My bettery recently went dead. I couldn't believe it. I had to get a friend to jump it to start. At the dealership, for a check engine light one week later, the tech just looked at the window on top and said, "looks okay now."
From what I remember a good battery will read 13.4V (or so). A battery that needs replacing will measure 11.8V.( or so)
Never heard of an Optima Yellow Top before.