Jerky motor

J

Jpwcamel

1 mW
Joined
Nov 14, 2023
Messages
16
Location
Denmark
Hey!

I’ve recently changed my display to a kt-lcd8h, and after programming the settings my bike gets kind of jerky at around 15mph/25km/h almost like the motor cuts out for a fraction of a second and back on again, this wasn’t a problem prior.

From what I can tell the motor wattage kinda jumps down and up at around max speed.

It’s a KT controller and a bafang RM G060 hub motor.

It’s 48v system.
IMG_5453.jpeg
 
Hi Jp,

Why is your c5 only set to 40 percent current?

Cryingmadman

“Ideas are easy execution is a bitch”

Marie Antoinette
 
You're limiting current via C5. Set it to 10 and see if the problem persists. You also have your maximum trip speed set pretty low, unless you want the system to cap out at 27km/h for some reason.
 
E-HP said:
You're limiting current via C5. Set it to 10 and see if the problem persists. You also have your maximum trip speed set pretty low, unless you want the system to cap out at 27km/h for some reason.
Click to expand...
The jumpy/jerky behavior seems to get worse the higher c5 is, 3 seems to be the sweet spot but than the bike struggles hitting max speed, at the slighest wind. The max speed is capped at 27 because I live in the EU and anything higher would make the bike illegal.
 
Jpwcamel said:
Hey!

I’ve recently changed my display to a kt-lcd8h, and after programming the settings my bike gets kind of jerky at around 15mph/25km/h almost like the motor cuts out for a fraction of a second and back on again, this wasn’t a problem prior.
Click to expand...
Your initial setting of 27 KM/H is quite close to where your engine stops working at 25 KM/H. You can change it to 40, for example, just to see if that is a problem.
 
B_c said:
Your initial setting of 27 KM/H is quite close to where your engine stops working at 25 KM/H. You can change it to 40, for example, just to see if that is a problem.
Click to expand...
So I’ve just done a few test rides, the bike sort of jerks when it hovers at 24-24.9kmh but once it passes that speed its riding smooth again.

Soo freaking weird.
 
Jpwcamel said:
So I’ve just done a few test rides, the bike sort of jerks when it hovers at 24-24.9kmh but once it passes that speed its riding smooth again.

Soo freaking weird.
Click to expand...
Does the same thing happen if you change the limit from 27 KM/H to some other limit, for example, 40 KM/H?
 
B_c said:
Does the same thing happen if you change the limit from 27 KM/H to some other limit, for example, 40 KM/H?
Click to expand...
I haven’t tested this yet, but I’ve made some new discoveries.

When using the throttle only, the bike runs smooth, no jerky / jumpy movements.

I’ve found that when I increase P1, the jumpy / jerky movement gets less noticable and the bike has no problem hitting the set max speed, which is weird because from what I can find the motor has a 1:5 reduction ratio and 20 maget poles, so the number should be 100.
 
The P1 setting is used for speed limit when the motor is engaged at 27 km/h in your case, or for walk assist, or for throttle function, and for cruise function, and that's why the gear ratio and the number of magnets are important.

In order for the controller to know all this, it utilizes hall sensors internally, which you don't see on the LCD. That's why there is another sensor called a speed sensor, and it is used so that you can see the speed on your LCD.
 
So, I’ve managed to narrow down exactly what’s happening.

With PAS the bike seems to almost be limited to 2 kilometers below what I’ve set the max speed to, making the bike stuttr when hovering around that speed.

However if I apply the throttle the bike has no issues reaching the set max speed, and will smoothly maintain full speed and not stutter.

An example; riding the bike with pedal assist in mode 5, the bike will hover around 24.6 - 25.4 km/h despite the max speed being set to 27 km/h, if while I’m pedalling apply the throttle the bike will shoot up to the set max speed of 27km/h and maintain that speed smoothly.

The same applies if I use the throttle only, it’ll shoot up to 27km/h without an issue and maintain the speed.

This seems to be a pedal assist setting issue.

Do any of you have any idea what could be going on?

Additional info: The PAS is a KT-V12L, the connection is fine and the sensor is fit snuggly.
 
Hi Jpwcamel,

Have you tried turning up the PAS sensor sensitivity via C1? (I.E. 6 or 5)



From a product description page…

”Note: This PAS only work with KT controller. Also,Kunteng controller normally set C1 = 2 as a defaullt setting for the 8 pole PAS, if you want to use 12 poles PAS, please set C1 =6 via the display, otherwise the PAS may not work.”


Regards,
T.C.
 
TommyCat said:
Hi Jpwcamel,

Have you tried turning up the PAS sensor sensitivity via C1? (I.E. 6 or 5)



From a product description page…

”Note: This PAS only work with KT controller. Also,Kunteng controller normally set C1 = 2 as a defaullt setting for the 8 pole PAS, if you want to use 12 poles PAS, please set C1 =6 via the display, otherwise the PAS may not work.”


Regards,
T.C.
Click to expand...
I’ve gone through value 3 through 7 and non of them made a difference unfortunately.
 
So after some more speculation and pondering, I’m pretty sure what I feel, is because the controller is a square wave controller.
 
Square wave controllers typically don't produce jerking unless they're mistuned or faulty.
 
I don't know anything about these controllers so i can't say. It could be some bizarre setting too.
 
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