Useful Electric Bike Terms

A watt is the standard international unit of power.  In electric bikes it is used when referencing both motor capacity and battery capacity.  For example you could say, "My Outrider Alpha has a 2,200 watt-hour battery and a 4,000 watt electric motor." 

HELPFUL FORMULA: Watts = Volts X Amps

A kilowatt is one thousand watts.  It's usually abbreviated as a "kW".  Example: My Outrider Alpha electric bike has a 4 kW motor (This is the preferred way to say it.  You could also say "My electric bike has a 4,000 watt motor", and you would be saying the same thing.)

 A volt is a measure of voltage in reference to electricity.  A common analogy compares electricity to water moving through a pipe.  In the analogy, voltage is the water pressure.  A word to the wise: Voltage drop during usage of a battery is "non-linear", so if you're using this to calculate remaining range, keep in mind that voltage in relation to range will have a bell curve.

 An amp is a measure of amperage, or "current" in reference to electricity.  Word to the wise: Amperage usage of a battery is "linear", so if you're using it to calculate remaining range, you can do so more easily than with voltage.  For example, if you have a 40 amp-hour battery and you know you can get 2 miles per amp-hour, you have a range of 80 miles (These are theoretical numbers and will vary from bike to bike based on efficiency, speed and terrain).

Watts, kilowatts and amps all need to be measured over time in order to obtain useful energy numbers. Really, when the term watt, kilowatt or amp are used on their own, the "per hour" is assumed but not necessarily included. For example: Take a 60 watt lightbulb. That lightbulb uses 60 watts ("per hour") continuously and if it runs for 1 hour, it will have used a total of 60 watt-hours, run it for two hours, and you'll have consumed 120 watt-hours. The same is true for amps. If you have a 25 amp hour battery, you can pull 25 amps for 1 hour or 12.5 amps for 2 hours etc.

Torque sensing refers to a particular way that certain electric bikes engage electric assist.  When using torque sensing, there is a sensor in the bottom bracket or pedals that senses how hard you are pedaling.  The harder you pedal, the more assistance you get - because the torque sensor believes that you must be encountering challenging terrain and would like an assist.  

While some riders may enjoy this aspect, others may find it limiting or frustrating that they cannot pedal hard without getting electric assist.  Outrider does not use torque sensing electric assist because it puts the bike in the decision making position, instead of the rider.  We believe our riders know when they do, and do not want assist, so we use a throttle based electric assist.

Recharge rate refers to the rate at which an electric bike - or more specifically the batteries on an electric bike, can receive electricity.  Put simply: How fast your batteries can charge.  Very few electric bike companies offer this information.  The value is usually indicated in miles per hour.  The value is influenced by the capacity of your battery (how much can it hold), the charge rating of your battery cells (denoted as "C", on a scale of ~1C to 10C, with the higher the number indicating greater ability to charge quickly), the source you are charging from (110V, 220V or 440V) and finally the output power of the charger you are using.  

For example: If you are charging a 1kWh battery that has a 1C rating, on a 110V outlet, with a charger that has a max charging rate of 500 watts, theoretically it will take about 2 hours to charge.  Realistically, it will take a bit longer because batteries usually have a bulk charge and trickle charge.  Think about this the same way you fill up a glass of water.  The bulk charge is the way you fill the first 90% of the glass with water.  The trickle charge is the way the fill the last 10% to make sure you don't spill any.  Battery chargers operate in a very similar way to this.

Aerodynamic is a term that refers to how an object moves through air (or inversely, how air moves around an object).  There are certain shapes that are more aerodynamic than others.  For example, a teardrop shape is more aerodynamic that a square shape.

 In the cycling world, a recumbent bicycle chassis is more aerodynamic that an upright bicycle chassis.  This is because an upright bike puts the rider's body in a position that "catches" a lot of wind, where as the recumbent position allows an easier flow of air over the rider.

Frontal area is often the foremost discussed aspect of aerodynamics, BUT! how the air moves around the object is just as important.  This in technical terms is called the coefficient of drag.  You can think of "drag" as the opposite of "aerodynamic".  As air moves over an object, it can "attach" to the surface.  As it detaches from the surface as the object continues on it's path, it can create "drag" - essentially that detaching air wants to slow the object down and keep it where it is, causing reduced efficiency.

Recumbent is a word that refers to the riding position of a bicycle or tricycle.  A recumbent riding position is reclined so that the rider's weight is on their butt and back, as opposed to their butt/groin on a traditional upright bicycle.  Compared to the upright riding position of a "normal bike", the recumbent riding position reduces stress on the groin, neck, back, shoulders, elbows, wrists and knees.  In most cases, a recumbent riding position is more aerodynamic (see above) and therefore more efficient.  This means that recumbents require less effort to go an equal distance.  You could also say that recumbents require equal effort (to an upright bike) to go a further distance.

The throttle is the mechanism that applies electric assist.  It is either actuated by twisting a handle (Akin to a motorcycle.  The more you twist, the more assistance you receive), or by sensing the torque produced (The harder you pedal, the more assistance you get).

The controller is the brains of the operation in regard to electric bikes.  It acts as the communication link between the batteries and the motor.  Example: You twist the throttle, the controller senses this action, and tells the motor how much power to pull from the batteries.  This all happens instantaneously, and yes - it is very awesome!

A hub motor is an electric motor that is placed within the hub of the bicycle wheel.  The spokes are laced directly into the hub motor.  The most common placement is within the rear wheel, however, it is sometimes placed within the front wheel.  In rare cases, bicycles are built with hub motors in both the front and rear wheels.

A mid-drive motor is an electric motor that is placed on the bicycle, and drives typically the rear wheel either by chain or by belt.

A function of a battery on an electric bike is exactly the same as the batteries you're used to interacting with.  They store electricity.  Their chemistry and dimensions vary.  Lead acid batteries (think car batteries) are used with electric bikes in many Asian countries, however they are rarely the best choice because they are very heavy.  Lithium batteries are a common choice with electric bike manufacturers, using either LiPo (Lithium Polymer) or LiFe (Lithium Iron Phosphate).  Lithium batteries are a common choice for electric bikes because they are very power dense - meaning that they can store a large amount of energy in a small space.  

Battery cells each have a certain voltage, amperage and recharge rate.  These cells are combined to create "battery packs" that can store a sufficient amount of energy to propel an electric bike, where as the individual cells would not be able to do this on their own.

The shunt is a small piece of copper with two "poles", where current passes from one to the other and can be measured.

On the low end battery capacity will be about 24V, 10 Amp-hours, 240 Watt-hours. On the high end battery capacity in an electric bike can be 48V, 48 Amp-hours, 2200 Watt-hours, which is the size of the battery in the Outrider Alpha. The average electric bike battery size is about 500 Watt-hours.

The low end is about 250 watts found on some hub-motors. High end electric motor power would be 4,500 watts.  The average electric bike motor power is about 500-750 watts. 

Low end electric bike range can be 10-15 miles. High end range for an electric bike is around 100 miles, held by the Outrider Alpha. You can expect the average electric bike range to be around 15-20 miles.

A poor low end recharge rate is around 10 minutes of charge = 1 mile, where as a great high end recharge rate is the Alpha at 1 minute of charging = 1 mile.  The average recharge rate for an electric bike industry wide is around 5-6.