Hub kit from CSC. Throttle and PAS problems.

[Norwegian54]

Hello folks.
How are you all?
I am having a serious problem here. One that could potentially be REALLY dangerous if not corrected.
I have a rear hub motor kit from CSC.
Its a 48v 1500W motor, a KT48ZWSRKT-SJT02L controller, PAS and throttle and a KT LCD8H display.
Completed with two 52v, 20ah batteries in parallel.
The menu in the display are the way it was delivered from CSC. No changes made except top speed.

Now for the problem:
Some times, when I start riding, or continues to either pedal or twist the throttle after idling, the motor starts pulling for a second, then power "skips" for about half a second to continue pulling as if nothing happend.
It has been like this since I got it, but a couple of days ago it almost ended with disaster.
I was riding along at about 50km/h when I let go of the throttle to slow down a little.
At about 40km/h I started pedalling slowly and then the "skip" happend again. This time it locked up the rear wheel completely for half a second and that resulted in the wheel axle destroying the rear gear shift totally and ripping completely loose from it's place.
It seems like the rear wheel tried to turn the wrong way for a second.
Good thing this didn't happen in dense traffic.

I have had the skipping problem ever since I got the kit, but never this badly.
And the skipping doesn't happen all the time.. Let's say about 10% of the time I pedal of use the throttle from idling.
I have replaced the controller with a identical new one but it didn't change anything.
Yesterday I had a look inside the rear hub but cant find anything wrong. Apart from the wheel being wobbly after the accident.
I checked the hall sensors, but they seems to be working ok too.
Measured the power in to the motor with the rear wheel in the air, and the power to the motor drops when the skipping happens.
But not the power to the hall sensors.
All cable connections checked and are ok.
I really need som help here guys.
Don't like the idea of ending up as another number on a statistic..
Anyone had something like this happen? And what can I do about it. I'm completely out of ideas here.

 

[Oli.Hall]

Hi,

It must be this setting that you mean I can use when disconnecting the motor hall sensors, right?

Just disconnect the hall sensors, there is no need to change the L3 parameter. The controller will switch to sensorless mode automatically.

I wouldn't completely rule out the batteries and wiring as you are using batteries that are outside the designed voltage range for this model of KT controller. Using a fully charged 14S battery at 58.8V is running very close to the overvoltage cut off of the KT controller. In high current situations, the inductance of the battery wires can cause transient voltage spikes in the supply that can cause the controller to fault and temporarily cut out. This problem is made much worse if you have long battery cables. This problem is seen most often in high current draw situations. i.e. when you first start to pedal, or when you first hit the throttle at a slow speed - exactly the times when you describe having this cut out issue!

But lets try without the hall sensors first!

Thanks,
Oli.

 

[Norwegian54]

Hi,

It must be this setting that you mean I can use when disconnecting the motor hall sensors, right?

Just disconnect the hall sensors, there is no need to change the L3 parameter. The controller will switch to sensorless mode automatically.

I wouldn't completely rule out the batteries and wiring as you are using batteries that are outside the designed voltage range for this model of KT controller. Using a fully charged 14S battery at 58.8V is running very close to the overvoltage cut off of the KT controller. In high current situations, the inductance of the battery wires can cause transient voltage spikes in the supply that can cause the controller to fault and temporarily cut out. This problem is made much worse if you have long battery cables. This problem is seen most often in high current draw situations. i.e. when you first start to pedal, or when you first hit the throttle at a slow speed - exactly the times when you describe having this cut out issue!

But lets try without the hall sensors first!

Thanks,
Oli.

