Instructables
Picture of Pedal Powered Battery Charger
Introduction: Generate enough power to charge 12 volt batteries.

There are increasing numbers of people who are behind on their utility bills and could have their electricity cut off. They need something to help reduce their dependence on the electric company, something that can also supplement wind and solar power generation. This may help.

This is a project to generate practical amounts of electric power by using bike pedals. I ended up using three stages of chain to drive a DC motor as a generator and charge a car battery. The use of chains turns out to be durable and efficient. The various sprocket sizes let you choose the speed that you need for the motor you have.

I used a discarded 24volt scooter motor in this project, but this thing is flexible enough to work with lots of different DC motors.

Everything in this project was from stuff I found in the course of my dumpster diving, including various bicycles and bike parts. I have no prices for any of this.

Above, you can see a photo of my contraption. Find a good, comfortable seat for this, otherwise your derriere will get quite sore.
 
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Step 1: Materials Needed

Picture of Materials Needed
1. Scooter motor with it’s chain and sprockets.
2. Cheap jumper cable.
3.  Two rear bike axles with nested sprocket.
4. Two small hinges.
5. Two bike frames.
6.  Two metal brackets.
7. Plywood. 16“x20“x5/8“ and 11“x16“x5/8“.
8. Lumber. two 2x6x18“, two 2x6x15“, one 2x4x28“, and one 1x2x14“.
9. Mounting board for the motor. About 6x6x3/4“
10. Two bike chains and chain tool.
11. Diode. 100 volt, 3 amp will do.

Absent a scooter motor, you could test various other motors by spinning the shaft with an electric drill while monitoring and comparing outputs.

Step 2: Find a junk adult sized bike.

Picture of Find a junk adult sized bike.
Once you have the bike, remove the front and rear wheels. The front wheel is not needed. Remove the tire, rim, and spokes from the rear wheel.

I used wire cutters to clip the spokes. They are tough and hard to cut. Another method may be easier. Photo 1 shows a closeup of the spokes gone.
tplim5 months ago

Thanks for sharing. Follow plus favorite. Cheers....

Would this work if the motor was rotated the opposite way?

commiejay1 year ago
Hmm, could this be rigged to an electric converted bike to charge the battery while peddling?
ShutterBugger (author)  commiejay1 year ago
You would need to drive two sets of chains. One chain to drive the rear wheel in the normal fashion, then another set of chains to drive the generator at the high rotational speed that it requires. The energy you produce would be divided between the generator and your forward motion.
oking2 years ago
Why not use the Alternator from a car?

They can be had for pretty cheap at the junk yard.

They come with diode packs and are designed to charge batteries.

You can run them with belt pulleys or be modified for chain pulleys.
ShutterBugger (author)  oking2 years ago
I tried an alternator once and found it takes much more effort to generate the same power. The alternator will draw power until you get it running about 3000 rpm, at which point it transitions to generating more than it uses.

Alternators do work well enough when run by a small gas engine.
I would have to see a side by side test on that. The using more power does not make sense. An alternator creates a 3 phase AC out that is converted to DC and then is run through a regulator to save a battery from damage.

Besides if there was a 3000 RPM issue then switch to a diesel alternator or change the gear ratio.

ShutterBugger (author)  oking2 years ago
Remember, there are no permanent magnets in car alternators. The rotor is an electromagnet that receives power from the battery through a pair of slip rings. That power must be restored by increased effort at the petals.
Hmmm I guess I would have to build a permanent magnet version then. I've seen plans for them online and are better than using a DC motor.
ShutterBugger (author)  oking2 years ago
On a solar power site, I found modified alternators for sale. The electromagnet rotors were replaced with a permanent magnet rotor. I don't have the link.
I hope you don't take me wrong I honestly like your plans.

I just think differently that most people and I had remembered that Tesla had used 3 magnets on an equal lateral triangle spinning on a shaft to create AC power. So I was shocked to learn that Alternators have brushes.

I have seen homemade 3 phase permanent magnet wind turbines. I often forget that manufacturing designs often don't make any sense.

I do apologize if I come off as being argumentative, I am not trying to be.

I just had remembered from design that using an electric motor as a power source was an inefficient method. Effective yes efficient no.

I am just always looking to eek out the last drop of power that I can from something like this.

Thank you for entertaining my questions and inquiries.
ShutterBugger (author)  oking2 years ago
No problem.
I have found great variation in how well a motor generates power. One way of testing a motor is to short the leads and spin the shaft. A shaft that becomes hard to spin will indicate a good generator. In some cases, after connecting one motor to another and spinning the shaft, you can see the second motor working from the output on the first motor.

If you want AC, use a stepper motor. Old printers, scanners, and copy machines often have stepper motors. It would be interesting to connect the output of a stepper motor to the oscilloscope and see how the voltage and frequency varies with shaft speed. Use a variable speed drill or Dremel tool to spin the shaft while monitoring output.
~Bob~
imbigman2 years ago
Nice Job. I wonder if you could do the same for the front and utilize the other sprocket atached to the pedles? Well done, we need more of these. Plus it will help us get in better shape.
ShutterBugger (author)  imbigman2 years ago
You could indeed find a way to use the front.... but, the work you do would be distributed among two motors, and thus reduce the output from an individual motor. It would also increase the friction in the system, due to added chains, and reduce your output.
~Bob~