I doubt there is a way to configure the sound in another way.

In case you search the file you find it here:
/usr/share/sounds/ui-tones/snd_battery_low.wav
or the snd_recharge_battery.wav if the phone is near dying

btw: using the Dolphin filebrowser of KDE under Linux, you can browse the phone in sync & connect mode like a folder on your computer with the url "sftp://user@192.168.2.15"