I've been wearing an Apple Watch Series 4 every day for the past two years. Until the watchOS 7 update came along, it generally had between 45% and 55% battery charge left at bedtime, which suggested that sleep monitoring was going to be possible with only slight modifications to my charging routine.
But the update to watchOS 7 seemed to ruin battery life. At first I made allowances: installation is a fairly demanding process and I spent the rest of Friday enthusiastically trying out new functions such as the handwashing timer and hearing health notifications. But by Saturday it was apparent that something more serious was going on.
Alarmed by the rapid battery drain the day before, I started to make regular checks. After a few minutes the battery was at 95%; after an hour it was at 80%. I took the watch off its charger at 7am, and it was all over by 2.30pm. And things were just as bad the next day.
I tried paring back the hearing health features, but quickly eliminated them as the cause of the problem. So what was the problem, and how could I fix it? I've found a radical solution.
Unpair the watch from its iPhone and reset it to factory settings. When you're finished, the iPhone will ask whether it should pair with the watch, but for the first time you get the option to set it up for a family member - this is new in iOS 14 and watchOS 7.
To be on the safe side, we set up the watch as new: don't restore from a backup, since this may contain the cause of the battery problem.
And this seemed to fix things. The solution is sustainable, as I found on Monday: after a one-hour bike workout I still had 95% charge, and in the evening it was still well over 50%. Sleep monitoring is again a realistic goal.
Jason Snell's solution was a little less radical, as he reports on Twitter. Faced with the same problems on an Apple Watch Series 5, he was able to fix things by simply unpairing the Apple Watch from the iPhone and then pairing it again, without having to reset all of its settings.