There's no question that electric bikes are far better for the environment than petrol-powered car engines. But that doesn't mean they're completely perfect. Making and disposing of batteries can be very polluting. Not only that, but an electric bicycle is still using energy that has to come from somewhere. You may think you're using clean green power, but the electricity you use for getting about might have come from a filthy old, coal-fired power plant or one driven by nuclear energy. (If you're lucky, of course, it might have come from solar panels or a wind turbine!) Electric bikes are nowhere near as environmentally friendly as ordinary push bikes, but nothing is ever perfect—and, as people often say, "the perfect is the enemy of the good." Electric bikes are certainly a step in the right direction. If everyone used them to get about instead of cars, global warming might be less of a problem, and the world would be a far cleaner and healthier place!
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.[43]
BMW has launched to the UK market their Active Hybrid E-bike priced at £2,500.  The e-bike available through their own website boasts up to 60 miles per charge from the 504 Wh Lithium-ion battery powering a Brose 250 W motor.  The integrated battery and crank motor system add to the masculine looks of this hybrid ebike.  Read our full review of the BMW Active Hybrid E-bike.

Bicycle manufacturing proved to be a training ground for other industries and led to the development of advanced metalworking techniques, both for the frames themselves and for special components such as ball bearings, washers, and sprockets. These techniques later enabled skilled metalworkers and mechanics to develop the components used in early automobiles and aircraft.
The battery is the pedelec’s power source. It supplies the motor with the electrical energy that is required to provide power assistance when cycling. So it is hardly surprising that there is frequent discussion and “talking shop” about the eBike’s battery in particular. What is the difference between batteries? How far can you go on a fully charged battery? What do you have to remember about storage? Thomas Raica, head of technical customer application, here provides information and advice.
DIY enthusiasts, with tens of thousands of converted bikes using throttle-only, 20+ mph kits, are now officially labeled Moped class. While these bikes handle and pedal-ride just as safely as the class 3 speed pedelecs in many cases, our DIY counterparts will be officially kicked out and left on their own for advocacy and legal acceptance in California. This is a big deal, without a class sticker, any DIY electric bike conversion kit is considered a Moped and not a bicycle.
Most of you are likely here for the electric bits, though. Those consist of a 500Wh user-swappable Bosch Powerpack battery and a 250W Bosch Active Line Plus motor that delivers 37lb-ft (50Nm) of torque and speeds of up to 20mph (32km/h). The battery takes up to 4.5 hours to reach a 100-percent charge and offers a range of up to 134 miles. With the battery and motor, it's markedly heavier than a comparable urban bike, weighing in at 46lb (20.8kg).
Despite the illegal status in the state of New York, enforcement of this law varies at the local level. New York City enforces the bike ban with fines and vehicle confiscation for throttle activated electric bikes.[113] However, Mayor Bill de Blasio has recently changed the city's official policy to legalize pedal-assist electric bikes that have a maximum speed limited to 20 mph. [114] Contrarily, Tompkins County supports electric bike usage, even providing grant money to fund electric bike share/rental projects.[115]
There's much less of a sensation of the Electrified S2 'fighting back' once you hit 15.5mph, as well. That's helped by the automatic 2-speed gear box, although this does take some getting used to. Because its cogs are very different sizes you can end up with all sorts of cadence problems as it auto-shifts from high back to low. With practice you can avoid this, or of course you could in theory fit a second cog that's closer in size to the first.