Adding head, brake, and tail lights to a KT controller

I have a headlight that works off battery voltage using a switch, and a separate, rechargeable brake / tail light / alarm that uses an accelerometer to activate the brake light. But I'd prefer brake lever operated battery voltage brake and tail lights, and I'd like those tail lights and the headlight to get turned on by the controller because I'm a glutton for punishment. Truth be told, this is my wife's bike and that rechargeable brake / tail light isn't very bright and has to be set a certain way for the brake light capability to work. She has a knack for mashing on her brakes for mysterious reasons so I want her to have a very bright brake light that works as soon as the bike is turned on so that I don't run her over.

I've read all I can find on hooking lights up but I'm a bit mystified. I got one of these 2-channel 5vdc relays https://www.ebay.com/itm/221962380923 and don't think the brake light will be an issue, I'll tie into the brake lever circuit. What I'm struggling with is the head / tail light signal.
This new controller has a light connection. I've read of people regularly cooking this circuit and they're told this circuit is only meant to send a signal to a relay to power on the lights, not to power lights directly. When the light connection on this particular controller is turned on by holding the up button on the handlebar, that light connector from the controller has 52v across the 2 pins. I was expecting 5v or even 12, but not 52v.
My question is: Is that 52v a sign that this controller is meant to power lights directly without a relay? This controller took over a month to get here so I really don't want to use it as kindling.
As always, any advice is greatly appreciated.

The KT light circuit is 52v, but you can only pull around 100mA through that before you will smoke it... Most lights, even leds will easily pull more than that... Use a solid state relay. I wired my lights separately through a discrete fuse and switch rather than using the controller to switch because of this.

Somebody posted this link not too long ago, and I thought enough of it to save it. It appears to be a nice clean way to add a set of lights to a bike that doesn't have any, or one does have lights that has issues. Simple, and pretty reasonable. That's all I know.

https://www.conhismotor.com/products/unique-design-led-headlight-tail-rear-lights-brake-light-turning-light-for-bafang-mid-drive-motor-kits

It would appear that it avoids that super lightweight KT power supply for their display switched light? Maybe even room for a tiny fuse in the switch housing?

ccihon said:

The KT light circuit is 52v, but you can only pull around 100mA through that before you will smoke it... Most lights, even leds will easily pull more than that... Use a solid state relay. I wired my lights separately through a discrete fuse and switch rather than using the controller to switch because of this.

Click to expand...

That's what I was wondering - whether 52v on the light circuit was a trick to lead one to think it could power a light directly. It would be so nice if there was some consistency to controllers from the same manufacturer. I thought I'd test it last night with the square wave controller I'm replacing, but it doesn't have a light connection. Both are KT 30A controllers.
I have a headlight working now, through a fuse and switch, but it's a good time to tinker while it's pulled apart.
I've looked everywhere for a solid state relay, the only one I can find is $33 which seems unrealistic, and is out of stock with a long lead time. So I'm trying to make it with non-solid state relays (analog?) and step down buck converters but I'm very space-limited so it's a struggle.
Edit to add: Looking again for solid state relays I remembered the problem with them - For the brake light I need one that is normally closed, and that seems impossible to find.

AHicks said:

Somebody posted this link not too long ago, and I thought enough of it to save it. It appears to be a nice clean way to add a set of lights to a bike that doesn't have any, or one does have lights that has issues. Simple, and pretty reasonable. That's all I know.

https://www.conhismotor.com/products/unique-design-led-headlight-tail-rear-lights-brake-light-turning-light-for-bafang-mid-drive-motor-kits

It would appear that it avoids that super lightweight KT power supply for their display switched light? Maybe even room for a tiny fuse in the switch housing?

Click to expand...

I have all those as discrete parts, but I don't have a Bafang mid drive or Julet connectors, so I'm trying to recreate it, and I would like to use the controller, no more handlebar room. I'd get wider handlebars but can't find suitable ones, they're all so narrow and it's a quill stem which limits choices. Plus it's a woman's bike so color coordination is unusually important, further limiting choices.

The reason I like the kit is because it taps the required power at the base of the 1-4 cable connector. Though they say Bafang mid drive, unless I'm mistaken that's the same pretty common format used on the waterproof KT and quite a few other controllers.

I get the convenience of the display switched lights though. Would be neat if you could combine that feature with a kit like the one in the link. Lights turned on/off with the "up" button are not that unusual.

AHicks said:

The reason I like the kit is because it taps the required power at the base of the 1-4 cable connector. Though they say Bafang mid drive, unless I'm mistaken that's the same pretty common format used on the waterproof KT and quite a few other controllers.

I get the convenience of the display switched lights though. Would be neat if you could combine that feature with a kit like the one in the link. Lights turned on/off with the "up" button are not that unusual.

Click to expand...

Yeah I don't have the waterproof version though so I'd have to cut it apart and figure out the wiring, or add Julet connectors all over and hope I match it up correctly.
The aspect of this that really rubs me the wrong way is that they provide a light connection from the controller that is essentially useless unless you have what amounts to an electric glow stick for a light. It doesn't provide enough current to run a decent light, and it provides too high a voltage for almost every relay out there so you have to step down the voltage to trigger a relay. If the controller sent out 5v signals for head / tail and brake, and provided 5v supply to power a relay it would be a breeze, or better yet provide connections and enough current to power them directly. It would probably cost KT 10 cents per controller to add that capability.
You're right though, it wouldn't be too hard to design a 'black box' small board that would accept the light, brake and battery voltage as inputs and have head, brake and tail light connections as outputs. Putting it together with separate components is way more trouble than it should be.

I had fried the resistor in the KT controller light circuit that I had and learned this the hard way. Fortunately, this failure only disabled the light circuit and had no effect on the other controller functions. Seems like the only real gain to setting this all up via relay is that you can use the KT display to switch lights on or off, and the light icon will display on the lcd. I don't think the KT controllers I have seen have any built in provision for "brake lights" so that would be a relay add-on also.

The front and rear lights I am using on my trike are rather bright, and work with anything from 12-60v or something. I used a motorcycle-style handlebar mounted rocker switch. One trick with these auto- or motorcycle switches is that while the simple ones seem happy at switching voltages well over 12vdc, the ones that include an indicator led are an issue since that will generally cook also if you try and use the indicator at much over 12.

I have a stepdown buck convertor for 12v but have no current use for that on the trike. Opinions may vary, but I think brake lights - that is, a rear light that is brighter to indicate the application of the brakes, are of limited use for cycling as cars would seem to have no real regard for bikes or trikes, regardless of whether they are slowing or not. I wired both leds in my tail light to be on all the time to maximize basic visibility.