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Debate, Stiffening Capacitors


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jmelton86 
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Posted: May 18, 2007 at 5:31 PM / IP Logged  
Alright. So you may have benefitted a little by adding cap. What amperage is the battery charger capable of?
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auex 
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Posted: May 19, 2007 at 5:01 AM / IP Logged  
Wow, just wow.
sparky3489 wrote:

aznboi3644 wrote:
a cap DOES drain...thats why the voltage will still drop

Well now that's strange. My oscilloscope says otherwise as does the dispaly on my cap. My equipment must totally wrong. Debate, Stiffening Capacitors - Page 5 -- posted image.

No, a cap does not FULLY drain, but it does drop about 0.7 of a volt though.

So I have a question for you. Do you really think that a cap stores voltage? I mean do you really think that? Can you tell me what a cap does store? Also, when a cap is "drained" won't the alternator have to replace an equal amount of energy that was drained? How long do you think it takes to recharge? Do you think that the alternator feels less strain because the cap just magically creates energy out of no where?
You also stated you had a 4V improvement during bass hits after adding the cap. I don't believe this at all. Maybe someone can do some math and find out how much power would be required to cause a 4V drop in V and how many farads would actually be needed to stabalize the voltage. Seriously, if this is true you have some major problems somewhere. 4V is huge so either you are running way too much stereo equipment off a WAY to small of an alternator or you have some wiring issues(big 3 and bad factory grounds).
Lastly, you state you have an O-scope. Why do you own one? Also why are you using an O-scope to measure DC voltage? Are you an EE? If so that would answer alot of questions.
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sparky3489 
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Posted: May 21, 2007 at 9:28 AM / IP Logged  

auex wrote:
Do you really think that a cap stores voltage? I mean do you really think that? Can you tell me what a cap does store? Also, when a cap is "drained" won't the alternator have to replace an equal amount of energy that was drained? How long do you think it takes to recharge? Do you think that the alternator feels less strain because the cap just magically creates energy out of no where?

1. Yes, this is measurable.

2. See #1

3. Electricity, typically what is supplied with a bit of current to back it up.

4. Since a bass hit is fairly quick and a cap is extremely fast to respond and charge, the alternator has no issues responding as well.

5. Because of a caps "charge time constant" and the fact that only a small percentage of the cap is "drained", it's recharge time is very quick, 0.5 second at the most.

6. I didn't know alternators "feel" anything. Must be a magic Artificial Intelligent alternator. The trem "stiffening" is an interseting concept, eh?

These were 4 volt peaks, the average voltage drop was about 1 volt or less, still significant. 

Well, an O-scope is a bit faster and easier to read than a DMM, especially to see transients a DMM cannot display.

You really needed an explanation for an O-scope here?

