Hi, and welcome to Apple Support Communities.
You can try resetting the PMU, but since the battery is completely dead, it is unlikely to help.
These are the four most common possibilities when the battery will not charge (in order of frequency):
(1) there is something wrong with the battery
(2) there is something wrong with the power adapter
(3) there is something wrong with the power input board (the part that contains the port where you plug in the adapter)
(4) there is something wrong with the logic board
The power input (DC-in) board (the part of the computer which houses the adapter port) may be going bad if it sometimes will charge the battery and sometimes won’t. Sometimes it will work intermittently before quitting entirely. If you experienced intermittent charging before it totally failed, suspect this. When a DC-in board quits working, the computer will run fine from the battery, but won't run from the adapter, and the adapter will no longer charge the battery. To diagnose a bad DC-in board, you need to make sure it isn't the battery or the adapter at fault by swapping out first one and then the other, If it runs from a known good charged battery okay, but won't run from a known good adapter, then you are going to have to replace the power input board.
Usually, if it is a logic board problem, the iBook simply will not run from the battery. This happened to mine. The battery showed up in the battery status indicator. It was recognized by the computer and charged by the adapter (as shown by the battery status indicator). However, when I unplugged the adapter from the iBook, it was just like pulling the power cord from the wall on a desktop Mac. The iBook immediately shutdown. Dead.
My husband’s problem was quite obviously the power input board because the adapter tip had broken off in the port. Often (and, sadly, in our case), this damages the power input board so that it no longer functions, necessitating replacement of the board as well as the broken adapter.
ok i found out it is the powe input board or the dc in. Because i switched out the batterys and the chargers and the charger wouldnt charge it so and the battery i tried had a charger and it turned on. So my question is how do i get a new power input board,where can i get one and how much would it cost
There is an AASP (Apple Authorized Service Provider) which still works on iBooks.
You could call and get an estimate on having the DC-in board replaced (if they still do it), but the cost may be more than the iBook is worth.