Replacement controller sought / advice sought

RustBuster

Finding my (electric) wheels
Apr 18, 2022
22
0
Hello all

I need to get a replacement controller, to replace the current one which appears to have failed.

It is currently a Sensored Controller DC 24V/36V 250W 6-FET 15A KT Sine Wave. This is for a bike that has both throttle and PAS ( I mention that in case it makes a difference). The bike is 36v 250W.

This is the one that we have currently (which itself was a replacement for the original one that came with the bike, which was built into the bottom of the battery case in a little cup / nacelle):

https://thelayerlaboratory.co.uk/products/ebike-sensored-brushless-motor-controller-dc-24v-36v-250w-6-fet-15a-kt-sine-wave . That one is now unobtainable from that source.

As the bike is currently configured, the julet connector to the motor has 9 holes (only 8 are used by the currrent controller though), the julet controller to the throttle / LED battery indicator has 6 holes.

I have been looking around for a replacement, and am getting somewhat confused.

Can anyone tell me, does "Square wave" mean a sensorless controller , and "sine wave" mean a sensored controller ? Or is it not as simple as that ?

Also, what do the initials KT / JN imply (if anything ) ?

Thanks

Best regards
 

matthewslack

Esteemed Pedelecer
Nov 26, 2021
1,725
1,256
Anyone who looks at 'whats new' will see posts in all areas - until yours is 'old' enough to be pushed out of the top page!

Good news is yours is a KT controller, well regarded, so an equivalent will be available.

Bad news might be form factor i.e. shape and size might not match. Worst case is mount in a different position and handle resulting wiring issues.

Square Vs sine is sophistication of control algorithm. Sine better.

Sensorless uses fewer wires to motor, no hall sensors used. 8 is normal for sensored motor, ignoring any internal speed or temperature sensor: 3 large phase wires and 5 small wires for power and signal to the halls.

More detail on KT models needs someone with specific knowledge I don't have.

Good luck!
 

saneagle

Esteemed Pedelecer
Oct 10, 2010
5,207
2,509
Telford
I think we need to take a step back. It's very rare for a controller to actually fail unless it's getting exceptionally harsh treatment that would destroy any controller. In order to solve your problems, we need to understand what's going on. Please answer all these questions:
1 Why was the original controller replaced?
2. What exactly are the symptoms.
3. Did your present controller ever work?
4. If it did work, what were the circumstances of its failure?
5. Which LCD are you using ?

Sins and square wave are the type of commutation. Squarewave knocks the motor round and side wave pushes it round. You can feel the difference. Sine wave is much better. You need more sophisticated software to get sine wave. The hardware between the two is probably identical, or maybe one has a slightly cheaper micro processor. I never checked.

Your controller is a standard KT available from BMSBattery Topbikekit and others. They're very good.
 

RustBuster

Finding my (electric) wheels
Apr 18, 2022
22
0
Anyone who looks at 'whats new' will see posts in all areas - until yours is 'old' enough to be pushed out of the top page!

Good news is yours is a KT controller, well regarded, so an equivalent will be available.

Bad news might be form factor i.e. shape and size might not match. Worst case is mount in a different position and handle resulting wiring issues.

Square Vs sine is sophistication of control algorithm. Sine better.

Sensorless uses fewer wires to motor, no hall sensors used. 8 is normal for sensored motor, ignoring any internal speed or temperature sensor: 3 large phase wires and 5 small wires for power and signal to the halls.

More detail on KT models needs someone with specific knowledge I don't have.

Good luck!

Hello Matthew

Thank you for your reply and your advice.

"Bad news might be form factor i.e. shape and size might not match. Worst case is mount in a different position and handle resulting wiring issues." - ha ha , yes, the original controller was built into the bottom of the battery (which is on the downtube), so the move the the current controller involved a lot of cutting / soldering etc. But at least it lasted 18 months or so (maybe more , I've lost track).

Best regards

RB
 

RustBuster

Finding my (electric) wheels
Apr 18, 2022
22
0
I think we need to take a step back. It's very rare for a controller to actually fail unless it's getting exceptionally harsh treatment that would destroy any controller. In order to solve your problems, we need to understand what's going on. Please answer all these questions:
1 Why was the original controller replaced?
2. What exactly are the symptoms.
3. Did your present controller ever work?
4. If it did work, what were the circumstances of its failure?
5. Which LCD are you using ?

