Throttle wiring KT controller

[Chris Maluszynski]

Hey.

I want to switch an old 36v controller for a 48v KT controller. I think I’ve figured most of the wiring out (I hope!). But what I think is the throttle is confusing. The old throttle which id like to keep, seems to be red,yellow, black whereas the new controller has red,black,blue (and will make it female-female). Are these even the throttle wires? How should I connect them? Or do I have to switch out the old throttle (painful wiring).

while I’m at it -are brake sensors necessary for this to work? It does not seem there are any brake sensor connections coming from the brakes to the old controller. (?) can they have been going straight from the brakes to the old display? (See second photo for all wires coming from the handle bar - I believe the blue/black is the light switch going out to the purple/black, the orange,brown,black,green,white must be the display and the last one has to be the throttle?) so no brake sensor wires…?

 

[saneagle]

All the KT controllers I've seen have throttle as either red white and black or red blue and black. They also use red white and black for the speed sensor.

 

[Chris Maluszynski]

That’s right. The KT controller connection is red blue and black. But how do I connect it to the old throttle which is red yellow and black? Or is it not compatible?

 

[Nealh]

Chris connection is Red/Red 5v, Blk/Blk Gnd & Blu/Yel Sig.
Cut the connectors off and solder /shrink the joints directly or if you must have a connector simply cut off one connector and fit new SM3 on the throttle side and sequence the wire order correctly.

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[Chris Maluszynski]

Thanks as always Nealh!
But what about the brake sensors? Why are the wires seemingly not going into the old controller? Where do they go?

 

[saneagle]

Thanks as always Nealh!
But what about the brake sensors? Why are the wires seemingly not going into the old controller? Where do they go?

You need a ground wire to go with the brake signal wire. When the switch joins the ground to the signal, the power is cut.

 

[Chris Maluszynski]

Ok but how do these come into the old controller? On the KT controller there are two brake sensor wires with three cables each. But on the old one I don’t see any even though there clearly are wires going to the brake handles.

Or maybe what I thought was the throttle (red,yellow,black in first picture) is actually the brake sensors (that then split into two at some point)? And the throttle would then be the black and blue wire? But what about the headlight then? It seems I’m missing one connection on the old controller?

 

[saneagle]

Ok but how do these come into the old controller? On the KT controller there are two brake sensor wires with three cables each. But on the old one I don’t see any even though there clearly are wires going to the brake handles.

Or maybe what I thought was the throttle (red,yellow,black in first picture) is actually the brake sensors (that then split into two at some point)? And the throttle would then be the black and blue wire? But what about the headlight then? It seems I’m missing one connection on the old controller?

You had it wired correctly. You just need to add the grounds. Any black wire is a ground anywhere in the electrical system. You need to splice two wires into one somewhere.

 

[Chris Maluszynski]

I think I finally managed to wire everything correctly (?). But when I try the motor on the 48v battery it makes a loud whining sound. Is this to be expected out of a 350w bafang wheel motor running on 48v? (I’m only trying it with the wheel in the air as everything isn’t mounted yet. Also the throttle seems to disengage by itself after a few seconds of holding it. Why could that be?

 

[saneagle]

I think I finally managed to wire everything correctly (?). But when I try the motor on the 48v battery it makes a loud whining sound. Is this to be expected out of a 350w bafang wheel motor running on 48v? (I’m only trying it with the wheel in the air as everything isn’t mounted yet. Also the throttle seems to disengage by itself after a few seconds of holding it. Why could that be?

The motor shouldn't wine.

If the throttle disengages, the perceived speed is probably exceeding the set speed limit for it. Is the speed showing correctly on the LCD? Did you set the throttle speed to full speed independent of PAS? Is the speed sensor set correctly? Does the motor work correctly using the pedal sensor?

 

[Chris Maluszynski]

throttle problem is then probably due to speed sensor that is on the front wheel and wasn’t turning when bike was upside down.
pedal sensor seems to be ok.
But what could the whining be?

 

[saneagle]

throttle problem is then probably due to speed sensor that is on the front wheel and wasn’t turning when bike was upside down.
pedal sensor seems to be ok.
But what could the whining be?

How many watts are showing on the LCD when the wheel spins at max speed in the air.

 

[Chris Maluszynski]

The LCD I have is a KT LCD5. It doesn’t show wattage as far as I can see. The sound the motor makes is not really whining. It’s a pretty bad screeching sound. I have a video of it but I don’t think I can share that here(?)

 

[saneagle]

The LCD I have is a KT LCD5. It doesn’t show wattage as far as I can see. The sound the motor makes is not really whining. It’s a pretty bad screeching sound. I have a video of it but I don’t think I can share that here(?)

Screeching sound is probably incorrect commutation. First check that your motor connector is all the way in to the line, then check whatever you have at the other end of the cable, then check that the cable isn't damaged anywhere, then, if none of those fixes it, you have to go through the 36 hall and phase wire combinations.

It's a shame you didn't get an LCD3, which would have shown whether there was a problem by looking at the watts. I guess you don't have a wattmeter either, because that would show it too.

 

[Chris Maluszynski]

So this could be an issue with bad connection? Since I didn’t have the right connectors I wired it temporarily and some wires (esp hall sensors) may have a bit loose connection. I’ll look at this. But it will take a long time as we’re about to move out of the summer house for the season. Thanks all for input.
ps where to order connectors for such projects?

 

[AGS]

JST connectors are commonly used on e-bikes and they are very fiddly to crimp.

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I prefer to use motorcycle connectors when I have enough room for them. They are much easier to work with.

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