Most battery related problems are a program that won't go idle. Or maintaining a 3G data connection with chat enabled, or wifi (not so bad) with chat.

Try this:
top -d 240

and leave it alone for at least 4 minutes.
Then look at the CPU % column and you can see what is using CPU time. Ideally everything should be 0%. Less than 1% might be ok.

or install one of the battery graph programs. I've used "BatteryGraph" to monitor what uses up the battery.