The first step to better the HTC Evo battery life is to stop the data connections from constantly checking for data and thus draining the battery.
Disable the "always-on" mobile data connection. Goto "Settings" and then "Wireless & Networks". Choose "Mobile Networks" and tap the box next to "Enable always-on mobile data". This will disable the always-on mobile data connection which will save dramatic amounts of battery on the HTC Evo.
The next step to reducing the amount of data being transmitted is to disable the background data. Background data is randomly sent by the Google Services built into the phone. Disabling background data may hinder some functionality of the Google Services however it will greatly save battery life.
Disable background data. Goto "Settings" and then go to "Accounts & sync". Un-check the box next to "Background data" to disable the background data service.
The next two steps will disable auto-sync and wireless network location services. Disabling these two options will again, hinder some functionality of the services on the HTC Evo. In exchange for functionality, they will drastically increase the HTC Evo battery life.
Turn off auto-sync. Turn off auto-sync by going to "Settings" and then "Account & sync". Un-check the box next to "Auto-sync" to turn the auto-sync feature off.
Turn off wireless network location services. Go to "Settings" and then "Location". Tap "Use Wireless Networks" and change the settings from there. Turning this off will disable your ability to see your location in the Maps application. Turn this service back on to restore functionality when necessary.
There are several other things that also cause poor HTC Evo battery life. The majority of the drain is from the aforementioned data services although several other features do cause battery drain. Below you will find information on how to disable these features to assist with increasing the HTC Evo battery life.
Turn off haptic feedback. Haptic feedback is a nice feature to have on the HTC Evo, however the constant feedback does use battery life and so it can be disabled. Go to "Settings" and then "Language & keyboard". Choose "Touch Input" and then "Text Input". Turn off the option that says "Vibrate when typing".
Turn off the phone vibrate. Phone vibration for incoming calls can drain battery life fast. This is especially true if you receive a lot of calls or text messages throughout the day. Disabling the phone vibration will also help with your HTC Evo Battery Life.