Russell wrote:lynchy wrote:I spoke with the Ananda engineers today and was told the following but do not have first hand experience as all the motors I've used have all been with hall sensors:
- big motors start smootly from standing start without hall sensors.
- small motors are not so smooth without hall sensors from standing start.
- you lose some efficiency without hall sensors. Ananda engineer said 2-3%, another engineer said 5%.
I would say the difference in sensorless performance is between DIRECT DRIVE and FREEWHEELING GEARED motors rather than large and small, though that does go hand in hand. I have a controller from ecitypower/bmsbattery that can run sensored or sensorless however operation with a freewheeling geared motor is frustrating. A freewheeling geared motor position can not be found until power is applied to it so initial throttle-on from a stop has to be very gentle until the controller can see some back voltage and determine the proper timing to pulse the phases. Once under way the combination worked ok as long as power was applied but let the throttle go to rest and the sequence has to be found when the throttle is activated again. I couldn't ride more than a mile like that.
The reason I keep saying freewheeling is to differentiate the performance of a geared motor running sensorless which doesn't freewheel. At 3,000 miles the hall wiring was damaged on my Bafang QSWXB motor and one hall sensor became defective, it was at this point I disassembled the clutch and locked it up so it could not freewheel. ( viewtopic.php?f=4&t=10458&start=45#p212576 ) Now the motor provided back EMF just like a DD motor all of the time and it works great with the sensorless controller. All that is needed for a smooth launch is the slightest forward movement and once under way there is never any hesitation or "hammering".
My experience does make me wonder how the new crop of Bafangs without hall sensors such as the QSWXK and BPM are working for their owners and if they fully freewheel when not under power(????).
I have a very limited experience of sensor less controllers but I will have soon as I'll have several models of the same controller both and without sensor for direct comparioson. I tried the new QSWXK motor without hall and it was both really smooth and very quiet. The climbers I tried were also without hall sensor and they were even smoother, more torquey and very quiet. I believe the comments that I said before may have not been as simple as big and small motors but it was what was briefly mentioned. Maybe he had meant small geared hub motor and big direct drive motor, I'm not sure. I've generally used geared hub motors but will pick up some bigger direct drive motors soon, to have a play with
I've been told that sensorless controllers are more difficult to implement and the programming is very critical to a good operation. Once I have a proper workshop and get myself a descent USB scope I can start to play with the controllers a lot more.
I have a real thirst for E Bike knowledge I was told by the Overseas Sales Manager in 1 of the biggest hub motor suppliers in China that he has never had a customer like me and my questions have driven him almost crazy I took it as a bit of a compliemt, don't think it was intended that way... I think he's used to people that are mostly interested in getting something that does the job at the right price.
Generally Chinese sales people do not like a lot of questions. Did you know that in the Chinese language the same word is used for both "Question" and "Problem", in Pinyin it is wenti. "Mei wenti" (mei means not) means no problem.... Says it all really So basically show me the money but keep your mouth shut