# 10 farad cap actually worked ... Anyone want to explain how ?



## JAG (May 6, 2006)

The debate over whether caps really work or not , is ALWAYS hotly debated. I'm not posting to open up a technical discussion , but rather tell of my experience this past week , and let YOU decipher what you want from it.
One of our fellow forum members hired me to fly to his home and install a competition level system in his new car, as well as provide the equipment. He purchased a great 1500 amp Odyssey Dry Cell battery, but his stock alternator is only rated at 80 amps !!! He's using three amplifiers in his system. One is bridged in to 2 ohms at 1400 watts on a sub. One provides 270 w/ch to his 6.5" drivers , and one is 170 w/ch for his tweeters ... That's a total peak output of 2280 watts .....
With his head unit's high 8 volt output , the gains on his amps are set at almost dead minimum , and yet the system will still play louder than a person really wants to listen to for long. Point is : His gains are set properly ....
He's using 1/0 power and ground wire , and the Big 3 were also done.
He went for a test drive and had VERY , VERY bad pulsating headlight dimming. WAY too much to be acceptable.
Now ... I reccomended a high output alternator , but he didn't like that idea at all at first. So after speaking with me about car charging systems , he decided to buy a *Stinger Hybrid 10 farad Cap .....*

After the Cap was installed , he has NO MORE DIMMING HEADLIGHTS !!!

Simply put again : You be the judge , but in this case YES .... A cap worked.
As a last note , he ended up finally deciding to go ahead with my suggestion and also buy a high output alternator that he should have in a couple of weeks .....

*I'm posting this here due to the generally more technical people who post here. Some of you Gurus speak in Vulcan after all  But the above story is true , and I'd really like to hear some interesting theories on just how this worked so very well.
Thanks much ....*


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## scott_fx (Mar 31, 2006)

i've never doubted if larger caps work, i think that caps are a band aid and thats why they get a bad wrap. caps do what they are designed to do and will give you it's stored energy when it's asked for...same thing that the smaller ones do internally in an amp


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## GMo (Aug 9, 2005)

AVI said:


> The debate over whether caps really work or not , is ALWAYS hotly debated. I'm not posting to open up a technical discussion , but rather tell of my experience this past week , and let YOU decipher what you want from it.
> One of our fellow forum members hired me to fly to his home and install a competition level system in his new car, as well as provide the equipment. He purchased a great 1500 amp Odyssey Dry Cell battery, but his stock alternator is only rated at 80 amps !!! He's using three amplifiers in his system. One is bridged in to 2 ohms at 1400 watts on a sub. One provides 270 w/ch to his 6.5" drivers , and one is 170 w/ch for his tweeters ... That's a total peak output of 2280 watts .....
> With his head unit's high 8 volt output , the gains on his amps are set at almost dead minimum , and yet the system will still play louder than a person really wants to listen to for long. Point is : His gains are set properly ....
> He's using 1/0 power and ground wire , and the Big 3 were also done.
> ...


Well it's obvious he's not loading the alternator with the amp's "peak" output (2280watts = around 200amps). 

So either the DC power converter of the amps are really sub-par, or the cap added enough resistance to lower the nominal voltage from 14V to say 13V or 12V - which results in lower VDrops. 

My definition of “works” would be to do something to the electrical system to actually benefit it.


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## cvjoint (Mar 10, 2006)

All this after I read a thread and decided to get rid of my cap....

Watch out when buying HO alts, idle output is very low. Just make sure the guy knows that there might be some tradoffs to swapping alts.


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## Guest (Nov 18, 2006)

The achilles heal of a large "stiffening" cap is _not_ the energy _storage_ ... it's the energy _delivery_. The equivalent series resistance of most over-marketed caps is too high to be useful. There's nothing wrong with basic capacitor theory, of course ... one just also needs to include ESR in the analysis 

And I'd bet my bottom dollar that the system never actually delivers 170 watts/channel to the tweets


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## JAG (May 6, 2006)

werewolf said:


> The achilles heal of a large "stiffening" cap is _not_ the energy _storage_ ... it's the energy _delivery_. The equivalent series resistance of most over-marketed caps is too high to be useful. There's nothing wrong with basic capacitor theory, of course ... one just also needs to include ESR in the analysis
> 
> And I'd bet my bottom dollar that the system never actually delivers 170 watts/channel to the tweets


Thanks for answering Werewolf .... You are definitely right about those tweets not getting 170 each , but that just happens to be what the amp is rated at  
If I'm reading you correctly , then you are implying the particular Stinger brand cap we used must have really good low ESR ? Am I reading you right ?


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## JAG (May 6, 2006)

cvjoint said:


> All this after I read a thread and decided to get rid of my cap....
> 
> Watch out when buying HO alts, idle output is very low. Just make sure the guy knows that there might be some tradoffs to swapping alts.


 Yeah .... We spent a good bit of time with Gus from Ohio Generators discussing the trade-offs .... He's building one that targets the entire RPM range , or at least trying to.


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## mvw2 (Oct 2, 2005)

The cap is mearly a buffer. It can help smooth out the variations in voltage leading to a smoother, more consistant flow. This effect is capable of reducing dimming. However, as was said, you have the induced resistance from the cap. If it's too high, you are actually limiting the capable current flow of the system. It essentially turns into a choke point or a throttling valve. In either sense, it can help prevent dimming, but how limited is power delivery? Are you only able to pull 60amps to a system that's capable of 200? Also realize that amps are nowhere near efficient. He may actually be trying to pull 300-400 amps to create 200 amps to his system. The rest simply dissipates as heat. What was it, an AB amp is 50-60% efficient, a D is around 80%? Something like that.

A generic OEM car battery may only be in the range of 300-500 cold cranking amps, perhaps less in a compact car. You're beginning to approach the draw limit of the battery. In this case, a better battery may be in order, or a dedicated set of batteries for the system. You could throw a couple in parallel so you have a system easily capable of quick amp draw applications. Then there's the charging. Luckly, peak wattage and what's actually used during normal music is vastly different. The average is much, much lower. This is why he can get bad dimming but not actually kill the battery. The peak amp situations are there during hard bass hits, but the total average remains lower than the capability of the system.


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## GMo (Aug 9, 2005)

A 10 farad capacitor doesn't reduce voltage fluxing significantly with anywhere near an 80amp load. It does help reduce ripple voltage from the rectified AC, very low energy density. It will not significantly help with overloading the alternator. And a load with high duty, which causes very short transient dips/spikes, isn't going to be noticeable to us. It would be like saying that I can see my LCD frame refresh the picture every 1/60th of a sec

There probably isn't a stiffening capacitor available which has a low ESR at bass frequencies (30-100hz). Like I said earlier, it's probably the capacitor dropping the nominal voltage of the circuit. So instead of having a voltage of 14V when the load isn't very high, the voltage becomes something more like 13V or 12.XX volts. When the higher load takes place the battery discharges, keeping the voltage drop less noticeable. This compounded with a poorly designed amplifier makes this scenario very realistic.


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## JAG (May 6, 2006)

GMo said:


> A 10 farad capacitor doesn't reduce voltage fluxing significantly with anywhere near an 80amp load. It does help reduce ripple voltage from the rectified AC, very low energy density. It will not significantly help with overloading the alternator. And a load with high duty, which causes very short transient dips/spikes, isn't going to be noticeable to us. It would be like saying that I can see my LCD frame refresh the picture every 1/60th of a sec
> 
> There probably isn't a stiffening capacitor available which has a low ESR at bass frequencies (30-100hz). Like I said earlier, it's probably the capacitor dropping the nominal voltage of the circuit. So instead of having a voltage of 14V when the load isn't very high, the voltage becomes something more like 13V or 12.XX volts. When the higher load takes place the battery discharges, keeping the voltage drop less noticeable. This compounded with a poorly designed amplifier makes this scenario very realistic.


One problem with your theory : The amps are designed by McIntosh. Not very low quality at all.


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## JAG (May 6, 2006)

mvw2 said:


> The cap is mearly a buffer. It can help smooth out the variations in voltage leading to a smoother, more consistant flow. This effect is capable of reducing dimming. However, as was said, you have the induced resistance from the cap. If it's too high, you are actually limiting the capable current flow of the system. It essentially turns into a choke point or a throttling valve. In either sense, it can help prevent dimming, but how limited is power delivery? Are you only able to pull 60amps to a system that's capable of 200? Also realize that amps are nowhere near efficient. He may actually be trying to pull 300-400 amps to create 200 amps to his system. The rest simply dissipates as heat. What was it, an AB amp is 50-60% efficient, a D is around 80%? Something like that.
> 
> A generic OEM car battery may only be in the range of 300-500 cold cranking amps, perhaps less in a compact car. You're beginning to approach the draw limit of the battery. In this case, a better battery may be in order, or a dedicated set of batteries for the system. You could throw a couple in parallel so you have a system easily capable of quick amp draw applications. Then there's the charging. Luckly, peak wattage and what's actually used during normal music is vastly different. The average is much, much lower. This is why he can get bad dimming but not actually kill the battery. The peak amp situations are there during hard bass hits, but the total average remains lower than the capability of the system.


Uhm .... You seemed to have missed that I posted that my customer has a VERY GOOD Odyssey 1500 battery.


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## Abmolech (Nov 2, 2006)

Interesting.

The reason why you get dimming is because the regulator has a forward voltage drop across the diode of at least 0.7 volts. For the regulator to increase the current flow to the alternator field windings it needs to have a step change of one volt. Coupled with the slow transient rise on the regulator there can be sufficient delay.

I guess at this point it is up to the battery to supply the required current.
As you mentioned you have a good battery, so the cap has to beat the battery to the "punch" As werewolf mentioned it is which ESR is better as to "who" will win this race.

