The clock on the wall with the for-show pendulum had an oddity a couple weeks back. There are slots on each side of the case to allow the pendulum to swing without hitting the case. It doesn’t really move outside the case or if so, not by much. Just enough to be seen at some angles and if the slots were not there, it would hit the case.
The oddity was that it was not swinging that far, or not all the time. At first I figured this to be an issue with the cell and the temperature. Electric cells are chemical devices and cold slows reactions, so logically there would be that bit less charge available in colder weather (The clock is on an outside wall). The only problem with that was the swing amplitude seemed to greater the colder it was, and the lesser the warmer it was. That made no sense, and I still am unsure how that happened.
But then the clock started “losing time” – the cell was older (or had been in use when I was still trying to the pendulum swinging, so might have drained faster than normal), so a simple replacement took care of things. Watching it for a few days, to be sure it was just the cell and not something revealed that was indeed the issue. Checking things a bit closer (actually far, but at a known angle with the right lighting) showed that the pendulum swing was not varying in amplitude any more. Or if it was, not enough to be noticed.
Looks like I have a “low battery” indicator even if doesn’t come out and indicate ‘BATTERY LOW’. And I can, perhaps, see this (if I remember for some time) before the clock loses time.