Hi all I did this last night and it worked wonders on my battery. Before this with screen brightness at about 20% and 10 hours of being on the battery would be dead. The screen on time was 3h15m at best before it would die. After I did this I tested my battery by playing a movie, games, web and texting. When I put my phone on the charger last night screen on time was 5h flat. I was amazed. So I thought I'd type this up for anyone with battery woes. You need to be rooted and Clockwork installed.
1. Dial *22899 and let it do its thing. This helped my battery drain while in standby. Now drains about 1% every 3 hours of standby.
2. Charge phone to 100% (phone on)
3. When the charge hits 100% power down the phone
4. A green battery will show on screen and show its not fully charged. Leave it on the charger until it shows 100% (phone will vibrate to let you know and state 100%, do not unplug phone)
5. Once it reaches 100% boot into recovery by holding both volume keys and power until the Samsung logo appears.
6. Choose "apply update.zip" (use the home key for selection)
7. You are now in Clockwork. Use the volume keys to navigate to "advanced" and the back softkey to select it.
8. In the advanced menu select "wipe battery stats" (there will be no conformation)
9. Back in the advanced menu select "wipe dalvik cache"
10. Now back into the main menu and select 'wipe cache"
11. Select "reboot phone" and wait for it to reboot (will take longer than normal)
12. Once fully loaded unplug the charger and run the phone until the 5% warning then plug back in