My understanding is most of these caps also have a diode to prevent discharge back to the battery? If this is the case it will also have a 1 volt drop before reaction.

If the capacitor is hot, it indicates that it is acting as a current limiting device as already posted. I suggest this would keep the alternator under a more constant load (IE it is wasting energy).

A more eloquent solution maybe a digital regulator with minimal voltage drop

something like this..

http://www.sterling-power.com/htm/ab1290.htm


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## GMo (Aug 9, 2005)

AVI said:


> One problem with your theory : The amps are designed by McIntosh. Not very low quality at all.


That's not really part of my "theory", that was more of a side statement.

The statement I made is from low ESR super capacitor experiments in college 5-6years ago. 

It sounds though like your purpose on here isn't to listen to actually what's happening, but rather try and prove that capacitors somehow work through a story.


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## GMo (Aug 9, 2005)

Abmoltech:

The voltage drop across the diode increases with current. But voltage regulation already accounts for a calculated drop, to maintain 14.xx volts.

At levels below alternator maximum output dimming without the cap is occurring because of the constant cycling of the alternator from a partial field to a full field due to the load. The alternator increases current when voltage is low, which causes more Vdrop. As the voltage is increased the field current is decreased. The alternator discharge has a couple of major factors controlling the current, external resistance (circuit) and internal resistance (source). 

I don’t know is if the alternator reaches the full field or not, obviously, but I’m guessing it does. 
We are on the same page with the capacitor wasting more energy, causing lower voltage in the rest of the circuit due to the same procedure with the alternator. This effect is increased with an increase in current. It’s a very real world example of what happens in a circuit with “low duty” loads (something like a bass waveform).


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## MarkZ (Dec 5, 2005)

I don't believe anyone has ever disputed that, in some cases, caps can reduce dimming. I think the debate has been whether or not it can reveal an audible improvement.


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## MarkZ (Dec 5, 2005)

GMo said:


> Well it's obvious he's not loading the alternator with the amp's "peak" output (2280watts = around 200amps).
> 
> So either the DC power converter of the amps are really sub-par, or the cap added enough resistance to lower the nominal voltage from 14V to say 13V or 12V - which results in lower VDrops.
> 
> My definition of “works” would be to do something to the electrical system to actually benefit it.


It did benefit it. He had dimming and now he doesn't.


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## MarkZ (Dec 5, 2005)

mvw2 said:


> The cap is mearly a buffer. It can help smooth out the variations in voltage leading to a smoother, more consistant flow. This effect is capable of reducing dimming. However, as was said, you have the induced resistance from the cap. If it's too high, you are actually limiting the capable current flow of the system. It essentially turns into a choke point or a throttling valve.


Actually, that's not how it works. First of all, there's no such thing as "induced resistance". Second, it never acts as a bottleneck. At worst it can act as an additional draw, but never a "throttling valve". It's not in the right part of the circuit for it to behave that way.


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## JAG (May 6, 2006)

GMo said:


> That's not really part of my "theory", that was more of a side statement.
> 
> The statement I made is from low ESR super capacitor experiments in college 5-6years ago.
> 
> It sounds though like your purpose on here isn't to listen to actually what's happening, but rather try and prove that capacitors somehow work through a story.


Sorry you feel that way , but you are dead wrong. I have ZERO desire to argue on the forum, or prove ANY point. The headlights stopped dimming , and that proved all that I personally needed to see for my own self.
*My purpose in posting this was a sincere desire to try and better understand exactly how this added cap worked so well.* I read your theory , and appreciated some of it , but took exception with your analogy of the possibility of poor amp design having something to do with it. I simply corrected THIS part of your analogy.
Furthurmore , I think the VERY FACT that a person can find NO END to contradictions on this subject is a fairly secure indication that this subject is VERY POORLY understood apparently by most car audio enthusiasts.
If you have noticed , I have offered none of my own theories or opinions here , ONLY asked for other's ....


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## JAG (May 6, 2006)

I am not Werewolf , nor Einstien .... But unless I'm reading things wrongly , some people are suggesting the lights stopped dimming because the cap brought the voltage down to a steady 12+ volts from a more standard 13.5 volts ? This makes ZERO sense to me. If the cap was doing this , it should REALLY heat up , and it is NOT doing that. 
Help me understand this better.


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## Abmolech (Nov 2, 2006)

> If the cap was doing this , it should REALLY heat up , and it is NOT doing that.


It would not have to dissipate a huge amount of heat for this to fit the hypothesis.
To maintain the alternator field in "neutral" I suggest a drop of 0.3 to 0.4 volts would be sufficient. We know the dimming of the head lights is caused by alternator cycling (otherwise the battery would be drained flat), so the question is how would the capacitor reduce cycling? We know the capacitor cant possibly have enough storage ability to keep the voltage consistent.(even a battery voltage "sags" under load of this type of load)


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## MarkZ (Dec 5, 2005)

AVI said:


> I am not Werewolf , nor Einstien .... But unless I'm reading things wrongly , some people are suggesting the lights stopped dimming because the cap brought the voltage down to a steady 12+ volts from a more standard 13.5 volts ? This makes ZERO sense to me. If the cap was doing this , it should REALLY heat up , and it is NOT doing that.
> Help me understand this better.


You should review some fundamental physics. There are a number of texts out there that discuss the basic operation of capacitors. You can also take a look at the bcae1.com page, which has an extensive capacitor discussion. In addition, you could look up the capacitor section of the FAQ for the rec.audio.car newsgroup -- I wrote part of that section, so I'm a little biased.  http://www.mobileaudio.com/rac-faq/

Anyway, the short answer to your question is: that's how capacitors behave in real circuits with real power sources. What happens is that during lulls in the current draw the capacitor is recharging (kinda an oversimplification). By doing so, it's acting as an additional load on the amplifier and as a result the source voltage is decreased in proportion. When the capacitor discharges, however, it's acting as a parallel current source which alleviates some of the current demands from the electrical system, thereby making the voltage drop lower than it would be without the cap. That's the principle of the operation of the capacitor and the whole point of putting it in the circuit -- supply current during peak demands and draw current from the alternator in between peaks.

However, I disagree with those who say the cap has caused the output to drop to 12v. That's far too extreme a drop. It's dropped only a fraction of a volt. But in the end, your problem is addressed by decreasing the amount of voltage swing created by the huge transients in current draw.

As I said earlier in the thread though, there isn't much debate about the usefulness of a capacitor if the goal is to eliminate dimming. It works, just not every time.


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## JAG (May 6, 2006)

MarkZ said:


> You should review some fundamental physics. There are a number of texts out there that discuss the basic operation of capacitors. You can also take a look at the bcae1.com page, which has an extensive capacitor discussion. In addition, you could look up the capacitor section of the FAQ for the rec.audio.car newsgroup -- I wrote part of that section, so I'm a little biased.  http://www.mobileaudio.com/rac-faq/
> 
> Anyway, the short answer to your question is: that's how capacitors behave in real circuits with real power sources. What happens is that during lulls in the current draw the capacitor is recharging (kinda an oversimplification). By doing so, it's acting as an additional load on the amplifier and as a result the source voltage is decreased in proportion. When the capacitor discharges, however, it's acting as a parallel current source which alleviates some of the current demands from the electrical system, thereby making the voltage drop lower than it would be without the cap. That's the principle of the operation of the capacitor and the whole point of putting it in the circuit -- supply current during peak demands and draw current from the alternator in between peaks.
> 
> ...


Perfectly explained .... Thanks for that. You stated the cap is an additional load on the amp ? Don't you mean the entire electrical system , or the alternator ?
Either way , in a VERY over simplified analogy , you saying it's kind of acting as a voltage stabilizer ..... That's kind of what it is basically supposed to do as far as I understand it.


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## JAG (May 6, 2006)

Hmmm ..... Has anyone ever compared the differenceces of using a cap when using on a regulated vs. a non-regulated amp ? I would think a non-regulated amp would be more likely to see any benefits.


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## MarkZ (Dec 5, 2005)

AVI said:


> Perfectly explained .... Thanks for that. You stated the cap is an additional load on the amp ? Don't you mean the entire electrical system , or the alternator ?


Yeah, I must have misspoke.



> Either way , in a VERY over simplified analogy , you saying it's kind of acting as a voltage stabilizer ..... That's kind of what it is basically supposed to do as far as I understand it.


Exactly.



> Hmmm ..... Has anyone ever compared the differenceces of using a cap when using on a regulated vs. a non-regulated amp ? I would think a non-regulated amp would be more likely to see any benefits.


I would think it would be the other way around. A regulated amp often increases the duty cycle (and therefore the total current) of the draw when faced with lower supply voltage. So a regulated amp could conceivably make the dimming problems worse. I would think if you could smooth out the voltage dips a little bit you'd be able to mitigate those effects some.


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## GMo (Aug 9, 2005)

AVI said:


> Sorry you feel that way , but you are dead wrong. I have ZERO desire to argue on the forum, or prove ANY point. The headlights stopped dimming , and that proved all that I personally needed to see for my own self.
> *My purpose in posting this was a sincere desire to try and better understand exactly how this added cap worked so well.* I read your theory , and appreciated some of it , but took exception with your analogy of the possibility of poor amp design having something to do with it. I simply corrected THIS part of your analogy.
> Furthurmore , I think the VERY FACT that a person can find NO END to contradictions on this subject is a fairly secure indication that this subject is VERY POORLY understood apparently by most car audio enthusiasts.
> If you have noticed , I have offered none of my own theories or opinions here , ONLY asked for other's ....


You’re definitely biased towards a capacitor somehow transferring enough energy to minimize dimming, and not droping voltage in the circuit. It’s obvious by your questioning and your neglect of particular answers. 
If you’re really concerned with how capacitors work, I recommend you visit a physics forum.


