Accessory KT Controller/Lighting trouble-shooting

[goldconch]

I've got a bit of an electrical trouble-shooting problem, of my own creation, that I need a hand with (if anyone else has done this): frustrated with the cheap/weak headlight packed with ebike, I retrofitted a 12v LED off-road "light bar" to cast a wider beam. It worked quite well for a short time, and then went dead. I was doing some other wiring tidying at the same time, and maybe wasn't paying enough close attention. So now I am testing to see where the problem is. The LEDs are good. The original LED light is good. The std "headlight" wire is very thin. I checked for a controller fuse in the control box, and couldn't find one. I'm wondering if maybe I pinched or crimped one of this frail wires too tight on my tidy job and maybe cracked a wire within the insulation? Other operating theory is that maybe there was a short that burned an internal fuse or the controller itself? Does anyone have any experience with the (new) KT controllers to know if there is such a fuse? I want to splice in rear rack red LED, and maybe discreet handlebar tip orange LEDs for position lights. Appreciate any trouble-shooting pointers...

 

[harryS]

I believe that the light output wires from most KT controllers were intended to drive a relay. Not enough current in the circuit to power a headlight,

 

[AHicks]

I believe that the light output wires from most KT controllers were intended to drive a relay. Not enough current in the circuit to power a headlight,

This is my understanding as well. The circuit that supplies the headlight power in the controller has a very low amperage rating. At this point, if you have no voltage coming from the controller when the lights are turned on, rather than replace the controller, I would just install an external switch.

 

[goldconch]

Thanks. Part of this is me tinkering beyond my technical ability without a schematic. I've deduced that the OEM Dolphin light is 6V, and I was trying to run a 12V light. I wouldn't think that would burn out a controller switch, maybe just be too much resistivity to work properly. The different gauge wire should have been my first clue. I'm goin to put a voltage sensor on the hot wire and see if there is any juice coming from controller. If no juice, I'll think about surgery or just replace the controller. It's really easy, and a $30 error on my side. Still want/need more rural path illumination though, which requires more juice than 6V...I think once I test hot wires, I'll need a DC-DC 6v to 12V step up converter...or this one.

 

[AHicks]

It's not only the amount of voltage available, but also the amount of amperage (or wattage). In this case, my best guess is that you have exceeded the max available of amperage/watts available on the controller's main board, which overheated the components - and you let the smoke out of them (burned them out). If you install a new controller, you're going to cook that one too, unless you do something differently.

 

[harryS]

A Solid state Relay takes little power. These are amazon for $5-$8.,

. You run pins 1 &2 off the KT. But you will need a DC-DC converter to drop the battery power to whatever is needed to power your light. Then use pins 3 & 4 on the relay to switch the power to the converter.

 

[goldconch]

It's not only the amount of voltage available, but also the amount of amperage (or wattage). In this case, my best guess is that you have exceeded the max available of amperage/watts available on the controller's main board, which overheated the components - and you let the smoke out of them (burned them out). If you install a new controller, you're going to cook that one too, unless you do something differently.

I'm definitely not an electrician, and maybe you are. Forgive the impertinence, but I don't quite follow how the controller is sending more amperage than the 6v/12Watt DC limit of its OEM design. Direct current (DC) is a one-way street flowing in opposite direction from controller, terminating at a still 100% perfect 12v LED component (which required 30Watts). Physics would suggest that all it could hope to do is fail to succeed in running the thirstier component, at the insufficient limit of controller design and wiring. If I am missing something, please help me understand. I don't want to die, or light my bike on fire. Off to hardware store for a new multimeter tool.

 

[AHicks]

You have it backwards I think. If my memory is right, you are trying to draw more current than this section of the controller's board is able to supply. When exceeding the components ability to supply power, heat is generated, which will eventually burn out the overloaded component.

I think the controller is only able to supply a couple of watts. That needs to be double checked. If that's right, it can supply only enough power to control a relay. No more. The one Harry shows above for instance.

It is NOT designed to carry a load (for example, your head light) directly.

 

[harryS]

Some of the KT controllers use a little circuit board to run the light relay. The 51 ohm resistor on it gets fried per this discussion if used to power a higher current module.If you have one like this, then you might be able to repair it.

Kunteng KT 36/48SVPRK light output

I have the funktion that when I turn on the lights on the LCD3 display, I get an output to the lights on the bike. The problem is, I don´t have any instructions for the controller. How much current can this output handle?

endless-sphere.com

I had one KT controller that had the little circuit board, but not seen it on the other ones I have,

 

[goldconch]

Thanks HarryS, that's very helpful...I did a little electrical engineering reading myself here and if I understand correctly, the 12v LED I added is the extra "load" in the circuit which exceeds design parameters, not "resistance" as I had assumed. I sent an email to Suzhou Kunteng Electronics Co Ltd, to see if they have a more robust circuit board I could retrofit, and run thicker wire...but I imagine answering my first world tinkering query is the last thing on their viral emergency priority list right now.

 

[goldconch]

It is NOT designed to carry a load (for example, your head light) directly.

In this case, the OEM headlight doesn't have any other external power source beyond the red and blue wires leading from the controller unit. I haven't opened up the controller yet, but I expect to find a burned out resistor if I do, and definitely my bad. Let this be a cautionary tale to those tinkering out there. Wish I'd seen HarryS's link earlier.

 

[AHicks]

It seems like now you have a better understanding of why you can't substitute a more powerful headlight for the "cheap/weak headlight packed with ebike" without doing a little investigating prior. I think many of us had to learn this lesson the hard way early in our "basic electricity 101" that many of us have taught ourselves. Welcome to the club! -Al

 

[goldconch]

There is some info here on what actually happens inside the KT Controller, and I expect to find the same.