Picture of DIY Bike Generator

Using easily accessible parts, it is possible to build your own bicycle generator that will charge your cell phone! This instructable is an extension of this instructable made by our friends. Eventually, this bike will stand on its own in our student union, so our classmates can sustainably charge their phones off the grid!

The basic setup of the bike is as follows: the back wheel of the bike spins a DC motor via fan belt, the motor is connected to a charge controller, the charge controller charges a lead-acid battery, and the battery is then connected to an inverter. You can then plug your phone into the outlets of the inverter!

Basic Materials needed:

Bicycle Stand

Bicycle Frame with Back Wheel

12V Lead Acid Battery

DC-AC Inverter

DC-DC Battery Charger

24V DC Scooter Motor

Fan Belt

Fan Belt Pulley

Wires, Screws, Wood, and a Metal Rod

NOTE: We added more to our bike to make it run better, but these are the bare minimum materials to get it up and running.

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Step 1: Assembling the Bike

Picture of Assembling the Bike

We attached our bike system to a 2' by 6' piece of plywood. We used a bike stand to suspend and stabilize the back wheel. You can bolt the back wheel stand to the board, but we thought it was unnecessary since other portions of the bike were attached to the board. Our bike was donated with the front wheel off, so we built a front wheel stand. Make sure you have enough room on the board to attach the motor behind the back wheel!

Building the front wheel stand: The forks had a 1 cm diameter hole, so we found a one inch dowel for it to rest on. In addition, we took a 1.5" x 3" wooden beam and cut it into two 9.5" and two 4.5" blocks. We drilled a 1cm hole 1/2" down from the top of each of the 9" blocks. We then put the metal rod through the blocks and assembled the stand (see photo above). We added some washers and nuts to make the connections more secure. The two 4.5" blocks should be cut to fit tightly between the 9" blocks, as shown above. After building the bike stand, the front wheel should sit snugly on the blocks. Next, we screwed the lower 4.5" block down to the plywood. Finally, we attached the upper 4.5" block for stability. Now the bike stand for the front wheel is complete and should sit snugly on the rod between the blocks.

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MM Ecology5 days ago

Hi. We're a group of 5th grade students at a Montessori school in Virginia and we are making a bicycle generator and we were wondering if someone could give us some advice. We are having trouble knowing which parts to buy. We would appreciate the help. You can email our teacher if you would like to help us. His email is Thank you!

Hey, nice job. But just a question - did you copy this from Chris Hackett's and Popular Science's book Big Book of Maker Skills? They seem pretty similar.

McgyverD1 month ago

I built one out of a exercise bike and used a chain and a treadmill motor that is giving me 12 volts at 50amps, I'm able to charge the battery and watch tv at the same time. And just going at the rate of 2 miles per hour riding it. I invented it my self the design.

SKSW47 (author)  McgyverD1 month ago

Thats awesome!

Kressle10 months ago

Don't know if anyone else has suggested this, but what about running neodymium magnets along the rim of the wheel and spinning those through a coil of wire like a wind turbine? More expensive, but you may get more efficiency with a better design. Thoughts?

dratman Kressle8 months ago

Magnets-on-bike-wheel would be great as an engineering exercise, but in this project, it is another kind of exercise that counts.

Billster369 months ago

I don't get the need for the inverter. Why not just hook up a standard cigarette lighter type outlet to the battery and charge the cell phone with the same sort of plug you would use in the car?

arizzotti10 months ago

You can vote for this Bike Generator to win a Nest here:

Bill WW10 months ago

Very nice, love the way you link the material list to the actual suppliers.

I always thought it would be great to connect a bike generator such as yours to a TV (as the ONLY power source). You would have to work out if you wanted to watch.

300w = 0.4hp, about the max a human can sustain.

Computothought10 months ago


fazlehaq10 months ago

exactly how long it took to charge that battery completely ?

loachridge10 months ago
Or maybe even make some refinements to the K-TOR to fit it into a bike frame.
loachridge10 months ago
Look up "12 volt dc hand generator".
This is essentially what was mounted to bikes I mentioned earlier.
Can you make this work dual purpose?
Put an LED in for lower consumption. Add a small Li battery for charge storage if your device isnt plugged in.
omikeo10 months ago

can you give us an indication of efficiency

like how long and fast one may have to pedal to make toast?

