# Myth about running ground wires



## 92blacktt

Im installing (2) nine.1 and (2) nine.2x and a small 2 channel amp I haven't found yet

The nine.1 is fused at 140A

nine2x fused at 80A

lets say the other amp will be fused at 30A

so thats a total of 470amps

Now I ran 2 0 gauge runs (wire supports up to 250A)

My buddy is saying that thats a lot of power and to run the grounds through the body will result in the pinch welds or the car getting damaged.

Sounds like a myth to me. Any truth to it?

Do I need to run 0 gauge ground runs directly from the battery?


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## sonikaccord

I lol'd a little. Your wires power wires would be destroyed before you come anywhere near sending too much current through a car's chassis. Is your friend a welder?


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## 9mmmac

You'll never run that much current through your grounds. The car's metal body is good enough, provided you covered yourself by following proper grounding practices. Also make sure you've done the Big 3.


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## Chaos

Damaged how? Like, the current flow will be high enough that it will generate so much heat that the resistance welds would be compromised? 

LOL. Not going to happen.


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## IBcivic

Bwahahaha.... tell your buddy to lay off the weed...eh?


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## Fricasseekid

Ask your buddy if he has ever saw anyone weld with a car battery? 

Then proceed to find some a new "buddy", I fear this guy may be a bad influence on you.


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## minbari

well you know all the eddy current caused by the grounds into the chassis will eventually cause the chassis of the car to become magnetized and then it will.......something I lost my train of thought (that is a joke BTW)

no way you will hurt your car, lol.


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## cubdenno

What you may find though is reduced voltage drop if you do run a dedicated ground. 

Yes you can use your car's chassis.

You will reduce the resistance if you run a dedicated ground. I did. I gained around .5 volts. My rear tail lights were brighter as well as the interior lights. 

Remember that carbon steel is a less than ideal conductor. not to mention in todays unibody vehicles that are stitch welded. Unless you are able to ground into the meat of the chassis, you will just have the potential for a better ground by running the dedicated negative run. 

Yes it's an added expense. I run just over half the amplifier power you do and had a measurable difference in voltage drop. It was worth it to me. That's going to have to be your determination for yourself.

If the chassis was good enough, why to SPL guys run dedicated negative runs? Answer: to reduce voltage drop.


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## Fricasseekid

Doesn't having a dedicated ground help also help reduce noise floor?


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## HondAudio

Fricasseekid said:


> Ask your buddy if he has ever saw anyone weld with a car battery?


MacGyver did that!


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## minbari

Fricasseekid said:


> Doesn't having a dedicated ground help also help reduce noise floor?


only if you have a noise problem in the first place. with balanced inputs on amplifiers you shouldn't see a problem with it.


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## 92blacktt

cubdenno said:


> What you may find though is reduced voltage drop if you do run a dedicated ground.
> 
> Yes you can use your car's chassis.
> 
> You will reduce the resistance if you run a dedicated ground. I did. I gained around .5 volts. My rear tail lights were brighter as well as the interior lights.
> 
> Remember that carbon steel is a less than ideal conductor. not to mention in todays unibody vehicles that are stitch welded. Unless you are able to ground into the meat of the chassis, you will just have the potential for a better ground by running the dedicated negative run.
> 
> Yes it's an added expense. I run just over half the amplifier power you do and had a measurable difference in voltage drop. It was worth it to me. That's going to have to be your determination for yourself.
> 
> If the chassis was good enough, why to SPL guys run dedicated negative runs? Answer: to reduce voltage drop.


That would explain it. He is an SPL guy. SPL guys have never been that bright though.


The frame on my car runs right next to my amps (thick metal). Its a unibody but there are clearly visible frame rails. I guess I can ground directly there and shouldn't need to run any grounds to help with voltage drop. I think I can also ground the battery on the same rails that run from the back of the car.

I also ran the wiring under the car (safely), to help with any noise.


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## wheelieking71

Fricasseekid said:


> Ask your buddy if he has ever saw anyone weld with a car battery?
> 
> Then proceed to find some a new "buddy", I fear this guy may be a bad influence on you.


i have stick welded with 2 deep-cycle 12v batteries wired in series! you can get a pretty nice weld in 3/16 mild steel with some nice dry 3/32" 6011! turned part of a headache rack into a tie-rod to get me out of the woods!  (NO B.S.!)


