The battery in my 2006 Gold Wing gave out on me. Bike started, I heard a POP, then engine died. Dim lights still evident. It was a cheap Chinese battery the P.O. had installed. Since replaced with a Deka battery. All is great again. . Trying to figure out how old the failed battery was. .It has 130815 branded into the top of battery. I am assuming the 15 was 2015. Is this a code like tires?