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Ground to battery. Right or wrong?

Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=86660
Printed Date: December 08, 2022 at 7:15 AM


Topic: Ground to battery. Right or wrong?

Posted By: dblboinger
Subject: Ground to battery. Right or wrong?
Date Posted: December 05, 2006 at 1:38 AM

Brand new member. Wish I had known about this forum sooner.

I'm installing a 5.1 system in my RX7. Total power will be about 1500 watts. I bought enough 1/0 gauge cable, both power and ground, to run all the way to the battery. When I mentioned to the guys at CarToys that I was planning to run the ground all the way to the battery they said not to because it will add noise. Seems to me this would be the best way to go and if anything should prevent noise.  Any comments on this?

Any recommendations on how to get 1/0 gauge cable through the firewall? Can I run through the floor back near my amps and run the cable underneath the body? Should I use conduit if I do?

Finally, I'd like to ask for some recommendations on my center channel. My car, a '93 RX7, has a center channel speaker. It appears to be maybe a 1" speaker. Not sure if the mount can be enlarged. Anybody ever dealt with this? What would you recommend?

,




Replies:

Posted By: Fastlearner
Date Posted: December 05, 2006 at 3:44 AM
Don't run the ground all the way up front. Just screw it to metal in the trunk. Also I think that running the wires under the car are probably best(protect the wire).




Posted By: cmrs2k
Date Posted: December 05, 2006 at 8:16 AM
Greetings.  If you do run under the vehicle, some type of conduit would probably be wise.  Also, not to cause an arguement, but I had my system setup with a 1/0 shot from the battery for power and then my ground went to the frame.  My bass amp kept giving up.  It kept reading the low voltage warning when it did.  I tried the ground at several different bolts, installed my own ground lugs, etc.  It still failed rather often.  I then ran a 1/0 ground shot from the battery.  No failures yet.  Now, I will say that this is probably more vehicle specific in this case, and that ground to battery or to frame is not the only variable. 

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Chris R.




Posted By: prosound
Date Posted: December 05, 2006 at 10:56 AM
I've always been tought you want your ground as short as possible, running it to the battery would be pointless...

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Stephen Theno
Pro Sound
Lawrence,KS




Posted By: DYohn
Date Posted: December 05, 2006 at 11:24 AM
Keeping ground as short as possible is always the best bet, however some vehicles (especially uni-body Fords) have very poor ground return resistance to the alternator (it's actually the case of the alternator that is the true ground in a car, not the battery negative terminal.)  So, if your ground return resistance is high, running a proper cable back to the battery or to the alternator case is sometimes the only way to eliminate ground loop hum.  Measure the return resistance, if it's less than 1 ohm you are not likely to gain anything by running a cable to the battery.

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Support the12volt.com




Posted By: sin0cide
Date Posted: December 05, 2006 at 11:34 AM

it could have something to do with the size of wire that a stock battery is hooked up with which is more like 4 gauge. I would rerun the ground wire with a thicker guage and run one to the actual frame aswel. (upgrade your big 3)





Posted By: geepherder
Date Posted: December 05, 2006 at 7:41 PM
Just to add to what others have posted, you're factory wiring (battery/alternator/grounds) should be upgraded to at least the size wire you're using for your system. That way, when you ground to the frame, there's no "bottle necking" so to speak. Read the "big 3" sticky. Also keep in mind if you're exceeding the current output of your alternator, that'll need to be upgraded as well.

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My ex once told me I have a perfect face for radio.




Posted By: dblboinger
Date Posted: December 05, 2006 at 10:36 PM

No dis to anyone who has replied, but what are your responses based on? Experience or just an opinion? The following is an excerpt from another thread posted by Rob @ Forbidden Audio. He appears to be present throughout this forum on a wide variety of subjects and he states:

"To add to this, a good ground for car audio applications will have a return resistance reading of 1/2 ohm or less. I have yet to have a return reading of 0 ohms. If a ground return reading cannot be made to get below 1/2 ohm by means of the "BIG 3", then it is adviseable to ground direct to the battery."

