If you run a 36v motor at 48v, it goes 33% faster, so a 201 rpm one becomes 260 rpm. The Q128H is lighter than the BPM. It's smaller, but spins faster internally and has a greater reduction ratio, so it still makes high torque. I'm just waiting for one to come from BMSBattery. Then I'll be able to tell you exactly how it performs.

The 260 rpm 36v BPM at 30 amps with a 36v battery will perform the same as a 260 rpm 48v one at about 23 amps with a 48v battery. When you increase the voltage, the torque and speed both increase more or less in proportion, so you have to be aware of what exactly the speed of your motor isvat any given voltage. If you make your motor go too fast for its power, it will run inefficiently. A 250w motor is OK up to about 20 mph, 500w up to 25 mph and 1000w for 30mph. It's not an exact dcience though because there's do many other variables.