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## 92blacktt

Do I need to run 2 0 gauge ground wires from the battery to the chassis?


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## Fricasseekid

92blacktt said:


> Do I need to run 2 0 gauge ground wires from the battery?


You don't need to but it wouldnt be a bad idea.


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## Fricasseekid

wheelieking71 said:


> i have stick welded with 2 deep-cycle 12v batteries wired in series! you can get a pretty nice weld in 3/16 mild steel with some nice dry 3/32" 6011! turned part of a headache rack into a tie-rod to get me out of the woods!  (NO B.S.!)


Lol
Reminds of all the times I've used beer as radiator or brake fluid to get me home safe. It's not legit unless you used jumper cable as welding leads! Did you?


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## wheelieking71

yes, as a matter of fact i did. but they were really nice custom built cables that were build with "welding in an emergency" in mind. we always has those cables, a tube of rod, a hood, and a good set of gloves with us when we were wheelin' back east.


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## cubdenno

92blacktt said:


> That would explain it. He is an SPL guy. SPL guys have never been that bright though.
> 
> 
> The frame on my car runs right next to my amps (thick metal). Its a unibody but there are clearly visible frame rails. I guess I can ground directly there and shouldn't need to run any grounds to help with voltage drop. I think I can also ground the battery on the same rails that run from the back of the car.
> 
> I also ran the wiring under the car (safely), to help with any noise.


No I am not an SPL guy. As for brightness, meh. Probably just fairly bright say 75 watter. 



92blacktt said:


> Do I need to run 2 0 gauge ground wires from the battery to the chassis?


Probably not. Utilize a ground run in conjunction with the chassis. Attach negative run at the same point under the hood as where you ground your battery and in the rear of your vehicle where you terminate your amplifier grounds at the vehicle body. According to some very good advice from a friend, this will not cause any damage if your negative run gets damaged or becaomes unattached somewhere. Plus you can test and see if in fact there is a reduction in drop before you run the line in your car.


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## 92blacktt

cubdenno said:


> No I am not an SPL guy. As for brightness, meh. Probably just fairly bright say 75 watter.
> 
> 
> 
> Probably not. Utilize a ground run in conjunction with the chassis. Attach negative run at the same point under the hood as where you ground your battery and in the rear of your vehicle where you terminate your amplifier grounds at the vehicle body. According to some very good advice from a friend, this will not cause any damage if your negative run gets damaged or becaomes unattached somewhere. Plus you can test and see if in fact there is a reduction in drop before you run the line in your car.


I meant, if I did not run a ground wire all the way back, do I need to run 2 ground wires from the battery to the chassis under the hood?


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## IBcivic

:inout:


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## Danometal

92blacktt said:


> I meant, if I did not run a ground wire all the way back, do I need to run 2 ground wires from the battery to the chassis under the hood?


No. For such a short length one run of 0 AWG is plenty. 

Btw, everything Cubdenno has said has been on point. A dedicated ground indeed has less resistance than a typical chassis of today's front wheel drive unibody cars riddled with spot welds. 

I drive a Saturn, and I was able to reduce my voltage drop by ~ 30% by running a dedicated run of 0 AWG from amp ground distro back up to the battery chassis ground termination point right next to the battery. No noise. Very little voltage drop.

Also, add a run of 0 AWG from your alt case to the battery negative (or the chassis ground point where your battery and your dedicated amp ground are now attached, either way is fine).


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## 92blacktt

I drive a rear wheel drive toyota soarer (lexus sc400 with a twin turbo engine). The car has solid metal rails running front to back. I am going to just try ground on those rails. I think I can get away with it.

Thanks for the help everyone.


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## 92blacktt

Danometal said:


> Also, add a run of 0 AWG from your alt case to the battery negative (or the chassis ground point where your battery and your dedicated amp ground are now attached, either way is fine).


I ran 4 gauge from the alternator positive to battery and from the alternator bracket to the negative battery terminal. I sanded everything to bare metal (alternator to bracket, bracket to engine)

Will 4 gauge suffice? or should I use 0?


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## Danometal

I would typically go 0 awg everywhere since you're already running that size power wire, but with the shorter lengths under the hood vs. the long power wire length to the trunk, it might even out just fine. You can test your voltage drop once your system is hooked up and then decide if you need to beef up your under hood grounds.

