[HTC Desire S] LaKraven:
UPDATE [11th September 2011]

Modified the SetCPU profiles:

Removed AC-charging Overclock (subject to temperature warnings mentioned in replies)​

Reduced some MAX values (has added 5 hours of real-world battery use and makes no noticable difference in performance)​

Added an optional < 101% profile to default the maximum clock speed to 729MHz (does not reduce performance, adds 2 hours effective runtime)​

Specified the Priority values (which I had forgotten to mention originally)​

Introduction - The Desire S Battery Problem

As a fellow Desire S owner, you no doubt agree that it is a lovely phone: sleek, thin, relatively light, feature-filled... almost everything anyone could ever want from a phone!

However...

As a fellow Desire S owner, you no doubt agree that the battery life (on the Stock Sense ROM, regardless of how strict your PWM settings) is rather pathetic.

I have two HTC Desire S phones (one for myself, one for my wife), and both of them have almost exactly the same runtime (give or take a few minutes) when run in identical test conditions... no more than 18 hours (almost all of which with the display turned off) between charges, and less than 8 hours average with light-to-moderate screen-time when in use.

Bottom line: it's rather pathetic, and unacceptable.

Thankfully, we have options now... and this guide provides you with the option I have chosen for my Desire S phones.

Introduction - The Sacrifice

HTC Sense is (to many) considered a very "pretty" GUI, with nice animated transitions, a rounded feel etc, however it comes at a price: it's a battery hog!

I have played with many Sense 2 and Sense 3 ROMs on the Desire S, all of which share the common result of dimished battery runtime...

Bottom line: The simplest way to get more battery life is to sacrifice Sense entirely!

Just to point out: HTC Sense is the only sacrifice this guide makes in the persuit of optimal battery life! Unlike other guides, this one doesn't compromise any other features, or ANY performance (in fact, I've found performance with the setup described here to be even better than the stock ROM... noticably so!)

DISCLAIMER

I cannot (and will not) be held responsible for any losses or damages resulting from your use of this guide or the materials it contains. If you brick your phone, you've done something wrong and the fault is your own.

You should follow this guide with a fully charged battery, and if possible perform all steps involving a PC from a Laptop, with your phone connected via USB to minimize the risks associated with sudden power loss on your mains supply.

Stage 1: S-OFF

Aside from a lucky few whose Desire S came with S-OFF as a factory default, most of us have S-ON handsets.

With S-ON, you cannot flash a custom ROM onto your Desire S... but fear not, as there is now a FREE (and insanely simple) way to unlock our handsets, giving us the precious S-OFF we require.

You will require the Android SDK to be installed on your system, as well as the USB drivers for the HTC Desire S (these are installed as part of HTC Sync, though you should close HTC Sync from the system tray before proceeding as the S-OFF process will refuse to run with HTC Sync running at the same time)

Head on over to http://revolutionary.io/ to download their tool. This guide presumes you are using Windows, though it should be easy enough - if you're a Linux user - to adapt this information for your Linux platform.

Once you press the link to download Revolutionary, you will notice that a form appears asking for certain information. You'll see a screenshot of this below, but before we get to that there's something you must do...

Open a Command Prompt window from the Platform-Tools directory of the Android SDK.

From that Command Prompt window, type adb devices. Presuming you have the HTC Desire S drivers installed correctly, and your handset connected to your PC via USB, you should something like this:

LEAVE THIS COMMAND PROMPT WINDOW OPEN, WE'LL NEED IT AGAIN SHORTLY

The third line of text begins with your handset's serial number.... you will need to enter this into the form on the Revolutionary website in order to generate your Beta key:

Once the Revolutionary zip file has downloaded, extract its contents into a folder on your PC (doesn't matter where, so long as you have access to that location).

Run revolutionary.exe following the instructions provided (it's a very quick and simple process... the automated portion of which shouldn't take more than 2 or 3 minutes to complete)

When it prompts you to install the Recovery mod, do it! You will need it for the next stage of this guide!

Your HTC Desire S now has S-OFF, is equipped with a version of ClockWork Recovery, and is ready to recieve the custom ROM! (All is good with the world).

Stage 2: The Custom ROM

IMPORTANT - THIS WILL FACTORY RESET YOUR PHONE (UNAVOIDABLE) SO DON'T FORGET TO BACK UP WHATEVER YOU NEED BEFORE YOU PROCEED WITH THIS GUIDE! YOU HAVE BEEN WARNED!

