Our smoke/carbon monoxide detector had been alerting us for three days that its battery is low. It started just with a high-pitched single beep, but we could never tell which of the two detectors in the room was doing it at first, the one by the front door or the one on the upstairs landing ceiling. We used an umbrella to press the downstairs detector’s test button. It’s the fancier unit and, in addition to blaring its alarm multiple times, also shouted “FIRE! FIRE! FIRE!” and “CARBON MONOXIDE DETECTED!” I then hauled our step-ladder upstairs to press the button on the less-fancy one. It beeped just fine. Our mystery remained.
The next night, the downstairs detector began blaring a single shrill beep and shouting “LOW BATTERY DETECTED!” It started this at 10 o’clock at night as we were settling into bed. I decided I was too tired to haul my butt upstairs to retrieve both a new 9 volt and the step-ladder I’d left up there. So we lived with it for the night. It only interrupted sleep on a semi-hourly basis.
The next night I marched upstairs for both the new 9v and the step-ladder only to find that the last 9v in the pack had no charge when touched to my tongue. (You gotta touch it to your tongue. It’s a 9 volt, after all!) So we lived through another night punctuated by *BEEEP* “LOW BATTERY DETECTED!”
Today I went to the store and purchased a new pack of 9 volts. I chose the two pack rather than the cheaper four pack because the only thing that uses them in the house are the smoke detectors and this will make twice we’ve had to change them in the past five years. No use letting another $10 worth of batteries die in the pack.
I returned home, climbed the step-ladder already positioned beneath the detector, removed said detector from the ceiling, and discovered that it actually took three AA batteries the whole time.