"The coil winder is used to wind up coil items, to store mechanical energy for later use. It can also use previously-wound coils as an energy source, thus allowing you to transport power in item form."
Power is provided or received from the back.
There is no minimum speed to wind up coils, but the torque determines the maximum energy that can be stored in the item.
For example a 512 Nm engine can wind up a Wind spring up to 512 kj. A High-Strength Spring, however, can only be wound up to 1/16 of that value, 32 kj, using the same 512 Nm engine.