I have most of my sound system in place now and to my surprise my headlights dim a bit at higher volume in bass heavy songs. I thought I would be ok until I added a second 10w6 and started getting 1500 watts out of my amp instead of the 800 watts, well actually its only set at about 500 watts currently while my sub breaks in. So I should really only be seeing 800 watts max RMS total for the two amps and maybe 1300-1400 peak. I didn't expect dimming.

We have stock 120amp alternators correct? Anyway has anybody done the big 3 upgrade? How hard was it in the 7th gen? Is the alternator easy to get to?

 

You can do the big three, but the ground and battery are more important.
Have you upgraded the battery?
What gauge wire are you running?

What amp(s) are you using?
The factory alt supports 1500w max, so maybe 1200w devoted to the stereo when the car is running.

 

My power and ground are 0ga OFC to the block and then about a foot of 4ga from the block to the amps. Amps are an American Bass VFL 100.1 & a soundstream STL4.500 for the door speakers. I had to send my American Bass 150.4 back for a new one so using the SS for now.

 

0awg is great, but I would still double check the grounding point.
Those amps don't pull enough that you should see much, if any, dimming.
If it is the stock battery, that could be a cause as well.

In my experience, most car frames are similar to 4awg, and when you start running a lot of power, running a dedicated ground back to the front can be beneficial.
In my last car, running 2600w rms, I ran 0awg to and from the amp to battery.

 

I was told at idle the stock alternator only puts out 60amps, so that would explain it. I have not noticed it at all while driving. The ground is good, my installer is great and he has it grounded under the back seat, the 100.1 is grounded directly it does not even go through the block. I saw him ground it when he installed it and he used a dremmel tool to grind it to shiny metal before hooking it up.

Edit: I just realized I didn't put in my first post that I only noticed the issue at idle when sitting in my driveway, I have not seen it while driving at all.

 

Then I would say you don't really have a problem.
At idle you are relying more on your battery, and not on the alt.

 

Agreed, I didn't realize the amps dropped that low at idle, my bad

 

You should still consider big3 and 0awg ground front to back (supplement to chassis) as well as better or additional battery and/or capacitor. During those low rpm times these options can help keep ur alternator from taking a crap on you, especially if you are relying on the battery at idle, it seems the alternator will be pulling OT to keep the battery charged... So i believe your OP still stands...

 

Yeah I still plan on doing big 3, I was hoping someone here had done it and could provide some good instructions.

 

Nobody has done the big 3 on their 7th gen?

 

I have replaced the alternator and it is difficult to get to. You MUST evacuate and remove the AC compressor, so plan on going ahead and doing complete AC service at he same time. Our stock Alternator is rated at 130amps at 5500 rpm or 65amps at 1500 rpm. Good luck!

 

i haven't done the big 3 but i do have the grounding kit. I'm pulling about 1600watts constantly to my subs. however i do have a capacitor cap so that helps alot and keep the system from killing my battery or alternator. so you may want to look into that. i have three tvs and lights so i'm pretty much tapped out for power. maybe a battery upgrade in the future. knock on wood.

 

^ your capacitor is hurting you! not helping.

 

Ack, well if I have to remove the compressor then it will just have to wait until I change to an HO alternator. I don't want to go through that just for adding the wire, especially if I end up needing an HO alt and have to do it again.

 

how do you figure its hurting me. i just noticed that its always fully charged i don't have them dimming of lights when the bass hits or when everything is on neither. plus im still running on the factory battery as of this moment.

 

It probably isnt. A capacitor is just a battery capable of discharging electrons extremely fast. That would be why you get dimming of lights...typical lead acid batteries really cant keep up with those high paced discharge rates, so other electric accessories suffer a current drop as a result.

Your biggest limitation is the stock battery. If your current setup works, then congrats. The alternator really doesnt do squat in the immediate moment of supplying current to anything. The battery is your only source of electricity to everything. The alternator's output is pretty messy and sloppy, hence the warning that disconnecting the battery with engine running can damage stuff (not a stable voltage). The battery also acts as a filter to supply a good clean stable voltage. If you are taxing the battery...especially one that isnt really up to the task, you are straining the alternator. The alternator senses a voltage drop faster and works harder to replace the electricity more quickly. The threshold between undervoltage with high duty charge rate and specified voltage reached is a much more narrow window with a crappy battery. A higher capacity battery has a much larger supply to draw from. I would upgrade battery ASAP. It is the best thing to do for the whole system. I would recommend the Duralast gel-cell battery from Autozone. Ive had it for a year and it has been phenomenal. Reserve power is much better than stock.

 

The rate at which capacitors discharge is measured in the fractions of a second.
Then your battery is recharging the cap and running the system. Capacitors were needed in the 80s when amplifiers didn't have much on board capacitor capacity. Now days amp design is such that you don't need an external cap.
The only place they are useful is in spl competition when doing bass burps.
Some people will use it as a power cleaner, on higher end systems. This just smooths the voltage input to the amp a little pit, but doesn't provide additional power, as it is implemented to never really fully charge or discharge.