House wiring is also A/C, not D/C - totally different systems.
42V systems would use a single alternator - just one built to produce higher voltage. The voltage is a function of the internal construction of the alternator. Change a few things, and the voltage can be changed. Aircraft often operate in the 400V range.
More applicable to us than the 42V systems, would be the 16V systems. They use a voltage tap, to give you 12V for your regular equipment, but allow you to also draw 16V for things like ignition systems, fuel pumps, etc. It requires significant modification of the wiring, and maybe the car - I doubt a 16V battery would fit in the stock battery box, so you'd probably need to do some custom work to fit the larger battery - but it would be very cool.
clar: amperage is a function of draw. Think of it like a volume of water (voltage would be similar to pressure).
Now, if you have a water tank, and tap it at a certain depth, you get a certain pressure, no matter how wide the tank is, or how large the pipe diameter. The pressure is just a function of the weight of the water, to that depth. That's like the 12 volts of your system.
If you put in a bigger alternator, that's like putting in a wider water tank. The pressure is the same, because the pipe attaches at the same depth, but there is more water available to use.
Add a few more loads to your system, and it's like adding more draws on your water main. Imagine that each load is a pump. If you have a bunch of pumps running, and the pipe is too small, you'll draw too fast, and run the pipe dry. This is like overheating a wire due to putting too many loads on a small wire.
So, you need to put in a larger wire/pipe, to prevent that. But if you put a large load at one point, you can make the pipe smaller after that point.
In other words, you need to go large-guage, to the point where the load is. So, it depends where you plan on attaching this large load. You need to run a large enough guage to carry the load, at any point. But the load won't be "pushed" into areas that you don't have a draw, so you don't need to run large wire to your wiper motor, just because you run a large amp and a large alternator to supply it.
It will depend on how you wire it, but let's look at a common example, where a second fuse box is attached at the main fuse panel, to connect some new equipment (let's say, an amp, an electric fuel pump, and a pair of electric fans). Let's say the fans each draw 20 amps, the amp draws 15, and the fuel pump draws 10 (note: I just made those numbers up - don't use them as actual estimates). And let's say that the car, itself, draws 80 amps at the main panel. So, you have 80 amps at the main, and you're adding 65 amps. So you'll need to run 145-amp wire from the alternator to the main panel, and 65-amp wire from the main panel to the second fuse box.
Make sense?
Joe
