Now that I've been playing with my Android phone for some time, I'd like to share my experiences how to minimizing battery drain to maximize the phones runtime. These are roughly sorted by their impact on the energy consumption with the most energy-hungry features first.
- Reduce the backlight intensity and active-time. When lit, this is the number one energy consumer so reduce the brightness and lower the timespan until automatic turnoff. Save even more, if you manually turn off the screen earlier when you don't need it anymore by pressing the red hang-up key.
- Turn off GPS. If you don't really need it, your phone doesn't constantly need to know its exact location. Use GPS OnOff to quickly toggle the GPS status.
- Turn off WLAN. WLAN detection and connectivity is another power-hungry feature. Turn on WLAN only if you need it. Use the WiFi OnOff widget for a fast toggle in case.
- Use 2G instead of 3G network. 3G is faster, sure, but it also comes with an energy-penalty. If you don't need a fast internet connection all the time, use 2G instead. The 2G-3G OnOff widget allows a fast toggle.
- Turn off Bluetooth. Mostly only used for Bluetooth headset anyway, just activate it when you're in your car. Fast switching is available through the Bluetooth OnOff widget.
- Turn off Internet access via mobile networks completely, if you don't need it. Apndroid allows you to toggle it with just one or two clicks (depends on the version).
- Prefer audible notifications. Vibration notification drains more power than a notification sound. And a loud notification drains more than a quietly notification or no audible notification at all. Use only as much as you really need to be notified.
- Disable Auto-Sync if you don't real-time notification of emails and so on. Again, there's a one-click-widget for this, AutoSync OnOff.
- Don't leave applications running in the background when you're not using them. In general only leave those background services active which you really need.
Of course, locking down your phone with all these measures won't be the ideal solution for all of you. I don't use all of them either. Just keep it to the minimum you really need to be comfortable with your own personal usage pattern of the phone.
A great application to automate many of those tasks is Locale. It allows a lot of custom settings for many of your phones settings depending on various conditions like current location, time, battery status, etc. When setting rules for locations it always requests ultra-accurate location detection via WLAN and GPS, but I found it accurate enough for me when I left it with only GSM cell detection. To give you some ideas how it can be used for minimizing energy-drain and location customisation, here are some of my rules. Many use the apndroid-plugin for locale to shut down the network access. This is not yet on the Android market but only available in the apndroid download section.
- at-work: a time and location based rule which turns off all network access, auto-sync and makes all notifications more quiet. I've got internet access all day anyway, no need for it on the phone to use it there.
- at-university: even more strictly this one turns the phone into silent mode and locks network access and auto-sync if I'm currently studying.
- at-night: when I'm asleep it doesn't make sense to sync mails or anything. So turn off network and autosync again between 10pm and 7am to preserve some battery. In case I'm still using the phone during that time, the screen brightness is furthermore reduced during the no-sun time.
Be creative and try find conditions during your average day where you do not need certain functionality of your phone, there is almost always something where it does not make sense to have your phone synched with your online account or to get notified about anything.
Also have a look at the excellent Lifehacker article An Exhaustive Guide to Saving Your Smartphones Battery which covers also the other mobile platforms like Windows Mobile, Blackberry, Symbian, Palm Pre and iPhone and gives some more general tips.
With Android 1.6 you now also have the possibility to check the components and applications running on your phone for their energy requirements. Go to Settings->About phone->Battery Use to check the energy hogs of your phone.