Turn on Power Saving in settings
It might seem that this should have been at the top, but I don't find it to be all that useful. Throttling the CPU makes the phone run slower and use less battery. Some people report it helps, some say it doesn’t do much. Some complain it makes the phone perform very poorly. I don't find it saves a lot of power, and does impact performance, but this probably depends a lot on how you use the device, so give it a try and see. If you know you're going to be away from a charger for a long time, turning this on may help you get through the day. The option to reduce the screen brightness and frame rate is also a tradeoff. I find this often makes the screen too dim to use comfortably, and the reduced frame rate will impact any animations and transitions. Again, though, if you know you're going to need to make your battery last as long as possible, this can help. Give it a try and see how it impacts what you do.Ultra Power Saving mode on the Galaxy S5 will, indeed, make a huge difference in your battery life, but will also have a huge impact on the usefulness of your phone. This should be viewed as an emergency measure, not as a routine way to improve battery life.Turn all radios off except when you want to check something You’ll find a lot of apps in the Play Store that purport to improve battery life. Some actually work, but generally at the trade-off of functionality. And you can do most of these things manually, but an app makes it easier. For the most part, they work in similar ways, by limiting the on-time and usage of the radios. If you turn off WiFi and Mobile data, and only turn them on a few times a day to check and see if you got any email, check your sports scores, or whatever, you’ll get much better battery life. I didn’t buy a smart phone to turn it into a dumb one, but if battery life is more important to you than connectivity this is a big one. You can automate this process with certain apps.
Juice Defender lets you schedule when the radios are turned on, so you can keep them off most of the time, saving battery, and turn them on briefly once an hour, for example, to let everything that’s been waiting to sync catch up. 2X Battery is a similar app. Snapdragon Battery Guru is similar, but claims to learn the best way to control syncing based on your usage patterns. There are dozens more. (But watch out for those that claim to improve battery life by stopping background processes. That’s almost never a good idea.)
These apps can make a big difference if you have weak signals and if you don’t care about being connected all the time. But when your wife / girlfriend / mother emails you that she’s headed to the hospital with chest pain, and you don’t get the email until 2 hours later because all your data was turned off, you may wish your priorities had been different. Yes, that’s an extreme example. I’m just making the point that there’s a trade-off between real-time access to data and battery life. Everyone has to make up their own mind how to balance that trade-off.Avoid Ad-Supported AppsI debated whether to include this in Parts one and two, or here in part three. You could argue this has no impact on functionality, but many apps exist only in ad-supported versions, so following this suggestion will both cost you money (to buy apps without ads) and limit the apps available to you.Why do ad-supported apps affect battery life? Because these apps repeatedly sync with an ad server off in the cloud and download the ad data to your phone. How much of an impact this is will depend on how frequently you use the app, how often is shows ads, and whether the ads are just a couple of lines of text or a full screen video.Don't run power hungry appsThis is really much less of an issue that it used to be. Android is much better at controlling apps that do background processing, and app developers have gotten better about coding their apps. Android L will hep even more by giving developers more ways to minimize power use. But you'll still occasionally run into an app that's a real battery hog. You can see what apps are using the most battery by going to Settings / Battery on your device, and scrolling through the apps listed. If there's an app you don't use very much that's using a significant amount of battery, you may want to look for an alternative.If it's a built-in app, you can use the application manager to disable the app, so it won't run anymore.Internet Myths / Things Not To Do
(Do Not) Use Task KillersAnd do not use the task killing function of battery saver apps that control the radios, as above. These are likely to cause more harm than good, both in terms of battery life and system stability. The theory is that apps running in the background use up battery, so you should kill those apps. The reality is that Google knows what it's doing, and you shouldn't mess with how it manages memory and applications. If you want to know why, read on:
Android is a multi-tasking OS. It's designed to have apps in the background. The only "wasted" RAM is empty RAM. Your running apps will use only as much memory as they need. Having a bunch of "extra" RAM won't make them use more or run faster. "Empty" RAM doesn't save battery; every bit of every byte of RAM in the phone is constantly refreshed whether it's "used" or not. Here's how Android works: When you switch away from an app, that app will continue to run in the background only if it's actually doing something. For example, if you start downloading a large web page, or a video, and then switch away, the download will continue to run. When the download is done, the program will remain in memory in an inactive state. Apps that don't need to do background processing, like like Camera, or a File Manager, or Docs To Go, just sit there, using no CPU and no battery until called upon by the system, or by you, to do something. Why does Android keep them in memory? Because it's likely that if you recently used an app or a service, you will use it again soon. If it's in memory, the OS can simply request it to redraw it's screen. If you've killed it, the OS needs to copy the program from storage (ROM) back into RAM, start it up, wait for it to allocate any resources it needs, and then redraw the screen. That takes longer, and uses more battery than if you had just let it sit in memory. If you start a new app that needs the memory an inactive app is using, Android flags that app as no longer resident, and allocates the memory to the new app.
The other thing to understand is that most apps in memory aren't really "running." They're in an inactive state, using no cpu, and no more battery than "empty" RAM.
The problem with task killers is twofold: Android doesn't know what they do, so it will assume an app is still in RAM when it may not be; and they tend to kill processes that Android needs to run. Google spent thousands of man hours making Android manage memory and applications effectively and efficiently. No guy coding in his basement and giving his app away for free, or charging a couple of bucks for it, is likely to do better than Google.
These apps simply are not necessary. Let Android do what it was designed to do. Your phone, and you, will be a lot happier.
(Don't bother with) Wipe Battery StatsThis has been thoroughly debunked by Google. The battery stats file simply records information. It has no impact on actual battery life at all.
(Don't worry about) Live Wallpaper
If you truly want every last milliamp out of your battery, then don't use live wallpapers. But these only use power when they're actively displayed. If the screen is off, or another app has control of the screen, live wallpaper has no impact. Unless you keep your screen on and stare at your wallpaper, these won't make much difference. (There is some disagreement about this, but I have yet to see LWP show up as a significant user of CPU or battery, and I've run cpu monitors to see what's happening.)(Don't worry too much about) WidgetsYes, many widgets do background syncing to get updates. And if you've got 20 widgets updating every 5 minutes you'd better buy a extra battery or two. But almost every widget lets you control how often that background sync happens. A weather widget syncing once an hour isn't going to use a lot of power. A sports widget updating every 5 minutes just might. The key here isn't to avoid widgets, it's to control how often they sync, and not go crazy with them. (Don't bother to) Turn off notifications This is a tricky one. It's not the notification that uses up power, it's the fact that an app is running in the background, and periodically checking for information (using the radios) that uses power. There's just enough truth in this to keep it alive, but let's be clear about what this can and can't accomplish.Turning off notifications in your email app, for example, won't accomplish anything. Your email still syncs, which is where the power usage is, it just won't tell you. That's not particularly helpful. If you want your email app to use less power, you need to change the sync settings, not the notification settings. The same is true for any app that lets you control background syncing or communication. But if you have an app that generates frequent notifications but gives you no way to control background syncing or communications, turning off notifications MAY reduce the power utilization of that app. It probably won't, because you're probably not stopping background processing at all. You're probably just preventing the app from telling you what it's doing. There's no easy way to know, so if you have this kind of app, feel free to turn off notifications and see what happens. You can turn notifications off in the Application Manager.