I have a Ryobi tools and they are cordless, I have recently replace two new batteries due to they won't last very long, and even went to lit batteries. Same senario charge them up and don't seem to last.
Right before I bought the new batteries I bought a newer charger as well. It seem to help a little at first with the older batteries, but again it doesn't seem to be making it. When their working the tools are fine plenty of tork, the problem is longevity.
Their are some companies that say you can alter and restore the life of the older, and newer batteries.

Ronald C. Baugh A.E.T., May 2011

If you know how to use a soldering iron, you can replace the batteries that are inside the battery packs, but you'll probably find it's uneconomical.

http://www.eurobatteries.com/

Big Softy, November 2012