Motors and drivetrains

The electric motor is the single most important feature of an electric bike. The different types of motors that can be found on most electric bikes are the front hub, rear hub and the mid-drive motor.
Front hub motors are located on the front tire and provide propulsion by spinning the tire. The motor creates the sensation that the bike is being pulled forward.
Rear hub motors provide propulsion by spinning the back tire. They push the rider forward which can feel more natural to traditional bike riders than front hub motors.
Mid- drive motors send power to the bike's drivetrain instead of a hub. Its central location creates a more natural riding sensation than hub motors
The drivetrain provides the power and torque necessary to manually turn the wheels of the bicycle. Mid-drive motors send power directly to the drivetrain, making chain cranking easier. Most drivetrains also allow the rider to shift gears. Electric bike motors are available in a wide variety of power ratings, from 200W to 1,000W or more. The legal limit within most countries is 750W, although different states can set their personal limits.
Think of this limit kind of like a horsepower. A better rating means that the bike could be capable of pulling greater weight with more ease but at the cost of the usage of more battery capacity whilst doing so. consequently, a 750W motor will drain the battery much faster than a 250W one, but it will be more powerful.

Batteries
Since the bike's battery affects the weight, the style, and the range of the bike, its choice is crucial. Batteries play a huge part in how electric bikes work. Most batteries you'll find being sold on the market fall into one of the following two categories:
SEALED LEAD ACID (SLA)
These batteries were once the appropriate battery type for most electric scooters and electric bicycles. These days, most electric scooters still use SLA batteries, while electric bikes (which often require human input) have opted for newer battery technologies to keep the bike as lightweight as possible.
Advantages: Inexpensive
Disadvantages: Heavy and bulky. Offer a shorter riding range. Shorter life span of about 100-300 full cycle charges. Require more maintenance, and need to be charged immediately after use
LITHIUM (ION/POLYMER/MANGANESE/ETC.)
These are the newest technology in batteries. A lithium battery has a lifetime roughly 2-3 times that of an SLA battery. Lithium batteries are much lighter and also are largely maintenance-free.
Advantages: Lightweight – high-capacity, 36V10Ah Lithium-Polymer batteries can weigh as little as 6 pounds! Offer a longer riding range – battery can travel up to 40 miles in pedal-assist mode (or 20 miles on throttle-only). Longer life span of about 800 charges or 3 years of virtually daily use
Disadvantages: More expensive – starting at about $1,500 to $3,000 and above

Controllers
Available in a variety of patterns, the controller lets you operate the electrical assistance on your electric bike and is an important component in how electric powered bikes work. The controller is placed at the handlebar for ease of use. There are different types of controllers – pedal-activated and throttle-primarily based controllers.
Pedal-activated structures provide electric powered assistance as you press down at the pedals. There is no need to engage the throttle – easy pedaling will do the trick. Electric bikes with pedal-activated systems have a controller mounted on the handlebar that helps you to adjust the level of assistance that you receive as you pedal. you can dial in the quantity of assistance you need, ranging from no assistance to a great deal of assistance.
Throttle-based controllers work with a simple throttle mechanism. The throttle will either be a twist-grip type or a thumb-press type. With a throttle, you simply pull back or press the throttle to get hold of the electric assistance. a few electric bikes require nothing more than activating the throttle, allowing you to ride with out pedaling.
By and large, electric powered bikes are easy to use, ride, and preserve. overall, they require little maintenance past that which a standard bike requires.