I know there have been all sorts of battery issues over the years but this seems new, or at least odd.

I bought a new Samsung S7 for myself and my wife, a couple of months ago. I know, not the most recent models but we don't use mobiles much and wanted to get something as small as possible.

Anyway, although my wife's phone has had a new battery installed after a heating issue, and although both phones have been behaving themselves for a few weeks, on the same day (yesterday) both of the phones started to drain the battery fairly quickly without the phone being used (in my wife's case) or only being used sparingly (in my case). Overnight, my phone battery decreased from about 53% to about 20% though it usually only loses a few percentage points in that time.

I've looked at the battery monitor for apps that used the battery but there is nothing unusual except, possibly, the Screen percentage being higher than I would have thought. The percentages of all apps (including Device Idle) only adds to about 25% of the total, so I've no idea what else is eating the battery. I've turned on maximum battery saving mode to see if that has an impact.

One thing that my wife has noticed is that the screen sometimes switches itself on, though I haven't noticed that.

To have both phones exhibit the same problem on the same day, even though one has had a battery replacement, suggests a software update but neither phone appears to have recent system software updates (in fact none since I bought them).

Any ideas, or has anyone else seen this in the last day or so?