Sabvoton vs kelly? Or does my setup just suck.

new2this

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Jan 27, 2023
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Long story short, I built an ebike last summer and it's got plenty of power but the controller sucks. I bought one of those standard Chinese 3000w brushless motor kits for a go kart and put it on my bike, had to cut my own sprocket and 3d print all mounts. The problem with the setup is that the gear reduction is insane, it's a 11T to 135T sprocket. As you can probably expect, if you breathe on the throttle wrong it will lift the front wheel, it's very hard to keep it on the ground from a stop, while moving it's a bit more manageable but it can still lift the front wheel whenever you want.

This controller is square wave and non programable, my theory is that the motor speed is directly mapped to the angle of the throttle so it just dumps current into the motor to match whatever speed it needs to reach. I have been looking for a new controller to replace this cheap one, preferably something that can do at least 80A continuous since apparently that's what this one can do. I've narrowed it down to between the Sabvoton MZ72150 and the kelly KLS7218S.

So my question is, will either of these controllers be able to fix this issue and allow me to create a throttle curve that is more comfortable or is the design fundamentally flawed? Ideally I would be able to reduce the amount of current outputted in the initial 40% of the throttle then gradually increase it. Having a mode switch that actually worked would be nice as well :).

Also if there are any glaring incompatibilities that might come my way please let me know as I'm not too keen on damaging this motor.

Thanks,
 
new2this said:
Long story short, I built an ebike last summer and it's got plenty of power but the controller sucks. I bought one of those standard Chinese 3000w brushless motor kits for a go kart and put it on my bike, had to cut my own sprocket and 3d print all mounts. The problem with the setup is that the gear reduction is insane, it's a 11T to 135T sprocket. As you can probably expect, if you breathe on the throttle wrong it will lift the front wheel, it's very hard to keep it on the ground from a stop, while moving it's a bit more manageable but it can still lift the front wheel whenever you want.

This controller is square wave and non programable, my theory is that the motor speed is directly mapped to the angle of the throttle so it just dumps current into the motor to match whatever speed it needs to reach. I have been looking for a new controller to replace this cheap one, preferably something that can do at least 80A continuous since apparently that's what this one can do. I've narrowed it down to between the Sabvoton MZ72150 and the kelly KLS7218S.

So my question is, will either of these controllers be able to fix this issue and allow me to create a throttle curve that is more comfortable or is the design fundamentally flawed? Ideally I would be able to reduce the amount of current outputted in the initial 40% of the throttle then gradually increase it. Having a mode switch that actually worked would be nice as well :).

Also if there are any glaring incompatibilities that might come my way please let me know as I'm not too keen on damaging this motor.

Thanks,
My advice is that if the cheap controller has the power you need, then put a Cycle Analyst in front of it to control the throttle delivery. Less of a hassle than replacing controllers. You may feel like you won't use a lot of the features the CA provides, but may later find them invaluable. My interim controller (temporary after my main controller blew) had a speed based throttle like you describe, but the CA tamed it, so it felt like a power based throttle.
 
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