that you'll need a 1A diode. I didn't have a 1A diode and didn't want to buy one, so I used this 3A one. But 1A is all you need. Wall chargers allow 1A.) 

Step 3:

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Before you solder the wires, you need to slip on your heat shrink tubing, and smaller one that goes on the black wire, push it towards the battery box so that it doesn't come in contact with any heat while you're soldering, otherwise it'll shrink and you'll have to cut it off and put on another. Now get a larger one and put it on both wires, but push this one toward the plug end. This one will cover both wires, the other one covers just the black one. Obviously the 2 wires cannot touch each other. The larger heat shrink tube is large enough to cover the soldered area and around the diameter of the diode, but not big enough to slip on and off the end of the cable. 

* Heat shrink tubing is cheap, and if you're a tinkerer, grab yourself a box of them, you'll use them all the time. But if you don't have any, all this can be accomplished with electrical tape, it just won't look as nice. 

Solder the black to black 1st, then wait till if fully cools before slipping the tube over the connection. Once on, heat it to shrink it, and move to the red. This is where the diode has to go. Make sure the diode is soldered in the right direction, otherwise current cannot pass beyond this point. The stripe on the diode represents the cathode side (negative) and it leads away from incoming current. So this side (see the picture) will be on the opposite side of the batteries, or the side that is closest to the phone plug. The solder the red wire coming from the battery box to the side of the diode that doesn't have the stripe (the anode). 

Wait until fully cooled and then slide the larger tube that you had already slipped on before you soldered the diode on. Heat to shrink.  

Step 4:

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At this point, you could leave it. I decided to put one more piece of extra large heat shrink tubing on the connection, just to reinforce it. The cool thing about this battery box is that is has an on/off switch.

Put in your batteries, close the lid and charge away.

* This box takes 4 AA batteries and if you know anything about batteries, you know that non-rechargeable batteries carry a voltage of around 1.5 volts. Most rechargeable AA batteries carry a voltage around 1.2-1.3 volts. We need at least 5 volts here to charge a phone. Your USB cord, whether plugged into a wall jack or computer, will allow around 5v to pass because that is the minimum voltage needed to charge a 3.5-3.7v phone battery. So 4 rechargeable batteries would give you about 4.8v, and even though technically this would momentarily charge a 3.7v battery, especially if it's a dead battery, it will take a long time to do so and would probably only give you about a 5% charge. 4 regular batteries gives you 6v and will not only charge the phone more, but also much more quickly. Since these are cheap at the $ store, this is what I used. With the cheap ones I get about 25-30% charge from a dead battery. If I put in Duracell bats, it will give be around 40-50% charge, but this is an expensive way to go. 

Step 5:

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And you're done. As you can see from the picture, it is plugged in and is charging as indicated by the orange LED at the top. Look at the phone and you can see the battery charging symbol next to the time at the top right. 

And that's it. Remember to turn the switch on!!  =)  Good luck. 


The intention of this project is to build a straight forward human powered generator from a used bicycle and to use it to power light bulbs, blenders, cell phones, laptops, and other small appliances. This project will help one develop engineering skills while learning about a clean way of generating electricity.

Before continuing with the actual bicycle generator, one should understand how it works, and the components that make it up.

Parts Tools

- 2" X 4" Wood
- Wrench
- V-belt
- Saw
- Diode
- Wood screws or nails
- Battery
- Hammer or Screwdriver
- Inverter
- Tape Measure
- Wire
- Screwdriver
- Motor (12-V or higher)
- Perforated plumbers steel
(if motor does not have mounting bracket)



You will need to unscrew the back rim to remove the tire and tube. Since the only part of the bicycle that needs to work is the chain and pedals, a junk bike or an old used bike would work just fine.


The design of the stand is completely up to you. A few examples are shown below. Just be sure that the stand keeps the bike elevated and secure. If your bike has pegs attached to it, make sure your stand accommodates that feature.

The stand should be built so that the rear wheel of the bike is about 5-7 inches off the ground. The dimensions of your stand will be specific to your bike.

Before beginning construction of the stand, be sure to draft a design with appropriate dimensions. A design on paper will save time and prevent mistakes.


Step3: Attach the drive belt along the back rim.

Picture of Attach the drive belt along the back rim.

A drive belt can be purchased at any auto parts store. You will need to remove the back rim to attach it. Make sure to measure the distance from the motor to the rim so you obtain the appropriate size.


Step 4: Attach the motor to the stand.

Picture of Attach the motor to the stand.


A 12-volt DC motor or higher is recommended. The wattage of the motor depends on what you want to power. The motor should be securely mounted to the stand. Mount the motor at a distance that will tightly secure the drive belt on the motor shaft. The belt and motor shaft should spin concurrently – make sure there is no slipping between them.

Step 5: Place a diode in series with the motor and battery.

Picture of Place a diode in series with the motor and battery.

Make sure the diode is only allowing current to flow from the motor to the battery. The cathode should be pointing towards the positive terminal of the battery.


Step 6: Connect battery to the diode.

Picture of Connect battery to the diode.

The battery should be connected in series with the motor and diode. The negative lead form the motor should attach to the negative terminal of the battery. The positive lead from the motor should be attached to the diode, and the diode to the positive terminal of the battery.


Step 7: Connect the battery leads to the inverter.

Picture of Connect the battery leads to the inverter.

You could use an adapter to connect the battery to the inverter, or you will need to solder or tape the battery’s leads to the inverter so the circuit is secure. Be sure to correctly connect the positive and negative terminals of the battery to the inverter or you will blow the fuse in the inverter.


Step 8: Plug the appliance of your choice into the inverter.

Picture of Plug the appliance of your choice into the inverter.

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