I have two new identical Q128 motors....one spins slower than other.

I bought two 36V 328RPM Q128 motors, one month apart from BMSBATTERY.
Using same controller/battery/etc. (only swapped out motor), here are my observations.
One spins at 425RPM with fully charged battery (42V)....the other spins at about 380RPM.
Gearing is same, so difference lies in windings?

PS: Very happy with first motor...so I bought the second one for t wife's trike.

As noted in a previous thread
https://endless-sphere.com/forums/viewtopic.php?f=2&t=98688&p=1445390#p1445416
BMSBattery is known for not sending the same thing all the time...if they ahve something that is "close", they'll send it, whether it is what you actually ordered or not.

So they probalby sent you the wrong winding one time or the other. They've done it to enough other people over the years....

pullin-gs said:

Gearing is same, so difference lies in windings?

Click to expand...

For sure. They just sold you wrong labeled product(s).

How'd you pay for it ? Make a complaint have them send you another motor they may just have you keep the first motor that they sent you and just send another one. Squeaky wheel gets the grease.

I noticed motors are labled differently:
#1) is a Q128C. Part# is AAA3616A. Described as 328RPM, 36V
#2) is a Q128 CST. Part# is BAA3616B. Also described as 328RPM, 36V

I asked for a repacement from vendor.

Give the wife the slower one and problem solved. If you put the faster one in a slightly smaller diameter wheel, then you'll enjoy better performance in every respect. That is as long as the factory didn't get lazy and use the same size wire and strand count at just put fewer turns on the motor. To find out measure resistance of the phases. If wound to the same copper fill (the correct way), the phase-to-phase resistance of the faster motor should have decrease by a greater % than the rpm increased compared to the other motor. The phase windings should be shorter by approximately the % rpm increase, and they should also be thicker.