That said, if your car has true frame rails vs. a funky unibody like my car, your results from choosing to add a dedicated ground vs. frame ground may be a wash. But, make sure to ground your amp and your battery to the same side frame rail.


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## 92blacktt

^^ I am not sure what to believe now. But I think I may have my answer. I should do one full ground run regardless.


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## BEAVER

I've never really thought too much about my grounds, honestly. Way back when I was 16, I purchased my first amplifier and installed it on my own. I ran a ground all the way to the battery. When a friend of mine saw it he laughed at me and said that this was an inferior ground, as compared to the typical chassis ground. His reasoning was that the entire body of the car made for a much larger and better conductor than any itsy bitsy little wire ever could hope to be. Seemed logical enough to me at the time...


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## cubdenno

BEAVER said:


> I've never really thought too much about my grounds, honestly. Way back when I was 16, I purchased my first amplifier and installed it on my own. I ran a ground all the way to the battery. When a friend of mine saw it he laughed at me and said that this was an inferior ground, as compared to the typical chassis ground. His reasoning was that the entire body of the car made for a much larger and better conductor than any itsy bitsy little wire ever could hope to be. Seemed logical enough to me at the time...


LOL! I heard/experienced a similar situation. Went along on the same theory as you until 2007. I was researching during my component gathering and came on the dedicated negative run info. I laughed at it. Well when it came time to do the install, I had grounding issues in my Toyota. Just way to much resistance. Running the dedicated negative made a huge difference in my opinion, and gave me the piece of mind that I was looking for. 

When we did my son's car with 3kw just on the subs, it really made a difference. but we went a little overkill. But it did make a difference in voltage drop and at those amounts of current pulled... It was a relatively cheap solution.


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## BEAVER

Since my new car has a trunk mounted battery I'm considering skipping the chassis ground entirely and just grounding everything at the battery.


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## 14642

92blacktt said:


> Do I need to run 2 0 gauge ground wires from the battery to the chassis?



Absolutely not. Remember, the resistance of the wire is what contributes voltage drop and the resistance of the wire is calculated by cross-sectional area (gauge) AND the length of the wire. The wire from your battery to the chassis nearby will be very short, compared to the wire from the battery to the amps.


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## Kpg2713

Spot on Andy. 

Is anyone also considering the fact that he will never pull 500 amps through this setup? He gave fuse ratings off the amps. This is not real usage. To push a nine.1 to use 140 amps, that's like 2000watts! Realistically he would be pulling half that listening to his system at a decent sound level.


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## Sarthos

Theoretically it's possible. But only if you do something like run the current to whatever part of the chassis happens to be the worst possible ground. Oh, and the weld would probably have to be rusted and weak to begin with.


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## NoMids

Danometal said:


> I drive a Saturn, and I was able to reduce my voltage drop by *~ 30%* by running a dedicated run of 0 AWG from amp ground distro back up to the battery chassis ground termination point right next to the battery. No noise. Very little voltage drop.


Is that 30% accurate? Just checking because it seems like a huge number. 

I used a chassis ground. My JL 500/1 v2 ran too hot to touch after about 25 min. The Leviathan never ran hot. Both are class D. I wonder if this is the reason.


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## minbari

lol, 30% of what though? if he had a 0.3volt drop before and then reduced it by 0.1 volts. who cares

if it was a 3 volt drop before, then he had a piss poor install to begin with, lol.


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## NoMids

You're right.

I assumed that he was getting around 12V instead of 14.4V so the 30% seemed like a big gain.


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## andrave

Were you measuring the resistance or the voltage drop? Just curious. As to some of the stuff that has been said, I disagree about a lot of things people have said. It is true that the ground from the battery/block to the frame is shorter than the run to the amp, so if all was equal you could run less wire. But the ground to the block and the battery aren't just carrying the load for your amplifiers, they are carrying an additional 90-100 amps for the rest of your car. I always recommend bumping up the grounds to the same size power wire as amps. To the original poster: The fuses that come in your amps aren't necessarily their maximum power draws and in fact often aren't even close. With a system like yours I'd find out how much current they are drawing at the impedance you plan on running them at for your wire size. 0 gauge isn't cheap and a double run is tough to fit through your average interior. I have a feeling you can run a single run of 0 gauge, and still have plenty of power for your amps. Remember, you fuse for the wire size, not the power draw.


