Battery Saving
This page aims to document "power user" techniques for extending battery life, i.e. automating various aspects of the phone's behaviour with a view to extending battery life. It is currently a stub/work in progress; the aim is not to reinvent the wheel but to draw together a variety of approaches to battery saving.
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Before you start
Do the obvious
The techniques here all involve automating the process of turning various things on or off according to the activity of the phone. Before there's any point in doing this, you'll want to have set the phone up more or less the way you like it, turned off anything you don't use, set reasonable defaults and made such optimisations as you can.
Install the relevant applications
You'll need DbusScripts and Kernel_power and you'll also want to have installed the status menu applets for manually adjusting screen brightness, radio switching, etc.
Background power saving techniques
Techniques in the "background power saving" section should have little or no negative impact on the performance or usability of the phone but should save power in the background when the phone is not actively being used.
Kernel settings
Use the Kernel for Power Users
Not just for Overclocking, the Kernel_power package helps to save battery power and makes it easy to configure the kernel. You should be using this for power saving, even if you never choose to go over the stock 600MHz.
Enable SmartReflex
Reports are mixed on SmartReflex; some users report crashes, while others use it with no problems and report improved battery life. There seems to be general concensus that it limits overclocking to 805 MHz and causes crashes in combination with overclocking above that figure. The author uses SmartReflex on VDD1 and VDD2 without problems, but does not overclock above 805MHz.
Actions on phone lock/unlock
One of the simplest uses of DbusScripts is to detect when the phone is locked or unlocked and run scripts to reduce the cpu frequency, system load, etc.
Suspend user processes
See Xagoln's post: http://talk.maemo.org/showpost.php?p=1005668&postcount=1
Change kernel powersave bias
Over on the Overclocking page, Fecn describes a set of scripts to modify the Kernel_power settings on phone lock/unlock.
Change radio mode (non-invasively)
Invasive power saving
Techniques in the "invasive power saving" section save power by intentionally limiting the activity and/or functionality of the phone. This can have unintended consequences, so be sure you understand what you are instructing the phone to do before you do it.