The failure mode the fuse is there to protect is an unintended short to ground somewhere in the circuit before the load, where the current flow will only be restricted by the resistance of the wire, not the load resistance. Typical scenario might be a wire chafing and shorting out on the frame. The closer to the 12v source you place the fuse, the better chance you have of blowing the fuse prior to melting any wires, because if the fuse is downstream of the short, its useless.I don't think it's common to fuse the negative side of the battery though at least one person here has mentioned it.
Not only is it conventional, it's the safe thing to do. The fuse goes as close to the non-ground terminal (positive on a negative-ground system) as possible so any short to ground will blow it out. If you put the fuse on the opposite terminal, electrons will flow unabated from the point of the short to the positive terminal. That's what starts fires, or at least releases the smoke that makes electrical stuff work.It is conventional to fuse as close as reasonable to the pos(+) post.
Nope.In a d.c. circuit current actually flows from neg.(-) to pos.( +) So following your line of reasoning, it would make more sense to place a fuse close to the neg. post..... No?
It is generally preferred to have nothing but a large gauge short wire between the ground plane and battery terminal so they are as close as possible in voltage potential. Adding a fuse into that path will create a voltage drop and cause the system ground to float a bit relative to the battery ground. You still get the voltage drop by putting the fuse on the other end of the circuit, but all parallel paths see the same ground voltage, and increasing the current flow doesn't cause the system ground to float even higher. Putting the fuse where you suggest would create a voltage drop that increases as a function of current load, and ground float would vary based on current draw.Sorry I wasn't a clear as I could of been..the frame is a common junction point... It might help to think of the frame as nothing more than an extention of the neg battery post. A fuse inserted in the wire before its connection to the frame would work for fused protection .
Derp! Just read that. Are you sorted out yet?I attached it to each battery post.....then the bike will not crank over, so......