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.
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.

80% of your personal Carbon Footprint is made up of three main things. How you POWER your House. What you EAT. How you TRANSPORT yourself. There are major changes happening in all three of these areas. In the next 5-10 years, homes will have economical options to incorporate Power Generation, Power Storage and putting Surplus Power back on the Grid. …
The Alpha has a  36V Brose 50W motor which is fueled by a “bridging” lithium-ion battery with 150 Wh of capacity, which is charged by the onboard 150 W PEM Hydrogen fuel cell. The fuel cell is fueled by a 2 litre compressed hydrogen gas cylinder, which can be refilled in about 2 minutes at a filling station.  In terms of cost per charge, this is likely to be more than a standard electric bike, however, the convenience of faster recharging may make it suitable for some riders, particularly commercial fleet operators using ebikes on shifts for several riders.

The recommendation depends a lot on what you plan to use the bike for and how you plan to ride. That said, I would recommend at least a 750 (if not 1,000) watt motor, and, if you want reasonable range, 48 or 52v cells with a minimum rating of 19ah. For shorter rides, you can use a smaller battery. Multiply battery voltage by amp hour rating to get battery watt hours. Divide the watt hours by the motors power rating to get a general idea of how many hours of heavy use you might get. I’d also recommend a mid drive as opposed to a hub drive, or to find a hub drive wheel rated to take your and the bicycle's combined weight.