If grounding to the battery is recommended when the "BIG 3" fails, then why would it not be recommended any other time? Maybe I won't gain anything, but I shouldn't lose anything either, except the cost of the cable and the time to do it.

BTW, I'm in the process of upgrading all power ground cables to 2 gauge. If I direct ground my amps I'll use 1/0, just like I'm using for the +12. This RX7 is a bitch to work with in some ways. And some of the things they did don't make any sense. For instance, they came off the battery + to a fuse box using 4 gauge. At the fuse box, paralleled on the input side is a 1 or 2 gauge cable going directly to the starter. After passing through the "MAIN" fuse there are 2 - 4 gauge cables running to each of 2 more fuse boxes. Talk about a "bottle neck".  I also don't understand why they ran through the "MAIN" fuse to go to the other 2 fuse boxes. What's the point? If anything on either of the "SUB" fuse boxes has a problem it's going to open a fuse in it's respective fuse box well before it opens the 120A MAIN. I'm seriously considering running the starter direct to the battery as well using 2 gauge and running new to the "MAIN" fuse box and new 4 gauge from the "MAIN" fuse to the 2 "SUB" fuse boxes. According to my calculations of current draw this should be more than adequate.  All my lugs will be soldered and I'm using Tsunami battery terminals.

Regardless, I appreciate all the input. Wish people on my other forums were this willing to help out. You guys/gals are great.





Posted By: aznboi3644
Date Posted: December 05, 2006 at 11:53 PM
DYohn] wrote:

Keeping ground as short as possible is always the best bet, however some vehicles (especially uni-body Fords) have very poor ground return resistance to the alternator (it's actually the case of the alternator that is the true ground in a car, not the battery negative terminal.) So, if your ground return resistance is high, running a proper cable back to the battery or to the alternator case is sometimes the only way to eliminate ground loop hum. Measure the return resistance, if it's less than 1 ohm you are not likely to gain anything by running a cable to the battery.


Question about this ford thing because I have a ford.

Are the 98 explorers unibody??

So the ford unibodys have bad grounding to the body and need a ground to the battery??

Sorry if this is kinda like thread jacking




Posted By: memphis9
Date Posted: December 06, 2006 at 9:53 AM

aznboi3644 wrote:

DYohn] wrote:

Keeping ground as short as possible is always the best bet, however some vehicles (especially uni-body Fords) have very poor ground return resistance to the alternator (it's actually the case of the alternator that is the true ground in a car, not the battery negative terminal.) So, if your ground return resistance is high, running a proper cable back to the battery or to the alternator case is sometimes the only way to eliminate ground loop hum. Measure the return resistance, if it's less than 1 ohm you are not likely to gain anything by running a cable to the battery.


Question about this ford thing because I have a ford.

Are the 98 explorers unibody??

So the ford unibodys have bad grounding to the body and need a ground to the battery??

Sorry if this is kinda like thread jacking

Explorers are not unibody. They have a full frame. I have done a few installs on explorers. I have never had  the problem of ground loop hum from grounding to the frame of a explorer.  I did have a problem of ground loop noise in my Mustang when I did ground to the body. But the problem was fixed when I grounded directly to the battery.



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G-Boys Customz
Northville, MI




Posted By: forbidden
Date Posted: December 06, 2006 at 11:43 AM
I have in a 01 Ranger and we all know that the Ranger and the Explorer share the same platform. The proper thing to do in all cases is break out the meter and check the return resistance yourself. This suprises even the best of installers.

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Top Secret, I can tell you but then my wife will kill me.




Posted By: aznboi3644
Date Posted: December 06, 2006 at 4:22 PM
Yeah...I tried drilling a hole below the rear seats but hell theres like 3 layers of sheet metal lol so thats not really an option...I'm still trying to find a good ground.

And no I didn't drill into my gas tank as there were no fumes and I triple checked by looking under my truck lol




Posted By: j_darling2007
Date Posted: December 07, 2006 at 8:15 AM
If it has true frame rails, it is not unibody.