Squidyman omikeo10 months ago

Giving an guesstimate, a toaster draws about 700 watts. You could probably create about 200-300 watts peddling pretty hard. It takes approximately 100 watts to toast a piece of bread so it would take at least 30 minutes to be able to toast your bread. You would need a shower after all that peddling, so any energy you saved by peddling is lost to the water and heat bill XD

omikeo Squidyman10 months ago
Yeah fig' it'd be a lot of work, I don't think people realize how much work would have to be done to create the energy they use. If they had to contribute in this form of muscle power to electric, conservation, I suspect would be the norm.

minus my spelling errors! :P

NovaKnightZer010 months ago

I think i might attempt this.

But im going to try and not take apart my bike and just make it so that i can just easily place my bike into the contraption pedal make electricity and when im need to go somewhere just take my bike off and go.

You don't need to take apart your ebike. After you place the rear axle on the trainer, just disconnect the power line that goes to the motor and hook it up to the 12 V battery. Mount a voltmeter on the handle bars and monitor the output voltage from the motor while cycling on the trainer. Just pedal hard enough to keep the charging voltage below about 14.5 V to prevent overcharging the battery. I think this is the maximum charging voltage for car alternators. At this charging voltage, my output was about 60 W.

Althenuker10 months ago

It's great to see projects like this in support of bike generators. Well done! However, you really need to look closely at your project from the energy production and consumption standpoint. I built a bike generator using a 350 W BIONX motor from my electric assist bike last Dec during an 8 day ice storm power outage. The best I could do was to generator 60 W for about 10 minutes before I was whipped. I'm sure you younger fellas could do better than me. I used it to charge my 12 V deep cycle battery, charge my cell phone from a USB port connected to a standard 12 V cigarette charger and run my 12 V internet satellite modem. After a couple of days, I was really beat and my 12 V battery was depleted. I reluctantly had to give it up and charge my battery using my truck while driving to the grocery store. Nevertheless, it was an interesting project and actually kept me warm during the frigid weather. Good luck with your project, but to get increased power you need several cyclists pedaling while hooked up to the same generator.

xarlock66710 months ago

I'm going to be a bit rude, so I apologize in advance: But WHY would you go to so much trouble to charge a cell phone? You have almost 200 worrth of equipment there that you could have put to MUCH better use. It is not an entirely worthless concept, but make it a LOT more useful by using a rectifier and making it put out 120v AC. That way you can charge several phones at once, perhaps a laptop or run a TV, etc... Good try.

SKSW47 (author)  xarlock66710 months ago

The inverter has a standard plug for it as well. You could technically charge a laptop with the basic set up, but we are planning on putting it in our student union and figured people would mostly like to charge cell phones. Thus, we only used a MOSFET rated for lower current because that is what we had lying around. If you omitted Arduino part of the bike, you can charge many other things as well.

Because you can XD

In all fairness, "Because you can" is the best reason to do ANYTHING. Therefore, you win.

loachridge10 months ago

When I was younger; dont go to far into that; I remember bike head lights being run from a generator attached to the bike.

A simple lever would lower the pulley side down onto the tire. That would generate enough to power a pretty good head light. Or is it headlight?

You could use the same principle here. Put another wheel, or something round rubber, on the generator. And work the mounts to take any bike. That way you can actually ride your bike. Or just like the old ones, mount the generator to the frame.

There is a lot of efficiency lost by relying on the tire to turn a small motor mounted to your bike. It would work, but it would take a long time.

I will disagree with you for now. I like to be "proven" wrong. ;-)
You have the materials all right there.
Why not give it a shot. It worked well in the '80s.
And those things weren't made for efficiency.
Consider it a challenge for you.

I may take you up on that challenge. I do have all the parts required.... But the 300 watt motor I have is quite heavy so the bike might have to remain stationary until I find a smaller one......

