# Can the big Three be done if your battery is in the trunk?



## stealthninja (Apr 26, 2011)

I drive a 08 chevy cobalt and the battery is in the rear. I am interested in installing the big three in it. should I do the big three from the power transfer box up front or run 1/0 to the trunk twice and once to the amp?
also roughly what all equipment did you use to install your big three? i.e:
How many crimp connectors ?
two battery connections (obviously)
anything else?
Thanks in advance,
Stealth


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## The Baron Groog (Mar 15, 2010)

You can do, though you must fuse the run from alt to battery


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## stealthninja (Apr 26, 2011)

So you reccomend the long runs to the battery in the rear? And you reccomend 2 fuse blocks? one from the alt to batt and one from batt to amp? 
Thanks in advance. I'm new to all of this.


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## The Baron Groog (Mar 15, 2010)

Yup, though i'm no expert! Someone who's actually done it should chime in.

I'd have 1 fuse close to the alternator and 2nd close to the battery on the +ve cable to the battery. 

Then 3rd fuse between battery and amp-as normal.


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## 808Munkyeee (Jun 6, 2011)

damm that some money


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## burzendowski (May 5, 2011)

808Munkyeee said:


> damm that some money


x2 it will cost 4-5 times more to do a big 3 on a car with battery in the trunk. I would also put 2 fuses one close to the alt one close to the battery. Never hurts to have them just in case of an accident.


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## stealthninja (Apr 26, 2011)

F*&k this is looking too expensive for this ride. Maybe a tax return project instead of a weekend paycheck project..... :/ damn I was looking forward to doing this soon...


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## Dre20xl (Jan 28, 2011)

What size is the factory bat to alt wire


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## Sleeves (Oct 22, 2010)

How much power are you planning on running? I've run two different systems over 1500 watts in my Cobalt with no charging issues while driving whatsoever.


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## nineball (Jan 17, 2008)

upgrading the engine grounds (negatives) is the real big thing to do here. the alt to battery line isn't really needed unless you have upgraded the alt to put out more power than the stock did. if you do run this line you must fuse within a foot or so of the alt and the battery in case that wire somehow grounds out in the middle - the fuses will save your car from burning to a crisp. 

also keep in mind it may be more than just 3 wires - in my daily driver, an 05 neon, there were 6 engine ground wires to upgrade (two of those connected directly to the battery).


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## XtremeRevolution (Dec 3, 2010)

What the hell?!?!

Why do you need 1/0 wire? I sure as hell hope its not CCA. For the record, 2 gauge copper holds more current for longer than 1/0 CCA. 

Replace your current wire with 2 gauge copper, or add a second 4 gauge copper in parallel with the current runs. Seriously shouldn't be costing you an arm and a leg if all you're doing is reinforcing what already exists. Wire, terminals, and a way to crimp them, and you're done. I would just add a second 4 gauge wire.


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## IBcivic (Jan 6, 2009)

nineball said:


> upgrading the engine grounds (negatives) is the real big thing to do here. the alt to battery line isn't really needed unless you have upgraded the alt to put out more power than the stock did. if you do run this line you must fuse within a foot or so of the alt and the battery in case that wire somehow grounds out in the middle - the fuses will save your car from burning to a crisp. .


Another option is to use a fused distro such as this one 
http://carjamz.com/zen/images/CBR44S.jpg 
and wire it straight to your battery (through a fuse, if the main runs are more than 18 inches) and wire both the + and - to the distro....no need to go nutz with long runs from the front to the rear (unless you upgrade your alt)


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## stealthninja (Apr 26, 2011)

So to clean up my mind and make things clear here. If I am only going to be running 1400 rms. I can get away with doing 2 AWG and still not even running a wire all the way to the batt? I am sticking with the stock 130 amp alt. , so just run the 2 AWG to the battery terminal box under the hood? Thanks guys , I realize this is a really dumb thing to ask.


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## stealthninja (Apr 26, 2011)

Sleeves said:


> How much power are you planning on running? I've run two different systems over 1500 watts in my Cobalt with no charging issues while driving whatsoever.


Do you have aftermarket batt or battcap? just curious..


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## IBcivic (Jan 6, 2009)

Why? Will you be mounting amps , under your hood?....think about it. Making your alternator wire bigger, wont make it any stronger. The stock wiring will handle your stock alt.


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## XtremeRevolution (Dec 3, 2010)

stealthninja said:


> So to clean up my mind and make things clear here. If I am only going to be running 1400 rms. I can get away with doing 2 AWG and still not even running a wire all the way to the batt? I am sticking with the stock 130 amp alt. , so just run the 2 AWG to the battery terminal box under the hood? Thanks guys , I realize this is a really dumb thing to ask.


I missed the 1400W part. At that point, you have more to worry about than your wiring. Your 130 amp alternator will not be able to keep up. Do keep in mind that's 130 peak amps, not cruising or idle. You should then consider that amplifies are not 100% efficient, and many of them are at best 80% efficient. Most class D mono amps are about 60% efficient, which means to deliver 1400W, you need to draw closer to 2240, or 162 amps at 13.8V. Meanwhile, there are other things in your car that use electricity. 

You should be fine running 2 gauge if you can actually deliver 1400W, which I'm severely doubting you can for any length of time. 2 gauge copper will safely deliver ~170 amps of power. 

