After looking at all of the answers, I was still feeling a bit skeptical, but I decided to pull a "Why The !&&* Not" move. I turned on my radiator and held my iPhone 6s to it for a minute or so, and it booted up right away. Very happy to know that strange things like this work. If you're around the cold a lot or move from one temperature to the next like I do for work, then this method will absolutely help you out. Try cleaning it out frequently to allow for the best charges. Once I plugged my phone in, after it turned on, it charged faster than when I first got it. Since I've started typing this, it's gone from 11% to 24%. Hope this helps!