Wire gauge recommendations

[KooK 10+ year member]

Vehicle:

Vehicle: 1998 Honda Civic

Alternator: Factory 70 amp

Setup:

Amps:

4 channel - (Old school) Rockford Fosgate x500 (62.5rms @ 4 ohm x 4 OR 125rms @ 2 ohm x 4)

Intended purchase Subwoofer - *unknown, going to buy*

Subwoofer:

Intended purchase Either x2 Sundown Audio SA-8 V2's or x1 Sundown Audio SA-10

Electrical system:

Intended purchase XS-Power aux. battery, either XP750 or XP950

I plan on keeping with one size ground and feed audio wire, so I will be doing the big 3, running my feed and an extra ground to the trunk/aux battery all on the same gauge; unless told otherwise here.

Audio system intentions:

This car is my daily driver, it will not be entered in competitions, I am planning on running a sealed box for the subwoofer(s). Music listened to is mostly rock, some rap, but not a whole lot of stuff that has long bass notes.

Questions:

I'm wondering if running a 4ga main power would be the correct size. Given my alternator output, a secondary battery in the trunk, and desired setup, I know I am going to be stressing my electrical a little, but if it's truly worth my while to run a 1/0ga I will. If it is recommended for me to run 1/0ga to the back, can I use 4ga for the big 3 considering alternator output isn't high.

Click to read more...

 

[CSCStang]

You can never go too big with electrical. I would do 1/0 on all the runs. From the rear batt, you can always go with 4 to the amps.

 

[n2audio 5,000+ posts]

For 500w?? Wow. //content.invisioncic.com/y282845/emoticons/eyebrow.gif.fe2c18d8720fe8c7eaed347b21ea05a5.gif

I'd run 8 awg and call it a day.

Big/extra batteries only means your alt's running at higher capacity MORE of the time.

Clearly that alt's not going to last forever, but let it run its course and get an HO when it's time.

Batts will probably just speed up the process.

 

[tc300 10+ year member]

4 gauge ofc wire...

 

[Popwarhomie 5,000+ posts]

Depends on what amps your going to run and which setup you decide on. 1 sa-10 or 2 sa-8s is double the power difference.

 

[KooK 10+ year member]

For 500w?? Wow. //content.invisioncic.com/y282845/emoticons/eyebrow.gif.fe2c18d8720fe8c7eaed347b21ea05a5.gif
I'd run 8 awg and call it a day.

Big/extra batteries only means your alt's running at higher capacity MORE of the time.

Clearly that alt's not going to last forever, but let it run its course and get an HO when it's time.

Batts will probably just speed up the process.

First off, if you look back at my post that I tried to lay out so pretty, you will notice I'm deciding on a 2nd amp and subwoofer setup.

Second, my thought with the second battery was that it's a cushion for any quick, loud beats.

Depends on what amps your going to run and which setup you decide on. 1 sa-10 or 2 sa-8s is double the power difference.

I honestly can't figure out what I want to do here. I'm tempted just to run a single SA-8 with a used amp and see how it is. The last time I did anything with car audio, well, this was my setup. Technology has come so far since I've last even touched this **** and power ratings are incredible to what they used to be. This is a 1990 Mitsubishi Eclipse, ran it with the stock alternator and a second battery, nice 4 channel setup, single 12 inch Treo, small aux battery, never had a hiccup with it and it sounded great.

 

[KooK 10+ year member]

I keep thinking I want to go with the SA-8 V.2 because it looks like it has a huge throw which would displace a lot of air. It just seems to me like I could get a lot of sound out of it with super low distortion.

 

[n2audio 5,000+ posts]

I have a similar set up.

Comp amp ~500w rms and sub amp of 1000.

Ideally, I'd run 4, and find a d-block that allows 4 in/4 out, then run 8 awg for the 500x.

Unless you're thinking sub power closer to 500-600 then you can do 4/8 with no problem.

Might as well get the big 3 done. When the alt goes the HO swap should be relatively painless.

I'm still not sold on improvements made with 2nd batteries unless you do a lot of engine off listening.

 

[KooK 10+ year member]

I'm still not sold on improvements made with 2nd batteries unless you do a lot of engine off listening.

