EBike Controller - Does 'current' affect driving speed?

Question

I wanted to ask if a brushless controller Current actually affects electric bicycle speed.
At the moment I have a 48V 250W brushless controller, rated current of 5A and maximum current of 10A. protection voltage is 42V.

Here is a more detailed picture about my controller plugs, etc:

So my main question is: if I switch to a same brushless controller but just this time with lets say a maximum Current of 17A, will it make any difference in any way?

I also tried talking with the manufacturer and I didn't get a flat answer; they said it won't affect on the speed but I read in a few places that it might.

My Battery: 48V 13Ah
My Motor: 48V 250W ( model: bafang swx02 )

Also another question, is there any way to make my ebike drive faster than 25 km/h without switching the motor?

Answer 1

To a first approximation (a flat, level road), increasing the current capability (not the current) will have no effect on your speed.

A BLDC motor is effectively driven at a certain AC frequency, and the motor turns at one revolution per cycle of the drive. As long as the motor gets enough current to produce the force necessary to overcome friction and drag, increasing the current available won't change anything. And you should note that, from a power perspective, it's clear that your battery and motor are well-matched. The motor is rated for 5 amps @ 48 volts (peak 10 amps), for a total of 240 watts (480 peak). The motor is rated for 250 watts, so the motor is the limiting factor.

So the first thing you would need to do is replace the motor. However, you would also probably need to replace the controller as well. I suspect there is a speed limiter somewhere in there.

Answer 2

The motor will draw whatever current it wants to unless the speed controller limits current for torque control or to protect itself. If your motor would normally draw less than 5A at top speed then using a higher rated controller won't make a significant difference (it might be very slightly faster due to lower voltage drop across the FETs in the controller).

Motor speed is proportional to voltage. If you want more speed (and can't gear it up) then use a higher voltage battery. Just realize that it will draw more power, which may damage the motor or controller if their ratings are exceeded. You will need a higher voltage controller as well as extra batteries, so you might consider replacing the entire drive chain.

Answer 3

Voltage correlates to raw (unloaded) speed, current correlates to torque and overall power (loaded speed). The current handling of your motor is going to limit your speed. There won't really be a way to go faster without changing out your motor.

Answer 4

open the controller, find the shunt and add a bit of solder it will increase amps output allowing more torque, as well as speed if the current was limited down low enough (which 5A sounds a little low to me) this would cost a bit off of the battery range.