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Original wiring capability

Discussion in 'Early CJ5 and CJ6 Tech' started by Kodiak12060, Jan 6, 2005.

  1. Jan 6, 2005
    Kodiak12060

    Kodiak12060 Sponsor

    Beacon NY
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    I think the original alternator on a V6 w/ 25 or 30 amp. If one was to go to a 60 or 90 amp alternator would you need a complete upgrade of the wiring harness?
     
  2. Jan 6, 2005
    beeser

    beeser Member

    Arizona
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    I could be wrong but doesn't there have to be an added load involved before the wiring is affected? In other words, just because there is additional generating capacity doesn't equate to more current flow. Have you added any additional circuits to the Jeep?
     
  3. Jan 6, 2005
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
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    What Beeser said. Also I think the alternator was at least 35 amp stock. Only wire that would have increased current is what you would have to worry about.
     
  4. Jan 6, 2005
    Hawk62cj5

    Hawk62cj5 Captain of OldSchool

    Brodnax Va.
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    another thing was it six volt ? if it was and now is 12 volt your wiring should be twice as heavy as you need it to be. I think
     
  5. Jan 6, 2005
    beeser

    beeser Member

    Arizona
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    Good point. Twice the voltage would increase the resistance two-fold if the current remained the same. Right?
     
  6. Jan 6, 2005
    w3srl

    w3srl All-around swell dude Staff Member

    Port Orange, FL
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    Actually, if your Jeep was originally 6 volt and you convert it over to 12 volt, the wiring will be TWICE the gauge needed according to Ohm's law.

    Amps equals Watts divided by Volts, or I = P / E To find the watts, Multiply Volts times Amps.

    Soooo, if you have a Jeep horn for example, that draws 3 amps at 6 volts that would be 18 watts. (3 amps x 6 volts) Applying Ohm's law, 18 watts / 6 volts = 3 amps, so we know we're good at 6 volts.

    Moving up to 12 volts , 18 watts / 12 volts = 1.5 amps.

    Capisce?
     
  7. Jan 7, 2005
    schardein

    schardein Low Range Therapy

    Success, MO
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    I suggest you may want to upgrade the charge wire from the back of the Alternator to wherever it puts power to the battery/entire system at, on Chevy trucks that is where the positive cable attaches to the starter solenoid at. That is where I have always done my conversions at and seems to wurk fine. One website that seemed to be very well researched and well written said to resist the temptation to run it directly to the positive battery post, even though that is where it ends up. They listed the reasons but is longer than we have here...
    6 volt is twice as heavy, as already noted...
    Other than that everyone nailed this one, just upgrade those wires that would see a heavier load due to other mods, if everything else is the same, you're good....
     
  8. Jan 7, 2005
    w3srl

    w3srl All-around swell dude Staff Member

    Port Orange, FL
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    Um, what did I miss? College physics was quite a while ago, but here's what I remember:

    AMPS= WATTS÷VOLTS I = P ÷ E or A = W ÷ V
    WATTS= VOLTS x AMPS P = E x I or W = V x A
    VOLTS= WATTS ÷ AMPS E = P ÷ I or V = W ÷ A
     
  9. Jan 7, 2005
    w3srl

    w3srl All-around swell dude Staff Member

    Port Orange, FL
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    Good point Greg, that charging wire should be able to handle the rated capacity of the alternator and then some for safety....
     
  10. Jan 7, 2005
    Packer

    Packer Slacker

    Livermore, CA
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    The following link has a nice electrical chart with Conservative curent values per wire size.

    Below the chart is a nice "calculator" that one can use to figure out wire size/current/Voltage loss from. It might keep you entertained for hours! ;) ;)

    http://www.powerstream.com/Wire_Size.htm
     
  11. Jan 7, 2005
    beeser

    beeser Member

    Arizona
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    What do you mean by "twice as heavy"?
     
  12. Jan 7, 2005
    Kodiak12060

    Kodiak12060 Sponsor

    Beacon NY
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    It was 12v originally but if I add off road high intensity lights or an electric heater plus the necessary radar detector and cell phone. I don't back out of my driveway w/o the detector! I'm wondering about fryin stuff. How would you hook up these extra items or increase the capacity of the wires going to the cigarette lighter?
     
