I found this article at Matt Dunmore Photography website and I thought this might be of help. Here's the article:
Disclaimer: This article is own and written by Matt Dunmore. You may visit his site by clicking on his name.
Here is a little tip I thought I would share. I learned this a while back from my friend Jason and then have heard it several times from different sources.
Teaming up your batteries can greatly improve your batteries life and longevity. Apparently there is something about using and charging your batteries together in the same set that helps them last longer when used and also improve their over all life. Don’t ask me why I just thought I would pass along the info.
I currently have 7 sets of 4 AA batteries and I have used a Sharpie to place numbers on the side. I also have a case that I can store them as sets so that it is easy to find the teams.