NOTE You will either need a spare MicroSD card, or to back up your existing MicroSD card and make it accessible to have files written to it from your PC (I use a card reader, but you can always use the USB Mass Storage feature of the phone itself to access the SD card in your phone from your PC)

The custom ROM of choice is NeoLojik's CyanogenMod 7, lovingly and paintakingly prepared especially for our HTC Desire S handsets, with quite probably the most prompt and spectactular support from NeoLojik himself.

I have chosen NeoLojik's CM7 ROM because it has proven (after exhastively testing other ROMs for the Desire S) to provide me with the very best battery performance, as well as all of the settings you will tweak as part of this guide.

Download (from the ROM's thread linked above):

The latest version of his ROM

The recommended Tiamat Kernel

The recommended version of the Google Apps package

To save time later, download The Android Market 3.1.3 APK

(You can download the APK from your phone directly after you've completed this portion of the guide, if you prefer)

Place the three ZIP files, as well as the Android Market APK, on the root folder of your MicroSD card (by "root" I mean the initial path of the SD card, which is whatever drive letter it mounts as on your Windows PC - e.g. "H:\")

Now, with your phone still connected to your PC via USB (and the SD card put back into your phone, if required), return to the Command Prompt window we used earlier and type adb reboot recovery

Now direct your attention to your phone

Once the Recovery Menu has loaded (should take about 30 seconds) we will follow some simple instructions below... but first, a few points on how to use Recovery:

Use the Volume Up and Down buttons on your handset to highlight one of the displayed options

Use the Power button to trigger the highlighted option.

wipe data/factory reset

wipe cache partition

apply update from sdcard

choose zip from sdcard

update-cm7.1.0-RC1-DesireS-Nexx-signed.zip (or whatever the ROM's filename is at your time of downloading... it will change as the ROM evolves)

apply update from sdcard

choose zip from sdcard

Tiamat_Saga-v1.1.2.zip (or whatever the filename is for the recommended Tiamat kernel at your time of downloading)

apply update from sdcard

choose zip from sdcard

gapps-gb-20110613.zip (again, filename might be slightly different for you)

Remembering with each selection to navigate to the "YES" option in the confirmation menu (this exists to prevent you from accidentally flashing the wrong file onto your phone)

Now, from your PC (or from the Recovery menu... doesn't matter which), you want to reboot your phone! To do this from the PC, you will just type adb reboot into the Command Line window we used previously.

Your phone will now boot with the new ROM (CyanogenMod), and has been factory reset (so you'll have to run through the first-run configuration wizard).

NOTE: Don't be scared if (after the boot animation disappears) the screen remains black for a minute or so! The first boot of the new ROM (especially with the Tiamat Kernel) does take a bit longer than every subsequent boot there-after. Just give the phone a few minutes, and press the Power button. You SHOULD see the Lock screen once the device is ready!

Run through the first-run wizard following instructions provided (fairly strait forward), though keep in mind that (at the time of writing) the wizard does not prompt for a WiFi connection until AFTER it attempts to log in to your Google account! Fear not, though, as when it fails to connect to your Google account (presuming you don't have Mobile Data available to you), it'll then prompt for a WiFi network and repeat the Google account login afterwards.

Once you have completed the first run config, open the "File Manager" app included as part of the ROM.

Navigate to /sdcard and run the com.android.vending-3.1.3.apk file. You'll be prompted to allow unknown sources, you want to tick that box and click on the APK again.

Once you've installed this, you will be running the latest (and greatest) version of Android Market, which (amongst other things) enables you to use a different Google account for your Apps (very useful if you want to install your paid applications on your wife's phone, as I have)

Welcome to CyanogenMod!....

Stage 3: Battery-saving Mega Settings [Menu-by-Menu]

The Settings I'm providing you here are the results of countless hours of experimentation (as well as logic and common sense). They have proven to provide the best degree of battery runtime with absolutely no performance or feature sacrifice!

If a menu or entry within a menu isn't mentioned, it's because it has no bearing on power saving!

Wireless & networks

Wi-Fi settings

Network notification = OFF

Press the Menu button, then Advanced

Wi-Fi sleep policy = NEVER​

Call settings

Vibrate on answer = OFF

Vibrate every 45 seconds = OFF

Vibrate on hangup = OFF (NOTE: I leave this ON as my one concession as it's the only way you will know if a call drops out on you unexpectedly!)

Vibrate call waiting = OFF

Always use proximity = OFF

Enable sensor rotation = OFF

Voicemail notifications = ON (it doesn't save power, but seriously... you want it on!)​

CyanogenMod settings

Display

Automatic backlight

Light sensor filter > Enabled = OFF (If enabled, unnecessarily drains more battery life! The feature itself is pointless as there is no difference to the UX with it Enabled or Disabled!)​

Light levels

Use custom = ON

Screen dim level = 14

Allow light decrease = ON

Edit other levels...

