iBook - iBook charger acting weird with new battery

Hi. I just bought a new battery for my 12" iBook G3 and I'm guessing it was made for a newer iBook since it isn't ice colored, but simply white. It works like it should, but when I use my charger to charge it up, my charger simply stops working. The little LED on the plug that indicates charge goes out after about 10-15 minutes. Has anyone else had this problem? I can't find anything in the forums or on google, it seems like it would be more wide-spread if it has anything to do with the pwer charger not being compatible with the newer battery. Maybe it's because my charger is a 45w model? IT shouldn't matter because the batteries are both 10.8v...