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Rewire ECU and speed control on 2007 Giant Suede E


I've bought an E bike with both a front 250w hub motor and a pedal assist motor mounted near the bicycle's pedal arms. The bike came with no battery.

I'm going to mount the front wheel and hub motor on a lighter mountain bicycle frame. I want to try to run it off a 24v 10a Lithium Ion battery.

I would like to use the bike's original ECU, power controler and twist throttle in the conversion. In accomplishing this, I am hoping to bypass the pedal assist and control panel. This would mean disconnecting the pedal assist motor and control panel from the battery terminals and ECU, pulling out the ECU and power controler and wiring the ECU and power controler to a new battery and existing twist throttle. 

BTW, if anyone is looking for a bottom-bracket pedal assist set up with no ECU and no battery, please contact me. I'm in Seattle.

This seemed complicated. I am hoping one of you all can help me understand, first, the difference between a power controler and ECU? Sorry for a pretty basic question, I'm a newbie.

Also, can anyone help me understand where I could get a wiring guide for the original Giant bicycle?

Would anyone recommend buying a new ECU and power controler for the twist throttle only? 

Thanks, Cory

Unless the bike requires the pedals to be rotating in order to use the twist throttle then you might be able to unplug the pedal assist sensor and the hand throttle will operate normally without it.

On most electric bikes ECU and Speed Controller are different names the same part. It sounds like your bike has two separate electronic boxes though which is unusual. If you are not able to get it running with the pedal assist sensor disconnected then you may need to install a new speed controller.

Unfortunately, we do not have a wiring diagram for the Giant Suede E electric bicycle.

It is our understanding that the Giant Suede E electric bicycle is a 36 Volt bike, in which case its original speed controller will not run the motor on a 24 Volt battery pack due to its low-Voltage cutoff feature. Also if the motor is run on 24 Volts it will be very slow and powerless. So we recommend using a 36 Volt battery pack with that bike.

If you need a new speed controller then we carry a 36 Volt brushless motor speed controller for 250-350 Watt motor which is our item # SPD-36350BLDC.

Please let us know if you have any questions.

Thank you so much for this response!! The Suede seems to only have one ECU. I assumed an ECU was separate from a speed controller because I found references to each in these pages. I'll hope to be able to pull a part number off the ECU and throttle and figure out the wiring by going through the manufacturer or another bicycle with similar components. Not sure yet if the throttle will only work if the pedal torque sensor is picking up my pedaling. Is there any way to test using a multimeter? For the twist throttle my understanding is there are three wires: input from the battery, a 5v out and a 1-4v out. Is the ECU in between the throttle and the motor or between the throttle and the battery? For the motor, I understand there are a set of wires called Hall wires that are designed to regulate voltage as the motor gets going. Would these wires be connected to the ECU? Could I safely bypass them without risking too much damage to the motor?
The only way we know to test if the motor will operate with the pedal assist sensor unplugged is by testing the operation of the motor with it unplugged.

I am not sure exactly how the Giant Suede E is wired, however, on almost all electric bicycles the throttle plugs directly into the speed controller (ECU). Throttles have a +5V input wire, ground wire, and 1-4V signal output wire.

The speed controller (ECU) is wired between the battery pack and controller, and the throttle plugs into the speed controller.

If the controller is a sensor/sensorless type then the motor's hall wires can be left disconnected. However, the motor will operate much better with the hall wires connected to the speed controller so they should be connected for best performance. If the controller is a sensor only type then the motor's sensor wires need to be connected to the controller otherwise damage to the motor or speed controller could occur.

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