Electric Bike


last updated: August 1, 2014


Design goals

  • Cheap
  • Minimal bike modifications – it should only take minutes to put the bike back in it’s original condition
  • Light – it shouldn’t be that hard to carry


The display


The display shows the following information

  • Speed (km/hr.)
  • Distance remaining under current conditions (km)
    Valid only when speed, power and peddling effort is steady
  • Power comsumption (Watts)
  • Odometer (km)
  • State of charge based on coulombs used (%)
  • State of charge based on voltage (%)
  • Amp-hours used so far

There are a variety of other values available to be displayed, but they’re not that important and there’s only so much room on the LCD.

Here’s the source code (Aug. 1, 2014)


The parts

  • Microcontroller (PIC 18F2620)
  • Current sensor (Allegro ACS756).
  • 5V switching power supply
  • Hall effect sensor


24V, 1200 RPM, DC, brushed, 4″D, 6″L, very heavy. I’d like to get a better one.


Motor controller

From Ridemore


The sprockets

There is a 9 tooth sprocket on the motor and 32 on the wheel.



3 5 amp-hour Lithium polymer packs from Hobby King in China. They are 3 cell, 20C. Total voltage ranges from 37.8V to 27V.




The cost

  • batteries: $300 for 2 sets, includes $100 for shipping
  • motor control: $150
  • sprocket: $20 including shipping and other costs
  • chain: $12

The rest of the parts I had lying around

 Posted by at 4:38 AM