Your battery is brand new, was it fully charged when you installed it? If so as Time to roll said your battery would not draw down in two days unless something is left on. I would disconnect your neg cable set your mutimeter to 10 amp scale and put your leads between the neg post and neg cable. What does it read? Next check the output of your converter what does it read? You said your converter was just replaced I doubt it is your converter either. If you can post these two readings you will get more accurate responses and what to do next to trouble shoot the problem.