It should be no surprise to anyone that phones get hot when we use them in different ways. These portable computers are capable of an incredible amount, and things like processors and wireless radios and batteries generate heat when used. (Whether a phone gets too hot is another thing altogether.) We also live in a world where smartphones are being made of more unique things every day, with parts on the inside assembled just a little differently each time, and that means those phones all handle heat a little differently.
Since we've been playing with the new Flir One this week, it seemed like a perfect opportunity to perform some relatively unscientific tests on some of the more popular phones out there today with this thermal camera pointed at them. Here are the results.
Here's a snapshot of each phone side by side doing absolutely nothing. They are all Verizon Wireless devices, all powered on, and all running as close to the same apps as we could reasonably manage. The warmest-appearing phone when doing essentially nothing was the Galaxy S6 edge, which clocked in at 88.6 degrees. You wouldn't know this phone was the warmest by looking at it or holding it — in fact had I guessed before setting these devices under the camera I'd have said the Droid Turbo was the warmest by holding it.
To get a feel for how these phones get warm, we installed the AnTuTu Benchmark app on each phone and ran them side by side. This app pushes the processor further than most apps in such a short time span, but offered as close to a uniform expectation of heat against performance as you could expect without including the warmth and insulation of a human hand. The benchmarks were initialized and the phones were flipped over, and through the Flir camera we could see the temperatures increase almost immediately.
The G4 was the first to go from purple (cooler) to yellow (hotter), but only in the top third of the phone. The warmest spot, to the left of the camera, became bright yellow on the screen as the other phones started to glow orange. The Galaxy S6 edge quickly became the warmest phone on the table as the benchmark reached its conclusion, while the M9 and Droid Turbo stayed within a degree of one another through the test.
We'd come this far, why not start the benchmark while the phones are already warm and see what happens when you really push things? As you can see in the photos every phone but the G4 became what most would consider uncomfortably warm, but the bottom two thirds of the G4 stay relatively cool even towards the end of the second benchmark. The all-metal M9 and carbon fiber Droid Turbo spread the heat just about everywhere to try and dissipate as quickly as possible, while the Galaxy S6 edge reached over 120 degrees right next to the power button.
A lot of what you're seeing here has to do with how the different materials used in the exterior construction handle heat. The M9 and Droid Turbo are going to be warm all over, but never get as warm as the G4 or the S6 in localized areas. It's a little strange that Samsung and LG both created devices that get hottest right next to the most commonly used physical button on a smartphone, but the way LG handles heat seems like the best for someone holding and using a phone that is currently doing quite a bit — the hottest area is far from your hand.
It's also worth pointing out that most tasks won't get your phone anywhere near this hot. You'd have to be playing an impressive 3D game for an extended period of time or doing something crazy like transcoding video to get your processor to work as hard as we pushed these phones. I wouldn't go so far as to say any of these phones have any heat problems based on this information, but it is interesting to see how these phones get hot and which can be used comfortably under intense situations.