There was a very worrying revelation last night on "fake britain" about cheap rechargeable head torches exploding. In the program last night a lady runner took her head torch off and placed it on her car seat, and only seconds later it exploded showering her and her car in parts of the battery. Luckily she was not hurt, however had it gone off on her head the outcome could have been horrific.
The brand of the batteries inside were "Ultra Fire" they are larger than the usual AA batteries, about the size of your thumb.
Once again it sounds like Rechargeable Lithium batteries were to blame, NOT the usual disposable AAA batteries.
There are more cases of the torches exploding elsewhere too and there is an article her from the fire brigade.