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.

On a trip to Palo Alto last year, we had the chance to ride Specialized’s pedal-assisted Turbo Vado and the model is still our favorite ebike on the market. Utilizing a 350-watt motor and 604-watt-hour lithium-ion battery, the Turbo Vado is capable of traveling a whopping 80 miles on a single charge, which should be more than enough for any daily commute with plenty of miles left over.
A new European product safety standard EN 15194 will be published in 2009. EN 15194 contains several new requirements for ebikes to be sold in European Union and European Economic Area, including weight and voltage limitations. EN 15194 also defines a specific name for EU approved electrically-assisted cycles, EPAC - "Electrically Pedal Assisted Cycle".
Electric bikes (also known as e bikes) are perfect for long-distance riding, or when you just don’t feel like giving your full effort. What differentiates them from electric motorcycles is the ability for the rider to pedal the bike at any time, so if you’re riding along and your battery dies, you’re not going to stranded. These are often very valuable bikes, but some models can be more affordable than you might expect, especially when you treat them as a form of transportation as opposed to thinking of the price in terms of regular bicycles.
Speaking of which, if you're used to non-electric cycles, be aware that e-bikes are heavy and capped at 25kph or 15.5mph. In many cases, that means the bike starts to feel like its actively fighting against you, if you try to push the speed higher than that by pedalling. That's especially true with heavier bikes, for obvious reasons, and can take a while to get used to. 
Earlier UK regulations required that the motor has an average power output limited to 200 W (250 W for tricycles and tandems) and weight limited to 40 kg (60 kg for tricycles and tandems). These regulations must come in-line with the EU regulations by (find deadline). For models sold before June 2003, e-bikes conforming to the speed, weight and power limits may also be considered pedal cycles. Electric bikes with higher power outputs, or those not meeting the "pedelec" definition are now treated as motorcycles and require a license.
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Around the turn of the 20th century, bicycles reduced crowding in inner-city tenements by allowing workers to commute from more spacious dwellings in the suburbs. They also reduced dependence on horses. Bicycles allowed people to travel for leisure into the country, since bicycles were three times as energy efficient as walking and three to four times as fast.
In a friction drive motor, a small, solid wheel rotates against the side of the tire in order to drive it. The first motorcycles used the same concept, with a motor mounted above the front wheel. The problem is that the drive rubs at the side of the tire. It's inefficient, and it quickly wears the sidewall away. Tires need to be replaced every couple hundred miles. For this reason, you'll seldom see electric bikes with this type of drive anymore.
To legally operate a motorized bicycle or electric-assisted bicycle the operator must be licensed, the motorized bicycle/electric-assisted bicycle must be registered in one of the following definitions and meet the required safety equipment. If the operator or the motorized bicycle/electric- assisted bicycle does not meet all requirements, they will not be legal for street/highway use (including the sidewalk).To qualify as a motorized bicycle under state law they need to have motor of a piston displacement capacity of 50 cubic centimeters or less, maximum of two brake horsepower, maximum speed of not more than Template:Convert on a flat surface, fully operable pedals for human propulsion are not required, but may be a part of the machine.

When last checked, no E-bikes satisfied this requirement, so ebikes cannot be registered in New Jersey.[108] However, NJ Bill A2581, introduced March 22, 2010, would permit the use of low-speed electric bicycles upon the roadways and bicycle paths in NJ, where a low-speed electric bicycle is defined as a two-wheeled vehicle with fully operable pedals for human propulsion and an electric motor of less than 100 pounds and 750 watts, whose maximum speed on a paved level surface is less than 20 miles per hour.[109] The bill has been referred to the state's Assembly Transportation, Public Works and Independent Authorities Committee.[110]
"Motor-driven cycle" means any vehicle equipped with two or three wheels, a power source providing up to a maximum of two brake horsepower and having a maximum piston or rotor displacement of 50 cubic centimeters if a combustion engine is used, which will propel the vehicle, unassisted, at a speed not to exceed 30 miles per hour on a level road surface, which does not require clutching or shifting by the operator.[138] The designation is a replacement for "scooter" and "moped;"[139] Vermont doesn't seem to have laws specifically for e-bikes.[140]
I found that by sticking it on 'Turbo' or 'Sport' mode (the upper 2 of the 4 electrical assistance levels) and leaving it in a middle gear, the Centros felt zippy when in full flight, but able to pull away from the lights with no problems. Less lazy riders than me might want to actually use the 10 gears, and will find that in the top gear, it's quite easy to push past the mandated 15.5mph electrical limit.