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## GMo (Aug 9, 2005)

MarkZ said:


> Anyway, the short answer to your question is: that's how capacitors behave in real circuits with real power sources. What happens is that during lulls in the current draw the capacitor is recharging (kinda an oversimplification). By doing so, it's acting as an additional load on the amplifier and as a result the source voltage is decreased in proportion. When the capacitor discharges, however, it's acting as a parallel current source which alleviates some of the current demands from the electrical system, thereby making the voltage drop lower than it would be without the cap. That's the principle of the operation of the capacitor and the whole point of putting it in the circuit -- supply current during peak demands and draw current from the alternator in between peaks.
> 
> However, I disagree with those who say the cap has caused the output to drop to 12v. That's far too extreme a drop. It's dropped only a fraction of a volt. But in the end, your problem is addressed by decreasing the amount of voltage swing created by the huge transients in current draw.
> 
> As I said earlier in the thread though, there isn't much debate about the usefulness of a capacitor if the goal is to eliminate dimming. It works, just not every time.


Even if the load on the line the cap is connected to is 40amps, the capacitor is going to account for a significant voltage drop. I guarantee the effective ESR is somewhere around .05ohm during bass musical loads. I’ve seen ultra low ESR rated super capacitors (.001ohm), at 12VDC in a low duty transient operation with ESR just under .1ohm.
Even with a .05ohm ESR with the 10 farad cap the energy transfer is going to be very insignificant to a 40amp load. The theoretical Vdrop on the line is 2V. The compensation drop at the alternator is very comparable over the course of the waveform. Having seen this many times, I would take the Vdrop on the line to almost equal the Vdrop at the source. 
My numbers are just best guessed, but it’s very realistic. Energy transfer from the cap to the circuit is not significant, the energy transfer to heat (voltage loss) it’s what’s causing the lessening in dimming. It is reducing dimming, but it’s also reducing available current/potential. That’s not a solution in my book. 
But I guess everyone has their own standards.


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## MarkZ (Dec 5, 2005)

GMo said:


> Even if the load on the line the cap is connected to is 40amps, the capacitor is going to account for a significant voltage drop. I guarantee the effective ESR is somewhere around .05ohm during bass musical loads. I’ve seen ultra low ESR rated super capacitors (.001ohm), at 12VDC in a low duty transient operation with ESR just under .1ohm.
> Even with a .05ohm ESR with the 10 farad cap the energy transfer is going to be very insignificant to a 40amp load. The theoretical Vdrop on the line is 2V. The compensation drop at the alternator is very comparable over the course of the waveform. Having seen this many times, I would take the Vdrop on the line to almost equal the Vdrop at the source.
> My numbers are just best guessed, but it’s very realistic. Energy transfer from the cap to the circuit is not significant, the energy transfer to heat (voltage loss) it’s what’s causing the lessening in dimming. It is reducing dimming, but it’s also reducing available current/potential. That’s not a solution in my book.
> But I guess everyone has their own standards.


The problem with your analysis is that it indeed has measurable effects. Thousands, including myself, have installed capacitors in some audio systems and seen noticable improvements in dimming. I don't even think that you are denying that, as you already indicated that you believe that dimming is decreasing due to lowering the mean voltage.

When you say that the energy transfer is "very insignificant", I think you have to be careful. Using your numbers as an example, an ESR of .05 ohms will result in a peak delivery on the order of 40 amperes for a 2v fluctuation in time. Of course, this is limited not only by the ESL but also the relatively long duration of transients, but the point remains: the current delivery is real and can be substantial, especially if you're pushing the alternator to its limits (where its V-I curve often becomes highly nonlinear). A difference in 10 amps can result in quite an impact.

As for your theory about it diminishing the mean voltage to near 12v (??)...it's just not plausible. First, the cap doesn't provide that kind of load even at peak unless it's broken. Second, the transients are often spaced too far apart for your theory to hold up, as the time between transients exceeds the time constant of the circuit. And third, look at the system voltage on an analog meter post-capacitor -- you'll find that it's not 12v.

Yes, capacitors can reduce dimming, and the mechanism by which it does so is EXACTLY the same as what you see in every elementary textbook about power supply design or general electronics.


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## Abmolech (Nov 2, 2006)

I'm with GMo and werewolf on this one, ESR is not good enough.

Your using transient voltage of the load, and not observing the transient voltage of the supply. Remember it is the voltage at the headlights your observing, not at the power amplifier. That is the cap is NOT supplying both the amplifier (it has a diode???) and the headlights. The reason for dimming is the "hunting cycle'' of the regulator.

The alternator can clearly supply enough current, even at peak loads. The response time of the regulator is reason for dimming.


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## JAG (May 6, 2006)

GMo said:


> You’re definitely biased towards a capacitor somehow transferring enough energy to minimize dimming, and not droping voltage in the circuit. It’s obvious by your questioning and your neglect of particular answers.
> If you’re really concerned with how capacitors work, I recommend you visit a physics forum.


Now hold on a moment GMo .... You are entitled to your opinion , but you do NOT have any reason to claim to know my mind or intentions !
As far as my questioning , it is for the purpose of me extending my knowledge, and satisfying my curiosity of other's views. 
As far as my neglecting answers , have you considered I may NOT find every single answer to be accurate ? Or that I may not understand exactly what someone is driving at ?
*As far as me being biased towards capacitors ..... I have seen 10 capacitors do NOTHING for a system , for every one capacitor that actually does improve things. Therfore I would like to have a better understanding of exactly just why this particular instance worked so VERY well.*
You seem to be trying to stir up trouble where there is none. this is a more mature and responsible forum , please let's keep it that way.


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## MarkZ (Dec 5, 2005)

Abmolech said:


> I'm with GMo and werewolf on this one, ESR is not good enough.
> 
> Your using transient voltage of the load, and not observing the transient voltage of the supply. Remember it is the voltage at the headlights your observing, not at the power amplifier. That is the cap is NOT supplying both the amplifier (it has a diode???) and the headlights.


No, it doesn't have a diode. In fact, it's in the wrong part of the circuit for it to make the audio system diode-isolated. And yes, I'm talking about the transient voltage of the supply, brought on as a result of the transient current draw of the load. Otherwise, the supply voltage remains relatively constant.



> The reason for dimming is the "hunting cycle'' of the regulator.
> The alternator can clearly supply enough current, even at peak loads. The response time of the regulator is reason for dimming.


Which regulator? The regulator in the SMPS of the amp? Or are you talking about the alternator?

The alternator can supply what it can supply. As the current draw increases, the alternator's output voltage decreases. It's initially linear (modelled somewhat effectively by a simple Vsource output impedance), but when you really begin pushing it things take a real dive, probably due to the fact that the alternator itself is a feedback circuit.


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## JAG (May 6, 2006)

GMo said:


> Even if the load on the line the cap is connected to is 40amps, the capacitor is going to account for a significant voltage drop. I guarantee the effective ESR is somewhere around .05ohm during bass musical loads. I’ve seen ultra low ESR rated super capacitors (.001ohm), at 12VDC in a low duty transient operation with ESR just under .1ohm.
> Even with a .05ohm ESR with the 10 farad cap the energy transfer is going to be very insignificant to a 40amp load. The theoretical Vdrop on the line is 2V. The compensation drop at the alternator is very comparable over the course of the waveform. Having seen this many times, I would take the Vdrop on the line to almost equal the Vdrop at the source.
> My numbers are just best guessed, but it’s very realistic. Energy transfer from the cap to the circuit is not significant, the energy transfer to heat (voltage loss) it’s what’s causing the lessening in dimming. It is reducing dimming, but it’s also reducing available current/potential. That’s not a solution in my book.
> But I guess everyone has their own standards.


 My problem with your analogy is two fold .... First , it is your opinion only , yet you are presenting it as if it is fact. 
Second would be ..... Have you actually had your hands on this particular Stinger capacitor and tested it's ESR capabilities ?
I asked for everyone's opinions , but dazzling me with technical jargon isn't helping anything , especially in the adamant way you are presenting yourself by accusing me of being biased , as if there is a hidden agenda to promote caps. 
* So let's go back to the basics of my original post , and it's intent :
I wan't to understand why this particular cap , helped SO VERY WELL to literally STOP rather bad dimming headlights , when usually caps do almost NOTHING.*


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## JAG (May 6, 2006)

Abmolech said:


> I'm with GMo and werewolf on this one, ESR is not good enough.
> 
> Your using transient voltage of the load, and not observing the transient voltage of the supply. Remember it is the voltage at the headlights your observing, not at the power amplifier. That is the cap is NOT supplying both the amplifier (it has a diode???) and the headlights. The reason for dimming is the "hunting cycle'' of the regulator.
> 
> The alternator can clearly supply enough current, even at peak loads. The response time of the regulator is reason for dimming.


I seriously doubt the 80 amp alternator can really supply enough current for the three powerful amps in this system. The lights and amps are ALL on the same circuit. After all , there is only ONE real circuit in the car in total. A cap on ANY part of the electrical circuit is going to affect the entire electrical circuit. This is by the very nature of a circuit being a closed loop.


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## JAG (May 6, 2006)

I'd like to change gears slightly with this thread. 
Instead of making this such a debate , or god forbid a pissing contest of knowledge , let's all try and work together to try and define the affects a cap can actually have on a system.
Here's what I am actually harboring in my feelings right about now through reading up , and years of actual experience : *It seems to me the validity of caps working is almost un-predictable from car to car , and cap to cap.* It's almost like a medical Dr. .... It's a " practice " right ? Not an exact science. Now I know mathmatical calculations and electrical formulas should be able to explain everything theoretically , *but if that were so , there should NOT BE so many varied opinions and direct contradictions * ! 
If that were the case , it also seems that someone could simply once and for all solve the questions with a definitive set of answers about using caps ! I have seen NOTHING but varied and opposite theories and opinions.
Here's my one tiny contribution to this thought process : Is it possible that Stinger in general may have simply gotten something just " right " with their Hybrid caps ? Or is there better expanations ?