haemphyst 
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Posted: May 21, 2007 at 11:24 AM / IP Logged  
sparky3489, first off, I took a bit of liberty with your quote. I am assuming you broke auex's question string into individual questions and answered them individually with your numbered responses. This is how I broke it down, and now I would like to respond in kind.
sparky3489 wrote:
auex wrote:
Do you really think that a cap stores voltage?
1. Yes, this is measurable.
I agree with this response.
sparky3489 wrote:
auex wrote:
I mean do you really think that?
2. See #1
See #1 Debate, Stiffening Capacitors - Page 5 -- posted image.
sparky3489 wrote:
auex wrote:
Can you tell me what a cap does store?
3. Electricity, typically what is supplied with a bit of current to back it up.
I am slightly confused with this answer. What are you saying here? Please elaborate a little bit on this response. I am truly not trying to be smart-assed about this, but I truly want to know what your answer means.
sparky3489 wrote:
auex wrote:
Also, when a cap is "drained" won't the alternator have to replace an equal amount of energy that was drained?
4. Since a bass hit is fairly quick and a cap is extremely fast to respond and charge, the alternator has no issues responding as well.
Here, I have an issue. The answer to auex's question is a RESOUNDING YES! However, your answer does show that you both understand and DON'T understand, completely.
Energy is drained from a cap in watt-seconds, or work over time. It also CHARGES in watt-seconds. (a watt-second, if you weren't aware, is one watt for one second) If you suddenly pull (let's just say, as an example, to keep the math simple) 100 watt seconds from the cap, but it happens in .1 second (fairly typical, actually), the current burst supplied by that cap is 1000A, for .1 SECOND. (I also want to stress that I am assuming a perfect cap and circuit, with zero resistance) Now, in order for that cap to be ready for the NEXT 1000 watt-second burst (in a bass line, at 4/4 time, what, a 1/2 second, maybe?) the source (the alternator, which we have all agreed MANY TIMES here in this forum is ABSOLUTELY the power SOURCE in a car with a RUNNING engine) must be able to charge that cap OVER AND OVER 2 times a second with 1000A bursts of current. Now, NO ALTERNATOR is capable of doing this, is it? BUT a SLA battery CAN. This is why the battery becomes so important in this circuit. Now, the battery is continually dumping this power to the cap, while at the SAME TIME the alternator is carrying the continuous load of the REST of the system's demands. That is, until the battery voltage drops, the internal resistance lowers, and the alternator's output is now being scabbed off to recharge the battery, while the battery is continuing to recharge the cap, and the alternator is trying to now power the system AND charge the battery... it's a vicious cycle, and the situation only gets worse, the longer and louder the system is played.
sparky3489 wrote:
auex wrote:
How long do you think it takes to recharge?
5. Because of a caps "charge time constant" and the fact that only a small percentage of the cap is "drained", it's recharge time is very quick, 0.5 second at the most.
See #4. BUT, while it is true that the cap is generally recharged to full capacity fairly quickly, (simply due to the low internal resistance of the SLA) the average recharge CURRENT DEMANDS are astronomical, when viewed strictly on a current scale. Average continuous current demands that simply CAN'T be addressed by an average alternator. All the time, pulling the average system voltage lower, and lower. The cap, because it is there for IMMEDIATE current peak demands, "covers the dimming headlights", (because the PEAK SYSTEM VOLTAGE remains where it is supposed to be, but the AVERAGE system voltage is slowly dropping... slowly enough that the lights DO dim, but not in "pulses" with the beat of the music.) and this is why many people think the cap is helping them.
sparky3489 wrote:
auex wrote:
Do you think that the alternator feels less strain because the cap just magically creates energy out of no where?
6. I didn't know alternators "feel" anything. Must be a magic Artificial Intelligent alternator. The trem "stiffening" is an interseting concept, eh?
The strain that auex is implying is "felt" by the alternator is the ever increasing current output demanded by the system drawing more from the alternator and battery combination than it was ever designed to produce on a continuous basis, all while the alternator and battery are working in an underhood environment where the temperature ever increases, reducing both of their efficiencies, causing more strain...
It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
haemphyst 
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Posted: May 21, 2007 at 11:28 AM / IP Logged  
Now, leave it alone... Caps:
1: Are the devil. (OK, not really)
2: CAN be beneficial, but only in limited situations.
3: 99+% of car audio issues and problems can be solved by upgrading MOST ESPECIALLY the alternator.
4: That SAME 99+% of the time, a cap will be a "band-aid on a bullet wound"
5: Should always be the LAST item added to any electrical system, and only if you want to "see the shiny red can"...
It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
tdsteele 
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Posted: May 21, 2007 at 2:17 PM / IP Logged  
Ok i want to throw a question in here about h.o. alt's. I have seen on here before people saying a h.o. alt does its job better at higher rpm's versus at idle speed, even read where they can put out less than a stock alt at idle speed. So, if those statements are true than, whats the point of paying the money to get one? Reason I make this comment is, I see more people really cranking there systems while parked than I do driving around at normal speed where the alt would be operating at the higher rpm's. So if the person was just parked and cranking the system, is that why I see people with x amount of batteries and caps instead of a h.o. alt? Just curious on this. I always just assumed a cap or extra battery would act like a "shock absorber" for the electrical system. I fully agree that once the car is running, the alt is providing that power, at least until it can't meet the needs, and if you go that far, the alt will eventually burn up. I dunno, just rambling.
auex 
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Posted: May 21, 2007 at 2:30 PM / IP Logged  
Just to clarify, question 1 as labeled, was meant to clarify if he thought all it held was V, as opposed to storing energy and not just V. It was more toward the fact everyone was focusing on V only.
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sparky3489 
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Posted: May 21, 2007 at 2:35 PM / IP Logged  

This is why, when refering to capacitors, I use this very statement:

sparky3489 wrote:
A capacitor is like an electronic fuel tank that holds a charge provided by the electrical system for sudden demands for short bursts until it can charge back up.
There is something called a "charge time constant" in a capacitor. This signifies how fast a capacitor can recharge after a partial discharge. Since a large capacitor (0.5 Farad or higher) doesn't fully discharge, it's re-charge time is pretty quick.

