I have a recumbent bicycle project that I am just starting. The bike has a a 26" rear, 20" front wheel. I would like to install a hub motor in each wheel. Why? Because I can!!! Is it possible to operate both motors with one string of batteries and one controller with the controller being sized for the max current draw of both motors together?
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- David Herron, The Long Tail Pipe, davidherron.com, 7gen.com, What is Reiki
Can you elaborate David? How would this work if they were brushless motors?
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It wouldn't.
You can't run two hubs off the same controller, unless you are putting them side by side welded together, and even then it probably wouldn't work.
The sensors would be out of synch.
You use two three phase controllers and perfectly match the throttle inputs to rpm, will require some tweaking, this is the poormans way. Amps will have to be the same at all rpms too or you stretch or squash your frame and forks.
The correct way is to use an EFUN 6 phase controller on two 3 phase motors. The reason to use theirs is it is really two 3 phase controllers that share some common control circuitry, but the phases and sensors can be split back into independent 3 phases, with perfect throttle and amperage already taken care of for you.
The original question said "hub motors" not "brushless hub motors". As I've only dealt with brushed motors my experience is with their simplicity. There's a guy who lives down the street from me who has a three wheel motorcycle driven by two etek's, one for each rear wheel, and powered by one controller. These are the old brushed eteks, not the martian brushless ones. Some hub motors are brushed.
- David Herron, The Long Tail Pipe, davidherron.com, 7gen.com, What is Reiki
Reikiman, the motors I would like to use would be brushless.(Less maintenance and wear)
Thank you Singlow. I will investigate the EFUN 6 phase controller on two 3 phase motors. My concern is that one wheel is 26 inch and the other is 20 inch. I think you are right in respect to your statement "you stretch or squash your frame and forks" In my case I think the issue would be "squash" because if both motors are spinning at the same RPM and the wheel diameters are 26in rear and 20in. front, the rear would travel farther that the front per revolution. My goal is to use one or both motors depending on requirement. I would like to be on the right track before I get started. The great thing about this project is that I have the full financial backing from my wife. I ride my bike everyday. My daily commute is 13.5 miles each way in the very hilly Northwest, WA. My average commute time is about 50-55 minutes each way.
I disagree with the the "stretch or squash your frame and forks." The way these brushless motor/controller combinations work is they will (for all practical purposes) cost and not provide resistance until your speed matches your throttle setting. At a low throttle the pulse width is small, and it will exert a relatively small force. So your speed gradually slows down until your speed matches the force the pulses provide. If one motor is pushing harder than the other, it will be doing (almost?) all the work in a two controller scenario. The difficulty would be to get both motors to share the load evenly and figure out how to turn since you'll want the front wheel moving faster than the back.
If you connect these BLDC hub motors together, you'll have a syncing problem with the Halls. Use two matched brushed motors and connect it to one controller, and you don't have to worry. All the EVers are doing that. To equalize the load you must put the two perm magnet brushed motors in series and it evens the load. They do this in RC cars too if you want to build a cheap prototype.
If you use an electric forklift motor controller, it's configured differently so that you'll have motor breaking if your speed is slower than your throttle, if you use a motor controller like that, then you really could get the problem of stretching and compressing in addition to the lost energy of one motor resisting another.
I've seen some fast eBicycles on youtube with two hub motors, so it's proven it can be done.
XM-3000...
-DC-DC converter replaced with a Dell D220P-01 power supply.
-72V mod
-Expensive bank charger until I come up with something better... Still trying.
-