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Thread: Suggestions

  1. #11
    Bj
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    Ah yeah, but what you don't seem to understand, is that what you are telling us isn't really all true. Sure if you get a bit of ****y gauge cable and mesure the voltage at the end, it will be the same for a chunky cable.
    BUT if you then put away your 20,000R load voltmeter and add a 4amp load to the end of the cable, instantly you have a voltage drop.

    When you load a cable of course it will loose voltage. The current drawn causes the voltage drop.

    gee where did you go to school......
    BjBlaster! Car MP3 & Carputer!
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  2. #12
    Bj
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    ps:

    If you put a piece of cat 5 in series with your battery cable, and start the car, you will either start a fire, or the solenoid won't kick in as the current drawn from your starter will burn the thin cable instantly.

    mind you the voltage at the other end of your cat 5 will be about 0.5 - 1V as the load is so great (200A or so on average) drawn from your starter, that the cable it basically shorted to the battery terminals. WRT the negitive term.

    So in answer to this post, heavier gauge cable will prevent a voltage drop to your PC and therefore stop shutdown of the puter when you are cranking, or idling at the lights.

    an average PC will use about 3.5A to 6A @ 12V. say it's 4A for an example.

    V/I*R

    if a cable has a resistance of 0.1R (ohms) per metre, and it's 4.5 metres from your battery to the puter, then the resistance of the cable is 4.5 * 0.1 = 0.45R.

    Then the voltage drop over that piece of cable is....

    0.45R * 4A = 1.8V

    This means that the voltage at the inverter is 12V(battery) - 1.8V(cable loss) = 10.2V.

    Not quite enough if you want to start your car as well.
    BjBlaster! Car MP3 & Carputer!
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  3. #13
    Retired Admin Aaron Cake's Avatar
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    Cool

    Get a new alternator.

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  4. #14
    Maximum Bitrate gizmomkr's Avatar
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    I'm not disagreeing with what your saying BJ. Based on mc's description, I just dont think that was the root of the problem.

    And no, I dont recomend using cat 5 as jumper cable. I guess you missed the sarcastic tone.
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  5. #15
    FLAC DodgeCummins's Avatar
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    The problem is heat and resistance.

    There is a bit of resistance over a length of wire, as a result the more current across it (Voltage is only potential, current is the actual flow) the more heat that must be dissipated.

    Also for very long runs there is a loss in power due to the resistance built up over time. 1 foot of cable may not show any, but 1000' will.

    In a car the distances are so short that cable length is negligible, however the big problem is the power (volts x current). Your fuse is a length of wire designed to take so much flow through it before it burns out 'blows'. Hopefully that amount is lower than the wires attached to it, or your wires will act as a fuse, getting hotter and hotter until they melt apart. probably after setting the interior of the car on fire.

    Since cars are 12v systems, the only variable you need to worry about is Amps (current).

    Bottom line. The more amps a machine is pulling, the thicker the wire needs to be, and the larger the fuse.

  6. #16
    Maximum Bitrate Raas's Avatar
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