Electric Bikes - Do you need a controller?
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08-19-12, 04:51 PM
I used to have an older Currie E-Zip, and once you got used to the weight (the batteries mostly), it wasn't a bad bike! Very reliable and dirt cheap. Sold it, and was thinking of building something for my current non powered bike. One thing I remember about the E-Zip....you can fry the controller if you overload things as I did once pulling a very heavy trailer. The up side to that experience is it gave me a chance to see how the bike was wired when I was trouble shooting it. Things looked a LOT more complicated than they needed to be for a simple electric bike, and the controller was the main culprit.
In my DIY electric bike project, I want things simple, simple, simple. Do I really need a controller? When I raced slot cars (remember those?), we had simple rheostat controllers to control the car speeds. Couldn't I use something like that instead of a controller? Or, if not, possibly a 3 or 4 position switch that would give me 3 or 4 motor speeds? That would be plenty. Thanks.
no...I believe controller is needed for the phase and halls wires, if you want a simple conversion, check this out;
very simple, 5 minutes if you don't have enlarge the dropouts for thicker axle. see video.
this still has a controller, got up to about 50v rating, even though kit is setup for 24v. this was my last years bike, I wanted a little more speed so I up it to 36v, no problem encountered, ran good and was quicker. Now I am running 12s lifepo4 at about 44v, still good.
throttle is a simple on and off button, they say most of the time when you are riding, it's either full or none.
this only comes front wheel drive only, to make it simple, no derailer or chain to deal with. derailer and chain still there when you pedal, and it is a gear hub not a direct drive, so freewheeling is no problem.
I don't know how much your ability is, but this is simple.
08-19-12, 06:23 PM
Simple is good, but I would want something more than full on or full off. That is a neat little kit though.
My mechanical ability is fine, but the electrics puzzle me a little. Way back when, I used to be a certified auto mechanic and actually specialized in electrics, but cars were, and are, VERY specific to the maker. You could be a wiz at VW's, but a Toyota would be like starting from scratch because everything would be so different. I just figure something real simple will last longer and be easier to fix, which is why I'd like to stay away from sealed boxes full of printed circuitry if I can. Nothing to do w/ controllers but replace them when they go bad.
My old bike had a twist grip throttle that worked great, but generally I had the throttle in only a few positions. So a switch w/ 3 or 4 positions should be enough. Maybe I just don't understand the mechanics of electrical flow, but I was wondering if I couldn't simply run wires from the battery, to a variable or 3/4 position switch, then to the motor. No controller. This would be w/ a brushed motor by the way.
08-19-12, 10:21 PM
Brushless Motor = The new technology, higher efficiency, usually Longer motor Life, but a complex electronic controller with at least three multi-directional current hot wires to the motor from the controller is required.
Brushed Motor = The old technology, lower efficiency, usually shorter motor life, requires brush replacement on a routine maintenance schedule, but a complex electronic controller is not required and if you wanted to you could go as simple as a simple toggle switch with one hot wire from the battery to the switch and then to the motor and a single ground wire from the motor to the battery.
Long story short the brushes in a brushed motor are a mechanical equivalent to the complex electronics in a controller just not near as efficient and subject to wear. There are still a few of the older style brushed hub motors out there if you look hard enough and if you are building your own mid-drive system from scratch there are plenty of low voltage DC motors out there to choose from but you will take at least a 25% hit on the power and/or range you will get out of the same battery pack and if you compare a really efficient top of the line brushless motor to a really inefficient brushed motor it can be as much as a 50% hit.
I do personally believe that there is still a limited niche market for a brushed hub motor. Specifically a low wattage, freewheeling, internal gear reduction, rear brushed hub motor that had a slow speed output that was geared down low with lots of torque specifically for helping a rider who normally pedaled without motor assistance climb hills. Something that pulled between 200 and 500 watts depending on input voltage, that being anything from about 18 to 36 volts that would run off of just a simple toggle switch and a water bottle sized battery pack. Something that would give you a bike that was just a pedal bike most of the time because the motor was geared so low that you could go faster on the flat with just casual pedaling then the motor would push you but when you came to a big steep nasty hill you could just flip a switch and have the motor kick in and help you up the hill for five or ten minutes and then when you got to the top just switch it off again. Something small and simple that was just made for climbing hills and geared down accordingly. It is amazing how strong and how well a little 250 watt motor can climb a steep hill if it is geared down enough.
Another thing I wish someone would make is a throttle control for bikes that plugged into the brushless motor controllers that the remote control guys use for their cars and airplanes. The brushless motor controllers they are using are like a third the price and a third the size and weight of the bike controllers and a lot of them are rated to take huge amperage loads, and yes provided the number of poles matches (usually 4-pole with 3-motor wires) they will work on the same motors we use. I've tried it, just that I don't want to have to hold RC controller in my hand to have throttle control. How the RC controllers work is that they have a small variable resistor in the little stick or trigger on the hand controller and the computer in the controller converts that to a standardized 8-bit binary code for the throttle position and transmits that over the designated radio frequency and the receiver in their little car or airplane reads that code and sends it via a standardized analog feed-back loop arrangement to the brush-less motor controller (a standardization originally intended for servos) and the motor controller responds to this "standardized servo language" tricking the receiver into thinking it is a servo and adjusting the motor speed accordingly. All of the RC brushless motor controllers for years and years have had directionally specific, no hall sensor required, start from dead stop capability that only the very best bike controllers have even begun to be capable of, and most of the better RC car controllers have both reverse, interference braking, and regenerative braking capabilities.
