E-Bike Tandem Electrical Problem - Please Help!


New member
Local time
11:54 AM
Jun 15, 2024
My first E-bike (Tandem) build has me banging my head against the wall, it looks great but doesn’t go. Please help me someone. I built it using parts from a Chinese electric scooter and a traditional 26 inch bike. I am a competent mechanic and auto electrician when it comes to classic cars, but speed controllers and BLDC motors are all new to me. While I think I understand it, I am definitely missing something.

I’d really appreciate some guidance from you E bike & Scooter enthusiasts out there.

I’ll try to explain briefly what what I have created. I have a 48v 1400w BLDC hub motor with a 48V 1500w speed controller, powered from a 48v 100Ah Lithium-ion battery and the standard Chinese scooter twist throttle.

From the battery, I have a Pos & Neg going to the Pos & Neg on the Controller. I have bridged the key switch wires from the controller (Red & Orange). I have connected the Red/Black/Green to the Red/Black/Green of the throttle. I have connected the Yellow/Blue/Green phase wires from the controller to the corresponding phase wires on the motor. Finally the Red/Black/Yellow/Blue/Green hall wires from the controller to the corresponding hall wires on the motor. But I have no life from my machine.

First I bought a new controller thinking this was the problem, but it’s still the same. I then recently I bought an E-Bike testing device. With the new device I have perfect test results from the throttle, motor phase and hall sensors, all shows up good. The only negative result was the controller, when tested, doesn’t light up the 5V output LED. I then tested the 5v output with a multi meter and I am only getting an output of 2.76V. Which in return from the throttle when ‘closed’ reads .82v and ‘fully open’ reads 1.98v. So my question is, should the motor turn slowly with this low voltage or is it normal that it doesn’t turn at all ?

Thanks in advance to everyone reading this. Steve.
Hi Motley,
The guide looks very complete. I just need to study it, understand it and go back to the Tandem to see if it gives me any clues.
Thanks very much, Steve.