Results 1 to 6 of 6

Thread: Grounding question

  1. #1
    Newbie
    Join Date
    Dec 2010
    Posts
    3

    Grounding question

    Hi Guys,

    I am kind of in a unique situation because my battery is located in the trunk, where I want to put all my other components (PSU, PC, AMPLIFIER, ETC).

    My questions are:

    1.) Can I / Should I connect all the grounds to the same grounding point (I'm not sure if that would interfere with the sound?)

    2.) Can I / Should I just connect all these ground leads directly to the battery, since it is available?

    Thanks!
    Jake

  2. #2
    Admin. Linux loser.
    Auto Apps:loading...
    Bugbyte's Avatar
    Join Date
    Sep 2004
    Location
    Corning, NY
    Posts
    7,364
    Blog Entries
    2
    Grounding to the same ground point is generally considered a good idea. Make sure that ground point is a *good* ground point with a good return path to the battery.

    I've heard both ways on the battery - yes and no, but in practice I've seen many installs where people ground directly to the battery and haven't had any issues. Where you may find a problem is if you have equipment this is NOT directly connected to the battery and is grounded to the chassis. If the ground connection is a higher resistance than your battery connection, it is that differential that creates the opportunity for a ground loop.

    As always, make sure you fuse the battery connection within a foot of the positive terminal to protect the battery if the cable accidentally grounds, and fuse again near your equipment to protect the equipment. Check the FAQs in the nav bar for more info and also visit the FAQ Emporium forum for additional FAQs in the sticky section.
    Quote Originally Posted by ghettocruzer View Post
    I was gung ho on building a PC [until] just recently. However, between my new phone having internet and GPS and all...and this kit...Im starting to have trouble justfiying it haha.
    Want to:
    -Find out about the new iBug iPad install?
    -Find out about carPC's in just 5 minutes? View the Car PC 101 video

  3. #3
    Newbie
    Join Date
    Dec 2010
    Posts
    3
    Thanks for your response Bugbyte. The way you describe the cause of ground loops makes good sense, and I recently did read something to that effect.

    Perhaps a good compromise on the two different ways to do it, is to connect all my (trunk) component grounds to the same grounding point to which the battery is directly connected.

    My plan as it is right now is to have a small distribution block for the (+) leads (all properly fused, and properly fused at the battery as well).

    I do have some experience in DC work, as I've done a lot to my 28' sailboat. However, I'm very unclear on what can cause audio interference in an automobile. If the ground loop (caused by differential resistance as you described) is the only real concern, I think I should have a good grasp on how to approach and at least diagnose if something goes wrong.

    Thanks again, and any more comments are also welcome.

    Best,
    Jake

  4. #4
    Raw Wave
    Join Date
    Nov 2009
    Posts
    2,119
    But long grounds can themselves be troublesome...
    Usually grounds are to the chassis/body etc (rather than from the front to the rear (battery) via cable) UNLESS that causes problems.
    IE - single-point grounds are used to overcome problems like noise from ground loops etc. (But power grounds are often separate from signal grounds with only a single interconnection...)


    As to grounding at the battery - it is usually the vehicle chassis/body that is ground. Strictly speaking, it is the alternator body hence the engine block etc.
    But that assumes the alternator is supplying the power, hence the alternator is "absolute ground".
    When the battery supplies the load, the battery -ve is absolute ground. This occurs whenever the alternator is unable to supply the full power required - eg, when cranking; during BIG amplifier outputs; switching transients (turning on headlights etc); or reduced RPM etc.

    Hence it depends on the system. Big audio will have a local (second) battery which is the ground & supply for the amplifiers.
    Standard setups will use chassis/body/engine ground.


    The voltage difference between all the above ground points is the resistance between them times the current through that resistive path.


    And even with big amps or winches etc, the ground us usually taken from a nearby body/chassis point since it may be too difficult to mount many or big cables to the battery. It should be inconsequential since the battery- to chassis/body cable should be the heaviest and shortest you can use - hence "negligible" resistance. (And that chassis/body point being for "common grounds" if needed.)

  5. #5
    MySQL Error soundman98's Avatar
    Join Date
    Jan 2008
    Location
    on the border of northern IL/IN
    Posts
    5,848
    what they said..

    the main reason everyone grounds to the car instead of the battery is because it is usually a very long run back to the battery, and that can cause problems with the electronics needing to 'push' the power down the line, causing heat, and premature-failure..

  6. #6
    Admin. Linux loser.
    Auto Apps:loading...
    Bugbyte's Avatar
    Join Date
    Sep 2004
    Location
    Corning, NY
    Posts
    7,364
    Blog Entries
    2
    Quote Originally Posted by OldSpark View Post
    As to grounding at the battery - it is usually the vehicle chassis/body that is ground. Strictly speaking, it is the alternator body hence the engine block etc.
    But that assumes the alternator is supplying the power, hence the alternator is "absolute ground".
    Ah, that makes sense. Thanks, OS!
    Quote Originally Posted by ghettocruzer View Post
    I was gung ho on building a PC [until] just recently. However, between my new phone having internet and GPS and all...and this kit...Im starting to have trouble justfiying it haha.
    Want to:
    -Find out about the new iBug iPad install?
    -Find out about carPC's in just 5 minutes? View the Car PC 101 video

Similar Threads

  1. Quick question about grounding LCD.
    By bthology in forum LCD/Display
    Replies: 2
    Last Post: 10-07-2010, 12:29 PM
  2. relay grounding question
    By mushrew0 in forum Power Supplies
    Replies: 2
    Last Post: 07-03-2005, 11:02 PM
  3. Grounding concern (not normal grounding issue)
    By supralightning in forum Power Supplies
    Replies: 2
    Last Post: 03-22-2004, 12:02 AM
  4. newb grounding question...
    By bstanton in forum General Hardware Discussion
    Replies: 6
    Last Post: 01-15-2003, 01:02 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •