Ibook would boot up on mains charger until it got to the point where it would check for battery power and would then crash. It was giving charging problems for some time ( months) before this and would constantly switch from charge to no charge at 1-2 second intervals.
I got the dc in board from Ifixit and used their very good installation guide. It took about 15 minutes from start to finish, and it solved the problem. My only regret is that I did not do the repair sooner. I printed out the screw sorter and taped the screws in the relevant place as I went along. Great idea from Ifixit, and no problem with lost screws.
Change the DC inboard as soon as you see charging problems. Sorry no pictures.