Unfortunately I can’t give to you any magic potion to improve the N9’s battery life, but just suggest some little hint that makes my device to survive to my daily usage; some of of them are obvious, I hope they will be useful though.
Have a good network coverage
Quite obvious, but frequent 2G/3G switches make the battery to drain faster. If you have a weak 3G coverage, lock the device to GSM connection. An handy app that allows you to do that easily is 2G3G.
I always keep brightness low, letting the brightness sensor adjusts it, sun readability of the N9’s CBD is great anyway. You can add a brightness slider to your status bar from the QTweak T mod. I’ve also setted the display timeout down to 15 seconds and disabled the Standby screen; it’s cool, but since I’ve installed LED notifications (another tweak from QTweak), I don’t need it anymore.
Audio and vibration
You can turn the display vibration off if you feel comfortable without it. Furthermore, you can set both system and display tones down to Level 1.
My N9 checks for any Twitter and Facebook update every 1 hour.
Unless you are a die hard mobile businessman, you can stand with a checking per hour. Both my MfE and Gmail accounts check my stuff every 2 hours from Monday to Friday, from 9am to 5pm.
If you don’t use this Nokia beta app, uninstall it straightaway. Even if I disabled all push notifications, it blew my battery out, with an unbelievable 84mA idle consumption.
Turn the Wifi search off
MeeGo scans Wifi connections every 5 minutes. Even if the battery consumption is neglectable, I’ve prefered to switch the Wifi search off. Unfortunately you can’t do this within your settings, the only way is to download and install ToggleWlanScan, that lets you switch on and off the setting quickly.
Change SmartSearch priority
SmartSearch indexes all your media content to be searchable within the Search app. Changing its priority won’t disable it (which I don’t recommend, because universal search is useful all in all), but just optimize your battery and CPU consumption. You can easily apply it via QTweak KK option. Just open QTweak and then type KK > 7 > 1 and reboot your phone when prompted.
Maybe it’s only a placebo, but since I installed this mod on my N9, not only the device feels smoother, but also the battery looks to last slightly longer. Guess where you can find it? In the every good N9 owner toolbox, QTweak.
Change your theme
N9 came with a beautiful AMOLED screen. AMOLEDs are well-know to consume less with black background and, since I love both AMOLEDs and plain black UIs, it was a quite obvious step for me. All you need to do is download and install ThemeSettings and ColorThemes ColorThemesInverted. Then go to Settings > Device > Themes; I’ve installed the BlackAndWhite, but you, of course, can pick any accent you want. This is the result:
I’m feeling comfortable with all of those tricks. Let me know which of them suit you and please don’t hesitate to share yours.