How long does the back up battery last on a garage door opener? Support November 23, 2022 20:21 Updated Only an estimated time of 1-2 days on normal usage in an electrical power outage. Related articles Why is my wall button working but my remote is not on my garage door opener? How can I order just a bare tool without the battery? Where can I locate parts and information? Where can I locate information about my pressure washer? How do I handle or claim a warranty on my tool? Comments 0 comments Please sign in to leave a comment.