UPDATE (2019-03-15): I've now got more than 110 miles on the bike and still loving it. The longest ride I did was 28.5 miles and the display was still showing about two bars left on the battery. But the battery gauge is not accurate. Even when it went down to two bars it would also jump back up to 4 bars and stay that way for awhile. So it's really hard to tell how much power you have left. On one ride, after 14 miles the pedal assist stopped working all of a sudden. I stopped and re-seated the cadence sensor and it started working again. Even when PAS didn't work the throttle was still working. It hasn't happened since. There was also a lot of rattling noises which I found was the battery rattling around in the mounting bracket.
I got this bike last week. I loved it! This bicycle is a very good value, since it can be used in either manual or electric mode. Both the handlebar and seat height and inclination are adjustable. The assembly and use instructions are clear. In the manual mode the bike acts like any other six speed, there is a little red button that switches between manual and electric with each push. The electric mode is used either with the handlebar twist throttle or by peddling which activates it. The pedal brings the bike up to full speed while peddling slightly and with the throttle the speed is adjustable. I am very happy with my purchase.
The new Electric Bike Kit Owners group on Facebook has taken off within the first week of its creation. Around 400 people have joined the online group with new members being added every day. E-bike riders are sharing the various ways that they have converted their bikes using the E-BikeKit Complete Electric Bike Conversion System. Each one of the electric bike conversions is more unique than the next. Some e-bike converters have added flashy lights, flags, and other features to make their electric bikes fit their personalities. One electric bike conversion kit was even used to build a three-seat electric...
We've also released our first native 72V battery pack in a conventional downtube battery casing, assembled using the high power Samsung 27100 40T cells so that even with the small 8Ah capacity it is able to deliver 40-50A continuous currents. This is an ideal battery for fast and sporty offroad ebike builds, allowing powerful performance without the weight or complexity of most 72V setups (either two 36V packs in series or a large triangle frame battery).
Besides voltage, batteries are rated by amp hours (AH). Although voltage seems to get the most attention, the amp hour rating of the battery is just as important. It is the measure of a battery’s capacity and provides a good indication of the range you can expect from an electric bike. Although lots of factors come into play in determining range (ie: rider weight, terrain, input, efficiency, etc.), a good rule of thumb is range is equal to AH. So under normal conditions, an average rider can expect 10 miles out of a 10AH battery (with no pedaling). With rider input, this number can be dramatically increased, so most 10AH batteries are rated “up to 20 miles” by the manufacturer which assumes pedaling. On pedal-assist bikes (which require pedaling), the range ratings are much higher because the rider is constantly assisting the motor and reducing the current draw.
I had gotten this to build an electric bike but I have never worked with wires before so I didn't realize that we needed to attach our own connectors to the wires. The person who I talked to at Joyisi was super nice and explained that to me and even offered to send me connectors for free. I had already ended up getting a different bike altogether though and so I just wanted to return the battery. But because I am returning it for my own reasons (as opposed to the battery being faulty), they would normally have me pay for return shipping and deduct the cost of shipping to me (which is a lot, because they are international) and the inspection fee from my refund, but they were super nice and offered to take on most of the costs and I would only have to pay for the return
"Moped" means a device upon which a person may ride which has two or three wheels in contact with the ground, a motor having a maximum power output capability measured at the motor output shaft, in accordance with the Society of Automotive Engineers standards, of two horsepower (one thousand four hundred ninety -two watts) or less and, if it is a combustion engine, a maximum piston or rotor displacement of 3.05 cubic inches (fifty cubic centimeters) and which will propel the moped, unassisted, on a level surface at a maximum speed no greater than thirty miles per hour; and a direct or automatic power drive system which requires no clutch or gear shift operation by the moped driver after the drive system is engaged with the power unit.
E-bikes mostly use motors and battery options from a few major suppliers: Bosch, Yamaha, Shimano, and Brose. A few other brands exist, but are less reliable or powerful. Some, like the Yamaha system, have more torque, and others, like Bosch’s Active Line, are nearly silent. But, generally, all four make good options. Look for motor output (in torque), which will give you an idea of total power. Just like car engines, more torque equals more power off the line and more boost to your pedaling. But watt hours (Wh) is perhaps a more important figure to use—it takes into account battery output and life to give a more accurate reflection of power (higher Wh equals bigger range).
At the moment this battery is in stock but for local pickup orders only as we are going through the certification testing required for shipping. We've been keeping the 21700 cell offerings on our radar as they start to catch up with the performance specs of the more mature 18650 series and this year it looks like they are finally making the grade. Expect more from us as the year goes on. 
Rad Power’s lineup of 2019 bikes start at $1,699 (there’s also a Cyber Monday special on their 2018 models), proving that electric bikes don’t have to be over $2,000 to have the amenities and quality you need for daily commuting. Of course, that’s still a steep price for some. But as prices keep dropping in the e-bike industry, affordability breeds better access, and this might be the key that our cities—and their traffic—so desperately need.
As with all these bikes, the assisted speed is capped at 15mph, but unlike some of them, the Gtech eBike City or its identical (spec-wise) sibling the eBike Sport (this just has a standard frame rather than a step-through one) is light and agile enough for you to be able pedal harder without feeling like the weight is fighting you back down to 15mph. You can even, at a push, use it without the motor on flatter roads.
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.[66]
E-bikes are typically offered in 24V, 36V and 48V configurations. Higher voltage generally means higher top speed – but that may not always be the case. Since the efficiency of a motor and drive system can have an effect on power and speed, a 24V setup could have the same top speed as a 36V setup. Generally you can expect 15-18 mph on a 24v setup, 16-20 mph on a 36V setup and 24-28 mph on a 48V setup. Although it far exceeds Federal laws, some conversion kits can even be run at 72V for speeds of 35+ mph! However, this puts significant stress on bicycle components. Consider that even the fastest athletes only travel 17-18 mph on a conventional bicycle, so 20 mph feels very fast to most riders. Anything over this speed can be unsafe and exceeds law regulations.
As of 2008 a standard class C license, proof of insurance, and registration (annual fee: $9.00) are required for operation of any motorized pedalcycle in Pennsylvania. Additionally, there are strict equipment standards that must be met for operation, including: handlebars, brakes, tires/wheels, electrical systems/lighting, mirrors, speedometer, and horns/warning devices.[127]
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