I have just been woken up three times in the night by my smoke alarm as I couldn't see how to remove the unit and think the battery has gone. Each time I looked at it I couldn't figure out where to "slide" it off as the casing taunted me as I grappled with it. This was the video that finally helped me to sleep!! When I took what was probably an old battery that was at fault, it still eked out one last scrawny beeping noise before dying. Thank you for reliving my boredom and I hope this helps someone.