An electric bicycle, also known as an e-bike, is a bicycle with an electric motor used to power the vehicle, or to assist with pedaling. Electric bicycles typically cost between US$500 and US$3,000, use rechargeable batteries and can travel up to 20 miles per hour (32 km/h), and in some markets they are rapidly replacing traditional bikes and motorcycles.
In many parts of the world, electric bicycles are classified as
bicycles rather than motor vehicles, so they are not subject to the same laws as motor vehicles. Electric bicycles are one type of motorized bicycle. However, electric bicycles are defined separately and treated as a specific vehicle type in many areas of legal jurisdiction.
Electric bicycle usage worldwide has experienced rapid growth since 1998. It is estimated that there were roughly 120 million e-bikes in China as of early 2010, and sales are expanding rapidly in India and the Netherlands. The “Electric Bikes Worldwide Reports – 2010 Update” estimates that 1,000,000 electric bicycles will be sold in Europe in 2010. The same report estimates that sales in the U.S. will reach roughly 300,000 in 2010, doubling the number sold in 2009.
In the 1890s, electric bicycles were documented within various U.S. patents. For example, on 31 December 1895 Ogden Bolton Jr. was granted U.S. Patent 552,271 for a battery-powered bicycle with “6-pole brush-and-commutator direct current (DC) hub motor mounted in the rear wheel.” There were no gears and the motor could draw up to 100 amperes (A) from a 10-V battery.
Two years later, in 1897, Hosea W. Libbey of Boston invented an electric bicycle (U.S. Patent 596,272) that was propelled by a “double electric motor.” The motor was designed within the hub of the crankshaft axle. This model was later re-invented and imitated in the late 1990s by Giant Lafree electric bicycles.
By 1898 a rear wheel drive electric bicycle, which used a driving belt along the outside edge of the wheel was patented by Mathew J. Steffens. Also, the 1899 U.S. Patent 627,066 by John Schnepf depicted a rear wheel friction “roller-wheel” style drive electric bicycle. Schnepf's invention was later re-examined and expanded in 1969 by G.A. Wood Jr. with his U.S. Patent 3,431,994. Wood’s device used 4 fractional horsepower motors; each rated less than ½ horsepower and connected through a series of gears.
Torque sensors and power controls were developed in the late 1990s. For example, Takada Yutky of Japan filed a patent in 1997 for such a device. In 1992 Vector Services Limited offered and sold an electric bicycle dubbed Zike. The bicycle included Nickel-cadmium batteries that were built into a frame member and included an 850 g permanent-magnet motor. Despite the Zike, in 1992 hardly any commercial electric bicycles were available. It wasn’t until 1998 when there were at least 49 different bikes. Production grew from 1993 to 2004 by an estimated 35%. By Contrast, according to Gardner, in 1995 regular bicycle production decreased from its peak 107 million units. Some of the less expensive electric bicycles used bulky lead acid batteries, whereas newer models generally used NiMH, NiCd and/or Li-ion batteries which offered lighter, denser capacity batteries. The end benefits usually varied from manufacturer; however, in general there was an increase in range and speed. By 2004 electric bicycles where manufactured by Currie Technologies, EV Global, Optibike, Giante Lite, Merida, ZAP.
In a parallel hybrid motorized bicycle, such as the aforementioned 1897 invention by Hosea W. Libbey, human and motor inputs are mechanically coupled either in the bottom bracket, the rear or the front wheel, whereas in a (mechanical) series hybrid cycle, the human and motor inputs are coupled through differential gearing. In an (electronic) series hybrid cycle, human power is converted into electricity and is fed directly into the motor and mostly additional electricity is supplied from a battery.
Pedelec is a European term that generally referred to an electric bicycle that incorporated a torque and/or a speed sensor and/or a power controller that delivered a proportionate level of assist and only ran when the rider pedaled. On the opposite side, a Noped is a term used by the Ministry of Transportation of Ontario for similar type vehicles which do not have pedals or in which the pedals have been removed from their motorized bicycle. Finally, Assist Bicycle is the technical term used to describe such a vehicle and Power-Assisted Bicycle is used in the Canadian Federal Legislation, but is carefully defined to only apply to electric motor assist, and specifically excludes internal combustion engines (though this is not the case in the United States).
Today, China is the world's leading producer of electric bicycles. According to the data of the China Bicycle Association, a government-chartered industry group, in 2004 China's manufacturers sold 7.5 million electric bicycles nationwide, which was almost twice the year 2003 sales; domestic sales reached 10 million in 2005, and 16 to 18 million in 2006. By 2007, electric bicycles were thought to make up 10 to 20 percent of all two-wheeled vehicles on the streets of many major cities. A typical unit requires 8 hours to charge the battery, which provides the range of 25–30 miles (40–50 km), at the speed of around 20 km/h.
A large number of such vehicles is exported from China as well (3 million units, worth 40 billion yuan ($5.8 billion), in the year 2006 alone),
Motors and drivetrains
There are many possible types of electric motorized bicycles with several technologies available, varying in cost and
complexity; direct-drive and geared motor units are both used. An electric power-assist system may be added to almost any pedal cycle using chain drive, belt drive, hub motors (an electric motor that is incorporated into a hub of a wheel and drives it directly) or friction drive. The power levels of motors used are influenced by available legal categories and are often limited to under 750 watts.