It depends on the situation. It's really basic math is the best way to figure it out. Amperage is Watts / Volts. If I buy a single SA-8 V.2 and have an amp pushing 600 watts at 13.8 volts, IF the amp reaches its max draw of 600 watts at 13.8 volts it is actually drawing 43.48 amps at that exact moment. Say I have the lights on and the AC running, I'm driving down the road and my car is currently taking 45 amps of power. Now that means that on hard bass hits I'm drawing roughly 88.5 amps from a 70 amp alternator, so it drains the system, lights dim for that moment.

Right there, what's happening to the alternator when it goes outside of its load range? Heat increases exponentially for each bass note!

Now, the factory battery is going to take some of the load off the alternator, so instead of the alternator receiving the entire 88.5 amp draw from the car and the bass note, it's now only receiving a 75 amp draw for that note because it's acting as a cushion which is a difference of 12.5 amps of overload the alternator isn't having to deal with.

What's happening to the alternator there? It's still going out of it's load range, heating up more than it should and the life is still shortened, but not as much because it doesn't have as much heat to it due to the peak draw being lower.

Finally, we add an auxiliary battery, it's not going to drop the 12.5 amps like your factory battery did, it's probably going to be more like a 6.25 amp drop from peak. So instead of the 88.5 draw with no batteries, the 75 amp draw with only one battery, we now have a 68.75 amp draw with two batteries, this will again decrease heat greatly because as I said, when the alternator goes out of its load range heat will increase exponentially.

BUT! Even though you're keeping that peak load off the battery, you are creating a more constant load because the batteries need to be recharged between bass notes. Ah, you see this is true, however I go back to where I state that the heat in the alternator rises exponentially when you get to the top of its range. If you were to evaluate X^2 (an exponential function) you will see that the higher the peak load is, the hotter the alternator will get vs a more constant high load with much lower peak values.

But what about long bass notes? Well that's why I specify what type of music I listen to. My bass notes are not long and drawn out in the music I listen to. If they were then the charging system would be much greater of a concern to me; if in a case I listen to Bass Nectar or something, I will probably have to turn off the A/C and/or turn the bass down a bit.

An auxiliary battery isn't something that will work for everybody, but it's something that will help out people in situations where the audio system is close to the peak power level of the charging system. You will shorten your lifespan of the alternator by putting this equipment in, in the first place. However you will lengthen the lifespan of the alternator from that if you were to install a cushion where there was not one.

 

[n2audio 5,000+ posts]

gobble-de-gook

Wow -- that was a lot of typing.

Whether you have 57 batteries or 1 -- in order to GET to the batteries the alternator has to be overloaded.

Therefore -- more batteries does not equate to less strain on the alternator.

Although more batteries will definitely mean less strain on each individual battery.

Also -- if you have multiple batteries wired parallel you have less resistance. Less resistance gives you more current flow which obviously means MORE load on the alternator, not less. And logically, since you're adding storage devices, that makes sense.

 

[KooK 10+ year member]

Wow -- that was a lot of typing.
Whether you have 57 batteries or 1 -- in order to GET to the batteries the alternator has to be overloaded.

Therefore -- more batteries does not equate to less strain on the alternator.

Although more batteries will definitely mean less strain on each individual battery.

Also -- if you have multiple batteries wired parallel you have less resistance. Less resistance gives you more current flow which obviously means MORE load on the alternator, not less. And logically, since you're adding storage devices, that makes sense.

[sarcasm] Sure, because the power draw from the system is going to be so much different whether you have 1 battery or 2. [/sarcasm] That or else you don't understand what 'exponential' means.

 

[n2audio 5,000+ posts]

Now, the factory battery is going to take some of the load off the alternator, so instead of the alternator receiving the entire 88.5 amp draw from the car and the bass note, it's now only receiving a 75 amp draw for that note because it's acting as a cushion which is a difference of 12.5 amps of overload the alternator isn't having to deal with.

From that point forward - you seem to be just making stuff up in order to support your faith in batteries. The battery does NOT "take some of the load off the alternator". It doesn't take ANY load off the alternator. It can't. The definition of voltage tells us that.

The battery is simply absorbing output (trickle charge equivalent) from the alternator until the alternator can no longer provide adequate current @ ~14v to respond to the demand of the electrical system -- that is ~70A in your case - whether you have 1 battery or 10 batteries.

Add batteries if it makes you feel better.