The problem might be that the pressure on the battery is too high?
The slightly bent-up metal thingy that the battery pushes down when inserted might be bent up too high maybe? Try pushing it down a tiny bit.
I've actually had similar problems with several tamas when I was younger, and left them with the battery inside for a longer time; no leaking, just a funny smell.
I think that it has been the pressure though...
Hehe, might be that. The bent-ish contact is a bit too high. I'll try to find a way to push them down.
EDIT: Oh, wait. I can't push it down. It's bent down enough. (Or is it? I don't know.)
EDIT2: I was gonna test it out with a new Hongwei battery. But as I held it, it smelled as if it were on fire. It had a
small red thing, and it almost got on fire! It almost burnt my hand, so I had to throw it to the floor, so it would stop. Mom said she'll look for brand batteries for me.
Edited by AggyK2, 12 November 2012 - 09:45 PM.