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  • What Gauge wires do I use?

    Okay, here is my problem. I purchased a book about installing car radio systems. The book has a chart that you use to for various volts and lengths for wires (for my power supply). According to the book, with my opus 150 watt power supply, I am suppose to use 8 guage wire. So I went to Lowes and purchased 15 foot 8 guage wire. The wire is huge!( round). I questioned the guy, and he had his own formula and calculated it out the same. He said that I need 8 guage. The book was refering to 150 Watt amplifier. I am confused. The Lowes salesman said that I can use 8 guage going from my battery to my in line fuse, then I can use something smaller like 12. So I purchased 15 foot of 12 wire too. When I look at the three wires from the opus power supply, they are not that big. However, I did notice that the red wire that comes with the power supply that goes to my battery is larger than the yellow and the black wire. So, I reckon it really does make a difference. My question is: What kind of wires do I actually need to go from my battery to the in line fuse and from the inline fuse to the power supply? Also, what kind of wire should go to the ignition switch and the ground. Any ideas?

  • #2
    Originally posted by Showmehow
    The Lowes salesman said that I can use 8 guage going from my battery to my in line fuse, then I can use something smaller like 12. What kind of wires do I actually need to go from my battery to the in line fuse and from the inline fuse to the power supply?
    Logically I think you need the same gauge before and after your fuse because current that flows thru the part before your fuse is exactly the same as the current that runs thru the part behind the fuse.
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    • #3
      I havent wired mine up yet but this is what im going to do.

      Im going to run 4 Gauge wire from the Battery to the back of the car, you will have to put an inline fuse as close to the battery as poss. This wire will go into another fuse box, im then useing 8 gauge wire from this to the Amp and 12 gauge wire from the fuse box to my Opus 150w power supply.

      Make sure you use the same gauge wire for the ground ie if you use 12 gauge wire to the Opus for power use 12 gauge wire from the Opus to the car chassie as the ground

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      • #4
        for something thats 150W yes u will need 8 gauge.. u can run smaller if u want but u will limit the power output of the inverter..

        the ground wire has to be the same if not a little bigger than the input.. and tmake sure there is a GOOD connection.. not good having 8 gauge if u stip off half the wires to connect it up..

        and the ignition switch only needs to be small. that is only a small 12v trigger ..
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        • #5
          Ripsurf is 100% correct. I would add that you may want to use high strand count wire as well. Easier to work with and less power loss if you are running long distances.

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          • #6
            lots of good info here
            http://www.the12volt.com/info/recwirsz.asp

            Bear in mind that your Opus is likley more efficient than an audio amp so a 150W Opus is probably closer to a 100W audio amp than it is to a 200W one. Another thing to concider is that you will likley only be using 70-100 W of it's capacity depending on what you have for hardware. Also the wire capacity ratings are (and should be) very conservative. You could run a 150W Opus over a 10' run of 12ga wire, it's not a good idea, but it's unlikley to cause a problem. As you start to exceed the ratings you will get a slight voltage drop and the wire will begin to heat up. For modest amounts of current over the rated values in the tables in the link I posted these two things will be hardly noticable.

            In my WRX I used 8ga wire to run from the battery(via a fuse right at the battery) to a buss bar i have under the center console. I then use 12ga wire to run 2' from that buss to my 90W opus under the drivers seat. I then run other wires from that buss off to power other things in my car like my cell booster (14ga) my Xenarc (14ga) and my amp (8ga)

            Hope this helps

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            • #7
              Ripsurf said "This wire will go into another fuse box,". What do you mean another fuse box?

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              • #8
                I think he meant a fused distribution block.

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                • #9
                  What is a WRX? What is a buss bar? What is a my cell booster? Sorry for the questions but I am very new at this stuff.

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                  • #10
                    Originally posted by Showmehow
                    What is a WRX?
                    You're kidding right?
                    It's my car, and what a great car it is....
                    http://www.subaru.com/servlet/showro...mmand=overview

                    Originally posted by Showmehow
                    What is a buss bar?
                    same thing as a distribution block, a hunk of metal with a bunch of wires screwed to it. 12v from the battery comes in on one big wire 12v goes out to other stuff over smaller wires.

                    Originally posted by Showmehow
                    What is a my cell booster?
                    it's an amplifier to boost the signal to my cell phone. workes great.
                    http://www.criterioncellular.com/amplifiers/index.html

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                    • #11
                      IG was right i did mean a fused distribution block

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                      • #12
                        Okay, One more thing... Can I just go from my battery to the in line fuse(15AMP) and then to my opus power supply? Why do I need the distribution block?

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                        • #13
                          Originally posted by Showmehow
                          Okay, One more thing... Can I just go from my battery to the in line fuse(15AMP) and then to my opus power supply? Why do I need the distribution block?
                          I don't thnk you need a distribution block since you only use the power cable for your Opus.

                          btw, which department in lowes you got ur 8 gauge wire? i couldnt find it in my lowes. and how much?

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                          • #14
                            Lowes department

                            It was the electric department, and it was 27 cents per foot. Then I got 12 guage too, but I don't think that I can use that. From what I read in these posts, I have to use the same guage for all. Right?

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                            • #15
                              Originally posted by Showmehow
                              Okay, One more thing... Can I just go from my battery to the in line fuse(15AMP) and then to my opus power supply? Why do I need the distribution block?

                              you need the distribution block to "distribute" power "safely" to your other devices such as your audio amplifier, and other device that needs 12 volts of power. altho all your stuff needs the same 12v of power, they do need different amps fuses. for example: dc-dc psu (like your opus) would need 15 amps, while audio amplifier would need 20amps fuse or so.

                              in my setup i don't have a distribution block, not because i don't need it, it's just that i am too lazzy right now. so what i have is a messy setup with 3 wires with 3 inline fuses of diff. amps capacity connected to each designated devices: my dc-dc homemade psu(10amp), 4 channel audio amplifier(20amp), and a wire connectedd to my main batt.(30amp). if you have more than one devices that would need a single power sources (e.g. battery), a distribution block would come in handy.


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