One of the few gripes people is having with the new EVO 4G is short battery life. While on 4G and medium to heavy usage, I’ve seen the 4G go from fully charged to almost dead in 4-5 hours. This is unacceptable for today Smartphone’s. It should last at least 8 hours or more if you’re not a heavy user.
1. Add widgets to your HTC Sense homescreen to control the radios (Bluetooth, WiFi, 4G)
2. Use the widgets to turn off select radios when not in use. If you're not using 4G, switch it off and fall back on 3G instead to gain better battery life.
3. Turn off network roaming. By default, roaming is turned on for the HTC EVO 4G out of the box, which means that the phone scans for the strongest CDMA/EV-DO signal. If you've got great Sprint coverage where you are and don't need to roam onto one of Sprint's partner carriers, turn off roaming so the phone doesn't need to constantly search for the best signal.
4. Turn on automatic brightness so the screen can adjust in light and dark environments rather than having brightness turned all the way up. Alternatively, you can also set the screen brightness lower by default.
5. Turn off live wallpapers--they're pretty, but they do use a little bit of extra processing power.
6. Carry an extra battery or plug into a car charger when you can.
Give these settings a whirl and see if it improves your battery life. Post a comment on your experience with the EVO’s battery and the things you do to improve the battery life. These settings should work but in the mean time, keep you charger handy especially if you live in a 4G area.