Tired of your smoke detectors going off at 3am because you live in the Midwest and turn your heat down at night??Here's the fix! For years I struggled with a random couple of beeps from my house-wire powered smoke detectors. There is a backup battery in them, and even though I replace the batteries every 6 months with quality copper and black name-brand alkaline batteries, they still never fail to beep at 3am once or twice for no apparent reason every time the weather gets cold outside. (By cold I mean -5 F or lower). We set our heat down to 67 at night, so it isn't ridiculously cold, but it's enough to throw the alkaline batteries in the smoke detectors into a series of one to 4 cycles of beeps and a wake up walk to get a ladder in just enough time to have it stop.....NO MORE with these batteries!Lithium batteries are not affected by temperature changes like alkaline batteries are, and have a MUCH longer output life. Like 5+ YEARS output life in a smoke detector application. Since putting these in, I have had ZERO late-night wake-up calls from my smoke detectors. Bliss and quiet.Sorry, but smoke detectors should either be better made to not require this kind of effort, or be clearly marked to use only lithium batteries. In the meantime, I will buy and use these batteries going forward and enjoy a full night's sleep--even in the cold weather.