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Thread: Power question.

  1. #1
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    Power question.

    I have my carpc on the bench. The audio outputs are connected to an amplifier and it all seems to work peachy. Music volume and sound are great. Touch screen works perfectly etc, etc. But now I have to get all this into the car, so...to instal the amp it recommends connecting it directly to the battery. Now here are the questions I hope someone can answer.

    Why do I need to connect it directly to the battery?
    If I do connect the amp directly to the battery can I power the carpc from the same cable?
    If I can't, can I connect the carpc to the 12V power supply that used to go to the head unit?

  2. #2
    Constant Bitrate
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    It's always best practice to connect anything thst draws high current directly to the battery. Yes you can connect the power supply of the carpc to the same power cable that connects the amp to the battery just make sure
    • Your power cable is big enough for all the loads
    • You use a fuse on all power connections to that line
    • the main line is fused properly at the battery


    You could power the carpc off the headunit powerline but make sure to connect to the correct lines. Most head units have both a switched and unswitched 12 volt line and you have to make sure the carpc main power is connected to the unswitched line. Also make sure that the headunit line is capable of supporting the current the carpc will need. If it doesn't then I'd run a seperate power line for the carpc with the correct size fuse to protect things.

  3. #3
    Maximum Bitrate kegobeer's Avatar
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    Buy an amplifier installation kit - it will include the power, fuse, and other cables/connectors you'll need. Don't go cheap when you buy the cabling. Trust me on this, you'll end up replacing crappy wire later on. I suggest getting at least 4GA wire to allow for any future upgrades and add-ons. You'll also want to buy a couple of distribution blocks, so you can connect the power and distribute it to the amp, your computer, and other hardware you'll buy later, and do the same for the ground. I use these, and they work great.

    It doesn't sound like you've done much car audio work, so I recommend you read up on how to install an amplifier, head unit, etc, before you go any further. Crutchfield has some pretty good basic installation guides on their website, and there are a ton of car audio forums that you can visit to get some basic info. You might also want to find a forum dedicated to your car, because there's certainly a few threads about how to run the power from the battery, through the firewall, and to wherever you are putting your equipment.
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  4. #4
    MySQL Error soundman98's Avatar
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    Quote Originally Posted by tag141 View Post
    Why do I need to connect it directly to the battery?
    because as much hassle as it is to run a new wire, the hassle of determining if the factory wire can support the load is even worse.

    and because factory wiring is typically 'just' enough to run the device that was factory installed, the wire is not meant to carry any more power then that device..

    there is also grounding issues-- many times, the factory grounds are not good enough for aftermarket equipment..

    and finally, there are many times where a single factory-fuse feeds multiple devices. to correctly use a factory wire, you not only need to determine what else is uses that fuse, but how much current they draw..


    you see, it is just plain easier to run your own wire. then you can control every aspect of the install-- what devices the wire uses, where it is grounded, and how big the wire is..

    Quote Originally Posted by tag141 View Post
    If I do connect the amp directly to the battery can I power the carpc from the same cable?
    this depends on the thickness of the wire. you did not state the power capacity of either the amp, or carpc, so i wouldn't go making claims of how big this wire needs to be(to others: how do we know if he is using a motorcycle amp + m1 psu, or a 1,000w sub amp + opus 360? both require drastically different wiring plans)

    if you account for the power draw of both devices while selecting the correct wire, then yes, it is fine to power both devices from the same wire. but if you are only accounting for the power draw of the amp when selecting the wire, then it probably won't be a safe idea to run the carpc off the same wire..


    Quote Originally Posted by tag141 View Post
    If I can't, can I connect the carpc to the 12V power supply that used to go to the head unit?
    again, it depends on the power draw, but i don't like connecting to any factory wires other then for the acc-signal. without knowing everything about that wire, it can be problematic...

  5. #5
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    Quote Originally Posted by that_kid View Post
    It's always best practice to connect anything thst draws high current directly to the battery.

    make sure the carpc main power is connected to the unswitched line.
    That's what I presumed but thought I would just double check. Measure once, cut twice as they say !! I have already determined which is switched and which is unswitched.

    Quote Originally Posted by kegobeer View Post
    Buy an amplifier installation kit
    That's what I was looking at when I bought the amp

    Quote Originally Posted by kegobeer View Post
    It doesn't sound like you've done much car audio work
    What gave it away!!

    Quote Originally Posted by soundman98 View Post
    this depends on the thickness of the wire. you did not state the power capacity of either the amp, or carpc
    I run a M2-ATX powering a mini-itx board and the amp is rated at 700W RMS running 50Wx4 ohms.

  6. #6
    MySQL Error soundman98's Avatar
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    then in that case, 4ga is fine:

  7. #7
    Raw Wave
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    Of course if the amp or connection goes faulty and blows the main fuse, you lose the carpc too.

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