What determines power management policies in Android?
Power management is determined by governors which set the CPU clock speed according to use. Each clock speed operates at a certain voltage and a lower voltage means less power. If you have root access you can change the governor and the allowed CPU clock speeds. Also there is sleep state into which the CPU will enter when the screen is off and nothing is working in the background. There are probably battery-charging functions that can't be messed with, but everything else can be changed even the cpu and dsp voltages.