https://s-media-cache-ak0.pinimg.com/originals/c6/c4/c9/c6c4c9d0fb8477969b5b0876d65f0f38.jpg
some models have hand-cranks so you don't even have to use up their batteries. (http://www.autoadmit.com/thread.php?thread_id=3983195&forum_id=2#36100019)