For many people, the EVO is an excellent phone, but extremely weak battery life is a huge detractor. Now, however, always-helpful user Pingpongboss has posted some instructions over at XDA-Devs for how to use the SetCPU app to significantly increase battery life. How significantly? He estimates that he could get 64 hrs with the screen off on a full charge. Pretty impressive stuff. Before and After graphs:

before CAP201007081156

The key is disabling Perflock – a bit of code by HTC that keeps the CPU running at a set speed, regardless of usage. By disabling this and setting custom profiles, the CPU can underclock when its use is lower. As Pingpongboss points out, some ROMs (such as Fresh) already do this, so if you’re running a custom ROM, check first.

His instructions:

Know what you're doing? Short version: Get latest SetCPU (version at least 2.0.0) and use Menu -> Perflock Disabler in the Main tab to enable underclocking.

Don't know what I'm talking about? Good, follow this tutorial:

  • You need to have ROOT. Unrevoked root method is confirmed to work, and so is Toast's root method. Usually I wouldn't recommend using Unrevoked, but it's just so fast to set up, and perfect for those who have no clue what ROOT means.
  • Buy SetCPU from the market, or download it from XDA forums for free. Please support the developer of this incredible app! The version must be at least 2.0.0
  • Be on the STOCK kernel. If you're on a custom kernel, chances are that perflock has already been disabled, and you won't need this tutorial to underclock. Some custom ROMs come with the stock kernel (like Fresh 0.5.3) and some don't (like Baked Snack .9.6)

Alright, got the prereqs down? Lets start this.

  1. Open SetCPU and give it root permissions as necessary. As a control, go into the Info tab and do the Long Bench a few times. You should get around 1000ms.
  2. Go to the Main tab, hit MENU, hit Perflock Disabler (read the warning!), and hit Disable Perflock Beta: May crash!
  3. It will work for a while, and then say it's successful. You can then click the X on the top right to exit the Perflock Disabler.
  4. Go into the Main tab and drag Max: all the way down to 245000 (245Mhz). Make sure the green xxx max xxx min label above the sliders show 245 for both and also disable any Profiles you've set. Go to Info tab, then hit Long Bench again. This time you'll get something ridiculous like 5000ms, meaning that the Perflock Disabler has worked!
  5. Change your settings Profile tab to something similar to my settings. You can mess around with the Battery < xx% profiles to fit your needs. Your exact Profile priorities do not matter, it's only important that some have HIGHER priority than others. On the Main tab, set Max all the way to the right (998400) and Min all the way to the left (245000), Scaling to ondemand, and check Set on Boot. Do not check Set on Boot yet if you're the super careful kind. You can check it later when you've tested that your phone isn't crashing

Hit up the source link to see the settings he uses, the questions people have had, and the answers Ping has given. He’s great about checking the thread and answering questions, so don’t hesitate to ask if you take the dive but have any issues.

[Source: XDA-Devs]

Aaron Gingrich
Aaron is a geek who has always had a passion for technology. When not working or writing, he can be found spending time with his family, playing a game, or watching a movie.

  • Nowhere

    I have used Fresh 0.5.3 ROM, stock kernal, and OverclockWidget and have exceeded 100 hrs on a single charge. This is not a standby time - the phone was actually used. I have the screen cap from the standard android battery usage if you want it for verification.

  • Robert

    Can you tell me the name of the app in the screenshots? With the battery stuff etc...

    • Aaron Gingrich

      Sure thing :) Found in the FAQ at the bottom of his post:

      "What is that cool looking battery monitoring app?
      That's SystemPanel, paid on the market. A free alternative is JuicePlotter, also on the market. Screenshots were taken with Drocap2."

      • Pigsfly

        Can you tell me a way to root HTC Evo 4g 2.3.3 (it's not a gingerbread) ?

  • David

    I got 3 days (72 hours) and a little change with 20% remaining before I decided to plug-in. That was under moderate usage (email, news, weather and facebook contacts -- not live-stream -- sync; a couple of phone calls; reading several emails on the phone; reading the news on the phone).

  • Pawel

    on my Evo 4g with latest software froyo 2.2 i get 445ms on longbench with perflock disabled and same enabled. looks like its not enabled in the stock rom.

  • Juan Walker

    i'm at 71% my battery as been last for 1 day 1 hr.I think that is awsome.