It's one of the unprotected batteries. I kept swapping it out until the effect stopped. Any idea as to what's going on with it? It's measuring 4.05 volts.
I think he also caries the same brands as DX? Trustfire or Ultrafire?
They are really luck of the draw, some work excellent some are complete garbage I have a few batteries here that have been working great since I started on this forum, still just as good as they were new, but I have also thrown out quite a few.