The original Motorcraft battery in my Explorer (3 years old) has the little "eye" hydrometer in it. While I realize that only monitors the condition of one cell, it had been green for years, then showed yellow about a month ago, and now is showing orange. Is it time to put in a new battery, or is orange condition better than yellow? I suspect the winter cold may have something to do with it, but that would be a first for me. I do have a new battery sitting right in my garage ready to be installed.