We had bought 15 pieces of these smoke detectors for our home and the homes of grandparents. All 15 we knew with the included lithium batteries. Then we spent days trying to figure out which chirped at irregular intervals. This was the case for all three families. Finally it turned out that all (!!!) smoke detector had this problem. We tried it with newly purchased block batteries. Even so not all worked. So once again buy new batteries from another manufacturer and tried. Conclusion: Still beeping Two of the twelve smoke detectors at very irregular intervals (30 minutes to 2 hours). We have now bought two cheaper smoke detectors in the construction market that worked immediately properly. The two defective smoke detectors, we can no longer change now after weeks of trial and error. From a retailer, we learned that a sending in of other smoke detectors of the same type to the manufacturer had no purpose. They came back with the remark that it was necessary to use only new batteries. We thought that you better buy smoke detectors of a brand company and rather spends some extra cash. Now we would not buy these smoke detectors.
