Currently the problem with every handheld device is that you need to charge them full overnight. Some of the phone provides 2-3 battery life but such phone are usually large in size. Some of the OEM like Samsung has come up with Ultra Power Saving Mode but that's only useful when to extend battery life by disabling smartphone features. Something work of battery life saving from the operating system is to be done and Android has with latest Android M introduces "Doze" which is power saving function in simple words.With the introduction of Android M [now called as Android 6.0 Marshmallow officially] at Google I/O 2015 keynote, Google takes battery saver function to the next level. According to Google, Doze is the power saving function which is available in most custom ROM and in some featured apps.
The feature on smartphone will get your device in "Doze" mode which actually means sleep. Working - it will use motion detection to kill apps which are hogging battery in the background and kill them. So it just like the sleep mode or hibernation as found on computers.
Google also tested the same function on Nexus 9 tablet - one with Android M having Doze feature active and other with Android Lollipop on it. The Android M gives twice the life when compared to former Android version. Until now we have to install third-party software's to kill the apps running in the background and also to kill any instant of running processes.
Well, so far we hasn't tested out it yet as it will be only available with Android M Developer Preview which is available for Nexus 5, 6, 9 and Nexus Player with manual flashing.