Electric bike hub types

Electronics
#1

I’ve had increasing interest in a DIY electric hub bicycle. This is becoming more feasible with the availability of Li battery packs and improved hub and mid drive motors. The general idea is to give a boost to the usual pedaling action and not strictly use a throttle to move the bike. But I wondered how many DMS folks have thought about it or were interested in it. There are a ton of cool engineering aspects to the implementation including torque controlled power assist, regenerative braking, battery technology, motor control.

But the reason for my post was really to point out something that I found that I thought was pretty cool for a non-geared hub drive motor. Apparently there are some hub motors that are really three phase induction drive motors rather than brushless DC or other technology. That can lead to some cool control techniques with the right controller. I’m no expert but my understanding is that variable speed control of 3 phase motors involves both a variable frequency and variable voltage. This is done with a VFD controller .

I came across several electric hub controllers on Alibaba and they mentioned that they were ‘sine wave controllers’. I was sort of excited because that sounded to me like a VFD, meaning there must some 3 phase electric bike hubs out there, meaning serious power, fine control and regen braking.

Unfortunately, the guys who sell these devices seemed clueless as to what they are selling. When I asked why ‘sine wave control’ in a DC system, I got answers like “Sine wave lower noise than square wave how many you want” I did not want to come out and ask if it was a 3 phase motor because I figured they might just say ‘yes’ not knowing what they were talking about.

However . . . I came across this controller and sure enough, it is described in pretty good english and says it controls 3 motor phases. It even mentions regen braking ABS braking.

Thought this was pretty cool for an electric bike hub. Who has thought about building one? With 2000W, you could have an electric motorcycle. E-bike is legally limited to 28 mph but that is plenty of speed on a standard bike.

An electric bike will actually make you do more exercise since you will get out there thinking you won’t be doing much work then gradually reduce the assist and get a good workout. It’s basically a range extender for a bike.

#2

They are brushless motors, I believe

https://www.digikey.com/en/articles/techzone/2013/mar/an-introduction-to-brushless-dc-motor-control

[quote]
While the motors can come in one-, two-, or three-phase types, the latter is the most common type and is the version that will be discussed here. [/quote]

#3

I wouldn’t mind adding one of those mechanical doping (http://www.bicycling.com/bikes-gear/news/how-does-mechanical-doping-work) type motors to my commuter bike. Read where someone added one to their commuter bike and noted that they don’t get anywhere faster, but that they are able to ride to places (distance-wise) that they would not have done previously.

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#4

https://www.amazon.com/gp/product/B00Q8JT9H2/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
This is what I used along with 4 7ah sla batteries. The lead batteries are very heavy, with the motor and all the accessories it added at least 200lbs. I can still go 30mph on flat ground.

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#5

I have not tried this but if you are just looking for a controller you can use a hobby grade esc made for rc planes and cars. You can use pick anyone for what voltage and amps you need. The stock controller that came with my kit was 48v and only 20a.

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#6

Yes, one needs to understand the logic behind an E-bike. I’m a pretty big cycling fan and I’ve commuted for years and done cross country trips and done mtn / road / recumbent and all sorts of bikes.

One frustration with commuting or doing errands on a bike is that maybe you just don’t feel like it or it may be too hot or too far for the amount of time you have to travel. (That is, as I’m running out of time to get to work, I realize I’ll have to ride really hard and thus it will take too long for me to cool off. Sometimes I abort my ride and get into the car when I could have done it with some assist.)

Darrent, with a good e-bike these days you can actually get there faster if you choose to use enough assist. It does take some assist just to overcome the added rolling resistance plus the MGH work of a hill climb with the extra weight. But after that, the added wattage translates to added speed. An average cyclist is working pretty hard to put out 200 watts for a while and for most that would not be a comfortable ride to work. I’m guessing that an E-bike with the extra wt takes an extra 50 watts to roll plus more on the hills. But if it has a true 500+ watt hub and perhaps a 500 WH battery pack then an extra 200 watts both ways on a one hr commute could really help. I’m just sort of guessing. I’ve ridden an expensive demo German E-bike but I don’t have one. I could easily to 20mph up a 6% grade (level 4 assist) on that heavy bike. On the flats I could use level 1 or 2 assist (out of 4) and easily do 20 mph with a fuel gauge reading of 75 mi on a full battery at that rate. You had a heavy bike. The German bike was around 60# and was pretty heavy duty re rims, tires, lights, fenders, etc. But it was $4.5k.

Anyway, I’m too much of a hacker to not build my own and learn about it and get a way better value.

And thanks, nclindberg . . . I did not know that RC stuff used 3 phase motors. (the controllers had 3 big wires so I’m assuming that’s what they are) But that makes total sense - you can have total speed control, do reverse, do braking, measure speed.

NCL - Is yours a 3 phase controller and hub?

I also have to say that if a bicycle makes sense for some situations and so does an E-car, then there is surely an amazing future of E-assisted and E-vehicles that we will see filling the space between these two options. Ha, I could haul a couple KWH of batteries or a powerwall in my old child carrier trailer and get some serious assisted cycling mileage.