thumb throttle for cheap Alibaba E-Bike

Hi,

im new. Have been following for some time.

Just got this bike form alibaba for cheap. So far everything looks good/okay. Pretty heavy though. Spokes are way to thick (min 2,3mm).
Can provide more pics and info later on. The display was sealed. Battery looks alright for cheap-chinese-pack, some copper strips were added .

For now i would like to add a common bafang-style thumb-throttle, but i dont know where exactly.

Do i need to weld it on the controller or the display? Can you tell me the exact spot? That would be great.
I think these thumb throttles have 3 wires.

Thank you.

Very bold of you to take it all apart! How cheap was cheap?

Thumb throttles do have three wires, Ground, Power. Signal. I take it you do not have one now, and the bike woks on pedal assist.

If there is no existing throttle, you will probably have to wire the new throttle to your controller board. The term is "solder", no weld. It will be connected to three of the holes on the controller card. Two of them, power and ground are easy to find. The third will take some detective work.

It might be safer to take a good picture of the back of the card, plus a picture of the throttle. Send it to the vendor with a simple query, like "where to add throttle?". If you got a buddy that can write that in chinese, you might even get an answer.

Most likely the signal wire from the throttle would go to the SP pad on the controller board, and the 5V (probably red) would go to any 5V pad, and the ground would go to any GND pad.

However, if the controller came with no cable for a throttle to plug into, only PAS, it is possible (even likely) that it is not programmed to be able to read the throttle, and will only respond to the PAS. This is probably not user-changeable. (sometimes there are LCD settings for it but you'd have to have the manual that gives you the menus to do that).

Hall-effect throttles are cheap enough; you don't need one with any accessories (voltmeter, power LEDs, switch, etc) on it, so you can try the experiment easily enough.

docw009 said:

How cheap was cheap?

Click to expand...

600€
https://www.alibaba.com/product-det...pm=a2700.7724838.2017121.5.64826fc5ns5f3U&s=p

amberwolf said:

Most likely the signal wire from the throttle would go to the SP pad on the controller board, and the 5V (probably red) would go to any 5V pad, and the ground would go to any GND pad.

Hall-effect throttles are cheap enough; (...) you can try the experiment easily enough.

Click to expand...

Thank you!
Thats what i thought, since the label on the controller says "Throttle adjustment voltage: 1.2V-4.4V"

So these handlebar throttles pickup 5V from the controller and give 1.2V-4.4V to the "SP" solder-spot?

There is also a "SP5V" spot in the controller... i will try that one too. Will post results once i'm done.
I thought others could use this information since these cheap controllers seem to be widely spread.

Do you think i could also add front- and rearlights?
The backlight of the display can be activted via the handlebar buttons, and then a little headlight symbol shows up on the display.
What could be the right solder-spot? How could i test with a multimeter?

CR HC SL SP AD1 BKL BKL SS TB RX TX TA HB SP5V 5VO SW VBO-

BKL BraKeLever
SS SpeedSensor
...

Thanks again!

On the controllers that I have, there is always 5V power for the pedal assist sensor and 4.5V power for the throttles. Based on amberwolf's hint that SP is the throttle signal, then your SP5V must be the throttle power. GND0 looks like ground. That is a nice looking controller board. Never seen one with connectors. It has 9 FET's even though it's only 15 amps.

If you're going to do this kind of work on your ebike, you should own a voltmeter. If it were me, I would confirm that SP5V is 4.5V and 5V0 is 5V.

I believe they use the lower voltage to power the throttle because it facilitates the design of circuitry that can detect a miswired throttle. For sure, when I have plugged in a miswired throttle connector, the error code for it comes up right away on a KT controller.

Adding the throttle worked perfectly! Thank you for helping.
It is a common 3-wire thumb throttle as shown before.
I soldered the green wire to "SP", the red wire to "SP5V", and the black wire to "GND0".
Throttle even works in PAS level 0. Just as i hoped.

Now i'm still trying to connect lights to the controller.
My goal is to turn them on via the handlebar button (then the display is backlighted and a little headlight symbol shows up)
Any ideas?
Thanky again.

Use a voltmeter with black probe to battery negative, and move the red probe from pad to pad on the unused solder pads (the ones with labels) of the controller board.

On each pad, test it once with the headlight on, and once with it off. If the pad changes state between them, then that is the control / output pad, and you'll know what voltage is available.

It's also possible that the output is inside the LCD instead, rather than the controller, so you could do the same test there if you don't find one in the controller.

But you won't know what current (and therefore what wattage light can be used), until you test it to the point of failure, at which point you'd either have to repair the controller (or LCD, or both) or replace them.

However, there may be no actual output pad, and the light may only be able to control the backlight itself, despite the little headlight symbol (like the LS controllers my Fusin came with).

Your best solution for lighting without taking the chance of smoking the controller would be to purchase a dc/dc converter and go directly (with a fuse) from the bike battery and put a switch on the handlebars.Search lights and converters.

bikedoctor123 said:

docw009 said:

How cheap was cheap?

Click to expand...

600€
https://www.alibaba.com/product-det...pm=a2700.7724838.2017121.5.64826fc5ns5f3U&s=p

Click to expand...

I'm curious, how did you purchased on Alibaba? I have always read that you need to be on China or is very difficult otherwise.