let it rip- Batt vs Cap discussion/debate...:hmmm:

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Eric D
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Post by Eric D »

It reminds me of a line I once heard,

"Those who can't, teach..."
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Eric D
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Post by Eric D »

Got "schooled" by member shawn k on May 10th, 2011...
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Hands down the forum's most ignorant member...
Don't even know what Ohm's law is...
mrblob
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Post by mrblob »

I thought the battery wants to stay at 13.8 V not 12. Also isn't the battery only used in the system when the overall voltage of the system goes below the battery's voltage? That's why adding another battery is useless because it just becomes another load on to the alternator to charge.

Also another time a cap is useful is when the alternator's regulator senses it needs to up the current and does so...for a split second some alternators are slow to react so a cap could buffer that delay.
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Eric D
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Post by Eric D »

Most batteries are 12.6V or close too it.

The output of the alternator is actually instant, the regulator does not "sense" anything, it is a very simple circuit. What takes time is for the current to make its way to the amplifiers in the trunk, through the cable which has resistance.
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Post by ttocs »

mrblob wrote:I thought the battery wants to stay at 13.8 V not 12. Also isn't the battery only used in the system when the overall voltage of the system goes below the battery's voltage? That's why adding another battery is useless because it just becomes another load on to the alternator to charge.

Also another time a cap is useful is when the alternator's regulator senses it needs to up the current and does so...for a split second some alternators are slow to react so a cap could buffer that delay.
you alt should be charging arond 13.8-14 v but your batter will stay at 12.5.

Now again, a cap is a voltage storage device not a current storage device. This is why it does not do much for your amp because your amp is current driven....
what else can I say I am a grumpy asshole most of the time.
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Eric D
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Post by Eric D »

Actually a cap is neither. It stores charge (electrons), not current, nor voltage.

Charge moving is current, quantity of charge and its configuration gives you voltage potential.

So really a cap can feed an amplifier current, just not a whole lot of it.
Got "schooled" by member shawn k on May 10th, 2011...
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Eric D
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Post by Eric D »

O, a battery stores charge as well, but a ton more of it than a cap.
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mrblob
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Post by mrblob »

Eric D wrote:Most batteries are 12.6V or close too it.

The output of the alternator is actually instant, the regulator does not "sense" anything, it is a very simple circuit. What takes time is for the current to make its way to the amplifiers in the trunk, through the cable which has resistance.

"If, on a long bass note, the lights dim just for a fraction of a second but return to their original brightness while the note/tone is still playing, the alternator's regulator may just be a little slow in reacting to the voltage drop"

www.bcae1.com/charging.htm


This situation is a good candidate for a capacitor I believe.
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Post by ttocs »

do your lights dim when you roll down your windows as well? Mine does so I am thinking about putting a cap on the power windows power wires.
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Eric D
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Post by Eric D »

And I need about 1 farad for my horn.
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Post by mrblob »

No, but the thing is, with music, you get a lot of bass notes. Dimming at the start of every bass note get annoying... Putting even a .5 farad cap in there might do the trick. That is the only time an alternator will not fix the problem.

I put in a digital cap for aesthetics (girls love large cylindrical objects lol) since I can't get an upgraded alternator for my car. Dimming headlights are a non issue for me since I have factory HID's which are basically powered by the ballasts, and they can operate as low as 9 volts.

My system will play at 14.1- 14.2 volts most of the time, but when I turn it up, it will start playing at 11.9-12.5. So my system struggles.

Correct me if I'm wrong, but PG amplifiers use unregulated power supplies, and put out depending on the voltage of the system. I remember the old ZX amps used to be rated to play full power at 13.8 V (not 14.4), which means PG amps nowadays are always putting out less WRMS (since most people do not upgrade their alternators).
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Post by Stryker »

mrblob wrote:No, but the thing is, with music, you get a lot of bass notes. Dimming at the start of every bass note get annoying... Putting even a .5 farad cap in there might do the trick. That is the only time an alternator will not fix the problem.

I put in a digital cap for aesthetics (girls love large cylindrical objects lol) since I can't get an upgraded alternator for my car. Dimming headlights are a non issue for me since I have factory HID's which are basically powered by the ballasts, and they can operate as low as 9 volts.

My system will play at 14.1- 14.2 volts most of the time, but when I turn it up, it will start playing at 11.9-12.5. So my system struggles.

