Adjusting start acceleration of trapesoidal KT controller to avoid motor freewheel damage

[Akx]

Hello everyone!

I've a 350W geared hub motor which I had to replace the gears mechanism on after only 3000KM because the freewheel got stuck (only rotated with the motor). I guess this could be happening because there's a startup "kick" when the motor starts with too much acceleration.
I use a 48V battery and the controller is KT26-60ZWSRMD with KT-LCD3.

So my question is if it's possible to adjust the controller so that it starts more smoothly with less acceleration.

There appears to be no KT-LCD3 parameters for startup acceleration or the PID loop.

If not adjustable I wonder if the sine-wave version of a similar KT controller has more smooth startup.

 

[E-HP]

It's not clear when you say "gears mechanism" whether you mean the nylon gears inside of the motor, or the external freewheel (assuming the motor has a freewheel rather than a cassette). Can you please clarify. If it's the latter, then changing anything with the ebike components won't make a difference, since the freewheel isn't under any load/stress except from your pedaling. If you're stripping the internal nylon gears, then that seems unusual with that little power.

 

[Akx]

The internal mechanism, not the external freewheel. Maybe freewheel is not the correct term here, but I mean the mechanism inside the motor which decouples the motor's case with the wheel from the axle so that the wheel can freely rotate when the motor is off.

The nylon cogs are fine.

 

[Akx]

The freewheel is inside the central metal piece on the picture below.

 

[scianiac]

Well perhaps not exactly the solution you're looking for but many people weld said clutch together to enable regen with geared hub motors, changes how the whole system works and you need a controller that has regen and a good torque arm but people claim it's worth it for the increased range, assuming your riding conditions are suitable for regen.

 

[Akx]

I see, didn't think about it. I like the freewheeling style, often I don't need much speed, just give it a nudge and then coast.

 

[E-HP]

The internal mechanism, not the external freewheel. Maybe freewheel is not the correct term here, but I mean the mechanism inside the motor which decouples the motor's case with the wheel from the axle so that the wheel can freely rotate when the motor is off.

The nylon cogs are fine.

Thanks. It's unfortunate that they refer to that as both the clutch and at times the freewheel, which adds confusion. The stock LCD3 firmware doesn't have much regarding adjusting the throttle ramping. However, there is open source firmware for the LCD3 that may be able have that functionality (not sure), so you may want to check out/search the threads on this forum. Search on something like "LCD3 OSF".

 

[amberwolf]

Are you using the torque simulation or the speed control mode?

 

[Akx]

Are you using the torque simulation or the speed control mode?

I'm not sure, is there an easy way to find out? I suppose it's whatever is the most basic thing, so probably speed control.

 

[E-HP]

If it failed after only 3000km, what leads you to conclude it happened due to the "kick" rather than a manufacturer's defect? If the problem was the "kick", then I'd expect to see numerous/frequent failures here on the forum. What motor are you using?

 

[Akx]

If it failed after only 3000km, what leads you to conclude it happened due to the "kick" rather than a manufacturer's defect? If the problem was the "kick", then I'd expect to see numerous/frequent failures here on the forum. What motor are you using?

It's just a guess, no sure way to know I think. It's an OEM which should be similar to MXUS XF08 because the replacement part with the freewheel (aliexpress calls it "clutch") is compatible with MXUS XF08 and the power is 350W according to the seller. The silkscreen on the board inside says XF15 but it's not 500W so I guess the same board can be used in both XF08 and XF15.

 

[Akx]

Sorry, I think it's XF15R after all based on the dimensions of the "clutch" part.

 

[E-HP]

It's just a guess, no sure way to know I think. It's an OEM which should be similar to MXUS XF08 because the replacement part with the freewheel (aliexpress calls it "clutch") is compatible with MXUS XF08 and the power is 350W according to the seller. The silkscreen on the board inside says XF15 but it's not 500W so I guess the same board can be used in both XF08 and XF15.

Ah, so no matter what steps you take, you'll have no idea about whether it successfully resolves the issue. What are you willing to invest on the "solution"? There are a few options to create a "soft start", but most aren't free.

 

[Akx]

I was hoping at an easy change to try to lower the chance of it failing again. If it's hard to do then you're right, it may not be worth it.

 

[E-HP]

) was hoping at an easy change to try to lower the chance of it failing again. If it's hard to do then you're right, it may not be worth it.

Got it. So, I don't think I've read whether this kick is happening when PAS is kicking in, or while using the throttle, but since you don't need much power, here are a couple of options that may or may not apply:
For throttle, there is a combination of P4 and C4 parameters (P4=1, C4=4), that control how much power is available when you twist the throttle, so in level 1, the throttle controls a lower range than level 5. With those settings, starting off in level 1 should be slower.
For overall power, C5 can be adjusted to below 10 (max), down to as low as 3. This leaves you with less power all of the time, so may not be preferable.