To answer your question on a more straight forward lvl, no, you do not NEED a capacitor. Chances are, it would not help as much as you think it would, and the upgrade of the big 3, a new battery and/or new, bigger alternator would be a lot better for you. Now, when you get an electrical system that is above par for your current electrical demands, then an external capacitor may be something to look into, simply because it would not be such a strain on your system. get me or do I need to go into the archives and pull up some threads as to why this is so?