power port not working, please help

I have a 17" G4 1.5 Powerbook. I have been having problems with the battery, it will indicate above 50% full but suddenly my computer will shut off. Now the battery does not re-charge at all but indicators on power cord and on menu bar say battery is charging. I can charge my battery in a friend's computer and replace it in my machine and it works fine. My power cord works fine as well. Do I need to replace the power port?