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Thread: Questions about grounding, fuses, amps, and whatever else I don't know.

  1. #1
    Newbie thejavabuddha's Avatar
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    Questions about grounding, fuses, amps, and whatever else I don't know.

    Ok, don't flame me too bad . I've searched till my brain hurt and still have a few questions about some of the details about wireing up a carPC/Amp for power.

    First off, let me run a couple of things I'm leaning towards and let me know if I've made any false steps so far. I decided to go with a Kolossus Fleks Kable 4 Gauge wire to run power from the battery to the trunk where the PC and AMP are, and a 0 Gauge equivilant for ground to chassis. This is to power my M2-ATX PSU and D945GCLF2 MOBO as well as my MTX Thunder564 Amp.


    1) OK, first question: I have been looking at distribution blocks. It seems most have just ports for the power wire with power comming in and spliting out. I don't see anything about ground wires in this equation. Does each component have to run it's own ground wire to the chassis?

    2) I have seen some "ground distribution blocks" like this one, but I'm confused about how these get hooked up. This one says it has:
    two "large" ports for 1/0 or 4 gauge cables and three "small" ports for use with 4 gauge or 8 gauge.
    how does it have only 3 outputs if each component has a ground wire comming back to it. Or am I missing something?

    It also says:
    ground blocks are "common" points, so there is no technical "in" or "out"
    I don't even know what to make of this. Does this mean It doesn't matter what I plug into it (power or ground) or where it gets plugged in at?

    3) Is there any bennefit to haveing (or reasons not to have) a "ground distribution block", i.e. ground loop problems etc.

    4) Yeah, I know this info is out there, and I'll do some more searching, but if anyone can point out the information or happens to know I would appreciate the help. What size fuse will I need to go from battery to distribution and what size for between distribution and carPC and AMP? I will probably be powering my lilliput 701 monitor off the M2-ATX and I'm sure I will add a few USB components as time goes by but nothing crazy.

    5) I also have to figure out where/how to ground this in my trunk of my '05 VW Jetta. So...if anyone happens to have a similar car or any usefull information on this subject I would also appreciate this!

    Thanks,
    Bill

  2. #2
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    Quote Originally Posted by thejavabuddha View Post
    I decided to go with a Kolossus Fleks Kable 4 Gauge wire to run power from the battery to the trunk where the PC and AMP are, and a 0 Gauge equivilant for ground to chassis.
    That's pretty massive overkill, but more is always better when it comes to ground.

    For what it's worth, chassis (or body, if a unibody vehicle) is actually not the most ideal ground point in a car, it's more of a compromise. The best ground is always the one which is nearest to the negative potential side of whatever power source is driving the load. When the engine is off, this is the (-) terminal of the battery. When the engine is running, this is the chassis of the alternator. If you research the OEM ground distribution diagrams for most vehicles (or at least, most modern Japanese vehicles) you'll find that the really critical grounds, like those for the ECU and related components, will usually terminate at the head or the engine block.

    Any current which you ground to chassis has to then pass through whatever ground strap(s) connect the chassis to the engine / battery in order to actually get to ground proper. So if you're going to run welding cable to ground electronics to chassis, at least make sure that the ground straps on your chassis are up to par, or it's all for naught.

    [/digress]


    1) OK, first question: I have been looking at distribution blocks. It seems most have just ports for the power wire with power comming in and spliting out. I don't see anything about ground wires in this equation. Does each component have to run it's own ground wire to the chassis?
    Yes, the expectation with those gizmos is that you'll run seperate grounds.


    2) I have seen some "ground distribution blocks" like this one, but I'm confused about how these get hooked up. This one says it has:
    two "large" ports for 1/0 or 4 gauge cables and three "small" ports for use with 4 gauge or 8 gauge.
    how does it have only 3 outputs if each component has a ground wire comming back to it. Or am I missing something?
    Well, with one 1/0 terminal and three 4/8 terminals, you can ground up to three electronic components through this block. It's quite likely that you can fit two or more device cables of a more reasonable diameter (10-14ga) into each one of the 4/8 ports, so that's additional devices.



    It also says:
    ground blocks are "common" points, so there is no technical "in" or "out"
    I don't even know what to make of this. Does this mean It doesn't matter what I plug into it (power or ground) or where it gets plugged in at?

    I'm going to digress for a moment and say that, IMO, this business of ground distribution blocks is a lot of overpriced hype. I can see the utility of power distribution blocks, in that they have internal fuses (though there are much less expensive ways of getting fused power distribution) but ground blocks? C'mon. Just take whatever point where you were going to run the big 1/0 cable to, and run the individual ground cables to it instead. [/rant]


    That said, if you want to do it all with these fancy blocks then you need two; one for power and one for ground. The power one will ideally be internally fused, while the ground one will just be a large hunk of shiny brass with holes in it.

    If your +12 block has one big hole and one small hole, and your ground block has the same, then you will run the power lead from your amp to the first small hole in the +12 block, and the GND lead of your amp to the first small hole in the GND block. Repeat for devices (and holes) 2,3,4. Then, a big wire goes from the big hole of the +12 block to either the alternator (+) terminal or the battery (+) terminal, and a big wire goes from the big hole of the GND block to either chassis, battery (-), or the engine block.


    3) Is there any bennefit to haveing (or reasons not to have) a "ground distribution block", i.e. ground loop problems etc.
    Benefit? Your wallet will be very slightly lighter (thus improving your posture and gait), however your car will be heavier by an amount equal to the weight of the block. Truthfully, that's about it.



    4) What size fuse will I need to go from battery to distribution and what size for between distribution and carPC and AMP? I will probably be powering my lilliput 701 monitor off the M2-ATX and I'm sure I will add a few USB components as time goes by but nothing crazy.
    Well, the amp is rated at 280 watts RMS, which would be about 23 amps at 12V if you were driving it with a pure sine wave, * maybe 1.5 for the efficiency factor. Figure another 15A maybe for the PC. The rest of your gizmos are of negligible concern.

    I'd fuse the block at 60A, the amp at 40A, and the PC at 20A. (I find it amusing that the picture of the amp shows three 25A fuses in it- wishful thinking?)

  3. #3
    Newbie thejavabuddha's Avatar
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    Ah, so a ground distribution block is to take in all the ground wires from the components and ground them to one wire? I though that it meant there was power AND ground for each component in one block. So I would then need one distribution block for the incoming power and ANOTHER for ground, correct? (if I wanted to do it this way)

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    That's correct. Each one of these blocks is just a single function, designed to take +12 from a single source and split it out to multiple loads, or to take the grounds from multiple devices and then concentrate them down into a single cable that actually connects to chassis/engine.

    The power distribution blocks can be handy, particularly the ones that are fused. You can find a lot of different ones inexpensively at Partsexpress.com

    Ground blocks, by comparison, are purely aesthetic thing in most installations. If you're bothering to actually run a ground cable all the way to the engine, then I can see some utility. If you're just running it to chassis, then from a technical standpoint you're probably better of just grounding every device to chassis individually, using the devices' own captive ground cable, and as short of a run as practical.

  5. #5
    Newbie thejavabuddha's Avatar
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    I still can't figure out WHERE in my trunk to ground to. I don't see any screws or bolts anywhere. I pulled up the spare cover and dug around where I could but didn't see anything.

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