where is the true ground?

I don't mean to stir up any emotions but i've stumbled on some compelling arguments of why it may be better to ground amps directly to the battery negative in the engine bay. The argument is based on the simple concept of. "All Connections start and END with the Battery." Now i've heard the "alternator case" is the "TRUE" ground but as the concept says, the alternator is also Connected positively to the battery and then grounded to the Firewall/Fram and from the firewall BACK to the Battery . So now im seeing the Frame of the and other metal parts of a vehicle as just Representations of the negative terminal. Its also said that Oxygen free Copper wire is Much less resistant than the frame of your vehicle. due to the rust, paint, rubber mounts, and dirt & things that cause resistance through out it getting back to the battery's negative terminal. So my final questions are really does this make the Battery negative terminal via 0ga wire the best ground in a vehicle for amps considering this concept? if not where is the TRUE ground? Thanks PS. this is just a question, im not saying that im stating any facts.I can't hear you!

Ground is just a reference point - it's wherever you deem it to be. (Though it's usually "earth" - not a chassis/body etc.) If you mean which is the lowest ground (potential), then it is the battery if the battery is supplying the load, or the alternator if it is supplying the load. (IE - the battery when not charging, and normally the alternator has the greatest voltage supply when charging.) But normally audio systems are connected to the battery for noise reasons alone. Besides - ever mounted 4G etc to a alternator (and what's the point)? Hence the audio-ground is the -ve terminal of the battery. Any other ground will never be as "low" as either the battery -ve or the alternator (ie, its chassis hence engine etc). Although OFC may have low resistance than bodywork, I doubt that cable resistance can compare to body/chassis resistance except where to different assemblies - ie, chassis to body; body to bonnet etc. If internal rust is that much of problem, the audio will disintegrate the vehicle if not motion itself. I have heard many say similar but have yet to see evidence (except for sectional bodies, fibreglass cars etc, and an old rusted out wood-framed vintage.....

rfhvhtoo wrote: Its also said that Oxygen free Copper wire is Much less resistant than the frame of your vehicle. due to the rust, paint, rubber mounts, and dirt & things that cause resistance through out it getting back to the battery's negative terminal.

A lot of things are "also said" . . . a lot of them are just plain wrong. Some people think that voltage will ONLY travel on the outside of a conductor. :D

Steel has a very low resistance as a solid condutive path and the paint, dirt etc doesnt play in to it.

Where there are two pieces making a questionable physical connection, this can be a limiter as corrosion, oxidation etc is a poor conductive path.

Having lots of clean metal together tightly will conduct huge amounts of current.

You have to balance fanatic mysticisms with the laws of physics and a measure of common sense.

So a capacitor will lower the ground and make up for corrosion? Cool! (That's crap - I'm joking etc etc). Not that I'm EVER one to question or quash spouse-tales (fanatic mysticisms etc), nor ever suggest that webland is full of errors, misquotes, misunderstanding, and DHs. Try my alternate check - if you can't measure the voltage drops (because despite being fanatical enough to have the best or an expensive system with improved cabling, you don't have or can't use a $10 voltmeter), just feel the heat along the various cable sections. This may require long hands for body/chassis paths. As to common sense (a la web logical but wrong), we all know that leads to a removal of cents from the common to the amassing few. (Don't we?) Only Idiots and Anons to afraid to ID themselves along with senile codgers and a host of others hereon would attempt to disrupt that traditional and expending practice. (Blessed are the Meek for they shall take the Earth....)

oldspark wrote: If you mean which is the lowest ground (potential), then it is the battery if the battery is supplying the load, or the alternator if it is supplying the load. (IE - the battery when not charging, and normally the alternator has the greatest voltage supply when charging.)

(just making sure i understand) So the Case of the alternator "When Charging" is the better ground than the Batteries Negative terminal. Unless the system is NOT being charged by the alternator (Engine Off) then the better ground is the battery negative... So would running a 0ga wire back to the battery have less or more resistance than the cab of a truck? Because i dont know about anyone else does but I have a 8inch 0 gauge wire connecting my frame to my cab... unless you have a ford f150 as well. I can't hear you!

When the vehicle is running, absolute ground is at the case of the alternator. When not running, it's at the negative terminal of the battery (or batteries). the12volt • Support the12volt.com

So will running a wire to the Absolute ground be better or "just as good" as going through the frame?I can't hear you!

oldspark you crack me up! Those cables just get warm from the engine heat. If you want to really find the difference in the grounding, you have to lick your fingers and place them far apart from the frame to the positive on the battery.

Just to be clear, when I say things about believing fairy tales and buying swampland in Arizona, I'm not pointing at anyone in particular.

In fact, really not anyone here, because let's face it, these threads are buried in raw genius :D

I'm going to side with the12volt: When the vehicle is running, absolute ground is at the case of the alternator. When not running, it's at the negative terminal of the battery (or batteries).

If voltage is the potential between two points in a conductive path, then the highest potential will be at the alternator output while the engine is running, making the alternator body the most absolute ground.

In the instances where your ground cable goes from your battery to the engine block, which is closely related to the alternator, you're still not far the the battery post\terminal.

"So will running a wire to the Absolute ground be better or "just as good" as going through the frame?"

It could be better, but if you have good clean connections with your grounding from the battery to the frame and a good clean connection to the frame elsewhere on the vehicle, you have good ground.

How much resistance does the wire have? (rhetorical question)

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anonymous1 wrote: I'm going to side with the12volt: When the vehicle is running, absolute ground is at the case of the alternator. When not running, it's at the negative terminal of the battery (or batteries)

Whatcha mean siding with 12volt? That's what I said! Though I added the case where the alternator is unable to keep up with the load - then it becomes the battery. For BIG sound, for that reason - and because it's the only practicable solution - you use the battery. When the alternator is above battery-full voltage (12.7V; shall we exclude surface charge?), it may seem sensical to use the alternator for 2 problems - how often do you see an alternator with 4G (etc) B+ connection, else how often do the alternators themselves use 4G (etc) internally from the rectifiers? And then there is the noise.... However, in that case, taking the ground from the alternator is feasible and does make sense... But of all the system voltage drops, the engine to chassis (and then battery -ve) should be the smallest.    The only time I recall alternator connections being regularly used was halogen lighting for rally cars etc. But that's where 0.1V and lower weight can make a big difference (allegedly). As to the warm leads, I was being serious. Maybe I should have stated temperature differential? But point taken. The test is valid though - eg, for starter cable/s after a cold start; battery cables before eBay heat up; boot/trunk wires. Whilst one could use a temp meter like my $10 DMM for the temp differentials, I think that loses sight of what you are measuring - namely the voltage difference along that path - ie, just a DMM, not a temp meter! I do admit however being somewhat jestive measuring chassis/body temp increases. Again, a DMM is easier!

Yeah that makes sense, I Just want the most efficient ground because i think i may have a unibody issue. I'm into trying things myself so I'll save 10$ a week for 3 weeks to get a 15ft strand of 0ga cable for experimental purposes. Thanks a lot for the insight, this helped a lot with my understanding of the TOTAL PICTURE of "Ground." I don't think A lot of people (mostly noobs) into car audio would know these small things that then lead to explain the BIG picture and explain important concepts like "WHY" your ground has to be solid or the metal has to be "cleaned/shiny" and its better soldered.I can't hear you!