Battery Life Optimization Guide
Rule 1: If you haven't taken these steps, you haven't done a thing in the way of actually optimizing your battery life, and please do not complain that your battery is bad if you haven't at least done steps 1 and 2!
Step 1: Use BetterBatteryStats: http://forum.xda-developers.com/show....php?t=1179809
This will diagnose battery drain issues. If you have apps that are sucking battery in the background, this will show it. Google the ones that have high partial wakelock, and usually you will get a diagnosis. It is also sometimes very easy to figure out what is sucking battery just by looking at the application that is holding wakelocks or having many alarm wakeups.
Step 2: Sync settings, make sure that all of them are either at push or as high as you're personally willing to allow between sync checkups. Any sync settings that happen too often will trash battery life.
Step 3: Radio based drain is a very big part of battery life! As such, if you do not need constant sync, you can turn off mobile data on your own when you do not need it, or go to the Mobile Network settings and disable always on mobile data. This can greatly increase battery life, but at the expense of sync not working when mobile data is off.
Step 4: Display brightness can greatly affect the power drain of the battery! You can either manually control the brightness, download Lux autobrightness to make your own autobrightness settings, or flash a custom autobrightness setting in the ROM in order to achieve this. It also can have the side effect of making the display of the right brightness when in the sun and in the dark, so it is always at ideal brightness to preserve battery.
Step 5: Make sure that the battery is calibrated. This is not very complicated. Download currentwidget from the market, put it on a homescreen. Charge the device until currentwidget indicates 0 mA charge. Use the phone until the phone shuts off. You might want to then go to hboot and drain the battery until it shuts off again, and then do a full charge again. Only do this once every 2-3 months, because this is bad for the battery.
Step 6: Adblocking! One big cause of battery drain and unnecessary network usage is downloading ads. If rooted, use Adaway and Adblock to block ads from ever being downloaded, and use Adaway's adware feature to detect and remove apps with adware!
Step 7: A radical step is to use Core Control or something similar to either underclock, undervolt, or just shut off cores. Undervolting is always highly suggested, as it will help reduce heat and give the phone a longer lifetime, but underclocking and shutting off cores will reduce performance!
Step 8: Custom ROMs and kernel experimentation might yield just a bit more in the way of battery life, and also give much more customization and features.
After this, you have likely topped out all that can be reasonably done to extend battery life. If you find that your battery drain is still poor, perhaps you have a defective battery, or maybe even a defective device (Highly unlikely, but who knows...). It is also possible that you simply have a use case that is much more than the phone can accomplish, in which case you can either use a battery case, or an external battery to charge the phone on the go.