how do you work without iCloud?

Yes, I realize alternatives exist, but this works so smoothly on Apple devices.

It’s a debugging technique not a permanent solution.

If logging out of iCloud does NOT fix the problem, you eliminated a bunch of potential issues at once.

Yeah, it's just to see if that is the issue. It's possible a massive or constant sync from Files or Photos is what is pulling down your battery.

I mean, switching to Airplane mode is another thing worth trying.

As is rebooting the phone.