This is a good comparison between the 2/0 awg on the left and 2 awg arc welding cables. The overall diameter is almost identical but the amount of actual wire and resultant current carrying capacity is dramatically different. Since the 2 awg cable wasn't labeled, I weighed the welding cable after trimming off the ends to find the weight per foot. Then looked it up in a table (on the Internet) to find the wire size. I will be using the 2 awg wire for the connections from the solar charge controller to the battery. It's kind of overkill since the maximum current is only 45 amps. But the maximum wire size supported by the charge controller is 2 awg and I just happen to have some lying around.
The two 50 amp circuit breakers are for the input and output of the solar charge controller. Output on top and input just below that. Note that the breakers are "tripped" with the red button so they work as switches. I still need to pick up some cable clamps that fit the knock outs on the Morningstar charge controller from the hardware store before terminating the cables. I also need some ground wire for the chassis of the inverter and the charge controller. I also ordered some cable clamps to keep the cables from moving or vibrating while traveling down the road.
I also plan to order one 100 watt, 12 volt solar panel to test the charge controller.