Our vehicle has 10 amp cigarette lighters ... not enough to power a 300 watt inverter charging a portable battery at about 200 watts.
Thanks Go Solar for clarifying to use DC input for calculating wire gauge. It seems the calculation depends on whether the circuit is considered critical or non-critical.
The instructions for using the wire gauge chart say:
Critical circuits, with 3% allowable voltage drop, include
Panel main feeders
Bilge blowers
Electronics
Navigation lights
Non-critical circuits, with 10% allowable voltage drop, include
General lighting
Windlasses
Bait pumps
General appliances
Would a circuit to a pure sine wave inverter, which has a built-in 40 amp fuse, be critical or non-critical?