Great question… a real world situation from someone doing their best to follow the law but also be realistic about time/distance. What follows is my opinion on the matter based on lots of electric bike riding experience, this is not legal advice. You can probably ride with electric assist across the dirt way with no issues and avoid any negative response that might arise as long as you’re polite to other cyclists and pedestrians and pedal along without going too fast. If someone called you out about it you could easily hop off, walk your bike and explain that you use the assist to help make your commute possible or possibly, like me, you have a knee injury and it’s difficult to pedal through softer terrain like gravel. Another different approach might be to shut the bike off completely before entering the gravel section, you could even take the battery off and put it in a backpack or as mentioned earlier… just walk the bike. Imagine if you had a motorized dirt bike and were just pushing it along a sidewalk… this kind of vehicle definitely is not allowed on sidewalks or most gravel paths like the one you’re describing but if you were escorting it carefully, you’d be honoring the spirit of the law and if an officer or pedestrian jumped out and started questioning you about your “motorized vehicle” it is my feeling that a genuine explanation and apology or request for guidance would go very well. I personally have never had issues riding electric bikes in part because I am thoughtful about how I use them. I do occasionally switch them off and sometimes I get off and walk. I have asked police in many cities across the US what they thought about ebikes and in every case I have received positive interest and support with guidance to ride safe with a helmet and follow traffic laws in the street. I hope this helps and I wish you well, it’s nice that you care enough to ask and I hope you’re treated well by others out on the road. The flip side of this response is that I have been harassed, yelled at and even swerved at by automobiles when riding bicycles and electric bikes. This usually happens in the evening after work lets out when traffic is heavy and I’m riding on the shoulder or in the street (where marked to do so) and I believe it has to do with territory, testosterone and socio-economic standing more so than laws or anything like that.
While falling gas prices have temporarily halted years of gains in the number of bicycle commuters, more and more of us are using the bicycle to get around. It’s economical, provides good exercise, and is much cheaper than owning a car. But unless you’re in really good shape, you aren’t going to get very far. Enter the electric bike: a glorious new contraption allows us to get around without having to worry about arriving at our destinations a sweaty mess.
This slick-looking commuter features a clean and quiet Gates Carbon Drive belt, which eliminates the maintenance that comes with a derailleur, and an internally geared Enviolo Trekking hub, which provides a 380 percent gear range. The Embark has 650b wheels, 47mm WTB gumwall tires, full fenders with mudflaps, and integrated lights—meaning you can ride long after the sun sets—or before it rises. A Bosch Active Line Plus mid-drive motor is light and quiet and provides pedal assist up to 20 mph, and the Bosch 400Wh battery has a claimed range of 50 miles. Everything about the Embark frame screams clean, stylish, and organic.
Even the humble bicycle hasn't escaped the clutches of modern technology. A whole herd of new e-bikes with electric motors are taking to our cities' streets. Adding a motor to a standard cycle does ramp up the price significantly, but it takes much of the effort out of cycling, making your commute to the office a sweat-free experience and allowing you to sit back and enjoy your suburban cruise. 

Government regulation is written and administered with a broad, dull, painful axe. Regulations do not mix well with independent, maverick, DIY programs either. Vehicle regulations get started when there is either a visible tragedy, or a rising conflict with the status quo (like the SFO scooters program). The ebike community cannot afford a deadly accident especially if it involves others and the ebike or ebike rider are at fault. The Ebike community is up against a tough status quo that consists of pedestrians, motor vehicle traffic, the large well-funded and battle tested regular bicycle community, and the environment (especially for MTB riding and off-road use).
Haibike ships the HardNine with 29-inch tires, 180-millimeter hydraulic disc brakes, a 100-millimeter front suspension fork, and a nine-speed Shimano shifting system. The bike’s LCD readout is affixed to the handlebars and displays the current speed, level of charge, remaining range, and current pedal assist mode. The company says the battery can be completely recharged in just four hours, minimizing downtime between rides.
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