Sins and square wave are the type of commutation. Squarewave knocks the motor round and side wave pushes it round. You can feel the difference. Sine wave is much better. You need more sophisticated software to get sine wave. The hardware between the two is probably identical, or maybe one has a slightly cheaper micro processor. I never checked.

Your controller is a standard KT available from BMSBattery Topbikekit and others. They're very good.
Hello Saneagle

Thank you for your reply and your advice.

The original controller was replaced as the bicycle was dead, i.e. no power was getting to the motor. At that time i purchased a special ebike test unit, and using that and the multimeter showed that the controller needed replacing.

The symptoms are that when the on-off switch on the handlebars is turned on, the LED battery status display does not light up, and turning the throttle / pedalling produces no motive power at the back wheel.

The multimeter shows that no 5v current is reaching the throttle or the PAS. The battery voltage is reaching the controller. The output from the controller to the throttle and PAS , on their 5v supply, is about 0.003 v.

The eBike tester shows that the motor is working ok. The battery has a good charge. The eBike tester's "Controller 5v " light does not light up when performing the test associated with that light.

Yes, the current controller did work, i replaced the original one in the autumn of 2022.

The bike doesn't have an LCD, if i am understanding the use of that term correctly, it has LED - on the throttle cluster, inboard of the twist grip itself (i.e. to the left), the plastic molding that wraps around the handlebar, has an on-off switch, and a little display which shows the state of the battery, in three colours arranged vertically - green (at the top), orange , and then red at the bottom. The battery voltage is reaching the on-off switch (42v), but the LEDs dont light up when the switch is turned on. The switch itself is ok going by the multimeter.

"If it did work, what were the circumstances of its failure?" - just in case it helps to set the context, we gave this bike to my sister-in-law four or five years ago (i cant remember exactly when) - I bought it new in 2017, when my right knee wasn't up to riding a manual bike. I used it for a few months, until (ironically) I broke my left knee cap, at which point i couldn't ride anything for some months, then i found that i could manage a manual bike again, so we gave the bike to my sister-in-law. She lives about 25 miles away from us, in the middle of nowhere and cannot drive, so all she has for transport is a bicycle / the once-a-day bus / lifts from friends with cars). She was thrilled with the bike, and used it until the late summer of 2022, at which point it stopped working (i.e. no LEDs, no response to twisting the throttle or pedalling). So i replaced the controller then. Just recently, she told us that the bike had stopped working again. ( I think it went through a brief period of sort of half-working, i.e. she would be rolling along being pushed by the motor, and then suddenly the "push" would disappear. But she's not technical and not very good at providing the detail. All I can say for sure is that the symptoms now, are just as they were in the Autumn of 2022). So i have brought the bike over to us to examine it.

Thanks

Best regards

RB
 

thelarkbox

Esteemed Pedelecer
Aug 23, 2023
857
259
oxon
One of the features of the KT controller range is the ability to use a number of different interface devices, and when a lcd dispaly is used you can also use it to configure and check the controller status, as well as get error codes in cases of failure..

It might be prudent to get a kt lcd display in advance of any replacement controller to confirm and validate the failuer mode or other issue with your current controller.. (it will be needed to configure any replacement controller,,)

YOu can also iirc transfer the config you set for your controller to a dumb led display too so if you prefer you can revert to your original display ..

Generally ebike control systems employ a display device to set and hold settings such as wheel size max amp output speed limits pas config etc and when the system starts up the controller and display 'handshake' and the controller gets its operating parameters and starts up...
 
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saneagle

Esteemed Pedelecer
Oct 10, 2010
5,207
2,509
Telford
I do don't think you answered question no.3, which was the most important one.

Normally, the controller doesn't work without an LCD. If you know what you're doing, there is a sort of workaround, but you don't give the impression that you know about these things.

The LCD is used to switch the controller on. One of the things it does is bridge the red wire (battery voltage) to the blue ignition wire that powers the controller. It might be possible to do that with whatever switch arrangement you have. When the controller is switched on by powering the blue wire, you'd have the 5v on the sensor red wires. You can test by disconnecting everything except the battery and bridging those red and blue wires on the LCD connector. In that condition and with the motor, pedal sensor and throttle connected with their wires in the correct sequence, the motor should work with the throttle full range and pedal assist bottom level.

Your throttle thing has about 6 wires. You have to figure out which three are for the throttle (red, black and signal) and connect just them to the throttle connector. If you connected your throttle to the LCD connector, you might have damaged something depending on which wire connected to which.