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## underdog

Can someone give me a general OD Diameter for decent quality 0 gauge wire.


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## onebluec5

underdog said:


> Can someone give me a general OD Diameter for decent quality 0 gauge wire.


The wiring (not counting insulation jacket) should be approximately 8.252mm in diameter


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## slowpoke

welds and sheet metal will flow electricity very well and in some cases maybe better than your wires. in order to cause any damages the the cars body/frame/ or weld you will have to flow an extreme amount of current. perhaps if you had about a 30000 watt rms system with bad grounds then it might cause some slight damage. its more likely something else like your amp or battery would burn up first. high power systems that end up with bad joints or welds is usually due to high vibrations from the subs and even the mids. rare but yes it does happen. thats why some people spend alot of money and time on sound matts and other types of sound proofing. most people think its just to increase there sound level, as that could end up being the result(but yet not always) thats not the full reason for doing it. fiber glass around the windows also help to prevent window seal failure. i had the windows on the barn doors of my 94 suburban pop out due to the bass level and of course having the sub right at the windows didnt help. i resealed them and then coated over the seal from the glass to the metal, stuffed the doors with great stuff and havent had any problems since. 

back to the topic at hand, no you will not cause damages for lack there of grounds. yes it does help the quality of the system to have good grounds. imo i like to have nearly 2times more grounds than power when possible.


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## HondAudio

My thinking on power wiring has always been of the hub-and-spoke model: All of your amplifiers, processors, etc. are wired to a single "hub" for both the positive (+12v) and ground wires. Each amp/processor is on its own "spoke", and smaller AWG wiring is acceptable, but the single wire coming from the "hub" would need to be a larger gauge - at least the minimum size for the amperage your system might pull.

From the "hub", you could ground directly to the battery if you'd like, but you don't have to, and most people would ground right to the frame. Keep in mind, of course, that the connection from the battery to the frame should be of the same gauge as the wire from the "hub" to the frame, and terminated properly to permit maximum current flow.


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## slowpoke

i recently started having bad alt noise once i installed my new amp. i now have 2 150.2, 1 300.2, 1 1250.1 and 1 4000.1. i knew off the bat that it had to be grounding. i have a full run of 0gauge from the fron batt to the rear 2 batteries. as i found out with more demand that was not enough. so not sure what part of this cured it but here is what i did:

all new grounds are 4gauge
under the hood
from the duel alt bracket to the block. 
from the block on 1 side to the neg of the front batt
from the block on the other side to the frame
from the neg on the batt to the body

rear batt distribution manifold.
from manifold with 1 0gauge to a duel 4gauge distribution block
1 from the block to the frame
1 from the block to the body. 

all of these are 10gauge wires
axle to frame
gas tank to frame
trans to frame
cross members to frame
isolated panels to frame
multiple point on the ifs to frame

i now have atleast to the ear 0.00% alt noise. about 1vdc drop at full tilt. and a warm and fuzzy thinking i could likely be fine after a bolt of lightning. it only took about three days but hey, i was bored and needed something to do.


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## kyheng

1V drop means you got high resistance somewhere.... 
I'll lay another run of power cable from the distribution block to battery's -ve direct....


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## slowpoke

kyheng said:


> 1V drop means you got high resistance somewhere....
> I'll lay another run of power cable from the distribution block to battery's -ve direct....


thats possible, but i didnt really think that was to bad with all of my audio system running at full tilt, front and back heater blowers running, about 600watts of lights since it was at night while i was driving,and a 12inch 1050cfm tranny fan on constant while the suburban is in motion. it wasnt enough voltage drop to even dim the headlights. it was just enough to see what appears to be about 1vdc drop on the dash voltage gauge.

ps: when at idle with nothing else running the voltage sits at 14.3vdc. the lowest that it dropped at the front batt at full tilt was to 13.1 and averages at 13.4 while at full tilt. not sure if all of that is good or bad but its staying above 13vdc so im happy


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## kyheng

I see... Anyway, did you apply some silicone grease on the terminals, sometimes it may help also, since you are driving under extreme conditions...


