During a live interview with Jordan from Project Atticus, BoatHowTo co-founder Nigel Calder goes into the details of wiring and overcurrent protection for high-output alternators.
In this video, Nigel made a mistake! He was doing the voltage drop calculations in his head during the discussion and screwed it up, luckily on the conservative side! He estimated the voltage drop with the 3/0 conductor at more-or-less twice what it will be.
If you run the calculations using our wire sizer you will find that from a voltage drop perspective Jordan can get away with a single 3/0 conductor so the second 3/0 conductor is not really necessary.
It would still have been better from an ampacity and overcurrent perspective to have used the 4/0 conductor but as Nigel says, given that Jordan’s alternator will not put out its rated output for more than a few minutes he would not lose sleep over this. Bottom line: we all make mistakes so it is important to run the numbers and not rely on guesswork!
If you want to learn more about the topic, we have a special case study on high-output alternators in our Boat Electrics 101 online course.