Pedal Power: Building a bicycle-powered generator.

By: Amy Darrell

I wanted to delve further into the world of pedal power. From my research, direct mechanical power is the sweet spot for powering things by bicycle. The bicycle blender I made and shared in a previous post is an excellent example of this; the spinning of the bike wheel directly spins the blades of the blender, replacing the need for an electrical motor to do so. 

However, it is also possible to produce electricity through a bicycle-powered generator which converts mechanical energy into electrical energy, and I wanted to try this next by building my own. I went into this project very aware that producing electricity by bike is pretty inefficient, and I am certainly not going to be any closer to being off-grid. Still, it could be a nice complement to my little solar system if the battery gets low on cloudy days or operate some small devices during a power outage. I also have some bicycle trips planned for this summer and could use the practice. So why not try it? 

First, I needed to do a lot of learning. This was the hard part. There are abundant YouTube videos from people who have built bicycle generators, and they make it seem so simple, but there is a lot of “figure it out yourself” amongst this genre of DIYers. I quickly understood the overall big picture of how to do it, but when I started to dig into it, I realized I was missing some essential details. Trying to find people to help me proved to be tricky. I discovered that folks at my local hardware stores were hesitant to give advice about tools and materials for a project outside of the “installing a new light fixture” norm. Due to the pandemic, I had some trouble at first getting in-person guidance from knowledgeable friends who would have been willing to help me. Some video chats would have to suffice. I did find some very detailed tutorials at this Pedal power generator (https://pedalpowergenerator.com/diy-byo/) site which helped me figure out some of the smaller details and, at the very least, put together a list of materials to take to the hardware store. The book Human Powered Home by Tamara Dean (https://newsociety.ca/books/h/the-human-powered-home?sitedomain=ca) was also an excellent resource. The rest was piecing together a lot of information from various online sources as best I could and just trying it.

Pedal-powered Generator Overview

A little Permanent Magnet DC motor is at the heart of this pedal-powered generator. I used a motor from an old treadmill. Inside a treadmill, this motor works by running electricity through a magnet/copper wire setup, which causes it to spin a shaft and wheel, which in turn makes the treadmill operate. The super cool thing is that if you run it in reverse, spin the wheel/shaft, which rotates the copper wire within the magnets, you will cause a flow of electrons, AKA Electricity. 

It’s pretty much how most electricity is made; some sort of force (i.e. water, wind, steam ) causes the spinning, which creates the electricity. For this project, the spinning action would come from a bicycle. 

What I did:

Materials:

• Bicycle Trainer Stand: $150 scratch and dent from a local bike shop (it is possible to get this way cheaper, but I was trying to find one at the beginning of the Covid-19 pandemic when everyone and their cousin was trying to find home exercise equipment and it was tough to get one cheaply)
• Treadmill Motor: $50 off Kijiji (I then got a couple from a friend for free)
• Solar Charge Controller ($17)
• Power Inverter ($65)
• 12 volt battery (I used a Lithium LiFePO4 Battery 20Ah 12V) ($165)
• Battery clamps ($7)
• 12 gauge stranded wire in black and red ($5)
• Various wire connectors ($5)
• Wire Strippers/crimpers
• Drill
• 2×4 pieces of scrap wood

Step 1: Set up a bicycle trainer stand.

The first step was creating a wooden base to raise the bicycle stand and allow the wheel of the treadmill motor to spin. I just used some scraps of 2x wood we had lying around and set one piece under each leg of the bicycle stand. I set a bicycle into the stand and moved the resistance contraption on the back of the trainer so it wasn’t adding any resistance to the bicycle pedalling.

Step 2: Position the treadmill motor.

Some treadmill motors will have a base that can be used to secure the motor to whatever. The motor I used instead has two bolts sticking out of the bottom. I drilled holes for these to rest into in one of the pieces of wood. This did a good job of securing the motor and preventing it from rolling away. I positioned the motor so that its wheel was right up against the back wheel of the bicycle. Now when the bicycle wheel turns, it spins the treadmill wheel. Yay friction! I could test that it worked by touching volt metre probes to the end of each wire as the wheel is spinning (you need an assistant for this). Note: if the volt metre reading is a negative number, you need to turn the treadmill motor around, so the wheel spins the other way. 

