I agree with both! Check your terminals on the battery itself, and get yourself a tender/charger. Cycle the battery a few times. If you don't have money for a charger, jump the bike, and take her on a really long ride, like 200 miles, making sure to keep the revs fairly high - highway riding is best, to make sure the battery gets charged up nice and full through the bike's charging system.
Also check electrolyte levels... Grab a pair of pliers and pull all the little yellow dots off the top of the battery and make sure there's enough electrolyte in the battery. If you have to fill it, be careful, it's acid. Don't spill on anything. My eliminator did this once, and it only had half of the electrolyte it needed. Once filled, it still romping, 5 years later!
If you've checked the contacts, checked the electrolyte, and gone on a massive ride to make sure it's charged, I would consider getting a new battery.
