Zte GRAND X4 User Manual page 152

You can touch Save location to choose the default location for
new data, such as photos captured, and voice recorded.
Touch Phone > Used space to get a detailed breakdown of
space usage by type. Touch a data type to see more
information or delete the files you do not need.
For more information about using the microSDXC card, see
Using the microSDXC Card as Portable or Device
Battery
Touch the Home key >
battery level, check what has been using the battery, and
optimize battery use.

Touch an app or service to adjust its settings in order to
save battery life. For example, touch Screen > Reduce the
screen brightness and/or screen timeout to change
screen brightness and sleep.

Touch > Battery optimization. Battery optimization
helps prolong battery standby time when you're not using
the phone. If there are apps that you don't want battery
optimization enabled, you can turn the feature off in those
apps. Just touch Not optimized > All apps, touch the app
name and then touch Don't optimize > DONE.

Touch > Battery saver. You can turn on or off the Battery
saver or configure it to turn on automatically in order to
reduce battery use and improve battery life.
> Settings > Battery to view the
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Storage.