An ampere is the base unit of electrical current.  An ampere is equivalent to a charge of one coulomb per second. The power of the circuit is given by the following formula:
P(Watt)= V(Volt) x I(Ampere).  By rearranging this equation you can calculate the value of electric current as follows: I(Ampere) = P(Watt)/V(Volt).  Here is an example as it relates to ebikes; a 48-volt motor system driving a 750-watt motor would use up to 15.625 amps of current. (750 divided by 48).

Ampere hours, or more commonly called amp hours or Ah, are a measure of battery capacity.  This is commonly used when discussing batteries and their amount of energy storage. The larger the number of amp hours listed, the more energy is stored in the battery.  It’s a measurement of how many hours a battery can put out 1 amp, or how many amps a battery can put out in one hour.

eBike battery packs are made up of individual cells whose chemical reactions create a flow of electrons in a circuit. Lithium-ion cells are the most common and can be linked together in both series and parallel to create enough power to drive the motor at a given power output and to do so for a long enough period of time to offer good range.  In other words, this is your ebikes power source, the juice that makes everything run.

The vast majority of ebikes use a traditional chain drive system, however there are a number of companies that have adopted belt drive systems.  Belt drives replace the metal chain with a single loop of rubber and are favored for their quiet drive and low maintenance.  However, belt drives are more difficult to put back on if they pop-off and require tools to do so.

Batteries are generally made up to multiple cells with lithium-ion cells bing the most common.  Cell sizes do vary with the most common being 18750 and 21700.  These numbers refer to cells diameter and length as measured in millimeters.  18mm x 75mm for 18750  and 21mm x 70mm for 21750.  The larger cells have greater capacity and therefore higher potential range.

Any time you fully discharge and then fully recharge a battery, it’s considered a charge cycle.  Any time you partially discharge a battery, say by 33 percent, it’s a partial cycle.  In this case, it’s ⅓ of a cycle.  Batteries are usually rated for between 500 to 2000 charge cycles before they will no longer have enough capacity to be useful.  It’s worth considering this when you buy a bike; ask if replacement battery packs will be available from the manufacturer 3-5 years after you purchase the bike.

The American ebike classification was developed in part by PeopleForBikes to help states have a standardized way to classify ebikes to make it easy to legalized ebikes for various types of roads, paths and trails. Class 1 is pedal-assist only and can go up to 20 mph. Most electric mountain bikes are Class 1.  As a side note, the same type of bike in Europe is limited to 25 km/h or 15.5 mph.

Class 2 follows the same rules as Class 1, but it also allows for a throttle and can go up to 20 mph regardless of whether the rider pedals or not.

Class 3 ebikes can have pedal assist and speeds up to 28 mph and can only be legally used on the street or designated bike paths.  They can also have throttles.

Some motor systems have apps that let you connect a smartphone app and/or control the system using your smartphone.  These systems typically allow the rider to customize various controls and offer a larger screen with more information.Connectivity can not only talk with the bike, but it can help add GPS maps and other information.

Think of the controller as the brain of the bike.  It connects the electronic parts of the drivetrain, including motor, battery, throttle, torque sensor and cadence sensors.  It takes their inputs, plus the mode/power level you’ve selected, and pulls current from the battery to offer the right amount of pedal or throttle assistance to the motor.

DC stands for ‘direct current’ which means the current only flows in one direction. Electric bike motors run off a simple direct-current design. Other batteries and electronic devices like TVs, computers and DVD players use DC electricity as well.

Direct-drive hub motors are the simplest type of motor used in ebikes.  The magnets in the motor are fixed on the inside surface of the hub and windings are permanently attached to the axle.  When power is applied, the hub is made to rotate around the axle.  The advantages of a direct-drive hub motor include quiet operation, few moving parts and simple operation. However, because the motor is always mechanically engaged they experience drag while coasting.  Direct-drive motors must also be larger and therefore heavier than comparable geared hub motors to achieve the same performance.

Most ebikes have either an LCD or LED display that show a variety of information including battery charge status, speed, peddle assist level and trip meter. 

Usually a smaller bike that can fold in half to become easier to transport and store.  Folding frames are often designed with a hinge in the middle and handlebars that fold down as well.

A ebike that has the hub motor located in the front wheel as opposed the the rear wheel. Commonly found in conversation kits and trikes.

Compared to a Direct-Drive motor, geared hub motors incorporate internal planetary gears to turn the hub and make the wheel and bike move forward.  These motors are often smaller than equivalent-wattage direct-drive hub motors and can be quieter.

Most modern ebikes use lithium-ion batteries.  They tend to be lightweight, energy dense, reliable and safe.  The risk of them catching fire, especially while charing, is infinitesimally small these days.  The ones that we read about causing fires are almost always off-brands that use cheap, poorly made cells.

Also know as LiFePO4, this is a step up from a sealed lead-acid (SLA) battery.  It offers similar performance to lithium polymer battery but tend to be heavier.

A type of lithium-ion battery that uses a polymer electrolyte, a semi-solid gel, instead of a liquid electrolyte.  These batteries provide higher specific energy than other lithium battery types and are used in applications where weight is a critical concern. (Think cell phones) This chemistry is also very rugged.

As the name suggests, mid-drive motors are mounted at or near the frame’s bottom bracket and connect directly to the pedals.  These motors offer the advantage of a multi-gear drivetrain and provide the rider more control of the torque output because the power runs through the rear gears.  This setup is similar to a motorcycle or manual transmission in a car, but without a clutch.

A Newton-meter, often abbreviated as N/m, is a measure of torque.  It’s the force of one Newton (the amount of force needed to accelerate 1 kilogram of mass at the rate of 1 meter per second squared in the direction of the applied force) applied perpendicular to the end of a moment arm that is meter long.  All ebike motors will have their power output amounts rated in N/m, Newton-meters of torque.

Pedal assist means that an electric motor helps you pedal when you pedal.  Without moving the pedals, you will get no help from the motor.  Ebikes offer different levels of assistance to allow the rider to determine how much effort they want to exert as they ride.  Bikes with throttles can get the benefit of the motors assistance either with pedaling or without pedaling.

A motor’s output power is measured in watts.  The number of watts is stated in the nominal amount, not the peak output.  A 750-watt motor may put out 1200-watt peak, but that doesn’t make it more than the legal limit.  The legal limit is based on the nominal output of the motor.

A device located on  the handlebar that controls motor power.  It can be incorporated into the grip or be a lever next to the grip.  Throttles can be used both while pedaling or independent of pedaling.

Torque is measured in Newton-meters (N/m).  It is rotational force, where power is linear force.  Think of torque as how much work a motor can do versus power that is the rate of work that can be done.  A motor with a lot of torque (120 N/m) can get you moving quickly and make climbing hills easier, where the power (750-watts) helps you maintain certain speeds.

This is the potential force of power flow from the battery to the motor.  It’s like water flowing through a hose – the higher the voltage, the more electrons can flow to the motor and allow it to do its work.Today most ebikes use either 36, 48 or 52-volt systems.

Power is a measure of the rate at which energy flows, and in electricity, it is measured in watts, abbreviated as W.  Watts are sort of like the miles-per-hour measurement of the electric world, they tell you how fast the electrons are speeding down the highway.  The higher the wattage, the faster you’ll use the energy stored in the battery.

Watt hours, of Wh, are a measurement of a battery’s overall capacity.  It is calculated by multiplying the amp hours by the voltage, i.e. a battery with a rated voltage of 36 volts and 14 Ah has a capacity of 500Wh.