What's connected to the LCD connector now and who did it?
 
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RustBuster

Finding my (electric) wheels
Apr 18, 2022
22
0
"I do don't think you answered question no.3, which was the most important one."

eh ? come again ?

"3. Did your present controller ever work?" - " Yes, the current controller did work, i replaced the original one in the autumn of 2022. "


"The LCD is used to switch the controller on" Surely it is the switch that would be used to switch the controller on ?

LCD
1 of 2noun
ˌel-(ˌ)sē-ˈdē

Synonyms of LCD
: an electronic display (as of the time in a digital watch) that consists of segments of a liquid crystal whose reflectivity varies according to the voltage applied to them


"but you don't give the impression that you know about these things." - how nice of you to say so. I don't pretend to be an expert on eBikes /electronics, on the other hand, i have successfully been doing practical things all my life - car , motorcycle, boat etc mechanics, i build and fly radio controlled gliders, i can do plumbing, domestic electrical installations, carpentry, etc, I have been a computer programmer for many years, etc etc.

What's connected to the LCD connector now and who did it? When you say "LCD" connector , i assume that you may be referring to some kind of plug arragment on the end of the output from the controller. The various wires from the controller, that go up to the throttle / switch / LED unit on the handlebar, all connect directly to the julet-style cable that runs up from the bottom of the battery holder on the down tube, that jule-style cable was the original configuration of the bike, before I changed the controller last time. If memory serves, in that julet-style cable, there are blue, green red, black, white , yellow wires going up to the throttle / switch / LEDs. I have all this written down somewhere, but it's not hand just now. If memory serves, the blue and green go to / from the switch, the red and black and white go to the to the throttle, the black also goes to the LEDs, as does the yellow. So at the bottom end of that julet cable, i.e. at the bottom of the down tube, there are joints between the various wires coming out of it, to the wires coming from the controller, that deal with the throttle / switch / LEDs. I made all of those connections, and it has all be working fine up until quite recently. Before we gave the bike back to my sister-in-law in the Autumn of 2022, i took the bike for a trip of several miles, as did my wife, and it performed without fault, and it has performed without fault for the sister-in-law until quite recently.
 

AGS

Esteemed Pedelecer
Feb 12, 2023
563
174
A photograph of your display may help.

KT does manufacture various LED displays, but none of them match your description of “three colours arranged vertically - green (at the top), orange , and then red at the bottom”.

If it indeed is a KT LED display that came with the bike then it must have been preconfigured to work with the original KT controller.

But if you are going to fit a new KT controller then it’s worthwhile also getting an up to date KT LCD display.

And if you buy the display and controller from the same supplier then the display will come with the correct connector so it’s plug and play.

It‘s unusual for KT controllers to fail so regularly, they are usually very reliable. Have they suffered from water ingress?

I think this is what you are looking for:

 
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RustBuster

Finding my (electric) wheels
Apr 18, 2022
22
0
A photograph of your display may help.

KT does manufacture various LED displays, but none of them match your description of “three colours arranged vertically - green (at the top), orange , and then red at the bottom”.

If it indeed is a KT LED display that came with the bike then it must have been preconfigured to work with the original KT controller.

But if you are going to fit a new KT controller then it’s worthwhile also getting an up to date KT LCD display.

And if you buy the display and controller from the same supplier then the display will come with the correct connector so it’s plug and play.

It‘s unusual for KT controllers to fail so regularly, they are usually very reliable. Have they suffered from water ingress?

I think this is what you are looking for:

Hello AGS, thank you for your post and the link to the potential source of a controller.

In case it helps, I never said that the original controller was KT, I have no knowledge of who manufactured it.

I take your point about the water ingress. I have not opened the case to look, so far. (Assuming that one can open the case).

I agree that some pictures would help, i was going to do that, I will attach some pics of the original controller, and of the LEDs/ throttle .

Thanks

Best regards

RB
 

Attachments

AGS

Esteemed Pedelecer
Feb 12, 2023
563
174
That display won’t run a KT controller properly. The bike may have worked, but it would have run very inefficiently because you weren’t able to configure the controller.

If you buy a display that is matched to the controller and set it up properly you will see a remarkable increase in performance.

I’m surprised that you managed to get the KT controller to run at all using that display. Or have you fitted a bypass plug to the display connector on your controller, like the one shown below?

IMG_0195.jpeg
 
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