I see what you mean about the batteries. Even so, I was informed by the guy that recomended this kit that it could cope with 52v batteries with no problem at all.
Regarding the battery cables, I have cut them down to about 15-18cm each.
It seems like we have found the culprits.
I disconnected the hall sensors in the motor and took it for a spin with thottle connected only, no PAS. And it actually performs very smoothly. Not much buzz from the motor either. Took a quick trip of about 5km and could not provoke the "skipping" or any noticable power loss on acceleration. Did quite a few slow starts from almost a stand still, but nothing at all.
Then I reconnected the PAS, and rode another km on PAS, with the throttle also connected, but could not produce the "skip" now either. And again, even on PAS, and no hall sensors in the motor, remarkably smooth starts, no half a second long power loss.
Could it be as simple at just leave the hall sensors disconnected and everything is ok?
That's WAY to easy :?
And the controller keeps nice and cool too.
And as you suggested, I did not change anything at all in the menu.
I'll be taking it on a longer trip as soon as I have both batteries recharged to see if the problem comes back but so far, I am a careful optimist.
Thanks a million, Oli.
I'll come back with the result of the longer trip.

 

[Oli.Hall]

Hi,

That's great news. I really hope that solves your problem. I am happy to help!

The hall sensors are most important when you start up from a complete stop as they help the controller to know what position the motor is in so that it can give you a smooth start. Once the motor is running above walking pace then the hall sensors are not needed any more as the controller can sense the motor position from feedback in the phase connections.

If you get jerky or noisy starts you can try and do some more troubleshooting with the halls. You have probably got a loose connection or a bad crimp in the hall plug, an intermittent break inside the cable, or a bad solder joint on the hall sensors inside the motor. Finding this would involve taking your motor apart and testing each of the wires in the cable individually for continuity while you wiggle around the cable and try to detect any breaks in continuity.

As long as you are happy you are getting good starts as it is, then it is fine to leave the halls disconnected permanently.

Do let us know if you have solved the problem!

Thanks,
Oli.

 

[Norwegian54]

Hi,

That's great news. I really hope that solves your problem. I am happy to help!

The hall sensors are most important when you start up from a complete stop as they help the controller to know what position the motor is in so that it can give you a smooth start. Once the motor is running above walking pace then the hall sensors are not needed any more as the controller can sense the motor position from feedback in the phase connections.

If you get jerky or noisy starts you can try and do some more troubleshooting with the halls. You have probably got a loose connection or a bad crimp in the hall plug, an intermittent break inside the cable, or a bad solder joint on the hall sensors inside the motor. Finding this would involve taking your motor apart and testing each of the wires in the cable individually for continuity while you wiggle around the cable and try to detect any breaks in continuity.

As long as you are happy you are getting good starts as it is, then it is fine to leave the halls disconnected permanently.

Do let us know if you have solved the problem!

Thanks,
Oli.

Home again after a 53km trip. And you know what? Not a simple, g... d... hickup. None. Smooth starts on both PAS and throttle, I was creeping along in some city streets, on the lawn along the beach, then when I came home, I even tried a very steep hill to climb from a stand still in the bottom. The motor rumbled a llittle when it took off, but no erratic behavior at all.
I think the problem is actually solved
I actually did check all the wires to the engine a few days ago, for continuity and possible breaks, but couldn't find a thing anywhere. Could it be a hall sensor that are a bit on the fritz? What I didn't do, though, was to move things on the print itself when measuring. So that could be a thing I guess.
But otherwise it doesn't seem to make any kind of difference in the display whether I use hall sensors or not. Wattage used are ok, voltage are ok and so are the speed.
And my lighting system and brake light are taken from somewhere else than the controller.
Before I say 100% fixed I'm going to have to ride a bit more, but it seems just fine after almost 60km in total.
And even the half a second voltage drop has disappeared.
All that's left now is to fix the ketchup effect of the throttle.
All the power is in the mid 50% of the turn.
And ride into the sunset :lol:
Thanks yet again, guys, for helping a desperate newbie out.
You all have a fine evening.
Cheers.
Ian.

 

[Norwegian54]

Another 88 km today. And not a single hickup.
I guess we can see the problem as solved.
Thanks a lot for all help, guys.
Have a nice summer.