Can you please advise how to change the battery. Have one smoke alarm detector alarm 240v/9v battery backup- brand Omega. . Have tried on advise of others- press on the side & the door will drop- no luck?? Have tried like other smoke alarms- grip & slide- does not move- please help as the beeping is driving us crazy....keeps beeping about 3 to 4 times at night & also throught the day. Keep silencing it & then , it starts again. Thanks for our help. Gerard