Total amps (fuse) near battery

[n2audio 5,000+ posts]

18" also handles alot more current than does 18'. Again, any wire sizing chart will confirm this if you don't believe us.

It ALL comes down to VOLTAGE DROP.

18' of 8 ga can supply 100A just fine. The problem is with car audio if we drop more than .5v or so it causes problems with our equipment.

All those cute little charts are founded on voltage drop.

http://www.bcae1.com/wire.htm

This link even states -- as you increase the current capacity of wire due to less resistance over a shorter length you're dissipating that same heat from .5v drop (or whatever you use) in a less massive piece of wire - which means it's going to get warm, possibly warm enough to melt the insulation, or at least soften it noticeably.

Just be careful running a lot of power through a small wire just because it's short.

 

[tractng 10+ year member]

Guys,

If I decided to stick with my current setup (xenon 600.1 & Pg 5.0:4) which requires 60 amps and 50 amps=110 amps, would a fuse of 100 amps at the battery and the main line is at 4 gauge be safe?

I will have a distribution block and the wire will be 4 gauge with a fuse holder going to each amp

Also, the main wire is less than 15 feet.

I am just a little paranoid.

Thanks,

Tony

 

[LBX2G 10+ year member]

yeah the fuse is for the wire.

 

[tractng 10+ year member]

Guys,

If I decided to stick with my current setup (xenon 600.1 & Pg 5.0:4) which requires 60 amps and 50 amps=110 amps, would a fuse of 100 amps at the battery and the main line is at 4 gauge be safe?

I will have a distribution block and the wire will be 4 gauge with a fuse holder going to each amp . Also, the main wire is less than 15 feet.

I am just a little paranoid //content.invisioncic.com/y282845/emoticons/rolleyes.gif.c1fef805e9d1464d377451cd5bc18bfb.gif .

Thanks, Tony

 

[Mac11 10+ year member]

Guys,
If I decided to stick with my current setup (xenon 600.1 & Pg 5.0:4) which requires 60 amps and 50 amps=110 amps, would a fuse of 100 amps at the battery and the main line is at 4 gauge be safe?

I will have a distribution block and the wire will be 4 gauge with a fuse holder going to each amp . Also, the main wire is less than 15 feet.

I am just a little paranoid //content.invisioncic.com/y282845/emoticons/rolleyes.gif.c1fef805e9d1464d377451cd5bc18bfb.gif .

Thanks, Tony

no need to go double posting when your question has already been answered like 4 times in this thread. //content.invisioncic.com/y282845/emoticons/banghead.gif.8606515f668c74f6de0281deb475b6fd.gif//content.invisioncic.com/y282845/emoticons/wowflash.gif.89a61f4caede63a11dac36e97d61323e.gif

 

[audioholic 5,000+ posts]

It ALL comes down to VOLTAGE DROP.
18' of 8 ga can supply 100A just fine. The problem is with car audio if we drop more than .5v or so it causes problems with our equipment.

All those cute little charts are founded on voltage drop.

http://www.bcae1.com/wire.htm

This link even states -- as you increase the current capacity of wire due to less resistance over a shorter length you're dissipating that same heat from .5v drop (or whatever you use) in a less massive piece of wire - which means it's going to get warm, possibly warm enough to melt the insulation, or at least soften it noticeably.

Just be careful running a lot of power through a small wire just because it's short.

Ive lost sight of exactly what your arguement is. You originally said "Fuse size has nothing to do with length. The current capacity is always the same. Length only effects voltage drop." This is incorrect, as length directly affects resistance for a given gauge of wire. As a given gauge of wire's length goes up, resistance goes up, voltage drop increases, current capacity decreases. But, I dont know where you are going with the notion that length has no bearing on wire sizing, or that this is all only about voltage drop. They are all pieces of the same puzzle, none can be ignored (including wire length).

 

[KaeZoo 10+ year member]

Ive lost sight of exactly what your arguement is. You originally said "Fuse size has nothing to do with length. The current capacity is always the same. Length only effects voltage drop." This is incorrect, as length directly affects resistance for a given gauge of wire. As a given gauge of wire's length goes up, resistance goes up, voltage drop increases, current capacity decreases. But, I dont know where you are going with the notion that length has no bearing on wire sizing, or that this is all only about voltage drop. They are all pieces of the same puzzle, none can be ignored (including wire length).

Two concepts:

VOLTAGE DROP is determined by both the current and the total resistance, which increases with wire length.

AMPACITY is a measure of how much current a wire can handle safely, before the heat build-up endangers the wire. The AMPACITY of a particular wire is not affected by the wire length.

When you're selecting a wire size, the VOLTAGE DROP is the factor you should take into account. That's the purpose of the various wire gauge/length tables; they're made for selecting the right size WIRE.

Once you've selected the wire, then the maximum FUSE size should be determined by the wire's AMPACITY.

Suppose I consult the voltage drop tables and find that 4-gauge wire will be enough for my system. At that point, I want to select a fuse. Since the purpose of the fuse is to protect the wire, then the maximum fuse rating will be determined by the wire's ampacity. If I look at a voltage drop chart to find my fuse size, it will be misleading, since it appears to show that I can use a larger fuse for a short run than for a long run. Ampacity isn't affected by wire length, so the same size fuse will work whether it's a 2-foot or 20-foot wire run.

So to sum up, you can use voltage drop charts to pick a wire size, but they're not the right charts to show you the maximum fuse size.

 

[audioholic 5,000+ posts]

Two concepts:
VOLTAGE DROP is determined by both the current and the total resistance, which increases with wire length.

AMPACITY is a measure of how much current a wire can handle safely, before the heat build-up endangers the wire. The AMPACITY of a particular wire is not affected by the wire length.

When you're selecting a wire size, the VOLTAGE DROP is the factor you should take into account. That's the purpose of the various wire gauge/length tables; they're made for selecting the right size WIRE.

Once you've selected the wire, then the maximum FUSE size should be determined by the wire's AMPACITY.

Suppose I consult the voltage drop tables and find that 4-gauge wire will be enough for my system. At that point, I want to select a fuse. Since the purpose of the fuse is to protect the wire, then the maximum fuse rating will be determined by the wire's ampacity. If I look at a voltage drop chart to find my fuse size, it will be misleading, since it appears to show that I can use a larger fuse for a short run than for a long run. Ampacity isn't affected by wire length, so the same size fuse will work whether it's a 2-foot or 20-foot wire run.

So to sum up, you can use voltage drop charts to pick a wire size, but they're not the right charts to show you the maximum fuse size.

I never said to use the wire sizing charts to determine the proper fuse. Ive said to use it only to detemrine the proper wire gauge. Im fully aware of the parameters and procedures for sizing the fuse, but thanks for the info.