I don't have a PB, but I checked and my iBook certainly uses a 45W adapter. Oh well, I tried to be useful anyway. I wonder if your battery charges faster than mine.
I just looked at the tech specs at Apple.com and it only says that the ibook comes with an AC adapter, lower down there is a link to optional accesories and clicking on the model number for the adapter takes you to the store for the 65W PB/iBook adapter.