Extending battery life on X200
I own the beautiful Lenovo X200 and run Ubuntu Intrepid on the machine. Its battery life is significantly lower than that under Windows and many users have reported that it runs hotter than under Windows.
With the changes below and a 9 cell battery I get over 9 hours on an idle system with backlight on but at the lowest level. Before the changes I was getting a bit over 5 hours. The system also runs a lot cooler.
The changes fall in 2 categories:
- Removing packages that create unnecessarily frequent wake up interrupts.
- These interrupts wake up the CPU, preventing it from staying in its most energy efficient state.
- I used Powertop from www.lesswatts.org for this task.
- Lowering the voltage supplied to the CPU.
- Lowering the voltage supplied to the CPU has other positive side effects beside battery life: my system runs a lot cooler and ... I do not need tpfan (sw fan control for the ThinkPad), the built-in hw controller does a great job and falls back to lower speed shortly after a CPU load subsides.
- It should be noted that this does not affect performance since the clock runs at the same speeds (22700, 22600, 16000, or 800Mhz for the X200).
- I used phc patches and phctools available at www.linux-phc.org for this task.