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Thread: Questions Regarding Wire Size, Battery Size, and Alternator Size - see here

  1. #1
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    Questions Regarding Wire Size, Battery Size, and Alternator Size - see here

    I just thought I would post up an entirely new thread with this information since it seems to be the basis of many questions.

    The proper Gauge Wire based on current demand and length of run:


    The proper battery size based on total RMS wattage of system:


    The proper alternator size based on total RMS wattage of system:


    The proper fuse size based on power wire size:


    If anyone has anything they would like to add or any comments or corrections that they would like to make, feel free!

    Hope this helps someone out there!
    Jan Bennett
    FS: VW MKIV Bezel for 8" Lilliput - 95% Finished

    Please post on the forums! Chances are, someone else has or will have the same questions as you!

  2. #2
    Variable Bitrate
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    Fusing (and most anything else car electrical related)
    http://www.bcae1.com/
    Scroll right hand side and pick...wait for it...fuses.

  3. #3
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    updated my post - thanks EricE - that page slipped my mind...lol
    Jan Bennett
    FS: VW MKIV Bezel for 8" Lilliput - 95% Finished

    Please post on the forums! Chances are, someone else has or will have the same questions as you!

  4. #4
    Newbie StalkS's Avatar
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    AWG Conversion table

    Hopefully this will be of use to some people who need an easy way to identify cables currently being used or that are floating around spare. It is an image from the following site tnt-audio.com

    [IMG][/IMG]

  5. #5
    Newbie
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    actually the alt. is measured fron the amps drawn from your amp. example... lets say your factory alt is rated at 105 amps and your amp has two fuses rated at 25 amps a piece well thats drawing 50 amps from your alt. leaving you with 55 to run your car... not good... so in order to get the right power for your car and audio you would need a alt with at least 155-160 amps

  6. #6
    Newbie
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    new on here

    question what size wire would i need to run from front of my motor home to back the which is 7 me long I am hopeing to fit a spare battery in the back and charge from the alternater thx slowpace

  7. #7
    Raw Wave
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    Just a quickie (LOL - from me?)... But I just saw this thread.
    Great OP RedGTiVR6!

    I could/might add related comments later, but I recently (again) referred to Bill Darden's Car And Deep Cycle Battery FAQ in Doesn't hold standby power if I crank the car right away (page 10). (Download the ZIP as described, or see my related comments in that reply.)
    That's the good oil if you want the truth about batteries...


    As usual, I try to dispel misunderstandings, clarify or paraphrase ambiguities or confusing stuff, and relate to the high-level philosophies that lead to rules etc.
    I have been known to comment on some sources - eg, bcae1.com can be a bit outdated or limited.


    Sorry slowpace, that doesn't answer your question, though my posts elsewhere cover that (ie, what max voltage drop do you want, hence at current I (Amps), gauge is found from V=IR => R=V/I where R is the gauge resistance per length times its length... BUT - remember and allow for ground return (cable/s) and maybe fuse and switching drops).
    Otherwise it is merely what cable is rated to carry your load current (probably as free-standing "transmission" and not as a bundled or harnessed cable).
    See too my posts on the "UIBI" (search google for "UIBI isolator") for a battery isolator (which is highly recommended, even if a voltage sensing aka Smart isolator, though the UIBI can be MUCH cheaper...).
    Last edited by OldSpark; 09-02-2011 at 07:38 PM.

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