Where is the shunt supposed to be? By the way, the Tongsheng TSDZ2 does not benefit from a 3rd party controller according to my trials. The OEM motor/controller combo is likely the best setup there is due to the brilliantly implemented torque sensor control. But this motor is NO speed demon! It's a genuine commuter utility unit that works perfectly out of the box. For me it functions best without display, just with a power switch on the battery and the rest is done with pedal pressure (torque sensing). The 48V 500W unit is the pick but any of other 48V units can simply be flashed to become the 500W model.