Android apps to save battery

Greenify

Initially created for rooted Android devices, Greenify helps extend battery life by automating the hibernation process, which keeps your apps from launching new background processes and sipping at that precious battery. In other words, Greenify puts misbehaving and otherwise thirsty apps to sleep without outright disabling or force closing them.

With Greenify, users can handpick which apps aren't always that important and have the phone put them to sleep.
Greenify puts your apps to sleep but doesn't kill them.

Go Battery Saver & Power Widget

Designed by the Go Dev Team, this one is as gorgeous as it is flexible. A simple tap of the screen lets you toggle preset modes, making it easy to go from reading and relaxing to online gaming. For those who don't like the standard modes, there are two other slots available for creating custom experiences.

Go Battery Saver & Power Widget keeps an eye on your apps to determine which are eating up battery more than others. By assigning a score to your battery, the app is able to determine which features you can enable or disable to extend its life. Tapping the optimize button, in essence, cleans up unnecessary, resource-sucking processes and tacks on some extra expected life. Doing this alone can provide an extra hour or more.

The app provides quick access to a number of settings with two home screen widgets. A number of skins or themes are available for Go Dev's own widgets, and you can also adjust how items appear in the notification bar.overall it was a good battery saving app.

Tasker

Tasker is the one that provides more than just battery extension and task-killing.
it allows to set times for sleeping and disabling of connections.

Tasker provides users with various automation options. Automate everything on phone. It is a paid app.

DU Battery Saver

The android power saver. Du battery saver is the simplest and easiest to keep your android phone working well. It protects against poor charging.

It features are fast battery saver, simple battery saver and many battery saver features.