Correct me if I'm wrong, but PG amplifiers use unregulated power supplies, and put out depending on the voltage of the system. I remember the old ZX amps used to be rated to play full power at 13.8 V (not 14.4), which means PG amps nowadays are always putting out less WRMS (since most people do not upgrade their alternators).
Large alts do solve the problem of dimming headlights as well as voltage drop. If your voltage drop is that much you must be killing battery's at an astounding rate because at 12.4v and lower your battery is in discharge and that is not healthy for it. A battery is mostly used for cranking an engine to start it(obviously) after that the alternator takes over and powers the lights ,heater, stereo etc...
Spend your money on doing the Big 3 with 0 ga, and forget the cap.
screw car audio, I'd rather go fast....errr, wait a minute.
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Post by gridracer »

Here is the best article on caps I have ever read. Unfortunately the links are broken in the thread this was copied from.I can't remember where I found this it was years ago.

The Truth about Capacitors Quoted from another source.
--------------------------------------------------------------------------------
After studying a little history on large 1 Farad capacitors in car audio, you'd be amazed that they even sell at all. How useful are they? What do they really do? Will a Cap 'improve' my sound quality? Will it Prevent my lights from dimming? Will it audibly affect my audio system in any way?

Before you get the truth to any of the above questions, chances are, you've probably spent $100 or more on one of these devices. However, let's study a little history regarding this issue.

A long time ago, in a land far away, 2 elves...Ok, Richard Clark & Wayne Harris (Carsound magazine and the inventor of DB Drag, respectively) separately came up with a solution to preventing their lights from dimming.

WHO WERE THESE GUYZ?

As you may know, Richard Clark is one of the founders of autosound2000 Tech Briefs, Carsound magazine, and a published author of the industry of mobile electronics. In SQ competitions, he posted a record of 1234 1st place finishes, and only ended up NOT 1st in his first event. I've heard that he had minor system problems, but judging by his record, he must have corrected it. (evidently, he needed a Capacitor )

Wayne Harris was previously a leader at Rockford Fosgate in their development. Later, in his free time, he created the organization we call DB DRAG. Wayne was the first SQ World Champion from the organization we know as IASCA (International AutoSound Challenge Association).

Both of these gurus are both legends, and considered the leading experts in the field. During their competition days, both guyz came up with a way to assist in the prevention of voltage drops. In SQ competitions, the look of your system is actually more important than the sound, and having your lights NOT dim under high playing levels is a competitive advantage.

As you may know, amplifiers are made up a bank of little capacitors, resistors, etc. What has been common engineering knowledge is that capacitors store energy, and more or bigger ones assist in balancing the power supply.

Wayne came up with the idea of putting several dozen 'little' (approx 100uF) capacitors on a circuit board to 'extend' the power supplies storage. At about the same time, or shortly afterward, Richard came up with the idea of one huge mondo capacitor (I believe it was 800,000uF or 0.8F) to do the job.

Eventually, Richard won. The large cylindrical tubes won over the complicated 48 caps strapped to a circuit board. However, what did this really accomplish? Let's start here:

WHAT IS A CAPACITOR?

Basically, capacitors are an energy storage device. Large, 1 Farad or more
capacitors store energy (electrons) between their plates. Capacitors differ
from batteries because batteries store energy in the form of chemical
energy--and rely on acid and lead plates, as the place of storage. For a more detailed
description of a capacitor, go here:

http://www.eatel.net/~amptech/elecdisc/caraudio.htm

Then on the right hand side, scroll down to CAPACITOR. Keep in mind the use
of capacitors in an audio system.

WHY DO PEOPLE BUY CAPACITORS?

The number 1 reason would have to be because their lights dim when their
system is playing HARD. In car audio, we are told that a capacitor is
designed to prevent the voltage drop associated with your lights dimming.
The number2 reason is that it is rumored to 'improve' sound quality or
'stiffen' the power supply/source.

WHY DO MY LIGHTS DIM?

Headlights brightness is in direct proportion to the source voltage. For
instance, if your car is running, system voltage is ~12.5 -14.4 VOLTS. Your
lights will be much brighter than when your car is turned off--where battery
voltage is ~12V. Most car alternators put out between 75 to 120 amps of
current. When this current draw threshold of the charging system is
exceeded, system voltage will drop as power demands are now shared by the
alternator and the storage devices (battery & cap). We are using battery
reserves beyond this point until the demand lessens

When playing your system really hard. Your lights dim because your
alternator can't keep up it's charging voltage (around 13.5V) and therefore,
demand exceeds output. When this happens, your electronic devices are
dipping into the power storage of the battery. Since the battery stores
power at ~ 12-12.5V, there is a 1.3 to 1.8V drop in voltage available. This
in turn is why your lights dim down.

HOW MUCH POWER DOES A CAPACITOR STORE?

1 Farad = 100 joules or 100W/second
850cca battery = ~2,200,000 farads


For storage purposes, you'd need ~2,200 1 Farad capacitors to equal the energy of your battery.

