I have 3 WIRED co / smoke detectors that have battery backup.
There is also 1 WIRED smoke detector that has a battery backup.
All were installed 8 months ago and needed to be changed out due to the height of our ceilings - can't reach the ceiling if the battery needs changing.
They all work, but I'm having trouble getting them to stay on the ceiling mounts. If you have Kidde and need new detectors, come and get these. They may work on your mounts - or it's just me not being able to get them to attach. A few batteries included.