electric bike motors
In the geared motor, a small and lightweight motor spins very fast inside. The electric bike motor then uses a planetary reduction gear inside the motor to reduce the rpm to the correct speed for a bike wheel.


Electric Bike Motor

An electric bike motor on an electric bike can be any kind of electric motor. There have been some very creative home brew e bikes that used any motor imaginable. But modern electric bikes today exclusively use permanent magnet type brushless DC motors. The incredibly strong magnets used give great efficiency, and eliminating brushes makes the lifespan of a brushless motor theoretically infinite. No more replacing burnt brushes!

How the electric bike motor gets the power to the wheel falls into 4 basic classes.  Friction drive, mid drive, left side drive, and hub motor drive.  Friction drive uses the motor to rub the tire, pushing the tire by friction. As you can imagine, a bit of water or mud on a tire could affect this method. Mid drive means the motor is mounted in the middle of the bike, near the pedals. Then the motor connects to the pedals, so the motor actually helps the rider pull the chain on the bike.  Mid drives work great, when the rider chooses the right gear. Choosing too high a gear can result in lots of chain and gear wear, and in some cases actually harm the motor or the battery. So with a mid-drive bike, you have to think about which gear to use at all times. Left side drive means a motor uses the left side of the rear wheel to transfer the power. It might be an additional chain and sprocket on the left, or it might be made so a rotating disc pushes on the spokes on the left side of the wheel. The main drawback of left side drive is noise. Most are very loud, with the extra chain and sprocket. The simplest and most elegant solution is the hub motor. With the hub motor, the motor is actually located right inside the hub of the wheel.  This makes it easy for the novice to install on a bike, and the result is a quiet ride that is never in the wrong gear. In fact, many users of a hub motor put the bike in one of the higher gears, and never need to shift gears ever again. E-BikeKit has chosen the hub type electric bike motor for all of our kits.

 How an Electric Bike Motor works.

The modern electric bike motor has no brushes, so how does the motor spin?  Magic?  It does it by the magic of the computer chip.  The motor has three big power wires leading into it. Each wire energizes one third of the motor. The microprocessor is in the motor controller, which sends a pulse of DC current down the wires in sequence, 123, 123, and 123.  In this way, the controller is constantly switching the magnetic polarity of the coils, and the energized coil is constantly attracted to the next magnet down the row.  Inside the motor, there are three tiny switches called hall sensors. Those sensors tell the controller which power wire to energize next, and when. There are electric bike motors without sensors, but they tend to run with a bit more vibration, and sometimes do funny things like trying to run backwards for a half inch, then starting up forwards. So the majority of e bikes use a motor with sensors.

The motor controller is the brains of the electric bike. The nerves are the wiring that goes to the rest of the bike. The wire to the motor is like the nerves to the legs, and the wires to the handlebars are the nerves to the senses. On the handlebars there is the throttle that controls the speed. There is a display that shows your speed and distance, the battery level, the power being used, and the speed limit level. The speed limiter lets you choose less than full power when you want maximum efficiency. And there are the electronic brakes. The e brakes don’t stop you electronically, they sense when you pull the brake levers, and tell the controller to stop the motor if you have a stuck throttle. Normally the throttle springs back when you let go, but if it does not, the e brakes will stop the motor from pushing. The e brake handle also has the familiar cable that actuates normal bike brakes.  The wire to the battery is like the bloodstream. It delivers the power to the body.

The battery is like your liver, it stores the energy and delivers it when you ask for it. Battery technology is evolving fast, with high tech lithium batteries revolutionizing everything from your phone and computer, to power tools.  The lithium batteries are very light, very powerful, and last many years. But even though lead batteries are heavier and wear out faster, the tried and true lead battery can still be a good choice, particularly when the electric bike is used less frequently, for short trips. If you use a lead battery, keep it fully charged at all times by recharging after every trip.  But if you rack up the miles at all, a lithium battery is always the lowest cost per mile. A lithium battery can be left overnight half charged with no ill effects. But it’s still a good habit, to charge it after each trip. To store either type of battery for the winter, charge it fully, and unplug it.  Then put it back on the charger monthly.  Store in a place that is cool, but not frozen.

There are two distinct types of hub motors.  Each has advantages for different types of bike or riders. So E-BikeKit offers both types of electric bike motor.  For most riders, the 500w geared motor is ideal.  

The Geared Motor

internally geared hub motor

The 500w Geared motor: light, high-torque, and fast.

In the geared motor, a small and lightweight motor spins very fast inside. The electric bike motor then uses a planetary reduction gear inside the motor to reduce the rpm to the correct speed for a bike wheel.  In this way, high power and torque is developed by a smaller motor that weighs less.  The geared motor also has an internal freewheel, so when you coast, or ride without the motor on, the motor does not have to spin unpowered. This improves coasting distance, and the motor does not add resistance to pedaling with the motor power off. Because of the internal freewheel, a geared motor cannot generate power by coasting.




The Direct-Drive Motor

direct-drive hub motor internals

The other type of electric bike motor is a direct drive motor.  This motor is usually about 4 pounds heavier than the geared type.  A larger motor with wider magnets spins at the perfect rpm for bikes. There is exactly one moving part in a direct drive motor, so it’s incredibly hard to wear one out. The direct drive electric bike motor is ideal for the harshest type of use.  That generally means more weight, and very long hills. So we have the direct drive motor for tandem bikes, cargo bikes, bikes that haul trailers, or for riders that weigh more than 250 pounds. There is a tiny bit of resistance created by a direct drive motor when you coast. This can be completely eliminated by running the motor on a tiny trickle of power.  This is where the 5 power level settings work great. Using the lowest power level, and a tiny bit of throttle, you can pedal or coast with zero drag, and nearly no power used.  It’s ideal for extending range by using the motor minimally.