thats not really what your battery is "charged" at technically its what your alt is charging at. when you first start it up it will be charging full bast to get your batt back upt o par. when it gets there it will back off into a normal charging range. most newer vehicles charge a hair over 15 when you start up then back off to 14.xx after a few minutes. Ditch the cap get a bigger batt. kinetik blows. you are better off with a deka. i would find an xs battery. You can find them from 150-300 depending onw hat model you get. i dont think you need a 3100 for that little of wattage. A solid g31 batt should suffice.