Yep, 3 hours would do the battery. Nothing more sinister than that I think. I've been told that if a battery has absolutely zero power left, it won't accept a charge. Can't hurt trying though.
If you need a battery, speak to Jason and he will help you get the cheapest battery. His number is 0400 277 888. Tell him you were referred by Ed from NSW Riders and he will look after you. Let me know how you go.