Electric bicycles use rechargeable batteries, electric motors and some form of control. This can be a simple as an on-off switch but is more usually an electronic pulse width modulation control. Electric bicycles developed in Switzerland in the late 1980s for the Tour de Sol solar vehicle race came with solar charging stations but these were later fixed on roofs and connected so as to feed into the electric mains. The bicycles were then charged from the mains, as is common today. Battery systems in use include lead-acid, NiCd, NiMH and Li-ion batteries.
Electric motorized bicycles can be power-on-demand, where the motor is activated by a handlebar mounted throttle, and/or a pedelec (from pedal electric), also known as electric assist, where the electric motor is regulated by pedaling. These have a sensor to detect the pedaling speed, the pedaling force, or both. An electronic controller provides assistance as a function of the sensor inputs, the vehicle speed and the required force. Most controllers also provide for manual adjustment.
Range is a key consideration with electric bikes, and is affected by factors such as motor efficiency, battery capacity, efficiency of the driving electronics, aerodynamics, hills and weight of the bike and rider. The range of an electric bike is usually stated as somewhere between 7 km (uphill on electric power only) to 70 km (minimum assistance) and is highly dependent on whether or not the bike is tested on flat roads or hills. Some manufacturers, such as the Canadian BionX or American E+ (manufactured by Electric Motion Systems), have the option of using regenerative braking, the motor acts as a generator to slow the bike down prior to the brake pads engaging. This is useful for extending the range and the life of brake pads and wheel rims. There are also experiments using fuel cells. e.g. the PHB. Some experiments have also been undertaken with super capacitors to supplement or replace batteries for cars and some SUVS.
The energy costs of operating electric bicycles are small, but there can be considerable battery replacement costs. Riding an electric bicycle to work or to the store instead of taking a car has long term financial gains.
Not all electric bicycles take the form of conventional push-bikes with an incorporated motor. Some are designed to take the appearance of low capacity motorcycles, but smaller in size and comprising of an electric motor rather than a petrol engine. Bicycles of note include the Sakura electric bicycle, which incorporates a 200W motor found on standard e-bikes, but also includes plastic cladding, front and rear lights, and a speedometer. It is styled as a modern moped, and is often mistaken for one based on its similarity in appearance.
Other, rarer designs include that of a 'chopper' styled electric bicycle, which are designed as more of a 'fun' or 'novelty' electric bicycle, rather than a purposeful mobility aid or mode of transport.
Various designs (including those mentioned above) are designed to fit inside most area laws, and since they both contain pedals, can be used on roads in the United Kingdom, among other countries.
Most electric bicycles can be classified as zero-emissions vehicles, as they emit no combustion byproducts. The environmental effects of electricity generation and power distribution and of manufacturing and disposing of (limited life) high storage density batteries must be taken into account. Even with these issues considered, electric bicycles will have significantly lower environmental impact than conventional automobiles, and are generally seen as environmentally desirable in an urban environment. The small size of the battery pack on an electric bicycle, relative to the larger pack used in an electric car, makes ebikes very good candidates for charging via solar power or other renewable energy resources. Sanyo capitalized on this benefit when it set up "solar parking lots," in which ebike riders can charge their vehicles while parked under photovoltaic panels.
The environmental credentials of electric bikes, and electric / human powered hybrids generally, have led some municipal authorities to use them, such as Little Rock, Arkansas with their Wavecrest electric power-assisted bicycles or Cloverdale, California police with Zap electric bicycles. China’s e-bike manufacturers, such as Xinri, are now partnering with universities in a bid to improve their technology in line with international environmental standards, backed by the Chinese government who is keen to improve the export potential of the Chinese manufactured e-bikes.
China has experienced an explosive growth of sales of electric bicycles and scooters, with annual sales jumping from 56 thousand units in 1998 to over 21 million in 2008, and reaching an estimated fleet of 120 million e-bikes as of early 2010. This boom was triggered by Chinese local governments' efforts to restrict motorcycles in city centers to avoid traffic disruption and accidents. By late 2009 motorcycles are banned or restricted in over ninety major Chinese cities. Users began replacing traditional bicycles and motorcycles and, in e-bike became an alternative to commuting by car. Nevertheless, road safety concerns continue as around 2,500 electric bicycle related deaths were registered in 2007. As of late 2009 ten cities have also banned or imposed restrictions on electric bicycles on the same grounds as motorcycles. Among these cities are Guangzhou, Shenzhen, Changsha, Foshan, Changzhou, and Dongguang.
China is the world's leading manufacturer of electric bicycles, with 22.2 million units produced in 2009. Production is concentrated in five regions, Tianjin, Zhejiang, Jiangsu, Shandong, and Shanghai. China exported 370,000 e-bikes in 2009.
Since 2002 federal legislation classifies any two-wheel pedal-driven vehicle with a maximum speed of 20 miles per hour (32 km/h) as a bicycle, removing doubts about the legal status of e-bikes. Nevertheless, there are restrictions in place at the state level, and most states limit power output to 750 watts.
New York State law bans motor-assisted bicycles from state roads and city streets, though the ban is not currently enforced and a bill is under consideration to allow electric bikes with a top speed of 20 mph and less than 1,000 watts of power.
As of 2009 the U.S. had an estimated fleet of 200,000 electric bicycles.