This is what I consider to be the most optimal set of levels:

Lower | Screen | Buttons

0 | 21 | 2

160 | 31 | 2

255 | 35 | 2

320 | 40 | 0

640 | 50 | 0

1280 | 75 | 0

2600 | 90 | 0

5800 | 130 | 0

8000 | 200 | 0

10000 | 255 | 0

Press Save & apply (scroll to the top to find the button)

NOTE: You may want to play around with some of the values in this table, as screen brightness is not a "one size fits all" affair, and what I can see clearly might not be so clear for you (or vice-versa). Basically, use those levels as a starting point, and tweak them from there until you find the best settings for you in various lighting conditions.

I will say this, you don't want to set the Buttons value above 0 if you can see the buttons even faintly at a given light level. The backlighting for the buttons is a surprising battery drain (it's calculated as part of the Screen's power consumption in the Battery Usage menu). Bottom line: if you don't need any lighting on the hardware buttons in order to use them even in pitch blackness, then set the value of Buttons for each set in the table to 0 and squeeze more life out of your battery!
​

Performance (press OK when the warning is displayed)

CPU settings

Available governors = SMARTASS ("SMARTASS" has been designed specifically [and brilliantly] to scale the CPU frequency with such a perfect balance of performance-on-demand versus power saving... it's the perfect choice!)

Min CPU frequency = 192

Max CPU frequency = 1036 (We'll be using SetCPU [full version, bought from the Market] to set up some magical CPU profiles later in this guide, saving us LOTS more battery life!)

Set on boot = ON​

Sound

Haptic feedback = OFF (Remember: The phone's vibrator consumes more power than playing a beep or other short tone through the speaker at even the highest volume!)​

Accounts and sync

Auto-sync = OFF (Auto-sync being disabled saves both battery power, as well as bandwidth on your Mobile Data tarif [2G and/or 3G dependant on carrier]. Really, you should just "sync on demand" as and when you want/need to!)​

This concludes the Settings portion of the guide!

Stage 4: SetCPU (for ROOT users) configuration

SetCPU for ROOT Users is available for on the Android Market for just £1.25 (or $1.99 USD). Not only does this program enable you to overclock/underclock your phone's CPU, but more importantly it enables you to provide Profiles, to scale the CPU based on the operational status of your phone.

This is well worth the infintismal pricetag, as the potential power savings (at no performance cost) is more than significant!

Open SetCPU, go to the Profiles tab:

Enable = ON

Notifications = ON (Really this is up to you! I like to have notifications for when the profile is changing to ensure that the CPU is scaling properly, and to ensure that my profiles are the best they can be for performance/battery balance)

Add Profile

Profile = Charging AC

Max = 1036800 (Potentially, you could set it up to 2GHz, but I have stability (and heat) concerns, and I can't possibly see any circumstance where 2GHz would be remotely useful! If you do elect to overclock (particularly whilst charging), you will need to add a profile (with 100% priority) to drop the Max value if the temperature exceeds 45 C)

Min = 192000

Scaling = smartass

Press Save​

Add Profile

Profile = Charging USB

Max = 1036800 (Basically 1GHz [original] CPU clock. We don't want to bleed into the minimal input of power provided by USB, so this is the best setting to use)

Min = 192000

Scaling = smartass

Press Save​

Add Profile

Profile = Battery <

Battery < = 75%

Max = 652800

Min = 192000

Scaling = smartass

Press Save​

Add Profile

Profile = Battery <

Battery < = 50%

Max = 576000

Min = 192000

Scaling = smartass

Press Save​

B]Add Profile[/B]

Profile = Battery <

Battery < = 30%

Max = 422400

Min = 192000

Scaling = smartass

Priority = 80

Press Save​

Add Profile

Profile = Screen Off

Max = 345600

Min = 192000

Scaling = smartass

Priority = 60

Press Save​

Add Profile

Profile = Time

Time = 01:00 - 08:00 (NOTE: Substitute the given range with whatever your daily sleeping hours are!)

Max = 345600

Min = 192000

Scaling = smartass

Priority = 70

Press Save​

The following profile is optional... and (if used) would specify your default clock speed

Add Profile

Profile = Battery <

Battery < = 101%

Max = 729600

Min = 192000

Scaling = smartass

Press Save​

Feel free to experiment with other profiles as well! Perhaps you may want to procedurally reduce your CPU speed based on Battery % in a more gentle way... this is certainly possible, and would squeeze even more life out of your battery.

You should also feel free to use lower MAX values for each setting (I would strongly advise against higher values) if you feel that the lower clock speed makes little-to-no noticable difference in performance as you use your phone.

Personally, I notice no difference between 729600 and 1038600!
​

Stage 4: Recalibrating your Battery

Install the Battery Calibration app (FREE on the Android Market).

If your phone isn't charged, charge it up so that it is showing 100% (with the Green LED lit).

Run Battery Calibration and press the Battery Calibration button. Immediately unplug the power/USB cable from your phone, and allow it to run (as normal) until fully discharged.

Once the phone has switched itself off, plug it into the AC cable (using the mains charger).... and LEAVE YOUR PHONE SWITCHED OFF until the LED indicator is lit green!

You may want to repeat the discharge/recharge cycle one or two more times (as many people claim that this provides a better calibration)... though really that just entails running your phone on the battery until it is fully discharged, then allowing it (whilst switched off) to fully recharge on the mains adapter (AC)... which is not what most people would normally do as a routine.

Potential Stage 5: Tasker

Tasker (£3.99 on the Android Market) enables you to create profiles which automatically change various settings based on one or more given criteria. This even includes the ability to switch on and off features of your phone such as WiFi, Bluetooth, GPS, GSM, Mobile Data and Airplane Mode.

By creating suitable Tasker profiles, you can squeeze even more battery life out of your phone!

If it's of benefit to people (let me know in the comments) I can expand this guide to include step-by-step instructions on creating the various profiles I would recommend in order to squeeze more battery runtime out of your phone without sacrifising features/functionality.

General Battery Storage/Maintenance Advice (Applies to all Lithium-Ion Batteries, including those used in Laptops)

To prolong the operational lifespan of your battery, you should not really allow your battery to run for very long below 50% charge, as "topping up" a half-charged battery generates less wear and tear on the battery, prolonging its overall lifespan.

NEVER leave your phone fully discharged for more than an hour, or the LiIon cells will begin to degrade, meaning your battery will never be able to physically hold as much charge. Indeed, the longer you leave a discharged battery, the less overall capacity your battery will retain.

NEVER store your battery (even if the phone is running at the time) in cold conditions! As a general rule of thumb, if it's "a little chilly" for you, it's unhealthy for the battery!

Both of the above tips form respectively the Number 1 and 2 causes of battery death! Don't let your battery become another statistic!

If - like me - you have one or more "spare batteries", you will likely be tempted to store them when they are fully charged (100%). This sounds like a good thing to do, but actually it can have (to a slightly lesser degree) the same damaging effect on the battery as leaving it fully discharged for any prolonged period of time!

The absolute best level of charge at which you should store a battery is at 50%, or as close there-to as possible!

Dependant on how often you find yourself recharging your battery, you should recalibrate it between every 3 to 6 months (the more often you discharge/recharge, the less often you should recalibrate).

Also, you should ALWAYS recalibrate after having flashed a new (or updated) ROM and/or Kernel!

My results using the exact configuration [excluding Tasker] detailed in this guide...

As I stated above, with the way I use my Desire S, I was lucky to get 8 hours of what I would call "light-to-moderate" use whilst running on the battery!

With the configuration detailed in this guide, I have now had a successful "100% to discharged" usage of 46 hours (under the exact same usage conditions as when I was using the stock ROM factory-installed on the phone (and updated OTA ~ a week ago).

This is a VERY significant improvement, though I must stress that results will vary heavily based on how much (or what) software you're running on the phone, how often you're interacting with it, how long you spend in calls etc.

Basically, every phone is different, and every operator (me, you, everyone) is different.

Please also keep in mind that your phone won't "settle in" to the new settings in terms of battery runtime until you've done 2 or 3 discharge/recharge cycles (as explained in the Battery Calibration portion of this guide)

Conclusion

There are plenty of third-party ROMs out there, and (obviously) I can't physically test them all! I have tested what I believe anyone would consider to be a perfectly suitable number (more than a dozen now), and have found the exact combination detailed in this guide to provide the very best battery runtime for me.

I understand that some of you will likely have your own ROM preference (for various reasons), but I hope that at least some sections of this guide will be useful to you.

If you just want to get the very best battery performance out of your Desire S, and either don't particularly care what ROM you use, or (like me) happen to love Cyanogen anyway... this guide will fit you like a glove!

Need any more advice?

No problem... post your comments and questions as a reply to this guide, and I'll answer anything I can, as promptly as possible (please consider that I have a company to run, and a life beyond the Internet... so replies might not always be "instant")

I hope you like this guide, and more importantly... I hope you enjoy your new-found battery runtime!