iBook G4 Battery Problem

Hey, i've had my iBook for about 2 months now. I hadn't had any problems with it save one dead pixel until about a week ago. I use my laptop alot at university and I usually just close the screen between classes and go. However recently the iBook has been shutting itself down when I do this. Even when it has full batteries, it no longer goes into sleep mode, just shuts down. Anyone know what this might be or how I might fix it?
Thanks

Hi! Welcome to the Best Mac forums site on the web! Not sure, buy bring it into an apple store, they sould help you and fix it 4 free.

Try opening your system settings and going to the energy saver option. There are seperate settings for when you are running off the battery and the dc adapter. Not sure if this problem an be fixed, but worth a shot. Maybe you just have the power options set to turn off when the lid i losed.