SetCPU: Absolute Battery Maximization

Recently, author Darren Meehan covered some great ways to improve the battery life of your Android phone. Today, we’re going to take a look at the app SetCPU. You will need to have root access to your device in order to run this application.


First off, lets explore one of the most fundamental and most overlooked reason behind your 16 hour battery life: CPU Clock Rate. Some of the most popular Android phones available — such as the HTC Desire, Galaxy S, Nexus One and HTC Evo — have 1GHz CPUs. Even when the device is not under load, the CPU still sits at that speed, eating away at your battery. SetCPU sets out to address this flaw.

First Look at SetCPU

SetCPU Main Screen

SetCPU Main Screen

When you first open SetCPU it will run a test on your device to detect the CPU clock rate. It will automatically set a low of 245MHz and for some reason selected 998MHz for the upper end for me as my phone’s default is 1GHz (but I’ve since manually clocked down to 806MHz).

Scaling Options

Scaling Options

Take note of the scaling options that you have; ondemand is definitely recommended for getting the most out of your battery.


There’s a huge number of profiles that you’re able to set, using the slider, allowing you to dictate the CPU speeds as well as scaling and the priority. The handiest feature here is being able to control the speed and set an alarm based on the temperature of the CPU. To be honest, just setting your preferences in Main will be enough for most users.

Profiling Options

Profiling Options

Advanced and Info

These are the two tabs that you’ll probably never need to use and are more suited for advanced users, as the name suggests.

Advanced and Info Screens

Advanced and Info Screens

Advanced touches on very particular settings, notably the sampling rate, which is the rate, in microseconds, at which the CPU will refresh its speed. Info is information about your phone; there’s nothing that you can change in here, although you are able to benchmark and stress test your phone, but if you’re like me you might just want to read it in order to learn a thing or two about your device.

Optimize CPU Speeds

The most important part of all of this is to play around with the CPU speeds and find what works for you. On my HTC Desire, I have the maximum clock speed set to 806MHz and I have not noticed any performance decrease anywhere. My battery life has never been so good; it’s now better than when the phone was brand new about a year ago. I can easily get 30+ hours out of my battery, and if I micromanaged it I’m sure I could get 40 hours. To add some perspective, an average day to me is a load of SMS, a good hour of internet over 3G, an hour or more of music, and a couple of phone calls.


SetCPU allows you to overclock your CPU, making it run faster than its natural rate. You can do this just by dragging the slider on the main screen further across to the right. Note that this is not at all recommended and could cause damage to your device, so use this feature with extreme caution if at all. (You can see now why rooting your phone automatically voids your warranty with most manufacturers.)


If you root your phone for one reason, this is it. The extreme increase in battery life makes this app worth every cent that I paid for it. Even if you don’t want a custom ROM, but do want to get more out of your battery, this is why you should root your Android.


An application that allows you to control the clock rate of your device's processor.