Adding a cap to a severely demanding system won't make any improvements.

If your total system power is more than 1000 watts RMS you may need to:

1. Upgrade the alternator to a high output alternator

2. Upgrade to a heavy duty deep cycle battery
3. Upgrade the "Big 3" - that is to replace the power wire between the battery and alternator, the ground from the battery to the chassis and the ground strap from the engine/tranny to the chassis with at least 1/0 AWG wire.

Failure to do this will result in you replacing them anyway as the alternator can eventually fail.

Never have I made the "caps are the only answer" response in ANY forum as it GREATLY depends on many factors as to when to use them.

The fact is that I have seen an improvement in my system using a cap is no indication they are for everyone or every situation.

This whole thread was started by jmelton86 who seems to have skipped out of the debate in the first place.

aznboi3644 
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Posted: May 21, 2007 at 3:49 PM / IP Logged  
tdsteele wrote:
Ok i want to throw a question in here about h.o. alt's. I have seen on here before people saying a h.o. alt does its job better at higher rpm's versus at idle speed, even read where they can put out less than a stock alt at idle speed. So, if those statements are true than, whats the point of paying the money to get one? Reason I make this comment is, I see more people really cranking there systems while parked than I do driving around at normal speed where the alt would be operating at the higher rpm's. So if the person was just parked and cranking the system, is that why I see people with x amount of batteries and caps instead of a h.o. alt? Just curious on this. I always just assumed a cap or extra battery would act like a "shock absorber" for the electrical system. I fully agree that once the car is running, the alt is providing that power, at least until it can't meet the needs, and if you go that far, the alt will eventually burn up. I dunno, just rambling.
There are manufacturers that make alternators that put out a good amount of current at idle speeds.
jmelton86 
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Posted: May 21, 2007 at 7:05 PM / IP Logged  

I only post when I'm at work. I work Mon. - Thu. nights. It's Mon. night so I'm back at work. What's up everyone?

-I added a cap before hearing about and applying the Big3 (fact. alt, tiny charge wire). I didn't notice any quality increase in the sound. I however did notice my headlights started slowly dimming (tis' a long drive home from work, system cranked) and the quality of  sound become bad, I thought I was loosing ground. I turned it down to about 1/2 way and turned sub amp off. The treble/mid started sounding better as soon as I turned my sub amp off! The factory charge wire, right after this instance it seems, turned brown right by the alt. The alt. must've been getting pretty hot, i'm glad I turned my sub amp off! This is the exact reason (I didn't get it til' reading the past couple of posts!) why I started this post -Since then i've done the Big3 and it seems to 'hold up' so i've left the cap. After reading the rest of this thread, though, i'm taking it off! -Thanks haemphyst!

Oh, sparky3489, had you been telling people just this;

sparky3489 wrote:

1. Upgrade the alternator to a high output alternator

2. Upgrade to a heavy duty deep cycle battery
3. Upgrade the "Big 3" - that is to replace the power wire between the battery and alternator, the ground from the battery to the chassis and the ground strap from the engine/tranny to the chassis with at least 1/0 AWG wire.

Failure to do this will result in you replacing them anyway as the alternator can eventually fail.

*****

i'd've had no reason to start this post because I had seen nothing like this until I started answering questions with 'the Big3' -it wasn't until I questioned you personally on cap usage that I somehow noticed it.

Anyways,, I hope everyone has/is learned/ing something from this thread. I've learned exactly what happend 'that night'. Cheers

2013 Kia Rio -90a alternator
DDX470HD GTO14001 GTO1014D (x3)
Big3 in 1/0G
1/0G to GTO14001
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