Things You Need to Know Before Buying an E-Bike'

So do don't want to work that hard to ride a bike, but you also don't want a steam bike:

Nothing can please you! Maybe you should try an electricity-enhanced bicycle. This here is part one of a guide about some things you should know before getting into e-bikes. 

(WARNING! TO GET THE MOST OUT OF THIS POST YOU WILL NEED A 5TH GRADER'S UNDERSTANDING OF ELECTRICITY AND MAGNETS! IF YOU FORGOT ELEMENTARY SCHOOL OR WERE NEVER EDUCATED, HERE'S A FUN VIDEO YOU CAN WATCH)


E-bikes are bikes, first and foremost, and their anatomy isn't that different than any other two-wheeled pedal machine. There are, however, five crucial aspects to an E-bike that are easy to overlook but are nonetheless crucial to getting the most out of the machine.

The vital components that separate an E-bike from a regular bike are:

1. Motor: Brushed or Brushless
2. Electronic Speed Control (Amp controller)
3. Battery Types: Lithium Polymer, Lithium Ion, NiCad, Lead-Acid, and so on
4. Sensor: Torque Reader, Speedometer, Thermal Regulators, etc
5. Assorted Bike Parts: Chain, Tires, Cogs, Brakes – all need to be modified for e-bike use

I will go into the differences between all these things in this an other articles.

First, Labeled Wattage, and why you shouldn't trust it:

The wattage number brandished on the side of your e-bike's motor is misleading for at least two reasons:

1. Wattage is usually a measure of input, as in how much energy the motor consumes, using the formula: "Amps" times "Voltage" equals "Watts." A 250 watt brushless (BLDC) motor will do a hellavulot more than a 250 watt brushed motor, for reasons I'll get into below, but the marketing label on the side of the bike doesn't show that. 
2. The wattage posted on the side of the bike and in the brochure might be wrong. The battery and amp controller have more to do with the wattage than the motor, and battery voltage can change depending on battery type and quality. 

I'll talk more about wattage in another post, for now let's focus on the motor.

Now, motor types:

E-bike motors come in one of two types: DC brushed or brushless. I'm going to simplify their explanation as much as I can, because there are plenty of engineering blogs that can satisfy any in-depth questions about how the different motor types work. I'm going to stick to explaining the benefits and drawbacks of each motor type for bicycle use.

Brushed motors:

The DC (direct current) electric motor exists now as it did over a hundred fifty years ago. The basic idea is that it sends an electric current back and forth along an axle, between two or more magnets with opposing polarities. –By the way, I'm going to use "axle" as a catch-all for all the parts of a DC motor that spin between the magnets (or stators, as they're usually called). This includes the "armature," the "windings or coils," and the "commutator," as well as the drive shaft in the middle of it all.

To keep the axle spinning, a set of brushes tap either the negative or the positive power terminals, switching the axle's polarity and causing it to spin against the magnetism of the stators.

The video above gives a more thorough explanation.

Advantages of a brushed motor for an e-bike:

1. Cost: brushed motors are the simplest, oldest, and least expensive type of motor.
2. Ease of maintenance: the brushes on the commutator wear out, as do the terminals. Luckily they're so easy to identify and switch out even a child could do it (indeed, I did it as a child).
3. Sparks: sometimes sparks shoot out of the air vents in a brushed motor and it looks cool.

Disadvantages of a brushed motor:

1. Poor heat dissipation: overuse can cause a blowout, and they need ventilation or heat sinks
2. Low speed range: the faster the axle spins, the more friction the brushes make when they strike the power terminals (and more sparks!)
3. Inefficient: batteries won't get you as far with a brushed motor
4. Excessive Inertia: The heavy axle tends to keep spinning even after the power turns off 
5. Electromagnetic interference (EMI): those pesky brushes disrupt the magnetic fields around them, so don't set your cell phone down next to a spinning brushed motor

Applications:

Less expensive e-bikes use brushed motors, specifically the cheap bikes that come direct from China in a cardboard box. Some hub-based hobby kits use brushed motors too. 

Brushless motors (BLDC):

Microprocessors and sensors that detect electromagnetic flow (Hall Effect) have allowed the creation of electric motors that remove all the downsides of their brushed predecessors. 

Brushless motors invert the design of brushed motors by wrapping magnets around the axle, and using the casing walls to hold the coils through which the alternating electric current flows. 

Brushless motors have only one moving part, the axle, and its only point of contact with the outside world is the bearing that holds the axle to the casing. This means that BLDC motors create very little friction, which means they don't make much heat or noise, which also means they don't need air flow, which means they can be hermitically sealed, and thus water-proof, foul-air-proof, and corrosion-proof. 

Hypothetically, a brushless motor can run for thousands of years without any repairs, so long as the operator replaces the axle bearing whenever it wears out. 

Advantages of a brushed motor for an e-bike:

1. They're the best performing option currently (pun intended) available. They improve or remove every single downside of their brushed brothers

Disadvantages:

1. Cost: Hall effect sensors and microprocessors aint cheap. 
2. Speed control: They need a special electronic speed control, which can cost as much or more than the motor
3. No Sparks

Applications:

Most – but not all – high quality e-bikes use a brushless motor. While it is more expensive, it's the superior option in nearly every way, assuming it's paired with the appropriate Amp controller (ESC) and battery. 

But it's also a component that a nefarious bike manufacture can skimp on without the customer realizing. The average person doesn't know the difference between e-bike motors, and neither do the sales folk at the bike store. The tendency for both is to focus on what they know an understand: gears, body position, frame materials, and so on. A company can slap a big old wattage sticker on the side of the bike and a lot of people will misunderstand that to be a good thing. Because motors are fairly overlooked they can be built and applied cheaply, and the customer is none the wiser until years down the line when the brushes on the cheapo motor wear out.