the ringtone, can be swapped out for low battery, as I've always have done since Samsung Galaxy s2, the default ringtone is saved as
LowBattery.ogg
simply make a mp3 file of what ever sound you want, then use a free online converter to convert to .ogg
the file location
storage/emulated/0/audio
you'll see the default name
you can download the file browser I use by
jrummyapps