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There are 3 kinds of people in the world, those who can count and those who can't




Posted By: dabear1029
Date Posted: December 07, 2006 at 9:37 PM
I have a 1997 Ford Escort that is a unibody. My amp is grounded to the rear deck where the rear speakers are. Never had a problem at all, we found a threaded hole up there, cleaned off all the paint inside and on there very outside of the hole, found the right bolt to fit the threads, crimped on a terminal and bolted it up there. My ground wire is only about 12 inches long, and the amp is not moving, so I don't have to worry about it ripping out of the amp.

Swick




Posted By: aznboi3644
Date Posted: December 07, 2006 at 11:26 PM
That doesn't really sound like a good ground....meter it and see what comes up




Posted By: stevdart
Date Posted: December 08, 2006 at 7:56 AM
dblboinger wrote:

If grounding to the battery is recommended when the "BIG 3" fails, then why would it not be recommended any other time? Maybe I won't gain anything, but I shouldn't lose anything either, except the cost of the cable and the time to do it.




It amounts to a matter of safety and good judgement based on the fact that the ground wire becomes a partially-hidden wire when it is run from trunk to engine bay. Known:
The ground wire is not a fused wire.
The ground wire must be constantly connected to chassis while power is supplied to the appliance (thus no fuse allowed).
A hidden wire is harder to monitor for defects than a short, visible wire.
Damage to the appliance will occur if the ground is disconnected while hot is still connected.

There are likely to be more reasons than I listed to attempt a short ground wire in plain sight from amplifier to chassis rather than just running the ground to the alternator casing from the get-go, but that's the short answer to your question.

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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.




Posted By: j_darling2007
Date Posted: December 08, 2006 at 5:45 PM
Stevdart, if this is true, which I am not saying it is not, wouldn't the cars be damaged when you disconnect the ground wire from the battery to do electrical work like the manuals and technicians say.

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There are 3 kinds of people in the world, those who can count and those who can't




Posted By: dblboinger
Date Posted: December 08, 2006 at 11:23 PM

[QUOTE=stevdart]

The ground wire must be constantly connected to chassis while power is supplied to the appliance (thus no fuse allowed).
Damage to the appliance will occur if the ground is disconnected while hot is still connected. 

Say what? Removing the ground is the preferred method of removing power from any electronic component, especially if microprocessors are involved (i.e. car stereo's, engine ecu's, etc.) Having worked in electronics for nearly 30 years I can tell you, I've NEVER seen a circuit damaged from removing/connecting the ground/common. The same can not be said about the supply. And can you imagine a car stereo where the wires are not hidden?





Posted By: stevdart
Date Posted: December 09, 2006 at 3:15 PM

j_darling2007, don't get confused about the answer.  The topic is about the amplifier's ground connection, not the circuit ground.  Of course it is correct to remove the negative battery cable  (see link below) to open the circuit and shut off power.  Once there is no circuit, there is no power to any appliance (including amplifiers) that are connected to that circuit.  With a dead circuit it doesn't matter if the power and ground cables are disconnected from the amplifier, or in what order.  But even so, even with the circuit open and no available power, the ground is always connected first to the amplifier and disconected last.  That is to say, you always ensure that the ground connection is made before the power is connected.

To the OP, you asked about the reason to ground the amplifier to chassis and I tried to give you a valid reason.   Here's another: 

Perry Babin said HERE in "Amplifier Installation Notes":

"If the amplifier's ground is properly connected to the body of the vehicle, it will provide a better return path to the charging system's ground than will a ground wire run back to the battery. This is especially true if the ground strap from the engine block to the chassis is upgraded."

Proper grounding of an amplifier can almost always be achieved through the floor pan, and with best possible results.  IF chassis grounding repeatedly fails after trying other nearby locations, you can run the ground wire directly through the car and engine compartment to a suitable grounding location.  By that time you will have tried and failed to get adequate ground return using the chassis, and so the next best hope for success is a wire directly to the source.

j_darling2007 mentioned the circuit ground, which the question doesn't pertain to.  But speaking of the circuit, if the circuit is live,  the amplifier is supplied power via two wires: positive and ground.  If the ground wire is long and snakes throughout the vehicle rather than being short at the amplifier's mounting location, there is a much greater chance of unseen damage that can occur to the wire.  Wouldn't anyone agree that a 15' wire has, at the very least, the potential of fifteen times greater risk of damage than a 1' wire?  And if this wire is severed or otherwise badly damaged while the amplifier is connected to a live circuit, what can likely happen?  



