Size of Amp cable

F4ntasia · 31-07-2008, 11:37

I understand everything so far from the stickied thread, except for the wiring sizes. I have 2 Alpine 900watt(Peak) 300watt(RMS) subs. And a Pyle Driver 1300watt(Peak) bridged amp with 500watt(RMS) x 2 channels @ 4 Ohms. (My subs are both 4 Ohms) However I just dont understand what size cable I require, or how to choose it. Can anyone help me out please?

wallopsri · 31-07-2008, 21:42

Quote:

Originally Posted by F4ntasia

I understand everything so far from the stickied thread, except for the wiring sizes. I have 2 Alpine 900watt(Peak) 300watt(RMS) subs. And a Pyle Driver 1300watt(Peak) bridged amp with 500watt(RMS) x 2 channels @ 4 Ohms. (My subs are both 4 Ohms) However I just dont understand what size cable I require, or how to choose it. Can anyone help me out please?

Taken from 'stickied' thread

Quote:

1, how do i know what size power cable to run?

the answer in basic terms is;

add up the on board fuses on each amp you are going to use, say your mono amp (for the sub/subs), is fused with 2x 40amp fuses,(80amps in total), and your second amp,(for the fronts or fronts & rears), is fused with 2x 30amps,(60amps in total), then you can work on the assumption your maximum current draw is going to be 80+60=140amps, so with this setup you would require 0awg power & earth cable.

So, what is the total of all amp onboard fusing in your system????
What approximate length will your power cable be??

1, fuses = 30amps or less at 12 to 15ft = 8awg...
2, fuses = 80amps or less at 12 to 15ft = 4awg...
3, fuses = more than 80amps at this cable length then 0awg....
4, fuses = more than 250amps at this cable length then 2 X 0awg power cables

If using multiple runs of 0awg power cable then the chassis will present earthing issues, so its at this point you need to earth direct to battery using similar runs of 0awg cable....

Example;

fuses = 600amps at 12ft = 3 runs of 0awg power cable & 3 runs of 0awg earth cable, (6 runs in total)....

Cable size/length denote main fuse size;

1, 30amps
2, 80amps
3, 250amps

As previously stated above, if draw exceeds approx 300amps, don't bother earthing via the chassis, (chassis will not support much more than this and voltage drop will become evident)....

F4ntasia · 01-08-2008, 11:18

Cheers, that clears things up quite a bit. Length Of cable will be a bit less as it is going into a pickup and will only be around 6ft. And the total fuses on board are 60AMPS.

So i'm assuming i'm best off with 4AWG? My book that came with the amp is suggesting 8Gauge, but to be honest I think they've just guessed at a ballpark figure. Can anyone confirm that 4AWG would be the best idea here? Cheers in advance. Rob.

wallopsri · 01-08-2008, 12:08

I'd go 4awg to cover any possible future amp upgrade....

8awg over 2mtrs, (6ft), will support approx 45amps
4awg over 2mtrs, (6ft), will support approx 120amps

Both cables would safely carry more power, but with higher resistance induced voltage drop...

Jasovanooo · 01-08-2008, 12:45

gotta get round to upgrading my 8 awg jobbie

total fuses is 4 x 40ampers and a 20

napalm_27 · 01-08-2008, 14:15

dnt use any small crappy wire i found that out wen mi cav set light from front 2 bck on the passenger side

F4ntasia · 01-08-2008, 17:05

Cheers for that, shall get myself some 4AWG. What price range should I be looking at? Dont fancy getting ripped off!

wallopsri · 01-08-2008, 19:34

You can either purchase it by the mtr or in 5mtr packs....

I think Halfords do Autoleads stuff at about £20 per 5mtr blister pack....

Or you could buy it by the mtr from HERE .....

rmheath84 · 06-08-2008, 15:43

I always use 0AWG on everything, better to be safe in my eyes, plus it comes out of each car I have when I sell it anyway so dont lose out in the long run.

If your investing in decent hifi, why skimp on cables

F4ntasia · 07-08-2008, 11:32

Got some 1AWG as it was fusion kit on offer for £35. You say you use 0AWG for everything? Don't you suffer any voltage drop on lower powered systems?

wallopsri · 07-08-2008, 12:05

Quote:

Originally Posted by F4ntasia

Got some 1AWG as it was fusion kit on offer for £35. You say you use 0AWG for everything? Don't you suffer any voltage drop on lower powered systems?

Voltage drop when using DC occurs due to cable resistance, by using a larger bore cable your increasing the copper cross sectional area, this lowers resistance.....

Cable resistance is governed by three main points;

1, cross sectional area of core material, (copper)....(larger = less resistance)
2, distance or length of cable between source supply and load, (battery & amp)....(longer = higher resistance)
3, Amps/current being drawn, (higher draw = higher resistance = increased voltage drop)....

points of high resistance can create issues with severe heat build up, it's quite possible to melt a distribution block or a cables outer sheath with relatively low draws....

So, to minimise voltage drop;

Keep power supply cable as short as possible, (take shortest most direct route from supply to load)....
Fit largest guage/bore cable possible....
Ensure all connections are good and tight....
Avoid tight bends & kinks, (tight bends or kinks cause the copper strands to open up inside the sheath, well one side of the core becomes tight & stretched, the other side becomes loose and bunched), this can cause a point of high resistance and heat build up.....