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## Abmolech (Nov 2, 2006)

> The alternator can supply what it can supply. As the current draw increases, the alternator's output voltage decreases. It's initially linear (modelled somewhat effectively by a simple Source output impedance), but when you really begin pushing it things take a real dive, probably due to the fact that the alternator itself is a feedback circuit.


True, but in this case I suggest it is within its linear range. 
If you have your headlights on and the motor at reasonable RPM, and switch on your stereo system, I guarantee the headlights will dim and then come back up again. Reason is the response time of the regulator, and alternator.


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## JAG (May 6, 2006)

This just in : Someone just E-mailed me stating that a simple $65 voltage regulator installed before the amps can stop ALL dimming lights in car audio systems .... Who knows about this possibility being correct ?


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## Abmolech (Nov 2, 2006)

> This just in : Someone just E-mailed me stating that a simple $65 voltage regulator installed before the amps can stop ALL dimming lights in car audio systems .... Who knows about this possibility being correct ?


Assuming the alternator can supply the required current, the answer is yes.


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## JAG (May 6, 2006)

Abmolech said:


> True, but in this case I suggest it is within its linear range.
> If you have your headlights on and the motor at reasonable RPM, and switch on your stereo system, I guarantee the headlights will dim and then come back up again. Reason is the response time of the regulator, and alternator.


 Yes , but in my particular case , once the audio system was turned on , the headlights dimmed drastically with every bass hit. This draw did NOT kill the very strong and quick reacting battery ( odyssey is definitely among the best batteries ) , *but yet it was taxing the alternator's ability to supply enough voltage/current to overcome the bass hits.*
Now , once a simple 10 farad Hybrid cap was installed , ALL dimming ceased completely. This leads me to have to wonder , _and I do mean wonder_ , *if the cap is actually charging , storing , discharging , and recharging in between the bass hits fast enough , and consistantly enough to actually lay claim to ACTUALLY be doing what the marketing hype says it is supposed to do ???* If so , this would indeed be a fairly substantial feat. 
Yet before i just blindly accept that , I want to try to rule out other possible scenarios , and do that by tapping into the pretty damned good knowledge base of the better minds who frequent this forum.


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## JAG (May 6, 2006)

Abmolech said:


> Assuming the alternator can supply the required current, the answer is yes.


Well .... No. That actually takes us back to ground zero. To the very fact the alternator can obviously NOT supply enough current , or the lights wouldn't be dimming in the first place  
I'm wondering if a regulator can overcome the alt not being able to supply enough current. My guess would be no .... But I really don't know , as I haven't tested this theory in practice.


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## Abmolech (Nov 2, 2006)

So the battery slowly flatterns off?


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## MarkZ (Dec 5, 2005)

AVI said:


> I'd like to change gears slightly with this thread.
> Instead of making this such a debate , or god forbid a pissing contest of knowledge , let's all try and work together to try and define the affects a cap can actually have on a system.
> Here's what I am actually harboring in my feelings right about now through reading up , and years of actual experience : *It seems to me the validity of caps working is almost un-predictable from car to car , and cap to cap.* It's almost like a medical Dr. .... It's a " practice " right ? Not an exact science. Now I know mathmatical calculations and electrical formulas should be able to explain everything theoretically , *but if that were so , there should NOT BE so many varied opinions and direct contradictions * !
> If that were the case , it also seems that someone could simply once and for all solve the questions with a definitive set of answers about using caps ! I have seen NOTHING but varied and opposite theories and opinions.
> Here's my one tiny contribution to this thought process : Is it possible that Stinger in general may have simply gotten something just " right " with their Hybrid caps ? Or is there better expanations ?



I don't agree with your interpretation. No one is providing mathematical calculations and electrical formulas. And yes, they would describe the whole operation of the system, if we had access to all the required parameters. So in that sense, it is predictable. But putting our hands on the parameters is not so easy, especially since we don't have the car in question or the inclination. But the point is that these are measurable quantities that aren't beyond the scope of what's known about electricity. Really, it's not a complicated circuit to understand.

Why does it not work all the time? Because all electrical systems aren't created equal, and neither are audio systems and (the third and very important variable) listening habits. A cap only has usefulness in a system in which it can provide substantial amounts of current such that the amount of current the alternator can provide can be operated in its normal range, thereby not generating such an extreme voltage drop.


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## MarkZ (Dec 5, 2005)

Abmolech said:


> True, but in this case I suggest it is within its linear range.
> If you have your headlights on and the motor at reasonable RPM, and switch on your stereo system, I guarantee the headlights will dim and then come back up again. Reason is the response time of the regulator, and alternator.


Simply switching it on shouldn't do that (it doesn't draw THAT much during turn on). But loud peaks in the music often do it. Then again, sometimes it doesn't. But this is simply a matter of drawing too much current from the alternator followed by drawing very little. This is why upgrading the "big 3" often reduces dimming as well -- if it was just the response time issue, it wouldn't.


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## MarkZ (Dec 5, 2005)

AVI said:


> This just in : Someone just E-mailed me stating that a simple $65 voltage regulator installed before the amps can stop ALL dimming lights in car audio systems .... Who knows about this possibility being correct ?


The problem isn't with the voltage on the amp side of things. It's about the voltage on the headlight terminals, which is varying because of transient current draws. A voltage "regulator" could only help you if it decreased the amount of current draw that was being drawn from the alternator. This can only happen two ways:
1) decrease the current draw from the amp by lowering its output
2) energy storage -- ie. capacitance somewhere.


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## MarkZ (Dec 5, 2005)

AVI said:


> This leads me to have to wonder , _and I do mean wonder_ , *if the cap is actually charging , storing , discharging , and recharging in between the bass hits fast enough , and consistantly enough to actually lay claim to ACTUALLY be doing what the marketing hype says it is supposed to do ???*


*

The cap recharges virtually instantaneously. It's dictated by its (really low) ESR/ESL, the total amount of capacitance, and the total voltage drop. What's more likely to have a time component is the alternator, which can exhibit rebound effects.*


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## JAG (May 6, 2006)

MarkZ said:


> I don't agree with your interpretation. No one is providing mathematical calculations and electrical formulas. And yes, they would describe the whole operation of the system, if we had access to all the required parameters. So in that sense, it is predictable. But putting our hands on the parameters is not so easy, especially since we don't have the car in question or the inclination. But the point is that these are measurable quantities that aren't beyond the scope of what's known about electricity. Really, it's not a complicated circuit to understand.
> 
> Why does it not work all the time? Because all electrical systems aren't created equal, and neither are audio systems and (the third and very important variable) listening habits. A cap only has usefulness in a system in which it can provide substantial amounts of current such that the amount of current the alternator can provide can be operated in its normal range, thereby not generating such an extreme voltage drop.


Thanks Mark .... That clears up some of my mis-conceptions. 
*You say car's electrical systems, different amps , and different listening habits all contribute to determining if a cap is going to work or not*. This itself makes this an un-exact science , due to the fact that VERY seldom will all of the variables be able to be known perfectly for a fact , as well as the facts that even different individual cars of the exact same model can vary , and listening habits can as well !! This pretty much makes choosing to use a cap or not , still be nothing more than a gamble , and we are no further than when I started this thread.
Thanks for EVERYONE's input !


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## JAG (May 6, 2006)

MarkZ said:


> The cap recharges virtually instantaneously. It's dictated by its (really low) ESR/ESL, the total amount of capacitance, and the total voltage drop. What's more likely to have a time component is the alternator, which can exhibit rebound effects.


 This must then mean that Stinger makes a pretty darn good cap then.
As far as the alternator , this is exactly what Gus at Ohio Generators said. I'm starting to believe there are simply TOO many possible variables in the equation to ever make this an exact science.


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## MarkZ (Dec 5, 2005)

It's an exact science in that it's fully describable by the relatively simple laws of electricity that are applicable. Just because there are a lot of variables doesn't mean it no longer follows these principles. It just means that it becomes more difficult to make the predictions you're after. But it's not impossible. If we benched the car's electrical system so that we had an understanding of the voltage-current relationship, INCLUDING the time-dependent (nonstationary) component that arises primarily from the alternator and battery, then we can make those sorts of predictions based on what we know about the amplifier in question. There will always be inaccuracies involved because it's a multivariable system that we don't want to take the time to fully characterize electrically.


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## JAG (May 6, 2006)

MarkZ said:


> It's an exact science in that it's fully describable by the relatively simple laws of electricity that are applicable. Just because there are a lot of variables doesn't mean it no longer follows these principles. It just means that it becomes more difficult to make the predictions you're after. But it's not impossible. If we benched the car's electrical system so that we had an understanding of the voltage-current relationship, INCLUDING the time-dependent (nonstationary) component that arises primarily from the alternator and battery, then we can make those sorts of predictions based on what we know about the amplifier in question. There will always be inaccuracies involved because it's a multivariable system that we don't want to take the time to fully characterize electrically.


Wow .... Perfectly stated.


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## GMo (Aug 9, 2005)

MarkZ said:


> The problem with your analysis is that it indeed has measurable effects. Thousands, including myself, have installed capacitors in some audio systems and seen noticable improvements in dimming. I don't even think that you are denying that, as you already indicated that you believe that dimming is decreasing due to lowering the mean voltage.


I did say that, and I believe decreasing voltage to solve dimming is a bad solution.



