An electric bicycle, also known as an e-bike or ebike, is a bicycle with an integrated electric motor used to assist propulsion. Both retain the ability to be pedaled by the rider and are therefore not electric motorcycles.
E-bikes use rechargeable batteries and typically travel up to 25 to 32 km/h (16 to 20 mph). High-powered varieties can often travel more than 45 km/h (28 mph).
E-bikes are classed according to the power that their electric motor can deliver and the control system, i.e., when and how the power from the motor is applied.
- With pedal-assist, the electric motor is regulated by pedalling. The pedal-assist augments the efforts of the rider when they are pedalling. These e-bikes – called pedelecs – have a sensor to detect the pedalling speed, the pedalling force, or both. Brake activation is sensed to disable the motor as well.
- With power-on-demand, the motor is activated by a throttle, usually handlebar-mounted just like on most motorcycles or scooters.
E-bike usage worldwide has experienced rapid growth since 1998.
China is the world’s leading producer of e-bikes. According to the data of the China Bicycle Association, a government-chartered industry group, in 2004 China’s manufacturers sold 7.5 million e-bikes nationwide, which was almost twice the year 2003 sales; domestic sales reached 10 million in 2005, and 16 to 18 million in 2006. In 2016, approximately 210 million electric bikes were used daily in China.
A total of 700,000 e-bikes were sold in Europe in 2010, up from 200,000 in 2007 and 500,000 units in 2009. Approximately 2 million were sold in Europe in 2016. In 2019, the EU implemented a 79.3% protective tariff on imported Chinese e-bikes to protect EU producers.
The two most common types of hub motors used in electric bicycles are brushed and brushless. Many configurations are 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 or friction drive.
E-bikes use rechargeable batteries, electric motors and some form of control. Battery systems in use include sealed lead-acid (SLA), nickel-cadmium (NiCad), nickel-metal hydride (NiMH) or lithium-ion polymer (Li-ion). Batteries vary according to the voltage, total charge capacity (amp hours), weight, the number of charging cycles before performance degrades, and ability to handle over-voltage charging conditions. The energy costs of operating e-bikes are small, but there can be considerable battery replacement costs. The lifespan of a battery pack varies depending on the type of usage. Shallow discharge/recharge cycles will help extend the overall battery life.
There are two distinct types of controllers designed to match either a brushed motor or brushless motor. Brushless motors are becoming more common as the cost of controllers continues to decrease. (See the page on DC motors which covers the differences between these two types.)
E-bike use was shown to increase the amount of physical activity. E-bike users in 7 European cities had 10% higher weekly energy expenditure than other cyclists because they cycled longer trips.
E-bikes can also provide a source of exercise for individuals who have trouble exercising for an extended time (due to injury or excessive weight, for example) as the bike can allow the rider to take short breaks from pedaling and also provide confidence to the rider that they’ll be able to complete the selected path without becoming too fatigued or without having forced their knee joints too hard (people who need to use their knee joints without wearing them out unnecessarily may in some electric bikes adjust the level of motor assistance according to the terrain). A University of Tennessee study provides evidence that energy expenditure (EE) and oxygen consumption (VO2) for e-bikes are 24% lower than that for conventional bicycles, and 64% lower than for walking. Further, the study notes that the difference between e-bikes and bicycles are most pronounced on the uphill segments.
E-bikes are zero-emissions vehicles, as they emit no combustion by-products, but the environmental effects of electricity generation and power distribution and of manufacturing and recycling batteries must be accounted for. Even with these issues considered, e-bikes have a significantly lower environmental impact than cars, and are generally seen as environmentally desirable in an urban environment.
A recent study on the environment impact of e-bikes vs other forms of transportation found that e-bikes are:
- 18 times more energy efficient than an SUV
- 13 times more energy efficient than a sedan
- 6 times more energy efficient than rail transit
- and, of about equal impact to the environment as a conventional bicycle.