aspire lite in screen goes out?

Whats happening with your laptop is a backlight issue. The LCD screen that laptops use displays an image with or without a light behind it, but if the backlight isn't functioning or present the image on screen will be very very dim, just as you described. Since yours is going on and off it sounds like the wiring might just be loose or some other connection that sends power to the backlight. If you're not comfortable taking apart the laptop's screen bezel (plastic around it) and other parts like the keyboard so you can check all the connections there's not really anything you can do to fix it. Hopefully its under warranty still, because that is definitely an issue that would be covered under almost all warranties. If you don't know I would call the manufacturer to find out if it is or not and if not how much it would cost to fix.

The battery shouldn't have a problem because if it was the battery, the whole laptop would lose power, not just the backlight.