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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.




Posted By: dblboinger
Date Posted: December 10, 2006 at 1:00 AM
stevdart wrote:

j_darling2007, don't get confused about the answer.  The topic is about the amplifier's ground connection, not the circuit ground.  Of course it is correct to remove the negative battery cable  (see link below) to open the circuit and shut off power.  Once there is no circuit, there is no power to any appliance (including amplifiers) that are connected to that circuit.  With a dead circuit it doesn't matter if the power and ground cables are disconnected from the amplifier, or in what order.  But even so, even with the circuit open and no available power, the ground is always connected first to the amplifier and disconected last.  That is to say, you always ensure that the ground connection is made before the power is connected.

Response: This has absolutely nothing to do with my original question. But to clarify the point of your statement, the damage caused by removing the amplifier ground is due to the fact that removing the amplifier's power ground does not completely remove what you refer to as the circuit ground. If you remove the power ground only, the amplifier will attempt to complete it's circuit through the RCA cables and will most likely blow out the front end of your amplifier because the input circuitry is not desinged to handle the amount of current common in the power ground. This is the reason there is a power ground to begin with.

 To the OP, you asked about the reason to ground the amplifier to chassis and I tried to give you a valid reason.   Here's another: 

Perry Babin said HERE in "Amplifier Installation Notes":

"If the amplifier's ground is properly connected to the body of the vehicle, it will provide a better return path to the charging system's ground than will a ground wire run back to the battery. This is especially true if the ground strap from the engine block to the chassis is upgraded."

Proper grounding of an amplifier can almost always be achieved through the floor pan, and with best possible results.  IF chassis grounding repeatedly fails after trying other nearby locations, you can run the ground wire directly through the car and engine compartment to a suitable grounding location.  By that time you will have tried and failed to get adequate ground return using the chassis, and so the next best hope for success is a wire directly to the source.

 

Response: If this is true there is absolutely no reason to ground directly to source, EVER. This also means there should be no such thing as a ground loop because all chassis parts are always at the exact same potential.

How anyone can say chassis sections that could be bolted together, loose, corroded or anything else short of being  welded, can possibly provide better continuity than a heavy gauge, multi-strand copper cable is beyond me.

 

j_darling2007 mentioned the circuit ground, which the question doesn't pertain to.  But speaking of the circuit, if the circuit is live,  the amplifier is supplied power via two wires: positive and ground.  If the ground wire is long and snakes throughout the vehicle rather than being short at the amplifier's mounting location, there is a much greater chance of unseen damage that can occur to the wire.  Wouldn't anyone agree that a 15' wire has, at the very least, the potential of fifteen times greater risk of damage than a 1' wire?  And if this wire is severed or otherwise badly damaged while the amplifier is connected to a live circuit, what can likely happen?  

Response: If, as you suggest above, all points on the chassis are at the same potential then it is irrelevant how long or short the cable is, or if it gets damaged. That is unless the cable is completely severed. If something significant  enough to completely severe a 1/0 gauge cable happens to my car, I doubt that an amplifier or two will be at the top of my list of concerns.

 






Posted By: stevdart
Date Posted: December 10, 2006 at 12:19 PM
Okay.

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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.




Posted By: j_darling2007
Date Posted: December 11, 2006 at 8:40 AM

I got what you are saying.  I thought you meant the entire electrical system, not just the amplifier.  Thanks for the response.

Jacob



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There are 3 kinds of people in the world, those who can count and those who can't




Posted By: jaybanga617
Date Posted: December 15, 2006 at 10:47 AM
P.S make sure you have a good crimp on the ground cable

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jay petrucelli





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