Sorry Andy, that's completely wrong. It would mean that everybody with a normal 14A or 15A controller is running more than double what the motor can take. 250W (motor rating) divided by 36V is 6.9 amps. No electric bike has ever run with a controller maximum set that low. You'd struggle on a 5% hill.
I think you should be careful about questioning OP's knowledge of electric bikes when you open yourself up to questions about whether electricity is your day job and whether you should be advising people based on your comments above.
Most motors can easily handle 20 amps provided that you're sensible about its use and you don't have a high-speed motor, like a 20" wheel motor in a 26" wheel.
It does not help people to throw comments around that many will simply not understand.
Generally saying that almost any motor of 250 Watt can handle 20 amps, without defining how long, whether there is a temperature sensor in the motor or not, is not going to improve the situation at all.
Manufacturers differ on the way they build a motor.....
How can the average e-biker know if his motor is one that will handle it or not?
I always try to err on the side of true facts that anyone here can rely on!
We all should do that.
Remember, the highest current drawn, is usually on steeper hills, then the question is for how long (eg. how long is the steep part!), and how hot will the motor get?
The 6.9 Amps is a very safe current level, that will not overheat or damage the motor.
But most controllers I have seen are usually set up to allow between 12 and 15 amps, that is just over double that safe level, for relatively short periods.
Plus some motors are underrated by the manufacturer, to make sure that the motor can do two things, one is not to overheat too quickly, and that the motor allows a rider to ride up many hills while still working at the legal speed.
It leaves a good feeling for the rider too....
Changing that to 20 amps, reduces the safety margins dramatically....except that many batteries cannot supply the current anyway!! A further built in safety margin.....
Next is that 3 x the safe current may be a "bridge too far". Only the manufacturer will know for certain.
Some motors are built to be able to be used on both 36 volts and 48 volts....difficult to tell from the outside of course.....
Also, even if the motor can handle it, the distance that can be covered by the battery, may vary wildly from the givens....just because a different way is being ridden....
If everything is set up correctly, there should not be widely variable "results"....
As most e-bikers I know, rely on around a certain distance per charge.....I do myself.
Andy
