Now that you know how to see what's draining the HTC EVO's battery, let's work on trying to lower some of those percentages and increase the amount of time you can use the phone between charges.
Maximizing battery life is often at the expense of user experience (a device at the lowest screen brightness setting with all wireless radios turned off may as well be a paperweight as far as I'm concerned), so assess your personal needs/wants and adjust accordingly. Some people may want to use the EVO to its fullest potential, even if it means carrying a spare battery with its own charger or using a slim higher-capacity one; others may just want the peace of mind of knowing that they'll be able to place a call at the end of a long day.
Wherever you fall on this continuum of user types, I hope you find something useful in the list of HTC EVO battery saving tips below. Some of the tips won't make a measurable difference in battery life, but in situations where every little bit counts, just about anything is worth considering.
Update: Calibrate your battery first.
1. Lower screen brightness. Go to Settings -> Sound & display -> Brightness. Slide the brightness switch to the left to lower it or check the "Automatic brightness" box to let the EVO use its sensors to adjust the screen according to the ambient light. You can also find dedicated screen brightness widgets in Android Market.
2. Turn off 4G, WiFi, GPS, and Bluetooth when you don't need them. The easiest way to manage these wireless radios is to use the Settings widget preinstalled on your EVO. Tap the + button on your home screen -> Widget -> Settings. Once your chosen widgets are on any of your home screens, a simple tap turns each one on/off. There are other widgets that do this in Android Market, but these are already preinstalled and they're a nice-looking set.
3. Disable WiFi and 4G network notifications. Go to Settings -> Wireless & networks -> Wi-Fi settings. Uncheck the Network notification box so the EVO isn't constantly scanning and looking for open networks to tell you about. For 4G, go to Settings -> Wireless & networks -> 4G settings.
4. Disable "always on" mobile data. This is one of the biggest battery savers. Go to Settings -> Wireless & networks -> Mobile networks. Tap "Enable always-on mobile data" to uncheck the box. I haven't found a negative consequence of disabling this feature, as Gmail and other apps/functions still work perfectly.
5. Turn off background data. If you're not using Google services, go to Settings -> Accounts & sync and uncheck the Background data box so that applications cannot sync, send, and receive data whenever they want to.
6. Lower the screen timeout interval. The EVO's screen can be set to automatically turn off when you don't interact with it for a predetermined amount of time: 15 seconds, 30 seconds, 1 minute, 2 minutes, 10 minutes, or never. Depending on what you're doing, a too-short interval can become annoying (especially if you didn't disable your lock screen), so choose wisely.
7. Manually turn off the screen when not in use. Since the screen timeout function ensures that the EVO's screen will turn off (unless you have it set to "never turn off"), it can be tempting to put the phone down when you're done using it and just let the screen turn off by itself. Instead, give the power button at the top of the EVO a quick push to turn it off manually.
8. Turn off auto-sync. Go to Settings -> Accounts & sync -> Auto-sync.
9. Change auto-sync frequency (Weather, News, Stocks, Twitter, etc). If you don't want to turn off auto-sync, you can adjust how frequently data is retrieved/updated. The settings vary depending on the app (and some don't offer the setting at all), but it's generally found in the same place: Settings -> Accounts & sync. Select an account from the list and then tap "Account settings" to change the sync frequency.
10. Disable wireless network location services when not needed. Go to Settings -> Location -> Use wireless networks. Note that this (or one of the other options) needs to be enabled if you want to see and/or use your location in apps like Maps.
11. Turn off window animations. I know it's nice to look at and fun to show off, but eye candy uses extra power (albeit not very much). To turn it off, go to Settings -> Sound & display -> Animation -> No animations.
12. Don't use a live wallpaper. Live wallpapers were one of the new features in Android 2.1, so it feels like a step backward not to use them. They don't hit the battery very hard when used, but they do make a small dent. So if you're trying to improve battery life, even if only incrementally, use a static wallpaper instead.
13. Use a dark wallpaper. Some say that dark wallpapers are more energy efficient than light wallpapers. Others say it doesn't make any difference. Either way, there's no harm in using a dark wallpaper so you may as well do it.
14. Change WiFi sleep policy. This may sound counter-intuitive, but leaving WiFi on when the EVO isn't being used and the screen is off is actually better than letting it sleep. When WiFi sleeps, 3G/4G wakes up to sync, get email, and retrieve other data. 3G will eat up more battery than WiFi, so go to Settings -> Wireless & networks -> Wi-Fi Settings. Press the Menu button and tap Advanced, then Wi-Fi sleep policy. Choose "Never" from the pop-up menu.
15. Monitor your running services (or consider using a task killer). Just because Android 2.1 is supposed to an intelligent operating system that will manage your running apps for you doesn't mean it will always do things the way you want them to be done.
You can take matters into your own hands by going to Settings -> Applications -> Running services, where you can view what your EVO is doing and manually stop certain activities. You can also download a third-party task killer from Android Market and kill selected apps to free up some resources and potentially save some power. Task killers are a polarizing topic in the Android community, so tread lightly when looking for recommendations or asking for help with them.
16. Choose your home screen widgets carefully. Widgets that need access to the internet to update information (e.g., Facebook, Twitter, Engadget, Slacker Radio, Weather, Stocks, News, Mail) can suck up a lot of juice if not managed well, so choose them carefully and set their sync/update frequencies to a reasonable interval.
17. Disable notification lights. This may not be practical if you're someone who really needs/wants to know when something happens on your phone when you're not looking, but for everyone else, feel free to turn off those notifications. Go to Settings -> Sound & display -> Notification flash and uncheck all the boxes.
18. Turn off phone vibration. If the ringer is on, why do you need the phone to vibrate? You're already in a loud environment that drowns out the ring; answering the call won't quiet your surroundings so you can hear what the person at the end of the line is saying. If anything, you're just adding to the noise by yelling, "What? What?" into the phone.
And if the EVO is set to silent, then an incoming call should be silent. Yes, the buzzing vibration may not be disruptive as your ringtone, but people still hear it.
So go to Settings -> Sound & display -> Phone vibrate and turn it off.
19. Turn off audible touch tones. In Settings -> Sound & display, uncheck Audible selection and turn off Audible touch tones.
20. Turn off haptic feedback. Once you get the hang of typing on the EVO's on-screen keyboard, you can turn off the haptic feedback that was turned on by default. Go to Settings -> Language & keyboard -> Touch Input -> Text input -> Vibrate when typing.
You can disable haptics in other areas of the system by going to Settings -> Sound & display -> Haptic feedback.
IMPORTANT: Please DO NOT copy-and-paste these tips in their entirety on forums, blogs, etc.
Got another tip to improve battery life on the HTC EVO? Please share it in the comments.