KT 36/48SVPRMB Ebrake light

Forlix

New Member
Region
Australia
So I'm modifying my electric scooter and it's got a tail light that lights up when I hit the brake on my standard controller, Id like to keep that function using one of the KT 9 fet controllers from PSWPower, any chance this could be achieved rather simply? The light runs off battery voltage if thats any help.
 

AHicks

Well-Known Member
Region
USA
City
Snow Bird - Summer S.E. Michigan, Winter Gulf Coast North Central Fl.
There's a little more to it than that. With a KT controller, using the power intended for lights while using the "up" arrow to turn them on and off, the power supply is TINY and very easily overwhelmed. Guys smoke them all the time trying to run headlights that pull more power than it can deliver. While the controller will still function, the ability to supply power for the lights will be gone, and they are not repairable. What little bit of power is available should be used to power a relay that can handle much more power.

Turning the brake light on should be pretty easy using the brake switch in the brake handle - assuming your scooter uses something like that to kill the motor when brakes are applied?
 

Forlix

New Member
Region
Australia
the scooter uses langfeite controllers normally, it also has standard 2pin n/o cutoff brakes.
so I can put the light in parallel with the cutoff circuit? run the negative side through the cutoff on the KT controller and hook positive to battery?

Sorry, I'm in the same boat thinking this should be easy, but dont really want to fry the controller, how would I go about switching the brake light on with the brake lever when its hooked up to the cutoff on the controller? Sorry if im not making any sense at all. Been at this for a few days now.
 

tomjasz

Well-Known Member
Google is your friend! ;)
A7052CF1-2DED-4DDA-8C8A-D1475AA595B7.jpeg
 

Forlix

New Member
Region
Australia
I cant help but notice that not a single one of the images available for that search even come close to what I'm asking....

Let's clarify, I need to have motor cutoffs still, I need to have the brake light come on at the same time as the brakes being used, any way to do this fairly simply without loosing the cutoffs...

Also, Id not post here if I had not used google first. How do you think I got here in the first place? ;)

KT controllers have 40v- on the low side of ebrake, 47v- on the other. I've run a wire from the display switch on wire (47v+ out only when controller is on) and attempted to run the negative through the ebrake on either side to find that the light is on regardless of brake enable/disable.

(The langfeite controller uses low side SL and GND to activate the brakes, SL is then fed out with VCC and that is used to power the rear light.) Pulling the brake grounds SL and turns the brake light on.
Worth noting that the langfeite's SL is around 5v when not grounded and doesn't set off the light.
Been sitting here trying for ages to no avail. KT controllers SL is 40v- and GND is 48v- so the brake light is always on regardless.
 

AHicks

Well-Known Member
Region
USA
City
Snow Bird - Summer S.E. Michigan, Winter Gulf Coast North Central Fl.
A simple light bulb (like out brake light for instance) needs 2 wires to supply power. A positive and a negative. You can install a switch in either the positive or the negative lines to turn the bulb on and off. That in mind, if you run a positive wire of whatever voltage to the light, then use the brake switch to supply the ground side, you should be in business....

The extra wire leading to your brake light should not affect the switch's ability to kill the motor.
 

Forlix

New Member
Region
Australia
the ground side is grounded from both sides of the switch as mentioned in my previous reply....
that leaves the light on regardless, just dim when the switch is open, brighter when closed.
The cutoff runs 40v- on one side and 48v- on the other, shorting them activates the ebrake.

This method works with the langfeite because it only has 5v- on one side and 48v- on the other, shorting them activates the brake and raises the - voltage high enough to let current flow through the leds. because there is more than 40v- on both sides of the KT controller this same method does not work...
 

AHicks

Well-Known Member
Region
USA
City
Snow Bird - Summer S.E. Michigan, Winter Gulf Coast North Central Fl.
Never tried setting up a brake light with a KT controller, so all I can do is toss ideas. I do know that they have a low side brake and a high side. Are both set up the same way with just a little difference in the voltage across them?

Have you considered an aftermarket/add on brake light switch for this job?
 

Forlix

New Member
Region
Australia
this build is for the missus so I'd rather not have to flip a switch as well as hit the brake, she'd never use it and bar space is all but taken up. Im not too sure about the low side as its not wired on this controller and I'm not sure which pin it is on the board.
 

AHicks

Well-Known Member
Region
USA
City
Snow Bird - Summer S.E. Michigan, Winter Gulf Coast North Central Fl.
For high vs. low brake, look at the wiring diagram for the controller. Usually there are 2 different pigtails coming from controller.

As far as the aftermarket brake light switch, do some poking around. I'm not talking about a switch that would need to be flipped manually each time you want the brake light to come on.

Maybe something like this (found through a google search)-

Regarding the additional switch, many options here....