MarkZ said:


> When you say that the energy transfer is "very insignificant", I think you have to be careful. Using your numbers as an example, an ESR of .05 ohms will result in a peak delivery on the order of 40 amperes for a 2v fluctuation in time. Of course, this is limited not only by the ESL but also the relatively long duration of transients, but the point remains: the current delivery is real and can be substantial, especially if you're pushing the alternator to its limits (where its V-I curve often becomes highly nonlinear). A difference in 10 amps can result in quite an impact.


A 10 farad capacitor over a 2V fluxuation can only transfer 20 watts into the circuit. The VA lost in the drop for a 40amp load at 2V is 80watts. That’s only ¼ of the energy totally ignoring ESR, that’s completely insignificant to anything we can observe with dimming due to source field or insignificant to amplifier output. We need around a 200lumen change in output of lights to notice any dimming/brightening.
As load increases, dissipated energy increases, and this energy the cap contributes to the circuit becomes less and less relative to the VA drop. That’s why I say a 10farad cap has no significant energy transfer into the circuit, because in reality it doesn’t. And as load increases, and the alternator is pushed closer to the max output, the significance decreases.



MarkZ said:


> As for your theory about it diminishing the mean voltage to near 12v (??)...it's just not plausible. First, the cap doesn't provide that kind of load even at peak unless it's broken. Second, the transients are often spaced too far apart for your theory to hold up, as the time between transients exceeds the time constant of the circuit. And third, look at the system voltage on an analog meter post-capacitor -- you'll find that it's not 12v.
> 
> Yes, capacitors can reduce dimming, and the mechanism by which it does so is EXACTLY the same as what you see in every elementary textbook about power supply design or general electronics.


Have you seen a real temp based ESR curve at slower pulse currents…it doesn’t sound like it to me. Spacing of transient current has no relevance to this discussion. 
The ESR of a capacitor increases with a decreasing frequency. Standard spec’d ESR of caps are rated at something like 25deg C at 500hz (I’ve seen it vary from 120hz to 10khz); where the ESR is .001ohm. Now do some real world measurements to it and you’ll find standard operating temp at any decent load is over 33deg C at a much lower pulse. The ESR skyrockets, at 40hz 35deg C the cap probably has an ESR of .2 or .3ohm.
That’s reality, and it gets more complicated with banks of capacitors….been there many times.


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## GMo (Aug 9, 2005)

AVI said:


> Now hold on a moment GMo .... You are entitled to your opinion , but you do NOT have any reason to claim to know my mind or intentions !
> As far as my questioning , it is for the purpose of me extending my knowledge, and satisfying my curiosity of other's views.
> As far as my neglecting answers , have you considered I may NOT find every single answer to be accurate ? Or that I may not understand exactly what someone is driving at ?
> *As far as me being biased towards capacitors ..... I have seen 10 capacitors do NOTHING for a system , for every one capacitor that actually does improve things. Therfore I would like to have a better understanding of exactly just why this particular instance worked so VERY well.*
> You seem to be trying to stir up trouble where there is none. this is a more mature and responsible forum , please let's keep it that way.


Hold on...who's stirring up trouble..
http://www.caraudio.com/forum/showthread.php?t=196644

Give me a break.


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## GMo (Aug 9, 2005)

AVI said:


> My problem with your analogy is two fold .... First , it is your opinion only , yet you are presenting it as if it is fact.


There is no opinion in my statements, I’m discussing typical capacitor functioning in a transient environment.



AVI said:


> Second would be ..... Have you actually had your hands on this particular Stinger capacitor and tested it's ESR capabilities ?


No, are you telling me:
- You know the ESR values of typical capacitors better than I do; or
- That Stinger capacitors function differently than low ESR super capacitors used in banks at substations; or
- That you have more time studying them than I do

If you’re going to learn anything you have to listen and ask questions or question specific statements.


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## GMo (Aug 9, 2005)

AVI said:


> Thanks Mark .... That clears up some of my mis-conceptions.
> *You say car's electrical systems, different amps , and different listening habits all contribute to determining if a cap is going to work or not*. This itself makes this an un-exact science , due to the fact that VERY seldom will all of the variables be able to be known perfectly for a fact , as well as the facts that even different individual cars of the exact same model can vary , and listening habits can as well !! This pretty much makes choosing to use a cap or not , still be nothing more than a gamble , and we are no further than when I started this thread.
> Thanks for EVERYONE's input !


It is an exact science. 

In situations where lights are dimming with an 80amp alternator, a 10farad capacitor simply doesn’t have the energy storage to supplement the circuit and lessen the dimming.


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## MarkZ (Dec 5, 2005)

GMo said:


> A 10 farad capacitor over a 2V fluxuation can only transfer 20 watts into the circuit. The VA lost in the drop for a 40amp load at 2V is 80watts.


I don't understand what you're saying here. If the capacitor delivers 40A, where is the loss occurring? It seems you're getting confused that there's an actual difference in potential that arises between the capacitor's terminals and the amplifier's terminals, but that doesn't happen. We're talking about a 2v drop if the cap wasn't installed. When the cap is installed, the cap voltage and amplifier voltage will be the same at all times (minus minor losses in wiring), so there's no 80 watt dissipation anywhere in that branch.



> Have you seen a real temp based ESR curve at slower pulse currents…it doesn’t sound like it to me. Spacing of transient current has no relevance to this discussion.


Of course it does. If the transients are spaced 2 minutes apart (an extreme example to prove a point), there's no reason to believe that the cap is going to lower the terminal voltage to 12v during that time. You've apparently never taken voltage measurements pre- and post-cap before.



> The ESR of a capacitor increases with a decreasing frequency.


Which is convenient, since the ESL causes the ESZ of the cap to be naturally higher at increasing frequency. Are you trying to modify your proposed ESR rating after I demonstrated that the cap delivers plenty of current with the first ESR you provided?


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## MarkZ (Dec 5, 2005)

GMo said:


> It is an exact science.
> 
> In situations where lights are dimming with an 80amp alternator, a 10farad capacitor simply doesn’t have the energy storage to supplement the circuit and lessen the dimming.


Yet it does exactly that. Your only theory for operation is that it decreases the steady state voltage to 12v, which is demonstrably false.


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## chad (Jun 30, 2005)

GMo said:


> It is an exact science.
> 
> In situations where lights are dimming with an 80amp alternator, a 10farad capacitor simply doesn’t have the energy storage to supplement the circuit and lessen the dimming.


That statement is VERY open. It is TOTALLY dependent on the duty cycle of the output, the power expected, and the effiency of the amplifier. A 10 farad cap would RUN my rig for a while.

Chad

I still don't believe in caps though, they CAN bandaid an issue...... At an expense of safety.


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## JAG (May 6, 2006)

Sorry GMo , but despite all of your technical spewing , I can't accept that the only way the cap actually helped the dimming headlights in this syetem , is by lowering the entire electrical system's voltage to a steady 12 volts. 
I apologize if that offends you, but I'm STILL trying to expand my knowledge base , despite your attempts to draw me into an arguement, and I'm just not buying your theory.


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## JAG (May 6, 2006)

chad said:


> That statement is VERY open. It is TOTALLY dependent on the duty cycle of the output, the power expected, and the effiency of the amplifier. A 10 farad cap would RUN my rig for a while.
> 
> Chad
> 
> I still don't believe in caps though, they CAN bandaid an issue...... At an expense of safety.


 If that Band-aid works Chad , doesn't that mean the cap did it's job ? As far as safety , I don't plan on licking a cap's terminals anytime soon


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## chad (Jun 30, 2005)

Hell Yeah! I have used many band-aids! I've held entire digits on with band-aids before 

As for safety.... There's a TREMENDOUS amount of current available at the terminals in an area where **** is allowed to move around. Insulate them well.

a Dead cap appears as a dead short to the charging source. I jump started a lady's son's car one day. He was off to school and she took it to the store and left the lights on. The battery and cap were dead. When I made the connection it arced so hard that I had to take the cable clamp off with a cutting wheel! Scared the **** out of me and I MAKE sparks that big and bigger for fun. Had I been unsuspecting and had a heart condition.......

Just think safety.

Chad


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## JAG (May 6, 2006)

chad said:


> Hell Yeah! I have used many band-aids! I've held entire digits on with band-aids before
> 
> As for safety.... There's a TREMENDOUS amount of current available at the terminals in an area where **** is allowed to move around. Insulate them well.
> 
> ...


He he he .... Yeah , I watched an in-experienced installer connecting a cap one time. I was acrosss the room when he finally went to place the positive wire on the terminal. Looked like a lightning bolt lit up the place. That installer _literally_ pissed himself !


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## GMo (Aug 9, 2005)

MarkZ said:


> I don't understand what you're saying here. If the capacitor delivers 40A, where is the loss occurring? It seems you're getting confused that there's an actual difference in potential that arises between the capacitor's terminals and the amplifier's terminals, but that doesn't happen. We're talking about a 2v drop if the cap wasn't installed. When the cap is installed, the cap voltage and amplifier voltage will be the same at all times (minus minor losses in wiring), so there's no 80 watt dissipation anywhere in that branch.


If voltage drops 2V the total energy transfer of the capacitor to the circuit without taking ESR into account is 20watts. That’s C*V^2. The rough energy dissipated or not present in a 2V drop @ 40amps is 80watts. So by installing a 10 farad capacitor on the line, its energy into the circuit is going to be insignificant compared to the energy needed to make any noticeable difference in dimming or amplifier performance (given there even is a difference to be seen). It becomes less and less insignificant as the load is increased (current in the line).



MarkZ said:


> Of course it does. If the transients are spaced 2 minutes apart (an extreme example to prove a point), there's no reason to believe that the cap is going to lower the terminal voltage to 12v during that time. You've apparently never taken voltage measurements pre- and post-cap before.


