Any time a new Android user come on board always complains about battery life, such a noob will start asking how to squeeze more juice from his battery, and this is the point where numerous android battery savers come in to play.
What is Battery Saver?
From my own understanding, battery saver is an app that controls the device hardware and software power consumptions.
So what do power saver actually do?
From experience, after using several power savers, these apps tends to lower display brightness, switch wifi, data, bluetooth, gps, engage and disengage Airplane mode and finally some kills background apps and lower CPU clock.
Does these Apps work or not?
Well, Yes and No. Yes in the sense that if a user prefers things automatically and lazy, for example, leaving bluetooth, gps and wifi on, may drain battery quick. No in the sense that, if a can manage all these toggles from the quick action bar provided in android, then there is no need
Why I consider all these apps to cause more harm than good except on application?
All these battery savers runs constantly in device memory when the device is up, eating RAM and consuming CPU cycles, draining battery life in the process. All the toggles they do can be achieved by dragging the notification bar. The killing apps consume more juice because once application is killed, the process will restart shortly, there by consuming cpu cycles, and in the process preventing the cpu from idling and starting the extra frozen cores. Android is built to manage resources in its core, so no need to alter.
Power saver that actually works is Greenify?
This app hibernates all greenfied apps, just like iOS handle apps, so your ram and cpu cycles are safe.

Defaramade: I use dx battery saver & yes it does help to save some juice but its efficiency depends on the user. Though ba3 savers won't extend a phone's ba3 life but they help to maximize the ba3 usage with some little manual tweaking & they also come with extra features which are really really useful.

Yeah. It's true. They cannot extend but help maximize if one cannot do it manually. I use dxtool box for other useful features

Working perfectly

Juice defender

DS battery saver

D ONLY BATTERY SAVER I CAN VOUCH FOR Z SNAKE BATTERY BOOSTER ,ONLY ISH WITH D APP Z D BIG NUMBER BATTERY ICON AT D TOP OF D SCREEN,HATE ANYAPP DAT REMINDS ME I AM GETTING LOW ON JUICE,65% NOW CHECK IT AGAIN ,IT'S NOW 62% WETIN DO 63 N 64.

seriously, no battery saver is working. Only if you are lazy as the op suggested. Why would anyone leave Bluetooth and GPS and other apps on?

To me, battery savers makes little or no difference.

It doesn't work! My battery life improved greatly after I uninstalled the battery saver.

OCTAVO: It doesn't work! My battery life improved greatly after I installed the battery saver.

optician calls

^^Corrected.

Android battery saver app are working perfectly.. U can even add up extra 50% to normal battery.. Life span and others.. I also made list of 5 best android battery saver apps... And they're working perfectly.

The best battery savers for me personally works better on rooted devices, greenify and power nap with Xposed framework.. My battery stats improved immensely since i installed these two apps, although power nap is buggy and still on experimental stage..