Introduction: B-Charge Team and Motivation

This project is a collaborated effort by Lizzette Corrales, Claudia Renero, Lulu Zhang, and X Sun.

We are a group of UC Berkeley students who build this prototype for a proof of concept of a minimalistically designed product that can allow you to use mechanical power (100% clean energy) to charge your phone or power bank while riding a bike. We are aware that some similar ideas have existed in the market. Our idea, however, is to essentially have a framework and guide of how such a product is designed on the internet; our hope is that every maker with access to some simple mechanical tools and a 3D printer could build this product with some commercially available electrical components.


1. We brainstormed and planed the project at Engineering 27: Introduction to Manufacturing and Tolerancing, along with Miles Luhn and Monica Tang (taught by Professor Hayden Taylor and Head GSI Brian Salazar) !

2. Jacobs Institute for Design Innovation (Thank you for their generous grant that made this project become real! And thank you for all the help from staff members!)

3. Thank you for Berkeley ME alumni Christian Castaneda's help!

Step 1: Collect All Materials

You can purchase all materials from Amazon, but same items from other sources should also work!

  1. Dynamo
    1. Please note that this product might not be able to fit every bike's frame, in which case we would suggest you to source out a dynamo that would fits your bike well
    2. If you are using this dynamo or any other dynamo that is using the bike's frame as the ground for the circuit, you will need to cover the area at where the dynamo contacts with the bike's frame (we suggest to simply use tape).
  2. AC to DC Bridge Full Wave Recitifier
  3. Step down DC voltage regulator (5V)
  4. USB 2.0 Breakout Board

Other common electronic tools needed:

  1. Quick Connector for connecting the recitifier linked above
    1. Wire Crimper
  2. Solid wire (18 gauge)
    1. Wire Stripper
  3. A power bank / phone ready to be charged & its usb charger (usb 2.0)
  4. Soldering toolkit
  5. Shrink Tube

Step 2: Build the Circuit

  1. Cut the wire that connects the light from dynamo: this wire and the metal frame of the dynamo will be the two poles of the AC current generated by the dynamo
  2. Using two pieces of solid wire connects the dynamo and recitifier (soldering needed). Note that because of the material that the dynamo's metal frame is made of, you can't really solder a wire on it, we suggest that you can just twist the wire around the little circle on the frame tightly.
    1. You will be able to find the recitifier's circuit on the amazon page we linked. Make sure to solder the wires to the right poles
  3. Using two pieces of solid wire connects the recitifier and the DC modulus (soldering needed)
    1. You will be able to find the DC modulus' circuit on the amazon page we linked. Make sure to solder the wires to the right poles and make sure the output voltage will be 5V
  4. Using two pieces of solid wire connects the DC modulus with the USB 2.0 break board (soldering needed)
    1. You will be able to find the USB 2.0 break board's circuit on the amazon page we linked. Make sure to solder the wires to the right poles

  5. It is recommended that you can use shrink tube to wrap all the wires at where the metals parts are exposed

Please Note:

  • Due to the limitation of testing, we have only confirmed that the device can charge Samsung phones with regular biking speed (0.26 amp, 5 voltage = 1.3 watts).
  • If we assume a typical Samsung charger can dry 2 amp and 5v from a wall outlet (10 watts), and thus using our device will require about 7.7 more charging time than using a wall outlet.
  • Many similar devices decide to include some capacitors in those systems in order to store extra energy to charge the phone, when, for example you are stuck in a traffic. However, after talking with some experienced user (special thank you to Greg!), we found that the capacitors do not last long at all, and thus we decide to not include those in this minimalist design.

Step 3: 3D Print the Electronic Housing

Step 4: Mount It on Your Bike!

You will just need zip ties to mount it on your bike!

The whole system should be easy to take off, and thus if you are concerned about thief stealing, you should be able to simply take the whole device off each time you park. You can use the system also to charge a power bank if the power consumption of it allows it (the power bank we linked works)!

Step 5: Contribute to Our User Survey!

Please do fill up the survey despite your background of biking (we wish to collect non-biased data) to help us further learn users' demand.

The data from our survey so far (31 people) is attached.