Due to its impedence (ESR & ESL), a cap's energy is only 50% available. What's worse, is that in order for a 1 Farad cap to discharge, first the alternator output must have maxed out, and the voltage must have dropped around 1.5 volts. But I thought a cap was supposed to prevent that (voltage drop)!!!!!????? Yep, you got the point.


IF A BATTERY = 2,200 CAPS, THEN WHY BUY A (PUNY) CAP?

My question exactly. Marketing is the reason why people buy caps. In many cases, upgrading wiring will help your system get the maximum transfer of current. Once that has been reached, adding a capacitor may have a minor effect on your system. 50W over the course of a second is not a lot of power considering an amplifier may draw 2000W to put out 1400 watts. Let's look at the situation from a resources standpoint.

Alternator 80 amps
Car accessories (minus stereo) 40 amps
A large Car Audio system (DRAWS ) ~200 amps AT FULL OUTPUT

In this case, you have 240 amps of draw, but only 80 amps of current from the alternator. In your case, you need 160 amps x 12 volts or or let's say 1920 watts of energy. Since a cap stores 50W, how much of a difference do you think it's going to make? A cap is basically a peashooter. W+e need a Howitzer cannon here, to do the job well.

Also, Once a cap is discharged, where does it get it's power from? The alternator, which is already overloaded. Once a cap is discharged, it's worthless. Like SWEZ says,
Last edited by gridracer on Thu Sep 23, 2010 8:33 pm, edited 1 time in total.
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Post by Stryker »

^^^^^
I've read that article too. great find!!! CAPS ARE JUNK PEOPLE!!!
screw car audio, I'd rather go fast....errr, wait a minute.
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Post by ttocs »

just curious, while I agree with the article you really should post who wrote it if you are going to cite it as a reference.
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Post by gridracer »

Unfortunately I can't remember where I found it otherwise I would have posted it if I am not mistaken it was on autosounds forum.
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Post by gbody805 »

Image

And I had an Ultra cool three cap install planned too.
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Post by THUMP-LUMP »

I only got though 1:20 of the first vid. What a load. I think caps are best left to wear on ones head.
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Post by ttocs »

I don't hate them. I think they look cool and are a nice piece of audio jewelry. If you want them in your install then do it!
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Post by gridracer »

I don't hate them either when installed to look good I just don't like them for the fact they don't do anything for you other than empty your wallet, I used to sell the odd one but usually I would talk the kid into a battery instead. If you look at the install I posted a while back that I worked on you can see they looked good in there.
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Post by eulogious »

I bought a cap a few years ago with the "fancy" lights and LED voltmeter on top of it thinking it would do something, but it never really did. But it did look cool :lol: I have it in my current install, just because I had it sitting around, and why not have a niffy voltmeter if it's just sitting around. I don't have it wired in "properly", meaning it's not after my fuses, infact it's wired in before my fuse block :lol: but the point wasn't for usefullness, it was for audio jewelery and nothing more. So as long as you know that your cap is just for looks, then I don't have any problem with them.

Here's a pic of mine I have currently installed, and as you can see I just threw it in for looks...

Image

Now upgrading my 55amp alt to a 90amp alt, that made a HUGE difference, unlike the cap. So if you are really looking for something useful, then batteries and alts are really the only way to go. I firmly believe this after upgrading my alt and seeing the difference it made.
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Post by Stryker »

They are nice jewelry. They also put a load on your Alt after it's been discharged. I remember way back when some guy had like 15 1 farad caps with Voltage readout wired in paralel, as the system was playing each cap down the line was reading less and less :lol: If anyone is seriuos about getting rowdy with large power a H.O. alt is a must, plus extra battery's never hurt.
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Eric D
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Post by Eric D »

Stryker wrote:They are nice jewelry. They also put a load on your Alt after it's been discharged. I remember way back when some guy had like 15 1 farad caps with Voltage readout wired in paralel, as the system was playing each cap down the line was reading less and less :lol: If anyone is seriuos about getting rowdy with large power a H.O. alt is a must, plus extra battery's never hurt.
Please provide some proof of this. That does not make any sense at all.
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Post by ttocs »

yea I am not sure why they would read different voltages if they are wired in parallel as they would share the same power source. IF they were wired in series, maybe it would make sence but unless the voltmeters are tuned differently when wired in parallel they would all show the same thing.
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Stryker
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Post by Stryker »

I would be hard pressed to provide proof :-s . I believe it was in a Boss Audio demo vehicle, not posistive tho. It was so long ago that it may have been in the 90's. It's possible it was in series it sooo long ago. nonetheless caps do put a load on your Alt. I will try to dig it up, Although I will only dedicate so many minutes :lol: to search the internet.it's possible it was in a car audio and electronics magazine article....
screw car audio, I'd rather go fast....errr, wait a minute.
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