I've spent quite a bit of time using my phone in the last couple of days, and I have a few thoughts on the heating issue:
- For me, the heating is not the screen itself, as I've experienced the heating (temperatures in excess of 40c/104f) with the brightness below 50% using Lux.
- I can say for sure that the phone gets a lot hotter when using LTE, rather than WIFI.
- I suspect that people not having this issue with LTE maybe have carriers or tower support better than others.
- I've been using Location "Battery saving Network Only", but I've now switched to Location "Device sensors only GPS"... I think, if I'm right that this will help.
My theory, based on what I'm seeing through GSam Battery Monitor, is that when I'm in certain LTE areas the Google services are constantly using the network to establish my location. When on WIFI, even in hot rooms, my phone does not heat up at all. (This theory is also backed up by at least a couple people writing that their phones heat up badly when using navigation.)
I'm not about to close off location services entirely, because I like Google's location-specific content and help.
I will update this post later this afternoon -- I'll go back out to the same spot I was just at, but with Location set to use GPS only -- letting you know how well my theory worked.
I should also note that these last 2 days I've been using my plastic back and Spigen neo-hybrid case rather than the black leather back (I wanted to see how it "feels" in my hand) -- and this may actually be affecting the heating issue, as the heat is perhaps not as able to easily dissipate. If my GPS vs LTE experiment doesn't work, I'll try switching back to the leather back tomorrow to see if that makes a difference.