Battery problems

I have had a sudden change in my battery charging ability. It worked fine on a recent trip and when I returned I left it on my desktop uncharged for a couple of days, then plugged it in. This morning I tried to use it and the computer died when I unplugged it. My battery won't charge! I press the battery fuel button on the battery and nothing. No lights, nothing!! I've removed the battery, cleaned the contacts and reinstalled without success. The adapter light goes to amber for about five minutes then to green all the while the percentage (of battery life) stays at 0%. Even when I remove the battery the charge light still stays green. I've tried zapping the PRAM and resetting the PMU (mac 10.3.9 - 15" powerbook G4 FW800) again without success. Do I need to get a new battery? Thanks for any suggestions.