Here's the wire sizing chart for max ampacity. This is the chart to use when sizing for fusing or over current protection, when the wires are not bundled.
Find your wires gauge in the left column then move over and find the jacket temp rating. Most "marine" UL wire has a jacket temp rating of 105C.
When sizing for voltage sensitive sources, or when ever voltage drops can make a difference, it is a good idea to size to the max ampacity of the wire rather than what your charge source can supply..