Bicycle generator to charge your phone

Topic: Bicycle generator to charge your phone (Read 136 times) previous topic - next topic

Bicycle generator to charge your phone

August 13, 2026, 09:58:15 AM

I talk to a lot of people about designing and building generators. One of the first things they usually ask is; “can you build one to charge my phone with a bicycle?”. It seems like a lot of people are interested in that.

So, I decided to build one and post it here so people that are interested can build one themselves.

I am building this little bicycle generator to test it in many ways and collect data. This will be a prototype.

Ultimately, what I want to do is design and build a generator that is optimized specifically to be powered by a regular average bicycle without making any modifications the bicycle. After all, not many people would like to have a bicycle just to run the generator, they would want to be able to ride the bike too.

After I run the tests and collect data, my plan is to design a generator that could be used in an emergency during a power failure. I want this bicycle generator to be able to charge phones quickly, and also to have enough power to run many low power devices that run on 12 volts.

Here are some of the parts that I will be using for this prototype.

I’ll try to get more done this weekend.

Ed

Re: Bicycle generator to charge your phone

Reply #1 – August 15, 2026, 08:30:44 PM

I was able to do more work on the generator today.
Here are pictures of the coil spools and the rotor and magnets.

Here is the generator, I assemble it to test the fitting of the parts.

I also got the coil winder ready to go.

Now all I need is find the time to wind the coils and build the stator.

Ed

Re: Bicycle generator to charge your phone

Reply #2 – August 17, 2026, 10:19:42 PM

Watching with interest.
I remember having a wheel-rim dynamo for my bike when I was a kid. It kept a headlight lit, barely, and only while moving forward.

Re: Bicycle generator to charge your phone

Reply #3 – August 25, 2026, 02:05:14 PM

I got the 6 coils for the stator all wound yesterday. Here they are looking pretty in the coil winder.

They are held together with high temperature epoxy. I didn’t want to wait 24 hours for the epoxy to dry, so to heat cure them, I baked them for 1 hour at 150 degrees F (65c)

Here are the 3 sets of coils ready for the 3-phase stator.

These coils are wound with 2 strands of 23 Ga wire, that is the equivalent of 20 Ga. There are 95 turns on each coil and they have a resistance of .36 ohms each.

I manage to wind them without cutting the wire, that way I don’t need to solder them together.

Next step is to get the stator done and then assemble the generator.

Ed

Re: Bicycle generator to charge your phone

Reply #4 – August 26, 2026, 10:38:16 AM

Looks like a small roast in the easy-bake oven

Re: Bicycle generator to charge your phone

Reply #5 – August 30, 2026, 02:32:55 PM

Quote from: Bruce S – on August 26, 2026, 10:38:16 AM

Looks like a small roast in the easy-bake oven .

On the rotisserie!

Re: Bicycle generator to charge your phone

Reply #6 – September 07, 2026, 10:22:31 AM

The stator is complete. Roasting of the coils in the rotisserie turned them well done

Since this is a prototype, this stator is also an experimental build.

I would like to be able to find a way to build stators that don’t require using a lot of polyester or vinyl ester. Those methods produce a strong, durable and rigid stator, but is a lot of work and messy. I would like to find an alternative way.

For this experimental stator, I am using a sheet of polypropylene. This material is rigid enough to be used in a low power stator like the one that I am building here. Polypropylene can tolerate a temperature of only 100c (212f) without distorting. This small alternator will produce about 75 watts max. so I think that high temperatures won’t be a problem.

I think that for bigger alternators, it could be possible to use FR4 / G10 Glass-Epoxy Laminate or Nylon sheets that can withstand higher temperatures.

Epoxy adhesives and potting materials don’t adhere well to polypropylene and nylon. But that problem can be resolved by making locking notches on the board to lock the coils in place, as I did with these coils.

Those notches lock the coil in place and by using the high temperature epoxy only around the notches and to coat the coil, there will be plenty of air circulating around and through the coil to provide good cooling.

I would love to hear other ideas and suggestions from others about possible ways to build a stator. 3D printing is also a possible way to do it.

I will be busy with other projects for the rest of the week. I’ll put the bike generator together next week.

I have to plant a new lawn in my back yard this week. I need to break up the soil by hand with a shovel and mix it with 2 yards of fresh top soil. (I love the workout). I did the front yard this past spring. About 80% of the yards in these neighborhoods were tore up last year by raccoons and crows digging for grubs.

Ed

Re: Bicycle generator to charge your phone

Reply #7 – September 08, 2026, 02:34:32 PM

Well, it's been a while since I saw a post showing a pancake stator!

Digging down the recesses of memory, I'd suggest that different resins combined with fiberglass had different results. Some are more sensitive to moisture, some to heat, or both. If this is a pedal-generator for an exercise bike, you don't have to worry as much about it out in the rain. If it's for a mountain bike, then it is. Give me some time to try to remember which resins are more robust than others.

Also, to address temperatures, why not bury a temperature sensor in the laminate when gluing them together? Then just keep an eye on the temperature in the stack while you go. Temperature sensors aren't very complicated, even if they do take some trial-and-error to get hooked up right and calibrated. The digital ones need a micro but the analog ones (you can still get them) are dead simple enough not to need one, and/or go ahead and use a micro with really simple code.

Re: Bicycle generator to charge your phone

Reply #8 – September 09, 2026, 05:19:11 AM

Polyester resin was the most used... mix of weather survivability and somewhat strong