E-bikes use rechargeable batteries and the lighter ones can travel up to 25 to 32 km/h (16 to 20 mph), depending on local laws, while the more high-powered varieties can often do in excess of 45 km/h (28 mph). In some markets, such as Germany as of 2013, they are gaining in popularity and taking some market share away from conventional bicycles, while in others, such as China as of 2010, they are replacing fossil fuel-powered mopeds and small motorcycles.
Depending on local laws, many e-bikes (e.g., pedelecs) are legally classified as bicycles rather than mopeds or motorcycles. This exempts them from the more stringent laws regarding the certification and operation of more powerful two-wheelers which are often classed as electric motorcycles. E-bikes can also be defined separately and treated under distinct Electric bicycle laws.
E-bikes are the electric motor-powered versions of motorized bicycles, which have been in use since the late 19th century. Some bicycle-sharing systems use them.
Operation
The VAE is a bike that has electric assistance. This assistance aims to provide a complement to pedaling. It consists of a motor, a battery, a controller and sensors.
The sensors detect the presence of pedaling, its cadence, the force exerted on the pedals, the position of a possible accelerator, and braking.
A controller incorporates the parameters that qualify the bike's behavior according to the user's profile chosen by the manufacturer. It regulates the current consumption and controls the motor in its various phases of operation: starting, continuous speed, acceleration, etc. from the information transmitted by the sensors.
The user has, depending on the model, the possibility of cutting or dosing the level of assistance while driving, through a selector or an "accelerator".
On some hub-motor bikes, the battery is automatically charged with braking and downhill. Braking is facilitated by the engine brake.
Engines
Hub motor: easy to install, it fits in place of a front or rear wheel axle.
Remote motor: the transmission is done by a belt or a chain acting on a transmission plate placed on the axis of a wheel. The position of the motor is free.
Pedal motor: it acts directly on the axis of the pedal of the bicycle. It consists of a block comprising all the components of electric traction: the engine, the sensors and the control electronics. It can only be installed on a specific frame.
Friction motor: roller friction motor on the tread of the front or rear tire. It was used on the Solex moped.
Batteries
For VAE, the lithium battery is mainly used; the other technologies, lead or nickel, have been progressively abandoned on VAE marketed in Europe.
The weight of the battery, long problematic, today benefits from significant improvements related to Lithium Ion and Lithium Polymer. Thus, a lead battery weighs about 13 kg, while a lithium battery weighs about 3 kg for equivalent voltage and capacity.
The full charge of the battery takes 3 to 8 hours depending on the technology of the battery and charger. Fast refills are possible with appropriate chargers and batteries. These types of accumulators do not support deep discharges, so it is advisable to recharge them as often as possible, or even to remain in charge during periods of non-use, modern chargers being particularly well studied for these cases.
Under the name "Lithium" exist several technologies with substantially different characteristics. In 2015, LiE-Ion, Lithium Polymer (LIPO) and LiFePO4 batteries are mainly used on the VAE. The first two technologies make it possible to obtain batteries that are very light but sensitive to cold and heavy loads / discharges. LiFePO4 is considered safer (fire), it accepts higher charging currents (lower recharge time) and above all it has a longer life (a thousand cycles and more).
The battery remains one of the weak points of the electric bike, as for electric cars. Even outside of its theoretical life, it is easy not to properly manage this element, and the replacement price is very important, several hundred euros for a lithium battery.
The battery of an electric bike is sensitive to temperature differences: manufacturers give an ideal temperature range in order to have the best possible autonomy.
Batteries are sensitive to shock: chemicals are contained in fragile envelopes that can pierce and even ignite.
Classes
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. Also the classification of e-bikes is complicated as much of the definition is due to legal reasons of what constitutes a bicycle and what constitutes a moped or motorcycle. As such, the classification of these e-bikes varies greatly across countries and local jurisdictions.
Despite these legal complications, the classification of e-bikes is mainly decided by whether the e-bike's motor assists the rider using a pedal-assist system or by a power-on-demand one. Definitions of these are as follows:
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.
