Dual battery wiring tutorial (and why)

[AlterEgo99 5,000+ posts]

WIRE 4
This NEG- wire is to connect the NEG- connections on your amp to the NEG- post of the rear battery. It is important that this wire matches the size (and quantity) of WIRE 2. Again, just like with WIRE 2, the size of this wire should be determined by your amps' inputs.

Some people again would tell you to not wire this to the battery, but instead to the chassis. This would be OK if you did not have a rear battery and you had a very small amp. But since this discussion is assuming the rear battery is installed, you need to wire the NEG- connection for the amp directly to the battery.

If both of my batteries are up front under the hood, would I still run the grounds to my amps all the way up front to the negative post of the 2nd battery? //content.invisioncic.com/y282845/emoticons/confused.gif.e820e0216602db4765798ac39d28caa9.gif

 

[andrewmoore13 10+ year member]

interestingly when i wire my amps to the negative posts of my rear batteries i get a ridiculous amount of engine/alternator whine... if i ground to the frame of the car, poof its gone.

explanations for this?

 

[audiolife 5,000+ posts]

interestingly when i wire my amps to the negative posts of my rear batteries i get a ridiculous amount of engine/alternator whine... if i ground to the frame of the car, poof its gone.
explanations for this?

Bad wire job between batteries...If a battery emitted noise it would emit through the frame as they would be connected to the chassis ground..........If you drive a car newer than 1985 you more than likely have a unibody car where you are not connected to the "frame" as you might think. People also say that running ground wire front to back is bad because it is not "short" if this were true your pos wire would be bad as well as all a circuit is is an electrical circle and if its good for one side it should be good for the other .......

 

[AlterEgo99 5,000+ posts]

Bad wire job between batteries...If a battery emitted noise it would emit through the frame as they would be connected to the chassis ground..........If you drive a car newer than 1985 you more than likely have a unibody car where you are not connected to the "frame" as you might think. People also say that running ground wire front to back is bad because it is not "short" if this were true your pos wire would be bad as well as all a circuit is is an electrical circle and if its good for one side it should be good for the other .......

Makes sense...it just seemed weird as everyone always says "Keep them amp grounds as SHORT as possible"...mine are presently about 18"...if I go to the 2nd battery under the hood, I'm looking at a run of about 10 feet.

 

[audiolife 5,000+ posts]

Makes sense...it just seemed weird as everyone always says "Keep them amp grounds as SHORT as possible"...mine are presently about 18"...if I go to the 2nd battery under the hood, I'm looking at a run of about 10 feet.

If they are telling you ground it in back in a unibody car of course it would be as short as possible...I have seen many a hifonics 1200-2000 watt amp grounded BAD and it gets real hot or goes into protect...think of your wire like blood vessels in your body...if they are shity you will end up needing surgery or a lifestyle change...same with car audio wire jobs in many cases. What might "work" for 350 watts might not be too good for 1200.

 

[AlterEgo99 5,000+ posts]

If they are telling you ground it in back in a unibody car of course it would be as short as possible...I have seen many a hifonics 1200-2000 watt amp grounded BAD and it gets real hot or goes into protect...think of your wire like blood vessels in your body...if they are shity you will end up needing surgery or a lifestyle change...same with car audio wire jobs in many cases. What might "work" for 350 watts might not be too good for 1200.

Good point. I never thought of it that way. I think I'm going to go with the Kinetik HC1800 to replace my OEM AC Delco and see how things go. I get "some" dimming, not a lot. If the HC1800 doesn't improve the situation, then I may go with the 2 battery setup and get anoter Kinetik. My present battery is located at the firewall on the passenger side....and there is an empty battery tray on the drivers side just behind the headlights. So as I said, if I go with 2 batts, they will both be unda the hood. //content.invisioncic.com/y282845/emoticons/cool.gif.3bcaf8f141236c00f8044d07150e34f7.gif

I'll just have to re-run longer power and grounds to the amps presently located inside my center console. But hey, if ya ain't tearin' something apart on a regular basis, I guess you can't say you're into car audio. //content.invisioncic.com/y282845/emoticons/tongue.gif.6130eb82179565f6db8d26d6001dcd24.gif

 

[bubbagumper6 5,000+ posts]

I was running my stock battery under the hood and my yellowtop in the trunk with no isolator and had no problems whatsoever. Never drained on me (and I even left my dome light on once). As far as if it shortened life span, I have no idea, but how can you possibly measure that?