If you are serious, **add** a 2 gauge wire to everything that would normally be upgraded, while leaving the current wire in place.


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## XtremeRevolution (Dec 3, 2010)

Sleeves said:


> How much power are you planning on running? I've run two different systems over 1500 watts in my Cobalt with no charging issues while driving whatsoever.


I can tell you right now, you're not delivering 1500W without completely draining your battery. 

Read why in my post above.


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## IBcivic (Jan 6, 2009)

lol. 
only if you listen to test tones at full volume for hours on end.....


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## Sleeves (Oct 22, 2010)

From _personal experience_ with my daily driver Cobalt, I don't think a full big 3 is needed if you're only running 1400 watts and the stock alternator is rated 130 amps. I would consider upgrading the engine ground (like nineball mentioned) and the battery-chassis ground. 

At the moment (my system changes frequently) I'm running a Kicker KX 1200.1 (conservative 1200 watts) and a Soundstream HRU.4 (~900 watts) and I only get about .5 volt drop (14.3 at low volume, dips to 13.8 while playing hard) at idle, and of course less while actually driving. I've been pleasantly surprised with the stoutness of the charging system in this car and if I were you I would not spend a ton of money on wire attempting to improve it for the power level you intend on running.

Edit: Thank you for your input XR. I've had decently power stereo systems in all of my cars over the past 10 years and I can say without a doubt this car has the best charging system for this out of the ones I have owned ('89 Ford Festiva, '98 Nissan 200SX, '89 240SX '01 Celica, '02 VW GTI, '04 VW R32, '95 VW Passat). I've run systems of over 1000 watts in each and every one of these vehicles and this Cobalt is the first one that I have not had to make some type of modification to the charging system to support my habits.


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## XtremeRevolution (Dec 3, 2010)

amitaF said:


> lol.
> only if you listen to test tones at full volume for hours on end.....


It doesn't take full hours for electricity to travel through a wire, nor does it take that long for the battery to be depleted. Nor is it very difficult to actually put that much power through a subwoofer.


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## XtremeRevolution (Dec 3, 2010)

amitaF said:


> lol.
> only if you listen to test tones at full volume for hours on end.....





Sleeves said:


> From _personal experience_ with my daily driver Cobalt, I don't think a full big 3 is needed if you're only running 1400 watts and the stock alternator is rated 130 amps. I would consider upgrading the engine ground (like nineball mentioned) and the battery-chassis ground.
> 
> At the moment (my system changes frequently) I'm running a Kicker KX 1200.1 (conservative 1200 watts) and a Soundstream HRU.4 (~900 watts) and I only get about .5 volt drop (14.3 at low volume, dips to 13.8 while playing hard) at idle, and of course less while actually driving. I've been pleasantly surprised with the stoutness of the charging system in this car and if I were you I would not spend a ton of money on wire attempting to improve it for the power level you intend on running.
> 
> Edit: Thank you for your input XR. I've had decently power stereo systems in all of my cars over the past 10 years and I can say without a doubt this car has the best charging system for this out of the ones I have owned ('89 Ford Festiva, '98 Nissan 200SX, '89 240SX '01 Celica, '02 VW GTI, '04 VW R32, '95 VW Passat). I've run systems of over 1000 watts in each and every one of these vehicles and this Cobalt is the first one that I have not had to make some type of modification to the charging system to support my habits.


No doubt, a 130 amp alternator is no slouch, but my math would indicate that you might as well run a 800W amplifier instead of a 1400W amplifier because you're not pulling enough power to deliver what its rated for anyway. Considering you need 2x the power to gain 3db of output, I'd say it would probably sound exactly the same.


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## Hillbilly SQ (Jan 26, 2007)

For real music the amp won't pull anywhere close to what they're rated anyway so I wouldn't worry about the short occasional bursts. I don't consider tones pleasurable and hope the OP feels the same way. I actually have an 80a main fuse on two big amps with 280a of total internal fusing and have never blown the fuse under the hood. I push the system pretty hard too. That should say something about realworld current draw.


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## Sleeves (Oct 22, 2010)

I'm with Hillbilly on this. I'm running a real world scenario in the same car as the OP mentioned, complete with voltage readings I just stepped out to my car to make. It doesn't get any more "real" than that. 

On a side note: I noticed on my way to get dinner that I had my subwoofer volume at a _slightly_ more reasonable level than usual because I was getting some mild dizziness the last few nights. For the sake of giving more accurate numbers, I just retested the voltage figures I gave previously and turned the headlights on also for good measure. My corrected figures at ghetto-blasting volumes, with the headlights on, at idle are 14.3 volts low volume and dips down to 13.6 playing much louder than is considered socially acceptable.


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## Hillbilly SQ (Jan 26, 2007)

Mine stays pegged at 14.7v with heavy metal playing as loud as I care to go.There's no upgraded wiring under the hood either. They did all the upgrades I was going to do with decently sized wire at the factory so didn't feel like it was worth the hassle.


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## subwoofery (Nov 9, 2008)

Hillbilly SQ said:


> Mine stays pegged at 14.7v with heavy metal playing as loud as I care to go.There's no upgraded wiring under the hood either. They did all the upgrades I was going to do with decently sized wire at the factory so didn't feel like it was worth the hassle.


Yeah right... That comes from the guy that uses a system where the front stage puts out 15 rms at most :laugh: 

Kelvin


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