Therefore, very broadly, e-bikes can be classed as:
E-bikes with pedal-assist only: either pedelecs (legally classed as bicycles) or S-Pedelecs (often legally classed as mopeds)
Pedelecs: have pedal-assist only, motor assists only up to a decent but not excessive speed (usually 25 km/h), motor power up to 250 watts, often legally classed as bicycles
S-Pedelecs: have pedal-assist only, motor power can be greater than 250 watts, can attain a higher speed (e.g., 45 km/h) before motor stops assisting, legally classed as a moped or motorcycle (not a bicycle)
E-bikes with power-on-demand and pedal-assist
E-bikes with power-on-demand only: often have more powerful motors than pedelecs but not always, the more powerful of these are legally classed as mopeds or motorcycles
Pedal-assist only
E-bikes with pedal-assist only are usually called pedelecs but can be broadly classified into pedelecs proper and the more powerful S-Pedelecs.
Pedelecs
The term "pedelec" (from pedal electric cycle) refers to a pedal-assist e-bike with a relatively low-powered electric motor and a decent but not excessive top speed. Pedelecs are legally classed as bicycles rather than low-powered motorcycles or mopeds.
The most influential definition of pedelecs and which are not comes from the EU. EU directive (EN15194 standard) for motor vehicles considers a bicycle to be a pedelec if:
the pedal-assist, i.e. the motorised assistance that only engages when the rider is pedalling, cuts out once 25 km/h is reached, and
when the motor produces maximum continuous rated power of not more than 250 watts (n.b. the motor can produce more power for short periods, such as when the rider is struggling to get up a steep hill).
An e-bike conforming to these conditions is considered to be a pedelec in the EU and is legally classed as a bicycle. The EN15194 standard is valid across the whole of the EU and has also been adopted by some non-EU European nations and also some non-European jurisdictions (such as the state of Victoria in Australia).
Pedelecs are much like conventional bicycles in use and function — the electric motor only provides assistance, for example, when the rider is climbing or struggling against a headwind. Pedelecs are therefore especially useful for people in hilly areas where riding a bike would prove too strenuous for many to consider taking up cycling as a daily means of transport. They are also useful for riders who more generally need some assistance, e.g. for people with heart, leg muscle or knee joint issues.
S-Pedelecs
More powerful pedelecs which are not legally classed as bicycles are dubbed S-Pedelecs (short for Schnell-Pedelecs, i.e. Speedy-Pedelecs) in Germany. These have a motor more powerful than 250 watts and less limited, or unlimited, pedal-assist, i.e. the motor does not stop assisting the rider once 25 km/h has been reached. S-Pedelec class e-bikes are therefore usually classified as mopeds or motorcycles rather than as bicycles and therefore may (depending on the jurisdiction) need to be registered and insured, the rider may need some sort of driver's license (either car or motorcycle) and motorcycle helmets may have to be worn. In the United States, many states have adopted S-Pedelecs into the Class 3 category. Class 3 ebikes are limited to <=750 watts of power and 28 mph.
Power-on-demand and pedal-assist
Some e-bikes combine both pedal-assist sensors as well as a throttle. An example of these is the eZee Torq and Adventure 24+ by BMEBIKES. The motor on this type of e-bike is activated by pushing the throttle or by pedaling.
Power-on-demand only
Some e-bikes have an electric motor that operates on a power-on-demand basis only. In this case, the electric motor is engaged and operated manually using a throttle, which is usually on the handgrip just like the ones on a motorbike or scooter. These sorts of e-bikes often, but not always, have more powerful motors than pedelecs do.
With power-on-demand only e-bikes the rider can:
ride by pedal power alone, i.e. fully human-powered.
ride by electric motor alone by operating the throttle manually.
ride using both together at the same time.
