Hi Trevor,
The voltage setting in the controller only changes the maximum and minimum voltages that the controller will operate on.
The motor will always draw full battery voltage when the battery voltage is within the controller's set voltage range.
Most ebike legislation relates to the maximum continuous power output from the motor rather than the voltage.
If the legal limit was 750 Watts, you could simply reduce the
Battery drawn current (A) setting to 20A with a 48V battery. This would draw a maximum current of 960 Watts from the battery, but the motor would only be producing an output of ~750 Watts of power if the motor was running at ~78% efficiency.
If you need to comply with a maximum speed limit as well, you can simply set the
Maximum forward speed (rpm) setting to the required rpm to match the legal maximum speed. The required rpm will also be affected by your tyre diameter too. Check out
this post for a spreadsheet to help calculate the correct rpm for a required speed.
As long as your power and speed are correctly governed, you will hopefully be street legal, unless the law specifies that throttles are not permitted.
I often run my Magic Pie 4 on a 29.6V 8 cell LiPo pack
(giving a fully charged voltage of 33.6V) but it still pulls up to 975 Watts of power from the battery under full load. That equates to a power output at the wheel of up to 780 Watts @ 80% efficiency.
If I use the same 29.6V battery pack on my MPII
(with the modified controller shunt) it can draw up to 1500 Watts of battery power, so using a 36V battery with a Magic Pie motor (which is rated for 750 Watts @ 36V) does not necessarily mean that the bike will be street legal because it is only using a 36V battery.
Alan
