Kunteng/BMSBattery/KT controllers - light output microcontroller pin and hardware differences?

Hello all,

I can't find this information answered on the forum but there may be knowledge out there...

I have two questions regarding a controller model KT24/36SVPR-HRD01:

- Is there a microcontroller pin on the controller that switches state when the LCD backlight comes on and off? I'd like to use this to control bike lights.
- What is the difference between the 6 amp and 7 amp version?

To expand:

The PCB has what could be a part number 'KTE-6S3-D3c' with what looks like a possible date of 170521. This makes me suspect the board is a possible slightly revised version of the board described here: https://opensourceebikefirmware.bitbucket.io/development/Motor_controllers--BMSBattery_S_series.html

I'd like to add an external light output to this. My question looks to be similar to this one: https://www.pedelecforum.de/forum/index.php?threads/lichtausgang-am-s06s-controller.26833/ - and it looks as though I would need to construct something like the light control PCB described here: https://opensourceebikefirmware.bitbucket.io/development/Motor_controllers--Other_controllers--BMSBattery_S06P--various_info--02.html

Much as in the pedelecforum.de post, I can't seem to find an obvious PCB pin which changes when the light is switched on or off. I'm posting here in case anyone knows if there is a microcontroller pin that has this output and could be wired to? I didn't really have a probe small enough to probe individual pins.

I can't see a light pin listed on the schematic at https://opensourceebikefirmware.bitbucket.io/development/EmbeddedFiles/32-BMSBattery_S06S-Kuteng_EBike_motor_controller_schematic.pdf - but this might just not have been reverse engineered.

Related to hardware differences of lamp output vs no lamp output: I have two controllers - both with the same part number. However one has rated current of 6A and max current of 12A. The other has rated current of 7A and max current of 15A. They both use the same FETs (110N7F6) and same heatsink so I don't understand how the max current differs. Do the boards have a different shunt value, or do they have a different software version to limit current, or are they in fact the same? I'm just curious.

Thanks for help!

egul said:

Hello all,

I can't find this information answered on the forum but there may be knowledge out there...

- Is there a microcontroller pin on the controller that switches state when the LCD backlight comes on and off? I'd like to use this to control bike lights.
- What is the difference between the 6 amp and 7 amp version?

Click to expand...

You should use the OpenSource firmware and ask there. As you can see for the links to the project you shared, there are a lot of knowledge and written notes by the developers (me included).

LCD backlight is a digital communication only from the LCD to the motor controller. Should be easy for you to add some small code on the motor controller to enable/disable any free pin on STM8 when lights are enabled on LCD.

Thanks for your reply.

I had already thought of using the open source firmware to do this, so glad you agree. I have an STLink programmer already- I just need to take time first to read through the long thread which is full of information!

I have other ideas for additions - having a solar trailer, integrating a heart rate monitor to automatically control motor assist/"interval training" modes, security system - so the open source software is definitely the thing to use as a base. Having this all controlled through the single display would be cool.

Thanks for your work with it - will keep you informed when I get around to installing it.

Following up from your hint about the open source code, I managed to get it to compile OK, so that's a start.

I decided to look through the code to see where I would add a light control, and there was a a commit on 25th May 2019 to all light control already, so it looks already to have been done!

It looks as though this commit uses GPIO pin C4 to control the light, so I will try to track this down on the board and begin building a switching+voltage regulator circuit in preparation for flashing the new firmware when time allows...

Thanks.

I have kt controller with light output. It gives out same voltage than your battery, but only about 100mA current, so i use this output to drive relay, and that relay is actually controlling my bike lights.

There is one topic where is posted picture that little pcb which is installed kt controllers with light output. https://endless-sphere.com/forums/viewtopic.php?t=97279

Also there is lot of info https://endless-sphere.com/forums/viewtopic.php?f=2&t=79763

Thanks for the links.

I think there are at least two versions of the hardware - one with the light output, and one without.

From the link you posted the version with light is here: https://i.imgur.com/BzNZp8z.jpg - model KTE-6S5
but the board I have is more like the one here: https://opensourceebikefirmware.bitbucket.io/development/images/2-6.png - model KTE-6S3

On the 6S5 board the light module appears to go between the resistor and voltage regulator IC, but there is no such connector there on the 6S3 board.

I'd originally hoped that the light module with the transistor was the only difference, and I could build such a circuit and perhaps connect it to the connector marked 'SOF' or the pins next to it. I didn't detect any change on any of the pins when I switched the light on or off. Looking at the photos again however I see there is another connector space visible under the yellow phase wire - I will open up the controller again and see if any signal is available on there, and see if I can see where the C4 pin used in the open source software is routed to on the board.

I'm also beginning to suspect there is no difference between the 6A and 7A controller versions. The LCD3 display power output shows '410w' on max throttle at~41v battery voltage, going down to maybe 350w at ~36v battery voltage. This makes me think it is limiting the current to 10A, which is neither 6A or 7A. I'll have to make up an adaptor to let me measure the current from the battery so I can at least tell if the LCD power output display is being accurate.

OK, so to answer my own question again in case it is useful to others in the future:

The KTE-6S3 controller *does* have a pin to control light, which seems to work with the stock firmware.

This pin is available on the 4pin connector marked "DDB" which is near the green phase wire connection.

Pin1 is ground, and Pin3 contains the light switch signal - 5v when lights are turned on via the LCD, and 0v when off.

So it looks as though this is probably similar to the 6S5 board mentioned earlier, but the connector is in a different place.

So I guess that the daughterboard with the transistor switch probably isn't needed, as long as the lights are controlled from a suitable step-down converter (to convert battery voltage to light voltage) with an control signal.

Thanks for the pointers.

To follow up for anyone still interested: I managed to get lights wired up, and switched on and off from the LCD3, so I'm pleased.

Looking at the light module schematic posted elsewhere in this forum, pin 4 appears to be used as a sense wire input to the microcontroller; without it connected the light would flash periodically. I wired pins3 and 4 together and all works well. (I guess pin 4 is probably used for short circuit protection, so should ideally be wired to the light output via a potential divider, but this works for now).

I used the original light power supply module from the bike. This takes 36v in and outputs 6v, with a white enable wire which was connected to the new controller. It fits quite neatly inside the KT controller case.



I would like to add lights to another bike with the same controller. Does anyone know where I can purchase a similar small module? Most converter modules I have found have been reasonably large. The PCB has "SZ_LIGHT48V/36V-12V/6V 10605102" silkscreened on the back, but my searches for this turn up nothing.

I thought I could perhaps modify a mobile phone car charger to work with 6v. I believe most of these use the MC34063 IC - but this is only rated to 40v input looking at the data sheet. Driving it from ~42v (when the battery is fully charged) I guess would be inadvisable given this is 5% over the maximum rated input voltage.

im looking for the same chip this one just burned out in my ebike