I had this happen once using Navigation on a cheap car charger.
I was in unknown territory, but as I got back to the main highway, I found myself knowing where I was going and stopped paying attention to my phone.
This lead to my phone getting hotter and hotter until it shat itself and would only display a black screen. I unplugged it and attempted to turn it off, which seemed to work. I left it off for an hour or so until I got home. It still wouldn't turn on for a while, so I stuck it on the charger. After a few minutes, it came up fine.
Main Phone: LG Optimus G E970, 4.1.2
Retired: HTC Inspire 4g, PACMAN
Auxiliary: HTC Incredible, tinyCM10.1
Auxiliary: Nook Color, MirageCM7