An insignificantly sized with any “super low” ESR cap is going to always lower voltage. There is a voltage drop on the line associated with the ESR of the cap vs current in the line. And dissipation in capacitors is very high. The ESR voltage drop increases with current, just like a resistor. If the transients are 4hours apart, the drop is occurring during the transient. This whole discussion is about dimming and loss of power during these transients. The spacing of the transients has nothing to do with this since they occur during a bass waveform. 



MarkZ said:


> Which is convenient, since the ESL causes the ESZ of the cap to be naturally higher at increasing frequency. Are you trying to modify your proposed ESR rating after I demonstrated that the cap delivers plenty of current with the first ESR you provided?


Impedance of a capacitor decreases with frequency, Xc=1/(C*2*pi*f). ESL is basically unimportant to audio; inductance only becomes significant much above 20khz. So capacitive reactance dominates inductive reactance.

Also, I’m not saying the cap has to have a higher ESR than .05ohm, in fact it can have a lower resistance. The fact is energy is dissipated due to the cap, and it’s very significant to the circuit.



Of course it does. If the transients are spaced 2 minutes apart (an extreme example to prove a point), there's no reason to believe that the cap is going to lower the terminal voltage to 12v during that time. You've apparently never taken voltage measurements pre- and post-cap before.



Which is convenient, since the ESL causes the ESZ of the cap to be naturally higher at increasing frequency. Are you trying to modify your proposed ESR rating after I demonstrated that the cap delivers plenty of current with the first ESR you provided?[/QUOTE]


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## GMo (Aug 9, 2005)

chad said:


> That statement is VERY open. It is TOTALLY dependent on the duty cycle of the output, the power expected, and the effiency of the amplifier. A 10 farad cap would RUN my rig for a while.


Not really. 
V*A lost in a circuit would have to be displaced significantly by the cap. A 10 farad cap simply can’t supply that energy, it couldn’t supply it even if it had 0 ESR. I’ve shown that. Because any typical cap can’t supply energy to be significant to the circuit, amplifier efficiency really has nothing to do with this. 

Duty cycle of an alternator really has nothing to do with this either. The most common alternators have around a 5ms duty. Size of the alternator is what matters. The cycling of the field from “partial” to full contributes to most of a car’s dimming when the alternator output’s isn’t near its max current.

I do believe they are a band aid as well, because they lower the voltage as a function of increasing current. So they really do the opposite of what they are “supposed to”, resulting in lesser dimming. It’s a bad all around fix.


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## chad (Jun 30, 2005)

I was referring to the duty cycle of the program material, not the alternator.

Chad


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## MarkZ (Dec 5, 2005)

GMo said:


> If voltage drops 2V the total energy transfer of the capacitor to the circuit without taking ESR into account is 20watts. That’s C*V^2.


But your V is wrong. There's no 2v drop. The 2v drop refers to the drop in output voltage there WOULD have been without the capacitor installed. There is no potential difference between the capacitor's terminals and the amplifier's terminals (minus the small losses due to the wiring between them).



> An insignificantly sized with any “super low” ESR cap is going to always lower voltage.


Again, sticking with my example to illustrate a point, there will be NO drop in voltage due to the presence of the capacitor in between the two-minute-apart transient (unless the capacitor is leaky!). So, if your hypothesis was correct, then the dimming would reappear during tracks where there are widely spaced transients -- but it doesn't.



> There is a voltage drop on the line associated with the ESR of the cap vs current in the line. And dissipation in capacitors is very high. The ESR voltage drop increases with current, just like a resistor. If the transients are 4hours apart, the drop is occurring during the transient. This whole discussion is about dimming and loss of power during these transients. The spacing of the transients has nothing to do with this since they occur during a bass waveform.


Of course the spacing has relevance. When a current demand is not occurring, the alternator voltage will be maximal, and therefore the lights brightest. So while you're indeed correct that the drop is occurring during the transient, our visual system uses the in-between-transient headlight brightness as a reference. So the voltage during that lull is important. It's one end of the the total voltage swing.


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## GMo (Aug 9, 2005)

MarkZ said:


> But your V is wrong. There's no 2v drop. The 2v drop refers to the drop in output voltage there WOULD have been without the capacitor installed. There is no potential difference between the capacitor's terminals and the amplifier's terminals (minus the small losses due to the wiring between them).


Mark, you’re wrong.
A 2V drop @ 40 amps is THE drop due to ESR. There is a voltage drop at the source to cause the capacitor to have an ESR or .05ohm at XX hertz. This voltage drop is occurring at 40 amps output. I didn’t specify what the Vdrop was at the source, but if significant dimming is occurring I’m imagining it’s more than 2V. Even if it’s not, it really doesn’t matter, caps still follow the laws of physics.
If no voltage drop occurs only a small ESR becomes effective in the circuit, due to leakage. But that’s a completely different situation.



MarkZ said:


> Again, sticking with my example to illustrate a point, there will be NO drop in voltage due to the presence of the capacitor in between the two-minute-apart transient (unless the capacitor is leaky!). So, if your hypothesis was correct, then the dimming would reappear during tracks where there are widely spaced transients -- but it doesn't.


There is a little drop, any capacitor has leakage. Leakage is a large factor in ESR, if a capacitor doesn’t have significant leakage it’s not going to have an ESR.
But my point wasn’t that a cap is going to lower voltage during a no voltage drop situation, I never even began discussing this. This conversation is regarding how a capacitor diminishes dimming. During the dimming a voltage drop(s) occurs at the source. 
This conversation is about the actual transient, not the time inbetween them.



MarkZ said:


> Of course the spacing has relevance. When a current demand is not occurring, the alternator voltage will be maximal, and therefore the lights brightest. So while you're indeed correct that the drop is occurring during the transient, our visual system uses the in-between-transient headlight brightness as a reference. So the voltage during that lull is important. It's one end of the the total voltage swing.


That’s not important to this discussion, because with an audio system which dimming is resolved with a relatively small capacitor the “brightest headlight” voltage is never going to be that different from the “dimmest headlight” voltage. This is music, Vdrops are occurring all of the time. Stay on topic.


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## GMo (Aug 9, 2005)

chad said:


> I was referring to the duty cycle of the program material, not the alternator.
> 
> Chad


I agree then. 

But Chad, I don't see very many people with high frequency loads high enough to cause significant dimming. Of course I admit the possibility 
-Grant


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## JAG (May 6, 2006)

GMo .... You may find it interesting that Gus at Ohio Generators told me *it only takes a .04 volt drop for headlights to dim ....* He knows his stuff VERY well.


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## MarkZ (Dec 5, 2005)

GMo said:


> Mark, you’re wrong.
> A 2V drop @ 40 amps is THE drop due to ESR.


Oh, then I agree. But I don't agree with the numbers (as I said in a previous post, 40A is an excessively high number, and only a few additional amps can work wonders under some circumstances).



> There is a little drop, any capacitor has leakage. Leakage is a large factor in ESR, if a capacitor doesn’t have significant leakage it’s not going to have an ESR.


Nah, there's no leakage. At least nothing substantial. For the effects to be as you describe, the leakage would have to be tens of amperes. That's not the case.



> But my point wasn’t that a cap is going to lower voltage during a no voltage drop situation, I never even began discussing this. This conversation is regarding how a capacitor diminishes dimming. During the dimming a voltage drop(s) occurs at the source.
> This conversation is about the actual transient, not the time inbetween them.


But I brought up the interval because it disproves your theory. If the interval is relatively long (it really doesn't have to be that long, but it simplifies the point if we imagine it being long), then there will be sufficient time for the voltage to rebound. If so, then the notion that the presence of the capacitor drops the voltage is demonstrably false because dimming would still occur under that condition (once the interval ended). So, clearly the mechanism at play is that the capacitor is providing current supplement.



> That’s not important to this discussion, because with an audio system which dimming is resolved with a relatively small capacitor the “brightest headlight” voltage is never going to be that different from the “dimmest headlight” voltage. This is music, Vdrops are occurring all of the time. Stay on topic.


On topic? The whole point is to compare the voltage during transients and the voltage in between transients. That's what sets up the dimmest and brightest portions of the headlight dimming.


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## solacedagony (May 18, 2006)

AVI said:


> GMo .... You may find it interesting that Gus at Ohio Generators told me *it only takes a .04 volt drop for headlights to dim ....* He knows his stuff VERY well.


Don't you vary more than that while just driving around? Or is that more a hypothetical COULD cause dimming in a specific situation kind of thing. Thanks to everyone for the debate, I'm learning a lot in regards to electricity in a car.


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## Guest (Nov 23, 2006)

i haven't kept up with this whole thread ... but LEAKAGE is a separate issue.

For our purposes, a real capacitor can be accurately modelled as an ideal capacitor with two additional elements : 

1. an Equivalent Series Resistor (ESR), introduced by contacts and effective plate resistance. This resistor tends to limit the cap's usefulness when required to supply large current over a short period of time (over a long period of time, the cap's usefulness is limited by it's own capacitance/energy storage  ). We want this resistance to be SMALL.

2. An Equivalent Parallel Resistor (EPR), introduced by non-zero conductance of the dielectric. This parallel resistance causes leakage, potential battery drain if not intelligently managed. We want this resistance to be LARGE.

ESR and leakage (EPR) are two different things.


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## MarkZ (Dec 5, 2005)

werewolf said:


> i haven't kept up with this whole thread ... but LEAKAGE is a separate issue.
> 
> For our purposes, a real capacitor can be accurately modelled as an ideal capacitor with two additional elements :
> 
> ...


