Tonight around 3 clock began one of our smoke detectors, deliver in minütlichem distance his empty-battery warning. I had to pick so that he finally gives him peace with a broom from the ceiling. We had the unit for a little over a year, it had 2 false positives in this time and now I read on the cover that you can not replace the battery. I would not buy the part again. In the beginning we were very pleased, because the magnetic holder was easy and safe to install, but the smoke detector itself is a disappointment.