I have been playing with the wonderful governors available with Cyanogenmod 10.1 coupled with the HIRO kernel. The GSAM battery app shows huge increases in estimated battery life - 15x to 20x greater. However, I found the phone would not be stable. Sometimes it would crash and reboot for no apparent reason. Often it would crash during the booting up animation.
So, I have returned to the Verizon leaked global RUU, and started playing with the few governors provided to us by HTC/Verizon.
One needs ROOT access, and there are other places to guide one through t he steps to unlock the bootloader and then to get root access.
Next one needs to download the free "Kernel Tuner" app which requires ROOT access to do anything useful.
So, basically, one clicks on "CPU" and selects:
1. For both CPUs, minimum is 192 Mhz
2. For both CPUs, maimum is 1512 Mhz
3. For both CPUs select "conservative" governor
4. go back to the main menu page
Click on "Governor" for the governor settings. I have read the following are good choices for the governor settings:
1. sampling_rate_min 200000
2. sampling_rate 200000
3. sampling_down_factor 1
4. up_threshold 80
5. down_threshhold 20 (I am experimenting with this set to 50)
6. ignore_nice_load 0
7. freq_step 5
Basically, this is what happens. The governor runs several times per second and looks at the CPU load. if the CPU usage is over 80% (up_threshold) then the CPU's Mhz is increased by 5% (freq_step). If the CPU usage is below 20% (down_threshold) then the cpu's Mhz is decreased by 5% (freq_step).
So, for example, one can slow down the moving up and down of the CPU's Mhz by changing freq_step to a lower percentage number.
I have been experimenting with raising the down_threshold, by setting it to 50. This gets the CPU's Mhz lowered earlier to save on the battery.
The risks in changing these settings is that the phone might feel slow or lagging, particularly when running a game.
The next menu item is MISC:
1. One can set the brightness of the capacitive buttons (home, menu, back, and search). Some people set it to 0% so that the buttons do not light up at all. However, I like the buttons for use when it is dark, so I just lower the brightness of the buttons to be 5 to 10%.
2. VSYNC - I have no idea what this is so I leave it OFF.
3. Color debt - 24 bit , I also leave this alone as I don't know the ramifications of changing it.
4. I/O Scheduler. I have read that row and noop are good choices; Since row is not a choice in the stock global ics ruu, I am using noop.
5. SD card Cache Size. I have read people using as high as 1024. I am leaving at 256 which I think is the default.
After exiting the Kernel Tuner program, these settings will automatically be applied every time one boots.
I am no expert in this, but if one wants longer lasting battery one needs to choose among the available governors and learn to tune them to work well with the expected phone usage.
Hope it helps some of you, since the battery life was always a major complaint among the people here.