 

[audiolife 5,000+ posts]

I was running my stock battery under the hood and my yellowtop in the trunk with no isolator and had no problems whatsoever. Never drained on me (and I even left my dome light on once). As far as if it shortened life span, I have no idea, but how can you possibly measure that?

When batteries that die in 2-3 years (or maybe less) instead of 4+ years.

 

[bubbagumper6 5,000+ posts]

Well idk about the stock battery (I got a new car) but that yellowtop is still going strong...

I mean basically all an isolator does is disconnect the batteries when the car is turned off, correct? Then wouldn't that cut your playing time significantly if your car is turned off? You'd only be pulling from one battery //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif

 

[1hawaii50 10+ year member]

Well idk about the stock battery (I got a new car) but that yellowtop is still going strong...
I mean basically all an isolator does is disconnect the batteries when the car is turned off, correct? Then wouldn't that cut your playing time significantly if your car is turned off? You'd only be pulling from one battery //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif

I believe that is one of the reasons of using an isolator. If you listen to the radio for too long with the car off, you'll kill the isolated battery, but you'll still be able to start your car off of the second battery.

 

[jco1385 5,000+ posts]

where the hell is loop?

 

[bubbagumper6 5,000+ posts]

Meh, I still think as long as the car doesn't sit for an extended period of time (months) without being run, then an isolator is unnecessary.

 

[profundus-sanus 10+ year member]

well... it all is relative to resting voltage...

if you throw say a pm d3100 that rests at 13.1v in your car while retaining your stock battery that rests at 12.6v then that will be harmful to the powermaster... because its going to be "charging" the stock battery until they've equalized voltage... although i definately don't see why the stock battery would be harmed.. i definately couldn't see any harm being done from running different size or age batteries from the same manufacture

another point i saw that i disagree with is calling a front/rear chassis ground redundant when there's a dedicated negative run..

the best example was one i saw on a db drag street B car a year or so ago. The vehicle had 16 runs of 1/0 off 1 battery(using buss bars of course).

first test was 8+ and 8-.. after moving more and more wires from positive to negative the loudest point was with 10+ runs 6- runs and about 6 1/0 chassis grounds front and back. I believe it yeilded .3-.4 db.. which if you know db drag thats a nice gain from something as simple as that.

It would be vehicle dependent but my point is that grounding in the back will always be helpful, even if you have a dedicated negative run.

 

[power-fanatic07 5,000+ posts]

well... it all is relative to resting voltage...
if you throw say a pm d3100 that rests at 13.1v in your car while retaining your stock battery that rests at 12.6v then that will be harmful to the powermaster... because its going to be "charging" the stock battery until they've equalized voltage... although i definately don't see why the stock battery would be harmed.. i definately couldn't see any harm being done from running different size or age batteries from the same manufacture

another point i saw that i disagree with is calling a front/rear chassis ground redundant when there's a dedicated negative run..

the best example was one i saw on a db drag street B car a year or so ago. The vehicle had 16 runs of 1/0 off 1 battery(using buss bars of course).

first test was 8+ and 8-.. after moving more and more wires from positive to negative the loudest point was with 10+ runs 6- runs and about 6 1/0 chassis grounds front and back. I believe it yeilded .3-.4 db.. which if you know db drag thats a nice gain from something as simple as that.

It would be vehicle dependent but my point is that grounding in the back will always be helpful, even if you have a dedicated negative run.

interesting

 

[Proximity 10+ year member]

another point i saw that i disagree with is calling a front/rear chassis ground redundant when there's a dedicated negative run..
the best example was one i saw on a db drag street B car a year or so ago. The vehicle had 16 runs of 1/0 off 1 battery(using buss bars of course).

first test was 8+ and 8-.. after moving more and more wires from positive to negative the loudest point was with 10+ runs 6- runs and about 6 1/0 chassis grounds front and back. I believe it yeilded .3-.4 db.. which if you know db drag thats a nice gain from something as simple as that.

It would be vehicle dependent but my point is that grounding in the back will always be helpful, even if you have a dedicated negative run.

Did they add chassis grounds as they added to the positive runs? Or were there always the 6 chassis grounds. Or, did they add the chassis grounds after the did 10+/6-? Are you saying the 6 chassis grounds added .3-.4db or the move from 8+/8- to 10+/6- did?