IBook Fixed!!
Since replacing my battery a couple of months ago, my iBook would make a popping sound every minute or so when on battery power. Jason has just started having the same problem and got some good responses. One of them pointed to macosxhints which had some tips for zapping prams and nvrams etc.

After completing the proceedure everything is working...no Pops and my battery charge now goes up to 100% rather than stopping at 95% like it has previously done.

I must file the hint away in the useful pile.