Controllers for brushless motors: E-bikes require high initial torque and therefore models that use brushless motors typically have Hall sensor commutation for speed and angle measurement. An electronic controller provides assistance as a function of the sensor inputs, the vehicle speed and the required force. The controllers generally allow input by means of potentiometer or Hall Effect twist grip (or thumb-operated lever throttle), closed-loop speed control for precise speed regulation, protection logic for over-voltage, over-current and thermal protection. Bikes with a pedal assist function typically have a disc on the crank shaft featuring a ring of magnets coupled with a Hall sensor giving rise to a series of pulses, the frequency of which is proportional to pedaling speed. The controller uses pulse width modulation to regulate the power to the motor. Sometimes support is provided for regenerative braking but infrequent braking and the low mass of bicycles limits recovered energy. An implementation is described in an application note for a 200 W, 24 V Brushless DC (BLDC) motor.
The Domane+ e-road bike is the electric version of Trek’s popular Domane. It’s designed for riders who appreciate that bike’s reliable comfort and IsoSpeed technology but want the added fun and function of e-assist. It’s also the ideal companion for anyone coming back from injury, slower riders who want to mix it up with a speedy group, and couples with different fitness levels. A Bosch Performance Line Speed motor provides a very welcome 28 mph of pedal assist, and the 500Wh Powertube battery sleekly integrates into the down tube. Also integrated: front and rear lights, which are powered by the battery—no charging required.
Another style is the recumbent bicycle. These are inherently more aerodynamic than upright versions, as the rider may lean back onto a support and operate pedals that are on about the same level as the seat. The world's fastest bicycle is a recumbent bicycle but this type was banned from competition in 1934 by the Union Cycliste Internationale.
State law defines a motorized pedalcycle as a motor-driven cycle equipped with operable pedals, a motor rated at no more than 1.5 brake horsepower, a cylinder capacity not exceeding 50 cubic centimeters, an automatic transmission, and a maximum design speed of no more than 25 miles per hour. Subchapter J of Publication 45 spells out the vehicle requirements in full.
A new European product safety standard EN 15194 will be published in 2009. EN 15194 contains several new requirements for ebikes to be sold in European Union and European Economic Area, including weight and voltage limitations. EN 15194 also defines a specific name for EU approved electrically-assisted cycles, EPAC - "Electrically Pedal Assisted Cycle".
Play it Safe, Make it Easy – E-bike manufacturers will offer you a large variety of styles, types, colors and utility, but the base specifications will be a bike producing less than 750 watts of power (1 horsepower = 746W) , and have its speed limited to 20mph on motor power alone. The majority of US ebikes meet that specification. Manufacturers do this for their own liability. Going this route assures you that your bike was built and sold legally. As a result, you will have about every privilege that a normal bicycle can expect. However, state and local laws may dictate reduced speeds and limited access to bike paths.
Artwork: Hub motors aren't the only way to power electric bicycle wheels. If you've ever watched a mouse scampering around inside an exercise wheel, you might have wondered if you could drive a wheel electrically, in a similar way, with something that pushes against the inside of the rim. A company called GeoOrbital has been developing an ingenious mechanical equivalent that can be used to power conventional bikes—and here's a simplified illustration of how it works. It has a motorized drive roller (red) that presses against the inner rim, powered by a battery pack (orange) that sits snugly inside the wheel. Two guide rollers (blue) mounted on a tensioned framework (green) take the place of the conventional arrangement of spokes. According to GeoOrbital, you can fit one of its wheels to a normal bike in just 60 seconds.
The federal Consumer Product Safety Act defines a "low speed electric bicycle" as a two or three wheeled vehicle with fully operable pedals, a top speed when powered solely by the motor under 20 mph (32 km/h) and an electric motor that produces less than 750 W (1.01 hp). The Act authorizes the Consumer Product Safety Commission to protect people who ride low-speed electric vehicles by issuing necessary safety regulations. The rules for e-bikes on public roads, sidewalks, and pathways are under state jurisdiction, and vary.