Werewolf, to clarify why leakage was brought up, I pointed out that it would be the only way for the capacitor to drop the voltage to 12v during an extended interval between transients. This is important because it demonstrates that the capacitor isn't acting in a manner in which its only effect is to reduce voltage, since dimming does not occur during peak draws that have been preceded by lengthy "downtime". Instead, it must be providing a significant amount of current to the load during transients. How much is "significant"? I'd argue that it doesn't have to be much.


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## JAG (May 6, 2006)

solacedagony said:


> Don't you vary more than that while just driving around? Or is that more a hypothetical COULD cause dimming in a specific situation kind of thing. Thanks to everyone for the debate, I'm learning a lot in regards to electricity in a car.


Good question .... Gus went on to explain that a car's electrical system would have already taken this into account and allowed for it , BUT when something like an aftermarket system is installed , and the alternator happens to be either a really weak design , or working near it's limits already , a simple .04 drop can cause the lights to dim. 
his point was , sometimes it doesn't take much for the lights to dim if the right circumstances are there. *This answer he provided , was to my question of just how this cap had worked so very well. *


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## JAG (May 6, 2006)

I'm glad you are finding this thread valuable Jake ... I too am trying to learn as much as possible, and this is why I started this thread. 
To this point , I have much better theories on what may be happening , but have definitely came to a couple of conclusions :
The cap I used worked PERFECTLY for what I was trying to accomplish , and there is NO WAY the voltage dropped down close to 12 volts. My digital multi-meter proved that wrong ! This leads me to believe the cap must be working as advertised , with a low nice ESR and fast re-charge rate , while coupled with a strong ability to store a reasonable amount.
I'm still open though to anyone who can point out something *valid* , that may prove another possible reason the cap worked so well, and thank ALL who are contributing.


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## Guest (Nov 23, 2006)

once again, I haven't kept up with the whole thread, but here's a few undeniable facts :

1. A capacitor added to any LINEAR, TIME-INVARIANT circuit can _not_ change the AVERAGE value of the voltage at _any_ node in the circuit.

2. A battery charging circuit is _not_ an LTI (Linear, Time-Invariant) circuit ... because there's something akin to peak-detection occuring. In a peak-detecting/limiting circuit, a capacitor CAN increase the average value of a voltage in the circuit.


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## GMo (Aug 9, 2005)

MarkZ said:


> Oh, then I agree. But I don't agree with the numbers (as I said in a previous post, 40A is an excessively high number, and only a few additional amps can work wonders under some circumstances).


Mark-
If the load on the line from the amp is 40A and the voltage at the source drops 2V, then there is a 2V drop @ 40A. That’s 80W of lost power (assuming a time variable). The capacitor is wired in parallel to the line. For the capacitor to make any type of noticeable difference to the circuit, it must provide a significant amount of power to the circuit relative to 80W. 
Now if the ESR is .05ohm at the average waveform frequency of the load, Vdrop=Iload(ESR +t/C). 
** I used V=I*R earlier because it was easier to understand.

Total energy available from a capacitor is;
(C*V^2)/2

The numbers I posted aren’t high. 40 amps is the load current. The fact is that even if ESR didn’t exist in a cap, the amount of energy available from the capacitor isn’t near enough to offset the lost power.



MarkZ said:


> Nah, there's no leakage. At least nothing substantial. For the effects to be as you describe, the leakage would have to be tens of amperes. That's not the case.


Leakage doesn’t have to be anywhere near 10A, I don’t understand your thought on leakage. I’ll show later how ESR and leakage are related.



MarkZ said:


> But I brought up the interval because it disproves your theory. If the interval is relatively long (it really doesn't have to be that long, but it simplifies the point if we imagine it being long), then there will be sufficient time for the voltage to rebound. If so, then the notion that the presence of the capacitor drops the voltage is demonstrably false because dimming would still occur under that condition (once the interval ended). So, clearly the mechanism at play is that the capacitor is providing current supplement.


It doesn’t disprove my theory. AVI asked how the light dimming was lessened, this happened during musical loads. By your own definition, music is transient. There aren’t going to be long interludes between Vdrops, they are occurring all of the time.


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## GMo (Aug 9, 2005)

AVI said:


> GMo .... You may find it interesting that Gus at Ohio Generators told me *it only takes a .04 volt drop for headlights to dim ....* He knows his stuff VERY well.


AVI, I don’t agree with him, I’ll show you why.

200 lumens is the minimal amount of light a bulb would need to output for there to be a noticeable difference. 
We’ll just say a typical car headlight bulb has 30 lumens per watt, and typical car bulbs are 45 watts.
That’s 1350 lumens. 
45watts @14V= approx 3.2A for a bulb.

Now take a .04V drop=13.96V * 3.2A=44.62W=1338.6 lumens.

Now lets determine how much of a voltage drop (without loss of current) it takes to make a 200 lumen difference. 
1350-200=1150 lumens.
1150/30=38watts
38W/3.2A=11.875V. 14V-11.875V=approx 2.1V.

These numbers are rough, because efficiency of the bulb isn’t a single ratio, and current isn’t a single amount.


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## GMo (Aug 9, 2005)

werewolf said:


> i haven't kept up with this whole thread ... but LEAKAGE is a separate issue.
> 
> For our purposes, a real capacitor can be accurately modelled as an ideal capacitor with two additional elements :
> 
> ...


Werewolf-
Leakage current is equated with an equivalent parallel capacitance ESC(a function of parallel resistance, Rp, and parallel capacitance, Cp). Typically we lump the ESC in to the ESR model, as ESC affects ESR. It’s expressed as;

ESR=Rp/[(2pi*f*Cp*Rp)^2+1]


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## Guest (Nov 23, 2006)

Yes ... parallel reactive circuits can be "transformed" to series circuits, and vice-versa. This transformation is valid at one frequency only, as your equation demonstrates.

But the physical fact remains, that an otherwise ideal capacitance ... with an ideal, zero-conductance dielectric ... can have a small series resistance assoicated with plate and contact metallurgy. And this capacitor, as defined, with never leak ... ever ... simply because there's zero conduction between the plates. It will hold it's charge indefinitely, even though it has a non-zero ESR.

That's why I've stated that ESR and EPR are fundamentally different mechanisms, with measurably different effects.


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## MarkZ (Dec 5, 2005)

AVI said:


> Good question .... Gus went on to explain that a car's electrical system would have already taken this into account and allowed for it , BUT when something like an aftermarket system is installed , and the alternator happens to be either a really weak design , or working near it's limits already , a simple .04 drop can cause the lights to dim.
> his point was , sometimes it doesn't take much for the lights to dim if the right circumstances are there. *This answer he provided , was to my question of just how this cap had worked so very well. *


.04? No, that's not going to happen. .4 will be very difficult to see, if at all. But there's a time component too there. Very brief transients that small will never have an effect on brightness, for the same reason that 60Hz doesn't have an effect on brightness in your incandescents in the home.


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## MarkZ (Dec 5, 2005)

GMo said:


> Mark-
> If the load on the line from the amp is 40A and the voltage at the source drops 2V, then there is a 2V drop @ 40A. That’s 80W of lost power (assuming a time variable). The capacitor is wired in parallel to the line. For the capacitor to make any type of noticeable difference to the circuit, it must provide a significant amount of power to the circuit relative to 80W.
> Now if the ESR is .05ohm at the average waveform frequency of the load, Vdrop=Iload(ESR +t/C).
> ** I used V=I*R earlier because it was easier to understand.
> ...


Why offset lost power? You can lose power during the interval between transients and it won't matter much to the headlights. The whole point is to reduce the load on the alternator during peaks, even if it's at the expense of the inter-transient interval. This is how "stiffening" caps are described as working in any power circuit.

It appears you're hung up on the 80 watt thing, but I fail to see how it's a significant number in relation to the question of how a cap supplements current during transients. First of all, I don't think 40A is a realistic number, especially since the time integrated current is going to decrease inverse exponentially the moment the transient hits. Second, although lossy, it's still supplying current, and that's all that matters.



> Leakage doesn’t have to be anywhere near 10A, I don’t understand your thought on leakage. I’ll show later how ESR and leakage are related.


I don't know how else to put it. You understand that I've demonstrated that the voltage can't be dropped to 12v during the inter-transient interval (if it's long enough) without steady state leakage, right?


It doesn’t disprove my theory. AVI asked how the light dimming was lessened, this happened during musical loads. By your own definition, music is transient. There aren’t going to be long interludes between Vdrops, they are occurring all of the time.[/QUOTE]

No, it depends entirely on the program material. I can list dozens of songs for you where the transients are huge and widely spaced.


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## MarkZ (Dec 5, 2005)

GMo said:


> AVI, I don’t agree with him, I’ll show you why.
> 
> 200 lumens is the minimal amount of light a bulb would need to output for there to be a noticeable difference.


Where'd you get that number from? It depends on a number of variables that you haven't addressed (eg. absolute luminance level, duration/duty cycle, etc).


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## GMo (Aug 9, 2005)

MarkZ said:


> Why offset lost power? You can lose power during the interval between transients and it won't matter much to the headlights. The whole point is to reduce the load on the alternator during peaks, even if it's at the expense of the inter-transient interval. This is how "stiffening" caps are described as working in any power circuit.


Exactly, I’m not referring to the time in between transient loads, I don’t know why you keep mentioning it. Offsetting doesn’t mean it has to after the transient, it’s a super composed offset if you’re looking at a graph.



MarkZ said:


> It appears you're hung up on the 80 watt thing, but I fail to see how it's a significant number in relation to the question of how a cap supplements current during transients. First of all, I don't think 40A is a realistic number, especially since the time integrated current is going to decrease inverse exponentially the moment the transient hits. Second, although lossy, it's still supplying current, and that's all that matters.


