oilsardine wrote:
got an Masters degree in Electrical Engineering myself...

Then I would have to assume that either eEnglish is a second or third
language for you or you have deliberately chosen to be a pendant. You
are right in that if the original poster intends to hook two 12V
batteries in series, but draw the same wattage over the same distance,
the conductor would require half the ampacity that would have been
mandated by a single 12v battery, since in order to provide the same
wattage the load would have to draw half the current at double the
voltage. The original poster never constrained the problem to the same
wattage -- and in homebuilt aircraft, I doubt that constraint ever
arises since the devices that one connects to the electrical system have
specific voltage requirements. Even if his system is exclusively
resistive loads, they are not likely to behave in purely linear fashion.

Charles