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## simplicityinsound

i always keep ground cable the same gauge as power cable and grounded to a solid part of the car's chasis as short as possible, or ground to frame on body on frame cars, also as short as possible.

its been a few hundred vehicles and never had an issue with ground related noise or other problems.


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## slowpoke

kyheng said:


> I see... Anyway, did you apply some silicone grease on the terminals, sometimes it may help also, since you are driving under extreme conditions...


since i just redone the ground points yes i used electric grease this time. it did not get used back in May when i first installed the wiring. i will be redoing the power wires sometime before x-mas. the suburban cant fit into the garage since its to tall with a 6inch lift and 34's so its getter done now or wait until spring


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## Mark the Bold

Here's a thread on this very forum discussing this:

http://www.diymobileaudio.com/forum...d/13675-grounding-amps-chassis-not-ideal.html

Without rehashing the whole argument, I believe the consensus was that you would need to run ridiculously thick ground wires to the battery (in a typical length) to achieve a better (lower) voltage drop from properly grounding to the chassis of a vehicle.


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## slowpoke

slowpoke said:


> thats possible, but i didnt really think that was to bad with all of my audio system running at full tilt, front and back heater blowers running, about 600watts of lights since it was at night while i was driving,and a 12inch 1050cfm tranny fan on constant while the suburban is in motion. it wasnt enough voltage drop to even dim the headlights. it was just enough to see what appears to be about 1vdc drop on the dash voltage gauge.
> 
> ps: when at idle with nothing else running the voltage sits at 14.3vdc. the lowest that it dropped at the front batt at full tilt was to 13.1 and averages at 13.4 while at full tilt. not sure if all of that is good or bad but its staying above 13vdc so im happy


well let me make a small correction here. i did some more testing and believe that combining a run of 1.0gauge from the front to back with using the frame is enough. atleast for my system. the average 1vdc drop is due to not enough power being generated. currently my duel alt system is using 1stock alt and 1 mildly beefed up rebuilt alt(i did it myself self) and the system is now drawing more power than what both alts are producing. none the less its not bad like it was before. ill just have to keep in mind to shut the audio down from time to time to allow the alt to cool and batts to charge until i get better alts. at 1300rpm or higher the drop was only .3vdc

bottom line this thread is what tempted me to explore my grounds which cured almost all of the problems. it is in my opinion that atleast 1 run of 1/0gauge from front to rear batt along with the frame should be used when power requirements are above 200amps of current. now this is based off of my own 1 independent test out of nearly 20,000,000 other motorist out there with large audio systems. so only take this as word of advice and not etched in stone by god.


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## iD Z24

If the chassis was good enough, why to SPL guys run dedicated negative runs? Answer: to reduce voltage drop. Some amp owners manuals state to run a ground back to the battery.


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## Danometal

iD Z24 said:


> If the chassis was good enough, why to SPL guys run dedicated negative runs? Answer: to reduce voltage drop. Some amp owners manuals state to run a ground back to the battery.


My car seems to have all sorts of epoxied panels and spot welds, so a direct ground fixed my problems by a decent margin.


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## iD Z24

It never hurts to try. I have had good luck with a direct ground.


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## Schizm

I have been mulling over what my cable needs will be for my amps in my truck (Peterbilt 387). It has 4 950cca batteries already. I have thought about adding another battery (or 2?) because I'll be running 3 or 4 amps and a 2000w rms inverter (that REQUIRES a dedicated ground) I won't be using the inverter and amps together. Well not loudly...

Inverters may cycle differently than amps and that could be why the manuals require the dedicated ground line

But since I need to run a line for it I was pretty much going to tie in the amps ground to it out of simplicity. 

Also I'm not entirely sure I can find actual chassis grounding IN the cab other than from power cables as these cabs are on air ride suspensions semi-isolated from the frame.


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## Quinn

As long as you have a good ground to the chassis, and your battery to a good ground. The easiest way to test the integrity of it is to do a voltage drop test. Hook one side of your favorite DMM to the ground on your amp, and the other to the battery positive. Pick out your favorite bumping song. If you voltage drop between the 2 should be .1v anything more then .5v indicates a serious ground problem. 

Personally, I would run a ground of at least 4 gauge, most likely 0 gauge from the battery to ground. Now remember when your vehicle is running the best ground is your alternator/s, its generating the power. So a solid link between the engine block and the chassis ground is a must.


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