Ive heard that a battery will work, but Ive never done it myself. I do know that the motors should turn with slight resistance by hand and cog slightly. Anything other than that means trouble. Ive bought a number of steppers off ebay and have had a couple that were junk. They were siezed, like what your describing. They would turn a half a revolution or so and then get stuck. Fortunately I didnt pay much ( 6.50 for three) and just trashed them.