[HO455]

In order to have some over current protection I needed a fusible link for the battery charging. A fusible link is preferred in this application over a fuse since it will not blow if it is momentarily shorted. The result of a having a momentary short would be a blown fuse, if the blowing of the fuse wasn't noticed and the alternator was still trying to charge it would soon self destruct. Many new cars are using fuses instead of fusible links these days but the vehicle's computer is also in communication with the alternator and would know if there was a blown fuse and then would shut the vehicle or charging system down before the alternator was damaged.
The idea of a fusible link is a short piece of undersized wire that will burn in two if the over current condition lasts long enough. The fusible links found in factory harness have been engineered to meet the intended use. For me it was not as cut and dried. I spent at least 2 hours searching the interweb for the answer. Finally I was able to conclude that for a fusible link work properly it needs to be 4 numbers larger than the wire it is protecting. Numbers not gauges! This is where it can get confusing as a wire's diameter gets smaller, the larger the number gauge it is called gets. To protect a 10 gauge wire you need 14 gauge fusible link wire. A 14 gauge wire requires an 18 gauge fusible link. From what I was able to learn the link is about 5 1/2" to 6" long and is attached to the end at the battery.
The other part of the equation is that fusible link wire has special insulation. As the wire inside overheats and melts in two the insulation is designed to contain the heat and arcing. This will prevent damage to other wires next to it and to help prevent it from shorting to the chassis.
I was not able to find an over the counter fusible link anywhere locally that was large enough. Finally I found that Napa carries fusible link wire in bulk 10' rolls. https://www.napaonline.com/en/p/BEL785856
Not exactly what I wanted but it was local and got the job done today. As the #6 AWG wire I used should have a #10 AWG fusible link. I can't see it being too small in the forseable future. Now I have a extra 9'6" of wire. They also have butt splices that allow you to have two different sizes of wire connect up correctly. I passed on them and soldered mine. (Photo 1). See photo 2 large red wire on the left becomes the smaller blue wire hooked to the positive post of the battery.