What is the True Range of an E-Bike?

The actual range of an Electric Bike is not always what is advertised

When we speak of “range” we are collectively referring to how far an electric bicycle will travel in miles before the battery loses it charge. Because they vary in the nature of how they are assisted, our focus will be on bikes propelled by motor and battery alone. Some rely on pedal input from the rider to compute their advertised range.

So, on an E-Bike using only the electric motor, range is determined primarily by a combination of 6 factors:

  1. The speed the rider is traveling

  2. The steepness of the terrain

  3. The weight of the rider

  4. The combined aerodynamic drag of the rider and bike

  5. The efficiency of the motor drive system

  6. The energy of the battery (measured in Watt Hours or Wh)

If factors 1 to 4 are identical, then range is solely a function of factors 5 and 6: the Watt Hour energy capacity of the battery and efficiency of the motor drive system.

Kilowatt meter

Simply put, the watt-hour capacity of the battery determines how far you can travel before recharging. Batteries are rated in either Amp Hours (Ah) or Watt Hours (Wh). Total energy output is given in Watt hours (Wh) and is a product of the Volts times the Amp Hours. For example, a 37 Volt battery with 10 Amp Hours has a capacity of 372 Watt Hours. This means the battery can put out 372 Watts for One Hour.

For long range touring purposes, Optibike pioneered the use of Lithium Ion batteries, with the largest energy capacity of any electric bike.

e bike

The efficiency of the motor drive system is also integral to electric bike range, all other factors considered equal. An e-bike can be thought of as a motorized bike, a motor drive system transfers power from the battery to the wheels propelling you forward. Optibike revolutionized motor drives with the introduction of its patented Motorized Bottom Bracket TM (MBB) system, extending electric bike range. The MBB has the highest power to volume ratio of any drive system, and is combined with a patented Derivative Power Control™ (DPC) system. DPC allows you to have both high acceleration and high efficiency, further extending your range over other electric bikes.

Battery Basics

Hub Motors vs Mid-Drive Motors

Power & Torque

Why Torque Matters

In an electric bicycle, torque is the ability to rotate the rear wheel. Higher torque will rotate the wheel easier and create more acceleration. This means a bike with higher torque is easier to get going from a stop or up a steep hill.

Image result for bicycle rider pushing on pedals

What is Torque?

The general definition of torque is the force on an arm at a distance from a center of rotation. In the picture below, the distance is 1 Meter and the force is 50 Newtons, so the torque is 50 Newton Meters.

Image result for torque

Torque Equation

The general equation for torque is below.

Torque = Force x Distance

or T = F x D

In a standard bicycle the rider pushes on the pedal to create a “Force” and the length of the crank arm is the distance. Crank arms are typically 175 mm or 7 inches long. If the rider weighs 200 pounds and stands on the pedal, the the torque is 1400 inch pounds as given by equation below:

Torque = Force x Distance

1400 inch pounds = 200 pounds x 7 inches

bicycle crank arm

Torque Units

In electric bikes, you will read about Torque in Metric Units (Newton Meters) or US units (Inch Pounds). You may also see torque measured in Foot Pounds.

A common torque for lower powered e-bikes is 50 Newton Meters,which can be converted to 442 inch pounds or 36 foot pounds.

50 Newton Meters = 442 inch pounds = 36 foot pounds

For comparison the Optibike R15 has 175 Newton Meters of torque.

175 Newton Meters = 1,549 inch pounds = 129 foot pounds

Electric Bicycle Glossary

Watts: A measure of power, 745.7 watts is equal to 1 horse power.

RPM: Revolutions per minute

Torque: Torque = Force x Distance, torque is the ability of the motor or rider to rotate the wheel, higher torque = higher acceleration

Power: Torque x RPM = Power: more power = more speed

Voltage (V, volts): Voltage is a force that makes electricity move through a motor

Current (A, amps): A measure of current in the battery or motor

Amp-hours (Ah): Capacity of a battery measured in amps per hour

Watt-hours (Wh): Wh = V x Ah, energy capacity of a battery that includes voltage

Pedalec Control: Electric bike where the power is controlled by the pedals

Throttle Control: Electric bike where the power is controlled with a throttle on the handlebar like a motorcycle