An iditarod musher friend of mine had a headlamp battery box explode under her parka one night on a long training run. It was a battery box that held 4 D cells and she had put one of the batteries in backwards. She said she was confused because she knew the batts were fresh, but the headlamp was pretty dim. She ended up with pretty painful acid burns on her chest and a long painful run home in sub zero temps.
It might not be common, but it can happen.....
