This actually happened to us. We don’t know how long the battery was dead. It was just a fluke that we tried the door handle without using our card (forgot we weren’t home), and the door easily opened. We opened and closed the door, and then tried it a few more times, and it just opened, with no lock engaged. When we called maintenance, they said they would repair it within an hour. We were on our way to dinner and didn’t want to leave the cabin unlocked. This surprised the maintenance department, but they came immediately to change the battery.