  13. Jan 7, 2005
    w3srl

    w3srl All-around swell dude Staff Member

    Port Orange, FL
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    Sounds like you ought to be considering the addition of a buss bar, which is little more than a solid copper bar that is insulated from ground and fed 12v with a big honkin' cable tied directly to the battery, or to the battery side of the starter solenoid. Use a #4 or bigger cable for the feed, and fuse each line coming off it for the accessories.

    I'd use a fused #10 wire for EACH lighter socket, and the same for the feed to the aftermarket lights. You *MUST* use a relay to feed the lights, or you will have to use #10 all the way back to the switch and back up to the lights, not to mention that you will continually fry the switch if you try to run that kind of amperage through it.

    HTH :beer:
     
  14. Jan 7, 2005
    schardein

    schardein Low Range Therapy

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    Beeser, When going from 6 volts to 12 volts, using the same accessories, the wires see 1/2 the amps they did before, that's what I mean be twice as heavy (gauge) then they would otherwise need to be. That is assuming they were the right guge to begin with, before the 12v conversion.

    Steve is right on in his recommendations. I'll add that a cell phone or radar detector won't draw enough amps to warrant using a 10 gauge wire to the cig lighter, however it is a very good idea, and is what I did on mine, just in case you ever use a higher amp device in the socket, ie power inverter, 12v drink mixer (yep, I got one), etc.

    As for a cig lighter, I mounted mine on a bracket under the dash so as not to cut holes. The bracket is actually just a straight piece of steel, so the cig lighter socket points down to the floor and is hidden from view yet easily accessible. This also prevents rain from getting in or on it when the top is off (prevent rust).
     
  15. Jan 7, 2005
    beeser

    beeser Member

    Arizona
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    Still don't understand. Are you saying that the current flow will be 1/2 the amount at 12 volts than at 6 volts assuming the same wires are used?
     
  16. Jan 7, 2005
    66cj5

    66cj5 Jeep with no name

    NorthWest Indiana
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    the wire will take half the amps at 12volt than 6volt. when you increase amps, voltage decreases. when you increase volts, amps decrease.

    So, if wire "X" carries 10 amps @ 6volt, it would have 5 amps @ 12volt. basicly any wiring from a 6 to 12volt conversion has plenty of volt/amp capitcity still in it.
     
  17. Jan 7, 2005
    beeser

    beeser Member

    Arizona
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    So, the resistance in wire "X" changes as well in your two examples?
     
  18. Jan 7, 2005
    schardein

    schardein Low Range Therapy

    Success, MO
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    I am by no stretch an electrical engineer, nor do I have ohms law memorized, but to put it simply the wires don't care much about the voltage, it is the amps that we are concerned with. Due to ohms law, when we increase the voltage of the system, the amperage flow decreases. If the wires were originally sized to carry 3 amps at 6 volts, then they are plenty capable of carrying 1.5 amps at 12 volts.

    One of the guys that knows ohms law can answer your question about does the ohms change. It will, but I can't remember the formula to figure it out (been a long time since I had to apply the "theory" part of it....)
     
  19. Jan 7, 2005
    william_cj3b

    william_cj3b 3BOB driver

    Milton, FL
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    When comparing 6 and 12v it's easier to think in terms of "power" rather than voltage or current draw. "power"=Watts. Watts=volts x amps.

    Lets assume that to turn over a Fhead requires 2400 watts of power. If the starter is six volt it will draw 400 amps. Thus 6v x 400a = 2400w or 2400w/6v=400a. A 400a starter load demands a cable 1/0 or larger.

    Now, later the vehicle is converted to 12v. It stills requires 2400w of power to turn the engine over. However, the starter (12v) will now only draw 200 amps. Why? Volts x Amps = Watts. 2400w/12v=200a. At a 200a load a no. 2 cable should suffice.

    Clear as mud??
     
  20. Jan 7, 2005
    schardein

    schardein Low Range Therapy

    Success, MO
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    Will, I'm tracking! Even though I don't use ohms law much, the ampsxvolts= watts is one I do know and use. Good for when you add 4 100 watt lights and want to know what kind of amp load you just slammed your alt with!! You can use 14volts also with the engine running and the alt working the system volts should be around 14-14.5 anyway. 400/14=28.5!
     
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