I have the same motor and fan running on a solar panel directly on another
coastline. It does run at lower voltages as the 20w solar panel only
generates under 10v when low sun etc.
I have it directly connected to the solar panel.
So I know that this motor can achieve what we need.
Ive just tested it too now on a 7vdc charger here and yes the fan runs slow and low revs. It seems to run at low volts fine
I have identical motor to which this shield with drive on vmh5019 at home to test.
Now, the last item I need is the right code to tell the motor to run at 50% or 200. then Im done and all works well.