I mean it sounds like a old slow speed drill.
Most of my steppers hit a place where they just peak out, and faster doesn't help.
Like 500RPM may be just as good as 1100RPM.
But many of them want a lot of speed before they do much.
Like 500RPM is about nothing, but 1100RPM has good* output.
Either way, I have not got a realistic (for wind) 100ma into a 12V battery with steppers, even a couple types that are maybe 3 pounds and rated 24V and 3A.
Good output being over 40ma at 12V.
G-