Now to get my parents to let me take apart that old electric bike XD

Random thought..... It would be awesome to be able to run a Raspberry Pi and a small screen off of the bike. If you stop pedaling, your computer turns off!

And consider that the motors on those bikes were probably 5 watts or less.

dark-shot66610 months ago

That looks like someone would have to put a fair bit of effort to keep the wheel spinning.

Have you considered adding on a freewheel to the rear wheel? Add on another 10-20 pounds so that when you take a break from pedaling, the wheel won't lose nearly as much rotational speed from the momentum stored in the freewheel. Just an idea.

Solid project otherwise! Great work.

beewrangler10 months ago

This is a great idea, but if you are only using it to charge USB devices why would you use an AC inverter? The USB standard is 5Vdc. You are loosing a considerable amount of energy in the conversion from 12Vdc to 115Vac and then back to 5Vdc. Why not start with a 6V battery and use a zener diode to drop down to and maintain a constant 5Vdc output to a standard USB outlet?

Squidyman10 months ago

A bit of advice....

Make an easier to understand chart on how everything connects with one another.

Nice project!

TorBoy910 months ago

Very interesting build, and you've done a lot of work.

You might consider adding a fender to the rear wheel so that scarves and other loose clothing will not get caught in between the belt and the rim. The rear stand will need to be permanently screwed down to the base, otherwise with natural cycling movement there will be a loosening of the belt, resulting in less efficiency.

A front handlebar bag that has a metal frame could be changed to support a flat surface, which will allow the use of a tablet or smartphone while riding.

Overall a very interesting build.

I think this is a good way of testing a concept as a bike generator has some potential as an overall power source for small devices. As mentioned it would be good to be able to ride the bike as a bike though as well(maybe build one for yourself), so the next stage would maybe to fit everything you have there actually to the bike, then you could go out for a cycle and come back with a charged up battery that you could then plug in a car type mobile phone charger to. Bit of an extreme measure to charge a phone but you get the idea :) or keeping you design as it is, try different motors/generators in place of your scooter one, for instance a car alternator needs to only spin at about 1000rpm to cut in, and they put out a fair wack of power when connected to a battery, then you could connect a mains invertor and run a laptop or something without barely touching the battery, although I dont know how much strain an alternator might put on the rider! I have thought about building a similar to test the car alternator theory! The advantage with the alternator is you dont need all the various charge controllers, you just have a light which goes out when your up to speed (which can be replaced with an LED/resistors) making it slightly more simple.

xtracycletony10 months ago

Couldn't you have replaced the rear cassette with another smaller pulley and reduce the overall size of the belt? The wheel technically wouldn't be needed, just the hub.

Great project over all though. Nice work.

SKSW47 (author)  xtracycletony10 months ago

The large diameter of the back wheel provides the 2800 RPM that the motor is rated at. It is the big to small ratio that lets us spin the motor fast enough to create a large voltage.

Mesa_Arch_Man10 months ago

Spelling error throughout article, nice job though.

Peddling is for drugs, pedaling is for bikes!

Maybe get the Arduino to display stats to the rider like estimated calories burned and a high score for the best (fittest) charger!

SKSW47 (author)  Mesa_Arch_Man10 months ago

Thanks! We'll fix that. Good Idea for the Arduino.

manuka10 months ago

Good idea, but capable of producing ~50-100 Watts (which is far more than a modern cell phone requires). If you just want to charge a phone then a simpler & cheaper solar charger (running into a simple storage battery of course) will usually do OK. An A4 sized 5Watt PV typically produces ~10-20 Watt.hours per day in even average lighting, which is good enough for daily charging of 2 smart phones. There are now numerous such PV designs around of course,although many "Altoid Tin" versions are too puny unless in bright sun.

Us humans are capable creatures & our legs & hands are better suited to more crafty purposes when needing exercise- gardening, child minding, dog walking, wood chopping etc !

Fyodor10 months ago

dc to ac to dc,..that should burn off some extra calories. This is a great project for a high school,..but the first time someone gets a finger stuck in the spokes the Nanny State will shut it down,..if you're in California or New York, that is.

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