Motor speed increase

Jérôme.BDX

100 µW
Joined
Jul 25, 2021
Messages
9
Hello!
I believe you can help me to answer one of my questions:
I currently run a 1000w 48V direct drive hub motor with a 48V 1000 w controller and SW900 display and a 48v 1000W 10ah battery.
I would like to increase speed of the motor by increasing the voltage with a 96V 3000W controller similar to this one :
€ 112,31 25%de réduction | Contrôleur vectoriel sans balais pour vélo et trottinette électrique, 72v, 84v, 96v, 120v, 3000w, capteur 80Amp, 36 MOS
https://a.aliexpress.com/_vOcs65

Does doubling the voltage will effectively doubling the motor speed with no load (to some loss approximation) or will the controller still limit somehow the rpm?

Thank to all of you for this incredible forum!
 
Please check out these sites, they are a very useful tool for some hands on learning. Play with different settings, look at the time it takes to heat or cook a motor, change the voltage, ah, current, slope

Very useful tools

https://ebikes.ca/tools/simulator.html

https://ebikes.ca/tools/trip-simulator.html
 
If you have the motor I think you have, the one commonly used in "48v 1000w" kits, its a 500w rated motor. It can easily handle 1000w, and tolerates 2000w pretty good. Such as 48v 40 amps. But to increase your top speed much, you do need to increase the voltage.

72v 40 amps is the typical increase for this size motor. Its 3000w, and typically gets you 40 mph when you first roll out the door with full voltage, and a solid 35 mph later in the ride when your voltage starts to drop.

With 72v, you get a decent ride before the motor melts. It really doesn't tolerate 3000w all that good. By the time you run 72v 10 ah through it using full throttle the whole way, it will be about to overheat. So about 30-40 min of ride time.

You can of course ride with less than full throttle with much less heating, and still have that power briefly when you need it, like a large busy intersection.

One option is to run 72v and 20 amps, which gets you about 30-35 mph of speed. But won't be so likely to overheat motors so quick.

To get real motorcycle speeds, you need the much heavier motor, one with about 10 pounds more weight of copper windings and magnets. When I put 100v into one of those motors, it melted really fast. About 20 min.
 
Jérôme.BDX said:
Does doubling the voltage will effectively doubling the motor speed with no load (to some loss approximation) or will the controller still limit somehow the rpm?

Yes. But the loaded speed will not, since wind resistance will increase the load as speed increases.

I ran 96V through my 1000W hub a couple of times and settled on 72V/20S, since the higher voltage introduces other issues with respect to throttle control. Even at 72V, the bike will wheelie from a start, assuming you have a battery to back it up, unless you have a controller or Cycle Analyst where you can program the throttle ramping. No fun in regular stop and go riding. 66V/18S was still controllable.
 
markz said:
Very useful tools

https://ebikes.ca/tools/simulator.html

https://ebikes.ca/tools/trip-simulator.html

What a great tool! Thank you for sharing this. I played with it and I'll continue :)
 
Many thanks for your answers! It's really interesting.
I think I will try 72V first and then 100V as I really need pretty high rpm. I know I won't double the loaded speed but the ultimate goal is to increase the max power rpm.
And the autonomy is not a concern for me :)

dogman dan said:
To get real motorcycle speeds, you need the much heavier motor, one with about 10 pounds more weight of copper windings and magnets. When I put 100v into one of those motors, it melted really fast. About 20 min.

Ok, it's great to know :thumb: as for my application I won't run it for any more than 5 minutes continuously. So I guess It's perfectly fine. Plus I would like to keep the setup lightweight.

Will any other problem appear doing this kind of overvolting? As I already had a controller problem running a 300w motor with 1000W
https://endless-sphere.com/forums/viewtopic.php?f=49&t=112806
 
E-HP said:
I ran 96V through my 1000W hub a couple of times and settled on 72V/20S, since the higher voltage introduces other issues with respect to throttle control.
Thank you for your answer!
The throttle issue you're talking about are wheelies?
Or is there anything else that could go wrong?
I'm concerned about the controller behavior as a 96v controller is probably made for bigger motor, will it be able to deal with smaller motor, different resistance, impedance and BEMF and still run it flawlessly?
(I already had a problem with another project: https://endless-sphere.com/forums/viewtopic.php?f=49&t=112806 )

Many thanks!
 
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