BBS02 Motor/Drive Electrical/Mechanical Specifications

[Nathan#1]

I work with brushless motors at the day job and would be interested in running some numbers, but I need to know some basic specs for the BBS02 motors. If anyone has these numbers, please post up.

1) BackEMF constant (with units)
2) Torque Constant (with units)
3) Phase-Phase Resistance
4) Phase-Phase Inductance
5) Internal gear ratio of BBS02

Also if you know if the internal controller is actually a sine drive or a trap drive, that would be helpful.

Thanks!

[max_volt]

1-4 no idea. 5 is 1:21.9

[Nathan#1]

I guess one more question that I can calculate some of the above numbers would be:
Q6) What is the max no-load rotational speed can the motor run (for a given voltage)?
For example, something like: With a 48V battery, the motor can run no-load at 3500RPM, which gives a crank cadence of 3500RPM / 21.9 = 159.8RPM

[Nathan#1]

Ok. One more try. Does anyone (...luna guys... ) have a disassembled BBS02 with the controller removed that I can physically borrow and analyze for about 1 day? It can be a unit with the controller burned up but the motor/housing is still intact. I promise I won't break it (I do this stuff for a living). I'll post all the numbers back up here for everyone.

[Rider]

I can’t help you with any of those electrical specifications, but I‘m curious why you need/want it. Do you want to back engineer it?

I’m no engineer, but I don’t think no load motor RPM relates directly to gear reduced pedal load cadence...

[Nathan#1]

The backEMF (amount of voltage the motor generates itself for a given speed) determines the upper limits of how fast you can spin at a given battery voltage. That is typically the primary contributor, but inductance and resistance can also be small parts of that equation....

So I'm interested because I think I have plenty of torque (current) left, but because of the wheel diameter and gear ratios (which are already at the extremes and I can't further modify due to mechanical constraints) my top speed is very limited due to backEMF and battery voltage. Based on the pedal cadence and the BBS02 internal gear ratio we can calculate the actual motor speed, and if I had the backEMF number I could see if I'm running into a battery voltage limitation for top speed.

The quick BackEMF test is to use another motor (power drill would work) to spin the BBS02 motor at a known speed and measure the phase-phase voltage that it makes while acting as a generator. Inductance and resistance can be measured directly with an LCR meter once you have access to the internal 3phase motor windings (controller disconnected). If I wanted to take an afternoon and completely disassembly my bike/BBS02 I could run the tests on the motor I have but I'm not that desperate yet. It would be much more convenient if I had access to an already disassembled BBS02 that was getting repaired or something.

[i-Zapp]

Nathan#1 did you ever locate (or generate) the info you were looking for?