Some power-on-demand only e-bikes can hardly be confused with, let alone categorised as, bicycles. For example, the Noped is a term used by the Ministry of Transportation of Ontario for e-bikes which do not have pedals or in which the pedals have been removed from their motorised bicycle. These are better categorised as electric mopeds or electric motorcycles.
Popularity
E-bike usage worldwide has experienced rapid growth since 1998. In 2016 there were 210 million electric bikes worldwide used daily. It is estimated that there were roughly 120 million e-bikes in China in early 2010, and sales are expanding rapidly in India, the United States of America, Germany, the Netherlands, and Switzerland. 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.
Today, 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.
Technical
Motors and drivetrains
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. BLDC hub motors are a common modern design. The motor is built into the wheel hub itself, and the stator fixed solidly to the axle, and the magnets attached to and rotating with the wheel. The bicycle wheel hub is the motor. The power levels of motors used are influenced by available legal categories and are often, but not always limited to under 750 watts.
Another type of electric assist motor, often referred to as the mid-drive system, is increasing in popularity. With this system, the electric motor is not built into the wheel but is usually mounted near (often under) the bottom bracket shell. In more typical configurations, a cog or wheel on the motor drives a belt or chain that engages with a pulley or sprocket fixed to one of the arms of the bicycle's crankset. Thus the propulsion is provided at the pedals rather than at the wheel, being eventually applied to the wheel via the bicycle's standard drive train.
Because the power is applied through the chain and sprocket, power is typically limited to around 250–500 watts to protect against fast wear on the drivetrain. An electric mid-drive combined with an internal gear hub at the back hub may require care due to the lack of a clutch mechanism to soften the shock to the gears at the moment of re-engagement. A continuously variable transmission or a fully automatic internal gear hub may reduce the shocks due to the viscosity of oils used for liquid coupling instead of the mechanical couplings of the conventional internal gear hubs.
Batteries
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.
Range is a key consideration with e-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. Some manufacturers, such as the Canadian BionX or American Vintage Electric Bikes, 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. E-bikes 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. While ebike batteries were produced mainly by bigger companies in past, many small to medium companies have started using innovative new methods for creating more durable batteries. State of the art, custom built automated precision CNC spot welding machines created 18650 battery packs are commonly used among Do-it-yourself ebike makers.
Controllers
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.)
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.
Controllers for brushed motors: Brushed motors are also used in e-bikes but are becoming less common due to their intrinsic lower efficiency. Controllers for brushed motors however are much simpler and cheaper due to the fact they don't require hall sensor feedback and are typically designed to be open-loop controllers. Some controllers can handle multiple voltages.
Design variations
Not all e-bikes take the form of conventional push-bikes with an incorporated motor, such as the Cytronex bicycles which use a small battery disguised as a water bottle. Some are designed to take the appearance of low capacity motorcycles, but smaller in size and consisting of an electric motor rather than a petrol engine. For example, the Sakura e-bike incorporates a 200 W 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.
Converting a non-electric bicycle to its electric equivalent can be complicated but numerous 'replace a wheel' solutions are now available on the market.
An Electric Pusher Trailer is an e-bike design which incorporates a motor and battery into a trailer that pushes any bicycle. One such trailer is the two-wheeled Ridekick.
Other, rarer designs include that of a 'chopper' styled e-bike, which are designed as more of a 'fun' or 'novelty' e-bike than as a purposeful mobility aid or mode of transport.
Electric cargo bikes allow the rider to carry large, heavy items which would be difficult to transport without electric power supplementing the human power input.
Various designs (including those mentioned above) are designed to fit inside most area laws, and the ones that contain pedals can be used on roads in the United Kingdom, among other countries.
Folding e-bikes are also available.
Electric self-balancing unicycles do not conform to e-bike legislation in most countries and therefore cannot be used on the road, but can be utilized in the sidewalk. They are the cheapest electric cycles and used by the last mile commuters, for urban use and to be combined with public transport, including buses.
