Only getting half hour battery life on 'better battery life' setting!

This is very strange because it only started about two weeks ago when I changed the energy setting on my iBook g4 to ''better performance." When I changed it back to 'better battery life,' I noticed the battery life still going down very, very quickly even when the only application running is Safari. Right now it's going from fully charged to 0% in about half an hour even with optimized energy settings. Anyone know what the deal could be? I'm wondering if it hasn't really entered energy savings mode even though it says it is, or if my battery is already out? Mind you I just received this battery in August 2007 because my old one was one of the freaky overheating ones that Apple recalled. Would appreciate your help.

I had a problem like this with my Powerbook except it went from 3 hour life to about 10 minutes in an hour if I'm lucky. So what I did was I left the laptop plugged in for 24 hours straight, no use or anything. Try that, I hope it helps

-Jordan