Is it *actually* time for a cap?

[jrwalte 10+ year member]

My system is in my sig.

Some additional information:

Big 3 done with 1/0 and 1/0 going to trunk. Have under .1 voltage drop in trunk.

My Memphis is 1500RMS and Eclipse is 400RMS

RD 15" is rated at 1000RMS and in a sealed 2.25 box with 2 lbs of polyfil. I don't let it distort (at least to my ears).

Problem:

I typically listen to rock/alternative/pop - a lot of big hit drum lines. Even with my HO alt, I am getting a slight headlight dim when volume is high and the 'big hit' occurs. During this time, voltage stays constant around 14.2-13.9. However, on an extended bass note I don't have dimming issues.

Understanding how alt works:

Alts power output is controlled through a regulator. This regulator watches the voltage of the electrical system and when it drops below a certain point, the regulator increases the power input to the magnetic field of the alternator, which in turn causes the alternator to output more power. Granted this probably happens in milliseconds?

To me, this makes the alternator a 'passive response' to electrical need. I suspect this is why I'm experiencing dimming. The power need is so great on that strong 'hit' the alt doesn't have the time to crank it's power output up fast enough.

Resolutions:

A capacitor

It is an 'active response' to power need at the voltage my alternator is. It will be there and available for the 'big hit' the moment it is needed and can provide the power to my amp until the alternator has its time to increase its output. I don't think it'll cause a strain on my alt because the alt can give the power (hence the no dimming on extended bass note), it just isn't giving it fast enough.

If I were to go with a cap, how many farad's would I be looking at to handle 1500 watts?

A battery in trunk

I'm throwing this out there for discussion. I don't really see how another battery in my trunk can help my situation. Since it is 12 volts my electrical will still have the momentary drop in voltage to cause the dim.

Please no flamming with "caps are worthless". Be constructive and explain your stance. Thanks for your input.

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[DDeitz 10+ year member]

im not touching this.

 

[sonic purity 10+ year member]

I have had caps in my systems, but never seen any benefit from them. In theory they sound really good, but they dont seem to work for me. Something I have wanted to try though, that I have heard and seen good results from is the batcap, or other hybrid storage units. But I think in any case, an extra battery would help with the dimming issue. Especially if the alt can keep up.

on that note, putting a cap in certainly would hurt. Give it a try and tell us how it worked for you.

 

[Grinder1989 5,000+ posts]

Why are you even worried about such an insignificant drop in voltage? I've got over 3200 watts RMS with a yellow top and a 140 amp alternator and I hardly dim at all. Get a dry cell battery, they help stop the dimming if your that worried about it.

 

[sonic purity 10+ year member]

Why are you even worried about such an insignificant drop in voltage? I've got over 3200 watts RMS with a yellow top and a 140 amp alternator and I hardly dim at all. Get a dry cell battery, they help stop the dimming if your that worried about it.

that what I was thinkin

 

[Grinder1989 5,000+ posts]

I noticed a very significant change in dimming issues before I even got my 3000D. I had my 1500D on a wet cell and I dimmed (didn't lose a ton of voltage, just dimmed more). Even with two bigger amps my dimming was no where near as bad as my 1500D. I'd save what you'd spent on a cap and put it towards a yellow top or whatever.

 

[jrwalte 10+ year member]

If you'd look at my sig I have a dry cell Kinetik.

Maybe I'm not understanding electrical well enough. How will another Kinetik or similar battery in the trunk prevent the dimming, which happens due to voltage drop?

And I'm not saying a cap is the answer...that's why I'm posting. I'm just explaining my reason for thinking it may help.

 

[jrwalte 10+ year member]

Why are you even worried about such an insignificant drop in voltage? I've got over 3200 watts RMS with a yellow top and a 140 amp alternator and I hardly dim at all. Get a dry cell battery, they help stop the dimming if your that worried about it.

I don't like the blinking lights while driving down the road //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[Grinder1989 5,000+ posts]

If you'd look at my sig I have a dry cell Kinetik.
Maybe I'm not understanding electrical well enough. How will another Kinetik or similar battery in the trunk prevent the dimming, which happens due to voltage drop?

And I'm not saying a cap is the answer...that's why I'm posting. I'm just explaining my reason for thinking it may help.

Sorry I missed that. Adding another battery should help because you have more reserve capacity so the voltage won't drop as much as fast. If your alternator couldn't keep up with current draw, you'd lost a lot of voltage. However if you have enough amperage between two batteries, the voltage drop should be minimal with almost no dimming. All in all, a battery is a much better choice than a cap.

 

[twisztdauthorit 10+ year member]

why not just add a good battery and get over it?

battery > lots of caps

 

[Techchild 10+ year member]

When I used to help build alternators the other guys used to install them an when there was a secound battery in the trunk they used a little distro type thing that made the battery in the back only run the amps and the battery in the front ran everything else so there was no dimming. I forgot what it was called thoe.

 

[mokedaddy 5,000+ posts]

Put a cap on your headlights.

 

[mokedaddy 5,000+ posts]

When I used to help build alternators the other guys used to install them an when there was a secound battery in the trunk they used a little distro type thing that made the battery in the back only run the amps and the battery in the front ran everything else so there was no dimming. I forgot what it was called thoe.

Probably an isolator.

 

[Techchild 10+ year member]

Probably an isolator.

Yep that sounds right.

 

[sonic purity 10+ year member]

turn the lights off, problem solved. LOL