To save more battery power for your device, try any of the following tips:
Activate Power Saver
Enable Smart saving and select your preferred mode in Settings > Power management > Power saver. NOTE:Ultra-saving mode is recommended when other modes do not meet your requirement. Please note that this mode disconnects network connection when the device is suspended.
Disable unused connections
You may disconnect Wi-Fi, location, network data usage, Wi-Fi hotspot, Bluetooth, or GPS, if they are unused. When Wi-Fi and 3G network are both available, set Wi-Fi as first priority. To do this, slide down the screen from upper area to access Quick settings then disable those functions.
Close background apps
Tap recent apps key and perform Clear All.
Slide down the screen from the upper area to access Quick settings and tap Boost.
Choose Battery used by app and Keep awake in Settings > Power management > Power Consumption Table and close those apps that drain battery quickly.
Use Auto-start Manager
Some apps that automatically start in the background may occupy memory, cause system lag and drain battery. Manage these apps using ASUS Auto-start Manager to free more memory, improve system performance, and save power.
Launch Auto-start manager, then select the apps you want to prohibit from auto-starting by changing their status from Allow to Deny . NOTE: Auto-start Manager is currently available on ZenFone 2 models only.
Disable auto-sync and auto-update
Google account: Disable individual sync function in Settings > Google > Accounts
Play Store: Open Play Store > tap upper-left menu icon > Settings > Auto-update apps > Do not auto-update apps .
Data usage: Settings > Data usage > upper-right menu icon > disable Auto-sync data.
Google Now cards: Settings > Google > Search > Now cards > turn off Show cards .
Adjust brightness of display
To do this, tap Settings > Display > Brightness .
Close live wallpaper
Tap and hold home screen (to access homescreen management) and then tap Wallpapers for settings.
Other useful tips
Adjust device sleep time in Settings > Display > Sleep .
Remove one of the two SIM cards if it is not used for a long time.
Disable Auto-rotate screen in Settings > Display .