ABers may like to know this. Sometimes when I go to use my digital camera, I am told that my batteries need charging even though I have recently charged them. I have found that by rubbing all battery contacts with a rubber found on the end of a pencil, everything works much better.
Working in electronics, we clean contacts using an ink rubber - more abrasive than a pencil end rubber, but still gentle enough to use on gold contacts. Most batteries use nickel-plated steel for the casing, and even slight corrosion can result in a poor contact. A tip to help prevent this is not to touch the ends of a new battery with your fingers when fitting it.