poor iBook battery an ideas?

All was well until I d/loaded this latest security upgrade, now my battery drains within half an hour. I have had the iBook for 15 months and am really pissed! I called Apple and basically because its out of warranty they couldn't care less. Is this normal to have such a poor experience with a battery?

Is it the upgrade as I am sure I heard other such updates affected the power management. Should I go back to my factory installed Tiger and see???

Cant believe I am going to haave to shell out anotther £88!! Any tips for getting apple to cough me up a free battery)

I am up-to-date on OSX, and my iBook G4 has had no problems. I have spoken to people who have had problems with 10.4.3 on iBook, but not concerning the battery.

I would just buy a new battery :-/ havn't heard about this problem with an os update.