Wire gauges get bigger as the numbers get smaller- - - -a "0" gauge is bigger than a "2", and a 2/0 cable is really big, just like "00" buckshot is bigger than #2 birdshot, etc. I like to use #0 welding cables for battery cables on 6V systems because there are hundreds of hair-fine conductors to make welder cables more flexible than battery cables. Since electricity supposedly flows over the surface of a copper conductor, the finer the individual conductors are, the less resistance the cable will have. Going bigger than #1 or #0 cable size is pretty much overkill on a stovebolt battery cable, even for 6V applications. The #4 cable used for 12 volt systems is too small, however.
Red insulation for the + cable just helps eliminate confusion when jump-starting- - - -it really makes no difference in the performance of the system whether the insulation is red or black. Have fun!
Jerry
