[bluegerman]

Sometimes my battery does not last long enough, and what I do is take a piece of paper and fold it several times to form a tip, then clean the battery contacts with the tip, and the phone contacts with flat paper. This somehow makes the battery last a bit longer and solves the Unknown battery massage in the 3 Moguls we own in the family. I do this every 2 weeks or so (don't know if is humidity related, I live in South Bay area in California.