Join Date: Oct 2005
Location: Kokomo, IN, USA
You asked me to comment on this, and I will oblige, but let me say this first. I discovered Monday I have and abscessed tooth which caused my severe swelling, including one eye to swell nearly shut. On top of that, I went today to get a root canal and they wont touch me until the swelling is gone. But, I am on some wicked drugs :-).
Anyway, I agree with everyone else, I wouldn't not put a relay in series with the alternator.
As far as fusing it goes, here is what I would do. On cars, the alternator output is generally not fused, they use a fusible link, which is basically just a fuse inside of a wire. I don't know where to get them, especially since automotive alternators usually start at 85A. However, don't be concerned about hitting that 45A number. The fuse protects the wire. I would probably look for an 55A fusible link, that way if you alternator ever goes wide open it doesn't accidentally blow the link. A 55A link will have adequately size wire to not cause a problem. So, how would you blow that fuse, well there are two ways. Let's say the voltage regulator developed a short to ground (shorted diode), then then the battery would start sourcing current into the regulator and would blow the link. The other possibility is that the link itself rubs against the frame and wears through the insulation. Again, the battery will try to source current to ground. Remember, the battery is the biggest voltage source. If the link were to short to ground on the alternator side, the voltage regulator * SHOULD * limit the current to 45A, so even if the fuse doesn't blow, the wiring should handle it and you will notice something else soon enough (like a dead battery).
I think wiring the accessory block straight to the battery is a good idea, but remember, you also need a fuse between the battery and the block. Again, I would put a 40A fusible link, with the link as close to the battery as possible.
I wouldn't tap into the line between the alternator and the battery. The reason is that you have a high current source at each end of the wire, so which end of the wire would you protect? If you now add in a third tap, it only gets more confusing.
"There are 10 kinds of people in the world, those who understand binary and those who don't"