andyme said:
my personal question would be: why would one buy a 36V motor if one owns a 48 V battery already
I think the big issue would be your pedaling cadence. These motors don't produce much torque above modest pedal cadences. i.e. if you pedal fast, the motor stops helping. This gets worse as the battery goes flat. The stock firmware is pretty poor for this.
If you like to pedal fast, using a 36V motor with a 48V battery will still give torque at high cadence. A 48V motor will probably run out speed.
Remember that the difference between the two is not that great only 4:3 , so don't agonise about it.
i.e If I pedal at 60rpm cadence using a 48V motor +48V battery, then with a 36V motor+48V battery I could pedal 80rpm.
The 48V motor will produce more torque for the same power output, but at lower max pedalling speed.
andyme said:
but as a rule of thumb i think it is safe to say that there are more advantages in a 48 V motor (more power, or same power with less current, less losses) than in 36 V motor.
The power output (how fast you can climb a hill) is exactly the same for both motors. The choice is do you pedal fast or slow?
The efficiency of the motor itself is the same (36V motor may even be slightly better, if the measurements of 48V motor resistance was accurate), and exactly the same amount of battery power is used for the same amount of shaft power.
If you want very high powers (750W), then the 48V motor does allow more power from the controller circuit.
Bear in mind that this motor is a small motor with poor thermal design, and probably cannot be run at high powers for long, so "750W" probably means "for a brief burst". (The motor itself overheats at a mere 27W motor dissipation) [I have not run motors beyond 350W, so someone else can comment on how fast they overheat]