after searching, i saw a picture of zling niki and it looks like a normal mp4 player. so try this
1. go to settings/system setup/system, then go to lcd and choose the 'black' option and then you can move the slider right and set the number of seconds after which you want the light to go off on the screen.
2. another thing you could do to save battery is decrease the brightness/contrast which is again there in settings=>lcd set
3. and last thing is that for swtiching of your player, you should switch off using the plastic switch like thing on top/side of the player after switching the player off using the play button.
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