Long story short, imagine a controller that already exists for another industry that average a third the cost, a third the size, a third the weight, can take more amps (a 50A rating is considered where the high load controllers start and anything less is merely standard load in those guys world), completely make hall sensors irrelevant and can start from a dead stop without one in whichever direction (forward or reverse) is desired on command, and in the better higher priced models have not only regenerative braking but programmable interference braking capability as well (basically strong braking action through the motor that does not charge the battery since with some kinds of batteries in some situations regenerative braking can hurt the battery) such that the full power of the motor can be used for braking without hurting the battery, motor, or controller even if you were to go down the back-side of a mountain pass using only the motor to do your braking all the way down. Add to that the capability of having a low speed motorized reverse option on a direct drive hub-motor if you wanted it.
What is needed is a simple and reliable throttle assembly for our bikes that one end mounts to the handlebars and the other end has an RC servo plug that talks directly to an RC type brushless motor controller in the universal electronic RC servo language so we can use their controllers to run our motors. I'm sure though that the current bike controller manufactures really, really, really don't want to see that happen.
08-20-12, 01:08 PM
Thank you turbo for a very detailed look at this. Great read. Upon thinking things through, I think I see the issue, and it's almost exactly as you decribed. If I were to wire the bike (using a brushed motor) directly from the battery to the "throttle" (a 3 or 4 position switch), then from there to the motor, I'd have to use heavy gauge wire capable of carrying the entire battery output. The throttle switch would also have to be rated for that sort of juice, and the wires from the throttle to the battery would need the same big wire. It might be a little cumbersome, but I could do it.
I'm sure there would be a current loss due to the wires, and another loss because it's a brushed motor. That's a fair tradeoff for what I'm after: a low cost, extremely simple electric bike that can be easily built and maintained by someone w/ even the most minimal electrical knowledge.
There's still a lot of brushed motors out there. Maybe it's old stock, but I see that the E-Zip Trailz bikes sold online from Walmart have those. If I was smart I would just get one of those for $435, put another SLA battery on it, and for around $600 have a bike w/ a realistic a 20-25 mile range. Heavy, but cheap and reliable. But then I'd still have what I consider to be an overly complicated and failure prone bike due to the sealed and unrepairable electronics. I already did that. It worked well, but when that controller burnt up it made me realize that something like that could happen anywhere, at anytime. No like!
One of the reasons I ride a bike is because it's wonderfully simple (and fun, of course). I can repair nearly everything on it. Putting something as simple as a little electric motor on it shouldn't require strong electrical knowledge, and shouldn't require calling tech support in some far off place just to trouble shoot an unrepairable component. That defeats the whole purpose of what's supposed to be a simple machine that's user serviceable.
08-20-12, 03:07 PM
Also note you run the risk of overheating the motor or overloading the battery if you run the motor without a speed controller and have it wired directly to the battery in some way. The controller not only serves to control the speed of the motor, but it also has a maximum current and voltage and prevents the motor from drawing too much current. It all depends on what your motor was rated for and how much current your battery can put out. Unlike computer electronics and other things, motors will pull whatever current they want from the battery depending on the load the motor has to deal with. So if your battery is rated to put out more current then the motor is rated to handle, then the motor could overheat and eventually fry it self. So instead of a burnt out speed controller (which would happen a lot less often if it's all wired up correctly) you got a burnt out motor and that could end up being more expensive to replace then your speed controller!
Of coarse it's possible brushless motors may not draw current in the same way as brushed motors, but if you had a brushless motor, you would need a speed controller for it anyway since brushless motors require some form of electronics to power it correctly since the commutator is electronic instead of being mechanical like a brushed motor.
You could of coarse use a fuse or circuit breaker if you really want to ride without a speed controller. Just know if you hit a hill or wind resistance you may end up replacing the fuse quite often. :P
I have a brushed motor and while won't last as long as a brushless, it will still go for quite awhile before I would have to worry about replacing the brushes. My speed controller is rather simple in terms of wiring. 3 wires going to the throttle, 2 for the battery and two for the motor. Really the only big change from that of a brushless is that most I know of (for e-bikes anyway) just have a third additional wire for the brushless motor. Some speed controllers may have additional "features" like security key wires, turning signal wires, tail light wires... stuff like that.
If your bike has one of those, you can simplify the wiring quite a bit by simply getting a lower tech speed controller. They aren't really that hard to work with once you make sure the wires have the right connectors on them so that you can service them when needed.
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