Tricycles
Electric trikes have also been produced that conform to the e-bike legislation. These have the benefit of additional low speed stability and are often favored by people with disabilities. Cargo carrying tricycles are also gaining acceptance, with a small but growing number of couriers using them for package deliveries in city centres. Latest designs of these trikes resemble a cross-between a pedal cycle and a small van.
Usages
The use of a pedelec offers several advantages (usually higher average speed than conventional bicycles, in some cases even higher than in cars, depending on the rider's condition).
The advantage is the lower emissions (low noise emission) compared to other motorized transport, especially to vehicles with internal combustion engines, if e-bikes or pedelecs are used as an alternative to these.
The acquisition costs are considerably higher than for a conventional bicycle. In addition to the costs for normal wear and tear, there is also the eventual replacement of the accumulator. In contrast to other means of transport, the electricity costs are a few tens of cents per 100 km.
There are different areas of use with different requirements:
Professional use: Postal services (Postal delivery), Police (in restricted traffic areas), Company vehicle fleets, Driving to work (commuters).
Tourist use: Rental stations at railway stations and tourist hubs, in holiday resorts or spas.
Private use as needed.
General Usage Experiences
Pedelecs can reach speeds of 25-45 km / h and more, depending on the performance of the engine, the person driving and the registration. Average trained drivers achieve with a fast pedelec about the performance of unmotorisierter bicycle athletes, come with the usual batteries (without exchange) but less far. The high average speeds of high-speed electric bicycles make them the fastest average vehicles on shorter routes in the city.
The earlier hesitant acceptance for electric bicycles resulted primarily from the history of accumulator technology. If the bicycle technology is considered mature, then the long time was not for the battery technology. Batteries with low or very diminishing range, memory effect, etc. hampered the popularity, especially in the low price segment. As European manufacturers in particular had their sights on the target group of over-50s for a long time, only appropriately designed wheels were placed on the market for a long time. This led to the initial "granny-wheel" image of the electrically assisted wheels, which still stops locally.
Modern electric bicycles today have traction batteries mostly based on lithium-polymer batteries, more rarely on the basis of lithium-iron-phosphate (LiFePO 4) -Akkumulatoren, In contrast to older technologies, modern batteries show clear advantages (high energy density, therefore longer range with lower weight, longer life, no memory effect). A battery must be designed for the short-term maximum power consumption of the motor. This is basically ensured with modern accumulators. In older lead batteries it was only given if you have used special high-current driving batteries. In the past, many e-bike batteries did not lastingly withstand the high current load because the cells used were not high current resistant, which in particular led to overloading when electric bicycles were frequently driven on slopes. This problem is excluded in modern accumulators by the so-called battery management, possibly
Range
A battery with a power of, for example, 36 V and 10 Ah (mass 1.9-5.1 kg)) has an energy content of approx. 36 V × 10 Ah = 360 Wh (for comparison: 1 kg of gasoline supplies 11,500 Wh). The conversion of electrical energy into mechanical work is dependent on the efficiency of the engine and the engine control, under heat loss. Typically, this results in losses of about 25 percent. Thus, a pedelec with a 70-kg driver (total mass ≈100 kg) purely computationally drive at 1.4% slope 21 km far with battery power - this calculation example in practice is never relevant, since the driver in a pedelec always yourself must join. The total range depends on many factors (weight, incline, size of the accumulator, tire pressure, selected support mode, etc.), so it is almost impossible to give a general range. Roughly overlaid this is the current state of the art in dependence of all these factors between under 40 to over 120 km. (Of course, this limitation of the action radius applies only to those driving in which a motor assistance is available). On some models, two consecutively switchable batteries are included in luggage bags as standard.
Only with direct-drive wheel hub motors (without freewheeling) is it possible to regenerate, the so-called recuperation. Here, as in a dynamo, the kinetic energy is used for charging during braking in electrical energy. As a result, the range can be significantly increased in city traffic or hill country. In independent tests, the range was increased by 11%. It is pointed out in test reports as well as in operating manuals of some manufacturer models that the outside temperature also influences the ranges by similarly high factors. Overall, the influences (with the same battery capacity) are described as so diverse that z. B. according to Derby Cycle"The largest range achieved can be up to 7x larger than the lowest range".
