Battery question
 

I don't know any battery forums but since micro R/Cs depend on batteries for their power, might as well ask it here.

Ok, I have a four-year old mp3 player (manufacturer even gave up on making drivers for XP). Well, so today I pop in a fresh pair of Rshack Xmod AAAs and I keep getting no power out of it. One thing I noticed was one of the batteries begins to get hot.

Now I'm thinking that it is batteries.

So I had a spare pair of regular AAAs and I decided to try them. They work! but one of the batteries is getting really hot.

Must be a problem with the mp3 player.

What do you guys think?

one is probably new and the other is old. one is trying to charge the other.