Just curious: I removed all the smoke detectors: Took the batteries out: Took them outside and put them in my car: Now I have 3 holes in the ceiling with wires hanging out: And every 28 seconds it chirps where one of the alarms used to be. There is nothing there but it still chirps. Any thoughts?

They are whole house wired. Happened to me too. I found a smoke detector on the ceiling going down the cellar stairs that I hadn't noticed. Are you sure you found all of yours? The direction the chirps are coming from can be deceiving.
(I'm not an electrician - just my experience)

If there is nothing there, it can't chirp. Joy is correct, there is another detector somewhere.

Removing the battery won't stop the chirping. The battery you remove charges another small battery that built into the detector which you can't remove. Eventually that small battery will run down and the chirping will stop.

You have another smoke detector... somewhere.