5% in 28 minutes is bad.
Would you try the steps in the
30+ Hours Battery Life on the Epic 4G Touch-How Long Can You Go?
In particular, would you let us see your battery usage screen?
What widgets are you using?
What apps?
What do you sync? How often? Have you tried turning off all automatic syncs?
What are your signal strengths?
Are you on WiFi?
Is 4G on?
What are your Menu>Settings>Power saving mode power management settings?
You have a battery sucker running that is killing you. When my Epic 4G Touch is just on but I am not using it, it loses at most 1% an hour even if I am getting a lot of emails, etc.