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.[43]
Update: I've had the bike about 4 months now and ride it almost everyday, it is my primary form of transportation, and I have been pleased with it's overall performance, the battery is holding up pretty well and I've never not made it home without juice to spare, the only issue I've had is with flat tires so I wanted to highly recommend putting green slime in the tires, you do not want to have to deal with getting the back tire off for a flat, but other than that the bike is running great, as others have said it is a little less powerful than you may expect but I am very satisfied with the build quality and quality of components. For saddle bags I got the type of bracket that wraps around the seat post and saddle bags meant for that kind of bracket and they have worked well for me, so I can carry my shopping and groceries easily on the bike now . http://www.amazon.com/gp/product/B0030RS5CA?redirect=true&ref_=cm_cr_ryp_prd_ttl_sol_18 http://www.amazon.com/gp/product/B00K6CEPGM?psc=1&redirect=true&ref_=oh_aui_detailpage_o08_s01
While I was waiting patiently for my 2017 model eBike to be manufactured and delivered, I came across an article in the local paper about a woman with a degenerative muscle disease who wants to take her eBike on forest service trails that are designated for mountain bikes. “What the hell?” I said, completely floored (what I actually said isn’t fit for publication). When I ordered this bike, the thought hadn’t even crossed my mind that it would be illegal to ride on mountain bike trails with my new, albeit electric, mountain bike.
Weight isn’t anything like a critical as one would assume. Weight distribution however is a different matter and this is where geometry, specifically the ratio of the front centre measurement to the chain stay length really comes into play. Battery placement is important too, and smaller batteries give an edge in the handling stakes while robbing the bike of range.
From their, you'll choose the motor size, and trust us, we’ve got plenty of motors to choose from. Whether you’re looking for a gentle 250w motor, a 500-750w motor to do some heavy cruising, or you're looking for a 1000w+ speed machine, we’ve got the ebike you want in your life. See why thousands of customers look to Bikeberry.com when shopping for an Electric Bike. 
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