This reminds me of a problem I had on one if my 14" G4 iBooks.
Whenever I turned on the iBook, the unit would power on fine some times, other times it would engage the fan to make a whirl sound but nothing on the display. After a while this problem became more frequent. The power adapter, battery and DC inboard was all replace with little success.
The problem was traced back to a chip on the logic board that had become detached from the board due to heat.
I wouldn't say this is your fault but its maybe likely.
The problem no doubt sound like a logic board related problem, as the battery is not charging and its not responsive to the PMU reset.
My advise would be, get the iBook tested at an apple store or approved repair shop.
Best of luck.