DC aircraft wire, sized for voltage drop and 35°C-rise ampacity per FAA AC 43.13-1B chapter 11.
The allowable drop is bus voltage minus the device's minimum. If the two are equal, a 5% design reference is used instead.
The answer is the smallest conductor from 22 to 2 AWG that keeps the drop within that limit and carries the current at a 35°C temperature rise, single wire in free air.
The device's own minimum governs, so a tolerant device may be allowed more than 5% drop. The result says when that happens.
