I was greeted this evening upon my return home from work by a high-pitched chirping tone emitting from all 3 of my smoke alarms, every 40 seconds or so. Since each of the alarms appear to be wired to some sort of recessed connection in the ceiling, I presumed that they were being powered from an electrical circuit within my home (and not by battery).
However, I could not find any circuit breakers with an obvious connection to the smoke alarm circuitry, nor could I find any reason for the incessant (and increasingly more annoying) chirping. I even tried disconnecting each alarm in turn (not recommended I know) but the chirping persisted as did my rising frustration levels.
Upon closer inspection of the label on the rear of the alarms, I discovered a very well disguised (and not very obvious) battery compartment, with a 9V battery inside. Even more impressive (and annoying) was the fact that the chirping continued after I removed the (now suspect) battery. There was nothing for it, I simply had to get into my car and drive to the local shop to buy 3 replacement batteries and eventually, almost 10 minutes after I’d replaced the batteries, the chirping finally stopped. This was indicated on the label though (the fact that it could take up to 10 minutes for the circuitry to recover from a replaced battery).
In hindsight of course, I am highly impressed by this little piece of technology. Firstly, it was telling me that the battery was wasted (nothing new there) but moreso by the fact that, no matter what I tried to do, there was no way it was letting me away with replacing the battery.
I’m just glad it didn’t try to tell me at 4am in the morning!