Well, The best stepper I have for 12V is a 8.6V 25ohm, 99 cents.
It gets like 150 or 200ma at 6V, about 60ma at 12V if its really spinning.
I have a little tiny stepper with a 1" wheel on the shaft.
It gets past 50VAC running it down the table edge.
It would be great for a 3 or 6V Nimh pack, about 100ma to either.
It puts almost 20ma into a 12V battery.
Most of the maybe 30~40 different kinds here make 12V open,
but only 3 to 25ma into a 12V battery.
Yes, I bought them all for wind power.
Nameplate ratings have nothing to do with what they will make.
In the last 3 days, I got 2 types of 24V 3A steppers.
BIG dollar stuff. Maybe 3 pounds each.
One makes 0.09VAC open (NOT a typo).
A 5 wire.
Connected it every which way too,
not just like it should.
The other makes 4.1VDC rectified open,
and 4A short. Only 3 wires.
Didn't connect it to a 2 AA Nimh pack,
seemed a little extreme on the amps.
BTW, it is 3 phase star (wye) wired.
G-