The battery can not be "refueled" in just a few minutes, as in a petrol-powered vehicle, a battery charging cycle takes several hours, depending on the model.
Despite the limited range electric bikes have a much better power to weight than conventional motorcycles.
Lifetime of the accumulator
The accumulator is exhausted after a certain number of charge-discharge cycles, so that the range drops too far. How many cycles it makes possible depends on the chemistry of the battery and the quality of the control and charging electronics used. With NiCd battery one counts with 1000, with NiMH with 700 and with Li-Ion with 500 cycles. With the lithium iron phosphate accumulator, cycle numbers up to more than 1000 are possible; after that, the capacity has decreased to about 60%. Advanced battery management conceptswith conditioning of individual cells during operation increase the lifetime. They are particularly found in high-quality lithium-based batteries. According to several studies Li-Ion batteries have a longer life, if they are often recharged only, rather than a completely empty battery always fully recharge. However, several partial charges only partially count as a charging cycle. Also, Li-ion batteries should not be stored unused when fully charged for a long time.
Health benefits
E-bikes can be a useful part of cardiac rehabilitation programmes, since health professionals will often recommend a stationary bike be used in the early stages of these. Exercise-based cardiac rehabilitation programmes can reduce deaths in people with coronary heart disease by around 27%; and a patient may feel safer progressing from stationary bikes to e-bikes. They require less cardiac exertion for those who have experienced heart problems.
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. Reaching VO2 Max, can really help your body as a whole. Professor Janet Lord of Birmingham University in the UK published a study that looked at older cyclists, ““The study looked at muscle mass, blood cholesterol, their VO2 Max, lung function, and in many of those measures we found they didn’t age! No loss of muscle, their bones were a little thin (but nothing like the general population), their blood pressure didn’t go up.
There are individuals who claim to have lost considerable amounts of weight by using an electric bike. A recent prospective cohort study however found that people using e-bikes have a higher BMI. By making the biking terrain less of an issue, people who wouldn't otherwise consider biking can use the electric assistance when needed and otherwise pedal as they are able. This means people of lower fitness levels or who haven't cycled in many years can start enjoying the many health benefits E-bikes have to offer.
Environmental effects
E-bikes are zero-emissions vehicles, as they emit no combustion by-products. However, 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, e-bikes are claimed to have a significantly lower environmental impact than conventional automobiles, and are generally seen as environmentally desirable in an urban environment.
The environmental effects involved in recharging the batteries can of course be reduced. The small size of the battery pack on an e-bike, relative to the larger pack used in an electric car, makes them 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 e-bike riders can charge their vehicles while parked under photovoltaic panels.
The environmental credentials of e-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 e-bikes. 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.
Both land management regulators and mountain bike trail access advocates have argued for bans of electric bicycles on outdoor trails that are accessible to mountain bikes, citing potential safety hazards as well as the potential for electric bikes to damage trails. A study conducted by the International Mountain Bicycling Association, however, found that the physical impacts of low-powered pedal-assist electric mountain bikes may be similar to traditional mountain bikes.
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.
One major concern is disposal of used lead batteries, which can cause environmental contamination if not recycled.
There are strict shipping regulations for lithium-ion batteries, due to safety concerns. In this regard, lithium iron phosphate batteries are safer than lithium cobalt oxide batteries.
Road traffic safety
China's experience, as the leading e-bike world market, has raised concerns about road traffic safety and several cities have considered banning them from bicycle lanes. As the number of e-bikes increased and more powerful motors are used, capable of reaching up to 30 miles per hour (48 km/h), the number of traffic accidents have risen significantly in China. E-bike riders are more likely than a car driver to be killed or injured in a collision, and because e-bikers use conventional bicycle lanes they mix with slower-moving bicycles and pedestrians, increasing the risk of traffic collisions.
Source from Wikipedia
没有评论:
发表评论