Choose a 36- or 48-volt battery with a capacity of 10Ah or 20Ah. Choose a battery designed for use on an electric bicycle, as it will come with a charger and be much easier to install. Make sure the voltage and capacity of the battery you choose is compatible with the conversion kit you purchased. The higher the voltage of your bike's battery, the more powerful your bike will be. When building an electric bike, choose a 36- or 48-volt battery to allow for speed and comfort.[5]
The company was founded in 2009 by Tora Harris who graduated from Princeton University with a degree in Mechanical and Aerospace Engineering. While at Princeton, Harris ran track and became a 2-time winner of the NCAA Championship in the High Jump and set several Ivy League track records in the process. Harris went on to win 2 USA National Outdoor Championship Titles and competed in the 2004 Athens Olympic Games.
None of this would matter if the VanMoof Electrified S2 (and its close relative the X2) wasn't fun to ride, but it is a blast. Like the Brompton, it pulls off the neat trick of powering you along but giving the illusion that you're doing the work, reacting quickly and cleverly to the speed of your pedalling and the difficulty of any incline you're on. 
There are dozens of good 25Km/h pedelecs. Our advice is to go the nearest good e-bike store and get it from there, because e-bikes may need good support. Only if you like servicing a bike yourself is buying from the Internet a good option. As of Spring 2013, a good benchmark to compare with is the Austrian KTM Amparo also called KTM Severo 8M or the German Kalkhoff Impuls or Agattu series. It has a reliable Panasonic middle motor and a good battery. If you want a more sexy design, try the SMART from the urban car maker of the same name.

Electric bicycles are considered as "bicycles" under Montana law as the law defines bicycles in a two part definition where the first part of the definition describes a conventional bicycle propelled solely by human power and the second part of the definition describes a bicycle equipped with an independent power source for propulsion in addition to foot pedals to permit muscular propulsion. (Montana Code 61-8-102).[104]
Electric Bicycles are defined by the California Vehicle Code [32][33]. In summary, electric bicycles are to be operated like conventional bicycles in California. There are several exceptions to this. A person must be at least 16 years old, and anyone riding an electric bicycle must wear a bicycle helmet. The e-bikes must have an electric motor that has a power output less than 1,000 watts, is incapable of propelling the device at a speed of more than 20 miles per hour on level ground, is incapable of further increasing the speed of the device when human power is used to propel the motorized bicycle faster than 20 miles per hour, operates in a manner so that the electric motor is disengaged or ceases to function when the brakes are applied, or operates in a manner such that the motor is engaged through a switch or mechanism that, when released, will cause the electric motor to disengage or cease to function.
But two other concerns are also front and center when it comes to biking: cost and convenience. Not many people have showers at their places of employment, and who wants to show up to work coated in sweat and stinky for the rest of the day? Electric bikes solve the convenience problem by making the process almost effortless; you can bike for miles—even up and down hills—without breaking a sweat.
They also served to teach the industrial models later adopted, including mechanization and mass production (later copied and adopted by Ford and General Motors),[76][77][78] vertical integration[77] (also later copied and adopted by Ford), aggressive advertising[79] (as much as 10% of all advertising in U.S. periodicals in 1898 was by bicycle makers),[80] lobbying for better roads (which had the side benefit of acting as advertising, and of improving sales by providing more places to ride),[78] all first practiced by Pope.[78] In addition, bicycle makers adopted the annual model change[76][81] (later derided as planned obsolescence, and usually credited to General Motors), which proved very successful.[82]
Nevada Electric Bicycle (NRS 482.0287) Bicycle 20 (motor only on the flat with 170LB rider, undefined if pedal assist is allowed to go faster) 750W (it is undefined as to whether this is input or output power, but in the USA, motors are rated on output power at the shaft) No none (use caution here because of "reckless endangerment" laws) no (not a "motor vehicle")
The Super Commuter is very aptly named. The 350w Bosch motor will help you sustain speeds of up to 28mph, and the burly, 2.4-inch wide, Schwalbe Super Moto-X 650b tires will keep you secure on even the roughest city streets, and Shimano Deore hydraulic brakes provide ample stopping power. Fenders provide welcome protection from road spray so you arrive at your destination fresh, integrated lights are critical for post-sunset riding, and a side-view mirror hanging on the left side of the handlebar gives a great view of traffic around you. After all, you can ride at the speed of urban traffic on the Super Commuter.
The Footloose has no chain, however -- it's entirely electrically driven. It takes very little effort to get to your destination, meaning you arrive at work without having broken a sweat. The downside is that when you run out of power, you're not going anywhere. And pedalling from a standstill, waiting for the motor to kick in, is an odd sensation that takes some getting used to.
Under the doctrine of One Country, Two Systems, Hong Kong has independent traffic law from mainland China. Electric bike are considered as motorcycles in Hong Kong, and therefore needs type approval from the Transport Department as other automobiles. All electric bike availble in Hong Kong fail to meet the type approval requirement, and Transport Department has never granted any type approval for electric bike, making all electric bike effectively illegal in Hong Kong. Even if they got type approved, the driver would need a motorcycle driving license to ride[14]. As a side note, Hong Kong doesn't have a moped vehicle class (and therefore moped driving license), and mopeds are consided as motorcycles too.

