Building an e-Bike

An electric bicycle (E-Bike) consists of an integrated electric motor, and a rechargeable battery pack.

Below are a list of parts required when transforming an existing bicycle into an E-Bike. Either you can go online and buy these parts or you buy the parts separately and attempt to attach them together. If you attempt to assemble your own system you'll need semi advanced micro controller knowledge to get the controller working.

  • Motor
  • Controller
  • eBrakes - turns off motor when braking
  • Throttle (gas pedal)
  • Must have battery (or battery pack): High torque motors result in faster discharge and shorter distances. Low torque motors result in slower discharge and longer distances.
  • Connecting wires

 

Motor

eBike Motors

There are four different types of Bike motors.

  • Rear Hub Motor
  • Friction Drive Motor
  • Front Hub Motor: Note Requires steel fork. Will bend aluminum fork.
  • Mid Frame Motor

Brushless DC motors are current activated magnets. The force is applied when current is sent through transformer coils which are wrapped around the magnet. The result is a magnetic pull strong enough to rotate the rotor which is constructed of permanent N-S pole magnetic pairs. The pull creates torque. Often the higher the voltage applied to the motor the greater the torque. 

 Brushless

Additionally, "More magnet pairs increase torque and smooth out so-called torque ripple, evening the power delivery from the motor. The downside is a more complex control system, increased cost, and lower maximum speed." Digi-key brushless info.

Some examples of motors you might find on the market include.

Option 1: 48V 1000W Powerful brushless gearless motor with 28mph (45km/h) speed; Restricted to 750W and 24mph (38km/h) speed by default as a road-legal pedal bike conversion kit.

Option 2: Voltage:48V Wattage:750W Motor Type:Brushless Gear Motor

 

Controller

If you're putting this together yourself you'll need to consider a couple things. Typically you'll need to control the following things.

  • 48V from battery to power motor, and graphical display
  • eBrakes
  • Graphical Display
  • Throttle
  • Brushless DC motor driver

Generally speaking what type of controller you use weighs heavily on the type of microcontroller board you are familiar with or want to learn. Typical speaking ARM Cortex-M series boards provide enough functionality. Some vendors build and ship boards specifically suited to be motor drivers. This means the circuitry that discharges the battery pack into the motor is built into the microcontroller.

 

Battery Pack

Below are some configurations you might find.

Option 1: 48V 13AH / 36V 15AH Lithium ion Battery with Charge. 3-5 hours before the battery needs to be recharged, riding Line distance up to 30 kilometers, battery for a 200-500W motor

Some packs provide an option of either using the 48V high torque mode or the 36V low torque mode. When in high torque mode the battery has only 13AH of life, but when in low torque mode the battery has 15AM of life. If an AH is the amount of energy in a battery that will allow 1 ampere of current to flow every 1 hour and these batteries are expected to last 3-5 hours it would suggest that these batteries are discharging about 3-5 amperes on average at any give time in high torque mode and 2-4 amperes on average in low torque mode. 

Option 2: 48V/36V Li-ion Battery for Electric Bike Scooter Electric Tricyle with Charger, Fit 250W 350W 500W 700W 1000W Motor

Option 3: 48V 10AH / 36V 10AH Lithium Li-ion Battery with Charger and BMS Protection Board, E-Bike Battery for 200W to 500W Electric Bicycles

 

Throttle

Sends signal to controller which controls torque of multi-phase brushless DC motor.

 

Brakes

Stop motor.