The most obvious way to power
an automatic chicken coop door opener when you don’t have a long enough
extension cord is to add a solar cell.
A blogger named Slinky had
such a set up, and took the opportunity to teach himself the art of
making your own DIY
6 volt charge controller.
The controller prevents the battery from getting over charged and
damaged, a danger that will be certain if you hook a solar cell up to a
battery without one.
Slinky deserves bonus points
for his detailed description of the process. Sure you could save a
bunch of time by purchasing a pre-made charge controller, but you’ll
get an emotional charge from doing it yourself and learn a few things
that may help in your next project.