If you’ve got the cash and want to get into ebikes, don’t buy this Rattan. My best advice if you have the money is buy a bike store bike with a Bosch/Brose/Yamaha/Shimano drivetrain. We review lots of them here but I’m currently riding a $2000 Raleigh. If you only have around $1,000+ to spend, head to Luna/Rad/Sondors or at least something from a company you’ve heard of with a Bafang motor.

"Bicycles" and "Electric Bicycles" are legally defined in the Texas Transportation Code Title 7, Chapter 551 entitled "Operation of Bicycles, Mopeds, and Play Vehicles" in Subchapter A, B, C, and D.[131] Under Chapter 541.201 (24), "Electric bicycle" means a bicycle that is (A) designed to be propelled by an electric motor, exclusively or in combination with the application of human power, (B) cannot attain a speed of more than 20 miles per hour without the application of human power, and (C) does not exceed a weight of 100 pounds. The department or a local authority may not prohibit the use of an electric bicycle on a highway[132] that is used primarily by motor vehicles. The department or a local authority may prohibit the use of an electric bicycle on a highway used primarily by pedestrians.

Photo: This typical electric bicycle, a Sanyo Eneloop (now discontinued), had a range of about 30–55 km (17–35 miles) and a top speed of around 24 km/h (15 mph). Note the 250-watt hub motor on the front wheel and the 5.7Ah lithium-ion battery pack (black, marked "Sanyo," just in front of the back wheel). Picture by kind permission and courtesy of Richard Masoner, originally published on Flickr under a Creative Commons (CC BY-SA 2.0) licence.
Having spent some quality time with Wing’s e-bike, I understand why so many people are excited about the growing popularity of electric-powered vehicles like bikes and scooters. They take a lot of the work out of getting from point A to point B, while retaining all of the joy. They can give you more confidence when navigating a treacherous city terrain that prioritizes cars over people. And let’s face it: bikes are cool, and always will be. 

Bicycles featuring pedal power were developed during the subsequent decades of the 19th century, with the most emblematic example being the bicycle we know today as the Penny-Farthing. The bike was named based on the substantial difference in its wheel size resembling the larger and smaller Penny and Farthing coins, respectively. These bicycles were wildly popular among the well heeled upper classes of Europe and America despite their penchant for launching riders head first over the large wheel, not to mention their relative difficulty to mount and dismount.
What's the Centros like? Big and heavy, but with enough power to overcome that, it really reminded me of a more upmarket Volt Pulse. You do tend to find that the weightier e-bikes give more of a feeling of speed, even though you're only doing 20mph or so at the absolute most (only up to 15mph with electrical assistance so you'll need leg muscles or a downward incline to get to that outlandish velocity).

Electric-assisted bicycles are treated as human-powered bicycles, while bicycles capable of propulsion by electric power alone face additional registration and regulatory requirements as mopeds. Requirements include electric power generation by a motor that cannot be easily modified, along with a power assist mechanism that operates safely and smoothly. In December 2008, The assist ratio was updated as follow: