[Samsung Epic 4G Touch] Dudebowski:
A bit dated of a post, but most if not all still relevant. We have a lot of non-TW ROMs for this phone which sacrifice battery life for improved functionality, not by choice, but mainly because Samsung's lack of GPL compliance with regards to sharing kernel sources. Our community devs have done an incredible amount of work with their kernel forks, but Samsung's paid development teams obviously have a lot more time and incentive to work on it, and as such our community devs' graciously find even more fixes once source drops, then merge them into the community kernels we're all using. So as we wait in limbo for them to share their JB kernel contributions to our community:

Anyone that wants to add anything to the list, post to the thread and I'll keep collecting.

Workarounds for D710 battery drainers:

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battery saver scripts:rmikulus found this sweet piece of development gold: if you know how to run scripts,"Die Hard Battery Calibrator" will calibrate your battery in only about 20 minutes (must be plugged in that entire time)

Probably better to use the latest and greatest here instead, much easier to install, just a simple CWM zip AIO scripts:

Jelly Bean Tweak Pack for Epic 4G Touch Fixes Various Errors

--appears to help battery life and other various issues.

Voodoo LOUDER (paid) supercurio - Project Voodoo

--not battery-related, probably causing opposite effect actually, but many find an issue with headphone audio being maxed out at lower dB than desired. I'll confirm this works on CM10 nightlies.

WiFi : Turn it off when not in use, just like anything else. Tasker does a great job of automating this process.

raise the network scan interval to reduce background wifi radio usage (Rom Toolbox allows build.prop tweaks such as this,)

change the sleep policy for the wifi to Never While Charging to allow wifi connection to die when phone is off (toggle is in the touchkey menu while viewing wifi settings.)

NOTE: WiFi is a more desirable data connection than 4G as far as batt life is concerned. 4G is auto disabled when wifi is on for most ROMs. 4G (WiMax) is a new technology that still has yet to be perfected, not unlike these latest developments in ICS.

4G Radio: Also turn off when not in use. Use the latest modems available. Note that modems won'tt install from ODIN/mODIN flashes, gotta use CWM zip installs.

Haptic Feedback: Turn off haptic feedback, vibration kills. (Particular to CM9 ROM, haptic is set too strong right now, TouchWiz-based ROMs are fine, but if you can live w/o it...)

LED notifications: Another wakelock offender. Turn them off for now, it's one of the reasons the device stays awake when it should be sleeping. Sleep is good.

Get BetterBattery Stats by chamonix : Take a look at it after a long period of uptime without restarting (quick or full) to allow a greater set of data to parse into stats. Some apps you use may be eating away at your battery from the background. Spare Parts Plus and it's root-friendly brother BladeBuddy is also valuable.

Use the latest kernels available. If you're flashing CM nightlies, you're good to go, kernel modifications are updated in the same process.

Touch sounds and screen lock sound: These still cause partial wakelocks , leading to some amount of battery drain. System Settings>Sound menu to turn these off for now. (thx coiledwire)

The CM9 Team put together a similar list with a few things not listed here. Check the 'Power Saving Options' section on the CM9 Blog

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Android-specific:​

BatteryStats.Bin This little file keeps a record of your battery usage, power amperage, etc. and every time you flash a rom, it gets wiped. The system's ability to track the exact power level of your battery is DIRECTLY dependent on this file, so if you don't allow the newly flashed system a few days to calculate averages over time, it won't really have time to realize how charged it really is. NOTE: this file has NOTHING to do with improving battery life, only calculating what the battery % shows in the statusbar (and in the battery statistics charts in the system settings menus.) I've sat at 5% battery life for an entire hour with screen on surfing the 'net. No way it was really 5% that entire time.

While wiping battery stats won't increase battery life, it will improve the calculation of the charge, if done properly. Stats are saved in /data, when a ROM is installed, initially the stats will not have much data to extrapolate from, and the battery probably isn't entirely full to begin with, therefore making a mess of a new ROM's recognition of the cell's true charge. It's best to wipe stats when your charge is above 4180mV (E4GT stock battery size.) I've seen mine as high as 4202mV. Also, if you've got aftermarket cells that aren't the same mAH rating, the results will be slightly wonky. Battery Calibration app can set a reminder to flush the battery stat counter file when the phone is charged, if you need to charge with your device on.

I notice that flashing roms with a battery @100% and charging will help in this regard, then once the system is fully booted, unplug it and drain it to 15%, then charge to 100%, then do :

Bump Charging is suggested by HTC developers to potentially DOUBLE your battery life.

Battery Tuning: We're running Lithium Ion batteries. Don't kill it to 0%. Ever. Tip: Condition your new cell phone’s battery to make it last longer (but be sure to condition it properly)

Live Wallpapers and other background services: If you can live without them, turn off the services. Many common apps trigger network connections on a periodic schedule, further causing drain. increase sync periods, or just sync manually.

Sync: Yet another form of background services. If your sync is running all the time from frequent emails, gvoice msgs. etc... and the like, try turning off some of your heavier data tranx and refreshing manually when you need it.

Again, please tack on posts for this thread if you have good additions to make, I'm just trying to collect a one-stop shop of battery life savers, and a place to point newbs when they start trainwrecking dev threads with questions about it. This is my humble way of giving back cuz I was one at one point.