How to open old smoke detector cover to replace battery
Some covers cannot be pried open to replace the battery because the units were ultrasonically welded shut. Other models are held closed by a hidden white cotter pin along the top perimeter that must be slid out first.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
Found another way around this?
Share your steps and trade-offs so fellow engineers don't have to reinvent the wheel. No account required.
- 1Twisting the top counter-clockwise with a quarter-turnDid this help you?
- 2Sliding out a retention cotter pin before twistingDid this help you?
- 3Replacing the entire expired or sealed unit instead of changing the batteryDid this help you?
- 4Placing the device in a freezer for 24 hours and then dropping it to break the weld.Did this help you?
- 5Inserting a punch into a lug hole and giving it a sharp tap to separate the pieces.Did this help you?
In their words
Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.
“Tried to pry it open but was ultrasonicly welded”source ↗
“Just hit a similar problem. I felt around the top perimeter and discovered a white cotter pin (sort of) that I needed to slide out first.”source ↗
“This is a 1990-92 model ... I am not able to open the cover to replace the battery.”source ↗
Where this came up
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