I carry a 4sevens Quark aa2 warm tint for work as an inspection/ work light as a mechanic. Now I usually only use it for a few seconds at a time, a hundred times a day.
I recently purchase a Powergenix charger and 4 aa batteries. They have been working fine, untill this occasion.
I was working late one night, and was using my Quark on a nite-ize headband as a headlight, on max power, for a couple of hours, untill it started dimming. I had never run it this long before. I went to push the button to turn it off, and had some trouble (light still on my head) I thought the switch was broken, jammed, so I too the light off my head and immediately noticed the switch boot swollen to huge size. So much pressure that pushing the button was difficult. I took a couple of pictures on my camera phone (I don't know how to post them here) and unscrewed the tailcap to let the pressure out. Puff! Now th weirdest part was that after I closed the light up, without even running it again, over the next fifteen minutes it built up pressure again, not quite as bad, but still visibly swelled the tailcap boot.
It has never happened since (i have never run it that long again) But I thought I should post it here.