Introduction: DIY Electric Bike

Converting your old mountain bike into a town zipping e-bike is within the skillset of any electronics hobbyists, bike frantic and/or everyday mechatronic tinker. It is a fun and relatively easy project as long as you have some knowledge about tinkering with bikes.


Step 1: Introduction

I repurposed a old Giant mountain bike into a hill crushing commuter e-bike and now I get to work twice as fast and with more energy left for the day. The parts to create this masterpiece are as follows:

  1. Old mountain bike (Preferably a hardtail with front shocks)
  2. Li-Ion battery
  3. In-hub wheel motor or mid crank drive motor kits
  4. Allen keys
  5. Pedal crank removal tool
  6. Adjustable wrench

When designing what kind of bike you want, you should start with what kind of Li-Ion battery you can get or want to pay for. I originally purchased a 36V, 13Ah battery (~$250) with my 36V, 500W rear wheel motor (~$170) you can go roughly 20-30 miles on a single charge (Granted I climb a net of 1000 ft to and from work everyday). The battery voltage MUST match the voltage of your motor spec. Additionally, make sure the dimensions of the Li-Ion battery fit in the inner triangle of the bike frame and that the rear wheel motor is the same size as your current wheel.

Step 2: Wheel and Motor Controller

Once you have gotten your motor or in-hub wheel motor and motor controller unpacked it's time to take out the bike tools. In my case I took off the rear-wheel and put in the in-hub wheel motor (With the disc plate for eventually putting in disc brakes) and zipped tied the wiring to follow along the frame. (See the photo attached).

Follow the built-in instructions to wire the motor controller to the throttle (See the photo attached of the handle bars), the in-hub wheel motor, the brakes and eventually the battery. Zip the wires along the frame and feed all the wires from the different components into the provided bike bag. Attach all the wires to the motor controller, following the color scheme.

Step 3: Pedal-Assist Sensor Installation

Take off the left pedal with the pedal removal tool and place the magnetic pedal-assist sensor on the bottom bracket with super glue. (See the photo attached).

Step 4: Test and Ride!

Install the battery frame using the bike bottle screw holes. Connect the red(power) and black(ground) wires together to the motor controller and wrap them with heat shrink. Check everything is wired up according to the instructions. Turn on the battery and turn on the whole system! Check the lights on the throttle and give it a test ride!

CAUTION: When playing around with Li-Ion batteries take care. DO NOT cross the black (Ground) and red (Power) wires by any means. NEVER connect or disconnect wires with the battery on. ALWAYS TAKE THE BATTERY OUT WHEN INSTALLING OR UNINSTALLING ANY WIRING.