[Galaxy S III I9305 (4G LTE + 2GB RAM) Q&A, Help & ] Oswald Boelcke:
Reports about Battery Life or Endurance

If you observe abnormal battery performance, duration or life from your point of view, please take and check battery statistics yourself!

Please do NOT post anything beforehand (e.g. in the Q&A thread)!

From my personal point of view, a recommendable application to check battery stats is “BetterBatteryStats” but there a lot of similiar apps available. The OP of “BetterBatteryStats” provides you with good information about wakelocks and battery life in general, too.

Take your stats for some hours or even better a few days (and nights). Try to figure out if wakelocks persist that are triggered by apps or processes. If you are able to identify e.g. such an app, try first yourself if the issue gets fixed by de-installation of such an app. Think about getting in touch with the app's developer.

ONLY if it’s finally ROM or kernel related, post in Q&A section or dev section but observe these prerequisites:

Battery stats screenshots, AND logs, AND as many details as possible.

Good battery endurance paired with a "smooth" system behaviour seems to be priority number one for everybody for obvious reasons. However, regularly nobody clearly defines what a good battery endurance or life means. Is it the 24+ hrs, which satisfies the one, but 16 hrs already the other? Discussions about the battery seem to continue just knowing the type of device and probably the ROM but ignore the overall system and especially personal behaviour and preferences of the device's owner.

Besides ROM and kernel, a lot of different things are obviously effecting the battery:

How do you use your phone? Heavy load gaming? Screen permanently on while staring on "grimacebook" or "whogivesa..."?

What are the application running on the device, and which have permission for auto-start at boot or to stay awake? Which and how many applications do run in the background, and are eating fuel?

Age, capacity, and type of the battery.

Mobile data always ON or not.

WiFi always ON or not.

Cell network coverage and reception.

Screen brightness level.

Abnormal wakelocks triggered by crappy apps.

etc. etc. etc.

Prior to a decision for a specific tariff plan, analysis of the consumer behaviour in regard to number, duration, network of calls, text messages, and data consumption is desired. In turn, evaluation of battery life appears to require a similar approach by assessing the topics stated in the list above. Literally, at least I personally deem to be unable to advice anybody else but me how good battery life is or how to improve it.

It's somehow useless for different users to compare or ask for battery life between ROMs / Kernels since we all have different behaviours, different ways to configure the phone, and different apps installed.

For completeness, I'd like to mention there're multiple applications and Xposed modules around, which are supposed to extend endurance of a battery, e.g. Greenify, Amplify, or Power Nap in order just to mention a few. A web search might drag you to the ones that are best suited to you, and you always need to evaluate for yourself if they serve the advertised purpose and your requirements. Be also aware that some of them require the Xposed framework to function or for full functionality. Some guides are linked at post#3. If interested in privacy I suggest to thoroughly read the reviews of the respective tool, have its point or country of origin in mind, and search the web. Nearly all are requesting root privileges and/or use the Xposed framework i.e. are going to have more or less unlimited access to your device. Good news are many of them are open source, and at least the ones I mentioned above don't require access to the internet to function. I'd personally ensure that they mustn't pass the firewall (e.g. AFWall+ by @ukanth or NetGuard by Marcel Bokhorst (@M66B).

(edited with the help of and thanks to @Wood Man):good:

EDIT (2016-10-11): In this thread, I tried to explain how I did enhance the battery duration of my SGS 3 LTE (GT-I9305); however, maybe it's also suitable to other devices (I'm convinced it is).