I'm just getting back into chickens after a 10 year or so hiatus. Previously we did not have a well designed coop--no door but did not have a problem with predators. Wild ones anyway. The door is an issue for me as I am gone from my house a night or two per week for work frequently and wouldn't be home to let them out in the morning or shut them in after dark. I've looked a bit at the automatic door openers but am concerned about the reliability of them. It gets very cold here in the winter. -20 isn't unheard of and batteries seem to fail when it's that cold. Is it possible to design something like a dog door with a flap to keep warmth in but does not necessarily rely on a human to continuously open and close? The chickens will have a fully enclosed run. I would love to hear opinions on this. Thanks!