It's not rocket science to tell the difference between an electric-powered bike and a regular bicycle. For one, the guy riding the regular bike is working a lot harder to pedal, while the electric bike rider is smiling and cruising along. Of course, electric bikes are much quieter than gas-powered bikes, so at a glance, it's hard to tell if a bike is even electric at all! The average person, unless they have a background in electronics, probably isn't aware of how easy it is to convert a regular bicycle to an electric-powered bicycle. Believe it or not, there are only three primary components needed to have a fully-functional electric-powered bike. If you can change a flat tire, you can turn your bike into an electric bike. Let's get to it!
Electric Bike Motor
The muscle behind the electric bike is the motor. Ranging anywhere from 200 watts all the way up to 1000 watts, this is the large rotating device that helps the wheels to spin on their own. Modern electric bikes have the motors built into their wheels, like the Sanyo Eneloop electric bike or the eZee Torq electric bike. Older bikes used to have an external motor that powered the wheel using a chain, like a scooter. These older motors also used magnetic "brushes" which would wear out over time. Newer electric bike motors are "brushless," and have a much longer life expectancy.
An alternative to the brushless hub motor is the bottom bracket motor, featured on the IF Reach DC folding electric bike. This motor actually cycles through all of the gears, making it slightly more efficient than a hub motor. It also turns the pedals instead of the wheel, so the rider feels a little more in tune with the motor, rather than feeling pushed or pulled by an external force.
Most electric bikes don't need a bigger motor than 500 watts, especially for commuting. The US law sets the maximum speed at 20 mph for electric bikes, so any motor that is bigger is sort of pointless. Smaller motors tend to conserve battery life a bit better. How long should a battery last anyway? Well I'm glad you asked...
Electric Bike Battery
Over the years, there have been many different types of batteries for electric bikes. The most common battery in the last ten years is a Sealed Lead Acid (SLA) battery. This is the same battery used in a lawnmower, golf cart, or go kart. You've seen these at any local hardware store - they're heavy, black, rectangular batteries. On an electric bike, they don't go very far. Depending on the bike, they have about a ten mile range. Luckily, technology has improved in recent years, and there are now much lighter batteries that have a much better range.
The most recent chemical of choice for electric bikes is Lithium. A bike running on Lithium batteries can run for 20-30 miles on a single charge, and some bikes even have the ability to recharge the battery while riding. The BionX motor kit Lithium batteries even have protection circuitry built in, so it's almost impossible to damage them from extreme motor power. Lithium batteries tend to be more expensive than SLA battreries, but the life span is also two or three times as long. There is no better battery on the market today.
Electric Bike Control
How does it work? Well you've attached a battery to a motor, so we're almost there. Now you need a way to control the whole contraption. Want this thing to move without pedaling? Just add a throttle. This is referred to as an "ebike," which is practically a moped. Ebikes are nice if you don't want to ride a bike, but they tend to drain batteries quickly. The most efficient electric bike utilizes pedal-assist, or pedelec, technology.
A pedelec bike works by measuring the rider's pedal power, and then spinning the motor at a corresponding speed, based on a preset on the handlebars. Plainly, if you select "MODE 3" you'll get 50% power from the motor, while if you select "MODE 4" you'll get 100% power. No throttles to worry about, it's all automatic. Pedelec bikes are also called Hybrid bikes because they are a "hybrid" of human power and motor power. The best part about pedelec bikes is that you feel like you're still riding a regular bike, just getting a gentle push as you go.
That's it! Just three components and you can turn a bike into a full-blown electric-powered bike! There are a bunch of different electric bike motor kits on the market, and each one has its advantages and disadvantages. Make sure you check out the motor, the battery, and control system before buying one, because you don't want to be stuck with something cheap!