Step 3: Attach the battery to the solar charge controller.

I cut pieces of black and red wire long enough to run from where I want the charge controller to where I want the battery. I stripped the ends of the wires using a wire stripper. Then I attached one end of the black wire to the black battery clamp and did the same with the red wire and clamp. 

Step 4: Add a switch to the red wire.

I wanted to add a switch to the system to prevent the charge controller from slowly draining the battery. Matt picked up a switch for me while he was at the store and, of course, for the most fun switch he could find. I feel like I am about to launch missiles. To add the switch, I cut the red wire in half, stripped the ends of each half, and attached female wire connectors to add the switch.

Step 5: Attach the battery wires to the charge controller.

I inserted the other ends of black and red wires into the negative and positive terminals on the charge controller. The terminals are labelled “battery,” so it is easy to determine which to use. Using a small screwdriver, I tightened the terminal, securing the wires. 

Step 6: Attach the treadmill motor to the charge controller.

I stripped the ends of the black and red wires coming from the treadmill motor and inserted them into the “solar panel” slot on the charge controller, securing them with a screwdriver.

Step 7: Test it out!

Now it was time to try it out. I attached the battery clamps to the battery and turned on the switch. The charge controller powered up and displayed the battery charge and energy flow. I ensured that the treadmill wheel was in place against the bicycle wheel and then hopped on the bike and pedalled. The charge controller began to indicate that energy was flowing from the solar panels, AKA bicycle, into the battery. It was actually working!

Step 8: Plug in!

The charge controller has DC USB slots on it, so I can directly charge a cell phone etc., without doing anything else. I needed to add a power inverter to power anything with an AC plug. Attaching it was simple. I simply clamped the power inverter clamps directly onto the battery clamps of the corresponding colour. Then you switch it on and plug something in, and it works.

How did it work?

The following are some thoughts on how it worked, what I observed and plans for improvement.

• It actually works. I am still finding it hard to believe that I made something that makes electricity. We will not solve any energy crisis with this generator. Still, it has a lot of promise for use during a power outage to operate and charge small devices or as a supplementary power source in conjunction with other sources. Especially if you want to exercise on a stationary bike anyway. 
• I attached a battery that had only a 15% charge on it. After 20 minutes of pedalling, it was at 40%. This progress slows a bit as it gets closer to full charge. 
• Fiddling around with the gears of the bike will change the amount of electricity I get out of each pedal pump. Also, as my leg strength grows, the electricity production will improve. 
• I can plug in a light, laptop and phone and still maintain the charge on the battery reasonably well by continuous easy pedalling.
• I set up a bicycle desk and was pleasantly surprised that I enjoyed pedalling while working. I thought I would find it distracting, but for most tasks, it was great. I have ADHD and have a hard time sitting still, so it was actually quite helpful. A comfortable bicycle seat is critical here. 
• At first, the generator did not work because I was running the treadmill motor backwards. It took me longer than I care to admit to figure that one out. I did not notice that the voltmetre readings were negative numbers. 
• I plan to work on the system’s efficiency by securing the motor more firmly against the wheel with straps etc. It has a wobble when I pedal faster, so I am probably losing some energy there.

Recently I was looking back through a 12-year-old journal, and I found a page that listed some things I would like to do/learn. On that list was “build a bicycle-powered generator.” Well, it took me more than a decade, but I finally did it thanks to my involvement with this project. I still have so much to learn, but I have come so far in my understanding of energy and electricity, and I am the tiniest bit closer to being able to power my life with sustainable, renewable energy.

The coolest outcome, however, was the many opportunities I have had to share my project with others. A summer camp used my solar ovens to bake cookies. I set up a pedal-powered smoothie stand at a community festival where people were able to use the bicycle blender to make their own smoothies. I helped 56 grade 5 students build tiny working wind turbines out of toy motors using the same concepts that I used to build the bike generator. And now, the bike generator will be used at a Repair Cafe as a pedal-powered charging station.

So much gratitude to the Moore family and Waterlution for allowing me to be a part of the Cautious Optimist Project and to Danielle for being such an amazing source of inspiration to us all.

Warmly,

Amy