Is This Acceptable??

[Frāmrāt]

It adds resistance, and it's pointless.

The reason the power wire is fused is to protect it from accidental contact with ground (about any metal in the car). When that happens the current spike blows the fuse almost immediately.

On the ground side that is clearly not an issue as the ground wire requires contact with the chassis (or (-) battery post) to complete the circuit.

If the fuse is 150A on the "in" side and the "out" side, how does it add resistance? If I'm only letting in 150 amps and I'm letting out 150amps...where does the resistance come from?

 

[Lasherž]

If the fuse is 150A on the "in" side and the "out" side, how does it add resistance? If I'm only letting in 150 amps and I'm letting out 150amps...where does the resistance come from?

Fuses work by breaking when they get hot. That one's set to break at 150A. Every wire is a resistor, so are fuses. Fuses are designed to be the highest resistance point on the wire so that no heat builds up elsewhere. Also heat raises resistance. Putting 2 raises the resistance more than a plain wire for no safety benefit. Parallel fuses = fine, series fuses = why?

The resistance rise is quite small for the most part, especially at low amperage, but there's no explanation for its existence. The only difference is that both might be damaged in the event of a failure instead of just one.

 

[Frāmrāt]

Fuses work by breaking when they get hot. That one's set to break at 150A. Every wire is a resistor, so are fuses. Fuses are designed to be the highest resistance point on the wire so that no heat builds up elsewhere. Also heat raises resistance. Putting 2 raises the resistance more than a plain wire for no safety benefit. Parallel fuses = fine, series fuses = why?

The resistance rise is quite small for the most part, especially at low amperage, but there's no explanation for its existence. The + cable fuse will blow first in identical fuses due to voltage drop and both might be damaged.

Thank you so much for explaining!!! I've removed the ground fuses but I was just curious.

 

[Lasherž]

Thank you so much for explaining!!! I've removed the ground fuses but I was just curious.

Not a problem, note the change after the moment you quoted it. Obviously the voltage drop would exist at both fuses so they'd blow at the same time. Didn't want to mislead you. They would either both fail if there was a lot of energy or one would fail and the other would be severely damaged if it was only a little bit over rated amperage. Most likely it would blow in the engine compartment first though due to that fuse already being hotter than the interior of the car, not voltage drop.

 

[wew lad 5,000+ posts]

Ground fuses can be very dangerous in certain situations due to the fact that they're tied into the chassis. Most people don't wire it in such a way where that's an issue, but if a ground fuse blows and another load is tied in, and it's not fused, or fused improperly, you're going to shove a ton of current through a wire not designed to handle it.

I've read stories of wires catching fire due to this.

This is the same reason why you need to wire your power leads from largest ampacity to smallest and fuse each step down in wire size along the way.