Adding a throttle to a non-throttle bike

[Kruse]

Hello....Sorry if this is a ridiculous question.
I have a Chinese ebike that uses a speed sensor.
I looked at the controller and it doesn't have cables for a throttle.
Is it possible to splice a throttle into the speed sensor cables somehow or would I need to replace the controller with a more advanced one that has throttle cables?
Thanks!

 

[harryS]

If it really is a speed sensor, that only counts the rpm of the back wheel. You may be looking at the magnet disk around the pedals, and that counts the speed of the pedals. Neither will allow a throttle input.

Usually, the least troublesome way to do this is to buy a new controller, plus the display that goes with it, and the throttle all together. It's still a lot of wiring work.

 

[Kruse]

If it really is a speed sensor, that only counts the rpm of the back wheel. You may be looking at the magnet disk around the pedals, and that counts the speed of the pedals. Neither will allow a throttle input.

Usually, the least troublesome way to do this is to buy a new controller, plus the display that goes with it, and the throttle all together. It's still a lot of wiring work.

Thanks. When shopping for a controller, would this be the relevant information to supply?:

Hello...I am looking to replace controller with one that includes a throttle connection.
Specs of my current controller/specs I need are:
Dimensions of the controller (not including cables) are 80mmx53mmx30mm.
Rated voltage:36V
Under-voltageprotectionvalue: 31+/-1V
Limit current:13A
Nominal current:7A
Rated power:250W
Wheel diameter700”
Drawing number:LD-SL-009
Protection date:20190103-0002

Cables I need are:
BIG WIRES
RED/BLACK: Battery
GREEN/YELLOW/BLUE: Motor
Small Wires
White/Black/Blue/Green/Yellow/Red – Hub Hall
Yellow/Green/Black/Blue/Red – Display
Blue/Black/Red – PAD Sensor
Grey/Black – BRAKE
Grey/Black – BRAKE
+I NEED A 3 WIRE THROTTLE CONNECTION

Please let me know if you can help or if you need more information.
Thanks,
K

 

[harryS]

If you replace the controller, you will need to find one that works with your display. What kind of display is it? Is there a brand on the bike?

 

[rich c]

What supplier are you going to supply all that information to? I think all they will need is motor model number and battery specs. Then they will sell you a controller, display, and throttle. You are dealing with basically a computer here, you just can’t splice into wires

 

[Kruse]

If you replace the controller, you will need to find one that works with your display. What kind of display is it? Is there a brand on the bike?

There is no brand on the bike or display but I was told the display is "Key Display Intelligent LCD display of E-bike; model: KD21C".

 

[Kruse]

What supplier are you going to supply all that information to? I think all they will need is motor model number and battery specs. Then they will sell you a controller, display, and throttle. You are dealing with basically a computer here, you just can’t splice into wires

I was looking on aliexpress.
I thought maybe splicing into the PAS sensor could trick the computer into thinking I was peddling and get the motor going. Looking for a controller/display/throttle setup, but all the displays look very dated and cheap. Also, I need to make sure it will fit in the small compartment it is designed for.

 

[harryS]

Tapping into the PAS sensor had been done by people that can program Arduino controllers. The PAS signal is a pulse train. Higher pulse rate --> more motor speed

You'll be limited if the long dimension on your controller is 80 mm. The shortest ones that support LCD's come in around 86-90 mm.

I bought something like this one a few years ago. It was only 13A and later changed to a 20A unit,

Amazon.com: 24V-36V/36V-48V Motor Speed Brush Controller, 250W/350W Electric Motor Controller with Waterproof LCD Display Panel for E-Bike Electric Bike Bicycle Scooter Brushless Controller Kit (36V/48V) : Sports & Outdoors

Buy 24V-36V/36V-48V Motor Speed Brush Controller, 250W/350W Electric Motor Controller with Waterproof LCD Display Panel for E-Bike Electric Bike Bicycle Scooter Brushless Controller Kit (36V/48V): Sports & Outdoors - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

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[Kruse]

Thanks for the help. I ended up ordering this package:

32.92US $ 25% OFF|Kunray Ebike Controller 48v Lcd E Bike Display Speed Controller For Brushless Motors 24v 36v 350w 500w Bicycle Conversion Kits - Electric Bicycle Accessories - AliExpress

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

Fingers crossed it arrives fast and works for me.

 

[harryS]

You might have an issue with this unit not showing the right speed or any speed with a geared motor. In which case you can install a $10 bike computer, which is more accurate anyway.

Controllers can calculate the speed from the motor rpm if they know the wheel size and the internal gearing. Since I didn't see any P-setting where you enter the gearing (although you can enter the wheel size), this controller must have a speed sensor input, but they didn't discuss it or show it in the wiring diagram. You'll know when you get it. There will be six wires instead of five om the Hall connector.

Does your e-bike have a display that shows speed? If so, then you already have a speed sensor in your motor or on one of the wheels.

Well, that's something to resolve when you get the unit,

 

[Kruse]

Shoot...I believe the controller's hall season input only has 5 wires, but they told me I could just ignore the white wire from the 6 coming from the hall sensor in the wheel. This means it'll work but I just won't have speed on the display? Like you say, it's not very accurate but nice to see anyways. And yes, my current display shows speed.

 

[harryS]

Here's how I think they work. The controller knows the engine rpm, since it's spinning the motor. With a direct drive motor, the engine speed is the wheel speed, so it takes the wheel size you entered and figures the speed, If it's a geared motor, it needs to know the gear ratio too and again they compute the speed. One thing about geared motors, they lose the speed when when coasting as the motor isn't spinning. To work around that, a separate speed input from the wheel is needed.

The KT controllers ask for wheel size and gear ratio info, They also have a separate speed sensor input which the user can enable. Covers all the bases. My Brainstorm controller calculates speed off the wheel sensor only,

Your controller doesn't ask for gear ratio, so it would need a wheel sensor sensor for geared motors. I can't believe it's only for direct drive, since few are made at 250W. Maybe it will surprise you when it arrives. SOunds like your Hall connector has 6 wires, so you don't have to buy a wheel sensor.

 

[AHicks]

There's no lead to accommodate an external speed sensor on this controller. Maybe no big deal if you are working with a direct drive hub. With a gear driven rear hub, IF you get a speed at all, it's going to go to 0 when coasting.

There's also the potential for wiring issues with the phase and hall sensor wiring. There's no universal color code, so even if the colors are the same and you wire them up color to color, there is NO assurance the motor will run correctly. This has caused a LOT of headaches, and it's easy to smoke the motor's hall sensors when done incorrectly.

The same can be said with the PAS sensor. You'll need to confirm the positive, negative and sensor colors/functions coming from the PAS sensor, and match the functions coming from the controller.

This can all be overcome with some patience and a lot of research on the subject. Don't assume this is going to be a plug and play by simple wire color matching.....