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Thread: 8ga to 18awg - How do I do it?

  1. #1
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    8ga to 18awg - How do I do it?

    Hi,

    I am in the process of wiring up a carputer and need some help.

    I have 4ga running direct from the battery to the boot where it runs into a distribution block and I have then have 8ga wires running from there to my amp and the carputer.

    The problem I have is that I have to connect the 8ga wire to the wiring lume of the carputer which is 18awg. What is the best way to connect the thick 8ga wire to the thin 18awg wire? I have no idea.

    Is it possible to buy a distribution block that I can put 8ga into and a thinner gauge out (I have looked on Jaycar website and can't see one).

    Thanks

  2. #2
    Newbie copter's Avatar
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    Just put the 18g into your distro block
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  3. #3
    Variable Bitrate tigergibb's Avatar
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    Constant Bitrate krnpimpsta's Avatar
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    What I did to get my 8 gauge power wire to the 3 thin (maybe 16-18 gauge?) wires on my Opus 320W power supply was:

    8 gauge ring terminal on the 8 gauge wire (eBay, hifisoundconnection, $3-4 for several)
    three 16-18 gauge ring terminals on the 3 thin wires (radioshack, $1-2 for a bag of them)
    1/4" bolt, nut, and washers. (home depot, $2-3)

    Then put all 4 ring terminals on the bolt, surrounded on each side by a washer, and the tightened the bolt. Then surrounded the entire thing in a few layers of electrical tape (you'll want several layers so if any of them slip or break through, you won't end up with an exposed power wire)

  5. #5
    Constant Bitrate cMags's Avatar
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    ^^ I wouldn't recommend this as you'll basically have a big ball of metal in the middle of your wire that's at +12V and I wouldn't trust electrical tape to keep it safe. Espeically in a car where summer temps can melt the tape's adhesive and allow it to slide.

    If you need to connect up an 18ga wire, then running 8ga is overkill. I would just run the 18ga to the distro block (fused properly - no higher than 15A I would say - 10A may be better if your load won't overdraw it). If you do need to use the 8ga for most of the distance and need to connect a smaller gauge wire to it, you'll need to put another fuse in to protect the smaller wire, or put in a fuse at the distro block that is fused properly for the small wire. If you attach multiple small wires to the big one, fuse them individually.

    For example, say you have your 8ga wire fused at 60A at the block, and hook up two 18ga wires to it for +12V and ACC to your PSU (for dumb PSU operation). If you were to get a short in one of those two small wires, they'd heat up and likely catch fire before that 60A fuse pops. This is why each of them would need their own 10-15A fuse connected between the wire and the 8ga.

    Cliffsnotes: Just run the 18ga to the block - easiest solution

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  6. #6
    Constant Bitrate krnpimpsta's Avatar
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    Two pretty good points.

    I'll have to bolt the two bolts into my carputer chassis next time I get a chance instead of letting them dangle.

    Also good point about shorts that may occur on an individual smaller gauge wire. I guess the best solution would be to stick another fused distribution block in the chassis to go from 8 gauge -> 3 thin wires. I wish Opus designed their P/S differently to have 12V/GND power terminals, instead of building it into one big harness with little wires.

  7. #7
    Constant Bitrate ronjon228's Avatar
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    I say just use a butt connector. Find one that accepts the 8awg and then run a small piece of 18awg wire out the other side (bout 6inches or so).

    Either that, or just run 18awg from your distro block to the CarPC. Seems to me this would be the simplest, cleanest and safest way to do so. No extra connections or parts needed.
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  8. #8
    Constant Bitrate cMags's Avatar
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    Quote Originally Posted by krnpimpsta View Post
    Two pretty good points.

    I'll have to bolt the two bolts into my carputer chassis next time I get a chance instead of letting them dangle.

    Also good point about shorts that may occur on an individual smaller gauge wire. I guess the best solution would be to stick another fused distribution block in the chassis to go from 8 gauge -> 3 thin wires. I wish Opus designed their P/S differently to have 12V/GND power terminals, instead of building it into one big harness with little wires.
    Well, if you're thinking of bolting the exposed power connectors to the chassis, that's obviously not a good idea.

    I had an Opus for a while, and ended up just using 10ga (because it's what I had a good length of) to run the power (and GND). I soldered the 10ga directly to the Opus pigtail. To keep the joint from being larger than my heat shrink, I ended cutting off half of the strands on the larger wire, soldered the thinner Opus wire to it, and put on the heat shrink. To keep things safe, I fused the whole thing at 15A. So, if the thinner wire gets shorted, the fuse pops at 15A, which is low enough to prevent a fire. This is safe to do (as I mentioned) as long as its just a single connection (not creating a "Y" wire), and the wire is fused properly for the *smallest gauge* portion of the wire at the battery/distro block.

    CarPC v2.5 up and running - all hardware installed, skin configured, and iG tweaked like crazy. Now for OBD-II, and voice control, and camera plugin, and... :nutz: - it never ends!

  9. #9
    Variable Bitrate tigergibb's Avatar
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    Or maybe running 14 gauge from the distro would be safer and easier to connect?
    2003 Nissan Xterra Worklog

    Total amount spent so far: $1196.64

    You will probably spend AT LEAST 2x what you initially budget for your CarPC Project!

    2003 Nissan Xterra - Modifications

  10. #10
    Maximum Bitrate FusionFanatic's Avatar
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    Quote Originally Posted by MyPetFly View Post
    I have 4ga running direct from the battery to the boot where it runs into a distribution block and I have then have 8ga wires running from there to my amp and the carputer.

    The problem I have is that I have to connect the 8ga wire to the wiring lume of the carputer which is 18awg. What is the best way to connect the thick 8ga wire to the thin 18awg wire? I have no idea.
    the best way is to not use the 8g wire at all (for your carputer). if the power supply uses 18g wire then there is no need for you to run 8g for it. if it will be run a long distance then you can increase it to a larger gauge (like 14g) but there is no need for wire as big as 8g.

    also, just like a chain is only as good as the weakest link, wire is only as good as the smallest gauge in the run. if you use a larger gauge wire, then run the larger gauge for the entire length, not just a section. if you run wire larger than 18g then remove the 18g wire from the PSU and solder the larger wire in it's place.

    Quote Originally Posted by MyPetFly View Post
    Is it possible to buy a distribution block that I can put 8ga into and a thinner gauge out (I have looked on Jaycar website and can't see one).
    maybe, but it's not really necessary. it's easy to use smaller gauge wire in a larger gauge distribution block. just tin the end of the wire so it can "clamped" down. if it's too small for the set screw to reach it then fold the wire two or three times, then solder it into a large chunk (up to the size of the 8g wire) so it will be big enough to secure it in the block.

    alternatively, you can use a simple barrier strip:


    then use the appropriate terminal lugs/connectors for each wire size:



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