[/quote]
I just used ½ of 80A (the alternator output) as a really rough average waveform=40A, it’s very realistic. 
The fact remains, that the cap may be transferring energy into the circuit, but as I’ve shown, IT’S NOT SIGNIFICANT in comparison to the power lost during the transient. And when ESR is taken into account, there is a voltage drop on the load current and the discharge. 
Using the integration of the waveform helps show that capacitor resistance/Vdrop starts from a lower # and becomes higher as we move to the Amplitude of the wave. This all works well with what I’m saying.



MarkZ said:


> I don't know how else to put it. You understand that I've demonstrated that the voltage can't be dropped to 12v during the inter-transient interval (if it's long enough) without steady state leakage, right?
> [/QUTOE]
> Yes, and Werewolf put it the best, in his last comment. I was just simply stating that leakage is a factor in ESR, And I really don’t care about time in between transients. This is music, the load is basically constant. High relative amplitude transient loads may occur every couple seconds, but it may take that time for the Vdrop at the alternator to diminish.
> 
> ...


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## GMo (Aug 9, 2005)

MarkZ said:


> Where'd you get that number from? It depends on a number of variables that you haven't addressed (eg. absolute luminance level, duration/duty cycle, etc).


I'm an MEP engineer for a general contractor (Mechanical, electrical, hydraulic), I know it from dealing with lighting engineers and tenant build outs. 
But Lumen is the SI for Luminous Flux. Luminous flux is the energy per unit time radiated form a light source. You don’t need to know more information than that for car bulbs.

200 lumens is the bare minimum.


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## GMo (Aug 9, 2005)

werewolf said:


> Yes ... parallel reactive circuits can be "transformed" to series circuits, and vice-versa. This transformation is valid at one frequency only, as your equation demonstrates.
> 
> But the physical fact remains, that an otherwise ideal capacitance ... with an ideal, zero-conductance dielectric ... can have a small series resistance assoicated with plate and contact metallurgy. And this capacitor, as defined, with never leak ... ever ... simply because there's zero conduction between the plates. It will hold it's charge indefinitely, even though it has a non-zero ESR.
> 
> That's why I've stated that ESR and EPR are fundamentally different mechanisms, with measurably different effects.


I see where you’re coming from.


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## MarkZ (Dec 5, 2005)

GMo said:


> Exactly, I’m not referring to the time in between transient loads, I don’t know why you keep mentioning it. Offsetting doesn’t mean it has to after the transient, it’s a super composed offset if you’re looking at a graph.


Then why do you keep bringing up the "80w loss" thing? It's of no consequence. Here's what you wrote:

"For the capacitor to make any type of noticeable difference to the circuit, it must provide a significant amount of power to the circuit relative to 80W."

My reply to that is: why? Any extra current provided to the system during transients is beneficial (for the dimming problem).



> I just used ½ of 80A (the alternator output) as a really rough average waveform=40A, it’s very realistic.


I don't think it's realistic at all. Remember that power is a time integrated quantity, and that current is essentially a rate. So even if there's a 2v drop across a .05 ohm DCR (as you put it), 40A would only be delivered for an infinitesimal period of time. If you integrated it over, say, a second, the amount of power delivered becomes substantially less.



> The fact remains, that the cap may be transferring energy into the circuit, but as I’ve shown, IT’S NOT SIGNIFICANT in comparison to the power lost during the transient. And when ESR is taken into account, there is a voltage drop on the load current and the discharge.
> Using the integration of the waveform helps show that capacitor resistance/Vdrop starts from a lower # and becomes higher as we move to the Amplitude of the wave. This all works well with what I’m saying.


But why does it have to be significant *in comparison to the power lost*? That energy was gained by the capacitor in between transients when it was chump change to the system. Losing it doesn't matter -- as long as SOME current is delivered during the transient.



MarkZ said:


> I don't know how else to put it. You understand that I've demonstrated that the voltage can't be dropped to 12v during the inter-transient interval (if it's long enough) without steady state leakage, right?
> [/QUTOE]
> Yes, and Werewolf put it the best, in his last comment. I was just simply stating that leakage is a factor in ESR, And I really don’t care about time in between transients. This is music, the load is basically constant. High relative amplitude transient loads may occur every couple seconds, but it may take that time for the Vdrop at the alternator to diminish.


No, the load isn't basically constant. 



> And in those situations, capacitors aren’t going lessen dimming noticeably.


They do. Thousands of people have reduced or eliminated dimming with capacitors. And if you've ever experienced dimming before, you'll realize that it tends to come with the bass hits which are usually spaced at least 500ms apart -- sometimes much longer depending on the program material.



> I’m against using capacitors, remember…


And I'm for them, because they have undeniable benefits for the dimming issue. You've never had one reduce dimming for you before?


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## MarkZ (Dec 5, 2005)

GMo said:


> I'm an MEP engineer for a general contractor (Mechanical, electrical, hydraulic), I know it from dealing with lighting engineers and tenant build outs.


I conduct research on the visual system. I know that your number is not correct because of the huge number of variables that you've discounted.


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## JAG (May 6, 2006)

If I may step in here a moment  LOL .... I tried a varied selection of bass heavy tracks , with hits spaced far apart , rock lines , and even stacatto double kick bass .... *The dimming was prevented on EVERY type of bass music I played * ...


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## GMo (Aug 9, 2005)

MarkZ said:


> Then why do you keep bringing up the "80w loss" thing? It's of no consequence. Here's what you wrote:
> 
> "For the capacitor to make any type of noticeable difference to the circuit, it must provide a significant amount of power to the circuit relative to 80W."
> 
> My reply to that is: why? Any extra current provided to the system during transients is beneficial (for the dimming problem).


2V drop @ 40amps…that’s the Vdrop causing the dimming.
That’s the lost power generated by the source. For the capacitor to have any effect on the circuit, it has to be able to offset this lost power to prevent the source from fluxuating its field and causing a Vdrop due to internal resistance, during the actual transient where the power is being lost. 
Why is this so hard for you to understand?



MarkZ said:


> I don't think it's realistic at all. Remember that power is a time integrated quantity, and that current is essentially a rate. So even if there's a 2v drop across a .05 ohm DCR (as you put it), 40A would only be delivered for an infinitesimal period of time. If you integrated it over, say, a second, the amount of power delivered becomes substantially less.


40amps average over whatever waveform integration, its bass and probably going to be around at least a second. I stated last post that the resistance will start small and increase until the time reaches the waveform amplitude. That’s part of my first explanation of how the resistance contributes to the overall lessening of the dimming.



MarkZ said:


> But why does it have to be significant *in comparison to the power lost*? That energy was gained by the capacitor in between transients when it was chump change to the system. Losing it doesn't matter -- as long as SOME current is delivered during the transient.


The lost power is causing the source to drop the voltage. As I said above. I don’t care about time in between large transients, that’s not an issue. 



MarkZ said:


> No, the load isn't basically constant.


There is always a load because it’s music. Amplitude varies, but load is always there.



MarkZ said:


> They do. Thousands of people have reduced or eliminated dimming with capacitors. And if you've ever experienced dimming before, you'll realize that it tends to come with the bass hits which are usually spaced at least 500ms apart -- sometimes much longer depending on the program material.


Thousands of people don’t experience anything with adding a capacitor. Like I said, spacing of large transients has nothing to do with this conversation. It’s the fact the capacitor adds ESR to the circuit based on the load on the line, which is typically the line which has the largest loads causing the source to drop voltage. 
I don’t think you understand this, large transient spacing has nothing to do with this conversation. It would only be important of the alternator could vary current output in a near instantaneous manner in relation to the load. 



MarkZ said:


> I conduct research on the visual system. I know that your number is not correct because of the huge number of variables that you've discounted.


Give me a break, Lumens represent the duty cycle through definition. Duration of the drop has nothing to do with this again. We are limited by our impulse recognition, around 20hz. If we have dimming it’s occurring over a duration longer than 1/20th of a second. 
Surrounding luminance does have something to do with our perception, but like I said 200 lumens is around the minimum perceptible change. It only goes up from there.

Like it or not, I’m right.


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## MarkZ (Dec 5, 2005)

GMo said:


> 2V drop @ 40amps…that’s the Vdrop causing the dimming.


The dimming isn't dictated by the Vdrop across the ESR. It's dictated by the Vdrop across the alternator's ESR. The Vdrop across the ESR is merely the RESULT of that.



> That’s the lost power generated by the source. For the capacitor to have any effect on the circuit, it has to be able to offset this lost power to prevent the source from fluxuating its field and causing a Vdrop due to internal resistance, during the actual transient where the power is being lost.
> Why is this so hard for you to understand?


Because it's a very awkward way at looking at things. Again, you've failed to illustrate why the capacitor can only have a positive effect if the load resistance is greater than the ESR. What you're talking about appears to be an analysis of the efficiency of the capacitor, which isn't very important to the end product. The cap could be delivering 1A (time averaged) to the load in one instance but dissipate 1000 watts across its ESR, or 1A to the load in another instance but dissipate 1 watt and the end result will be the same: 1A for the load. The alternator, then, will be forced to supply the rest of the current to the load, which would cause the voltage drop across the effective output impedance of the alternator to be the same in both cases. The voltage at the terminals of the headlights would therefore be the same. So the ESR of the capacitor isn't the limiting factor. 

ANY current the capacitor can provide is of use. I agree that the capacitor's capabilities are greater with lower ESR (assuming it has the capacity to handle long enough transients), but as long as the end result is the same then the ESR is of no importance, and therefore can't be the benchmark with which to judge the effect a capacitor's effect on supply voltage.



> Thousands of people don’t experience anything with adding a capacitor. Like I said, spacing of large transients has nothing to do with this conversation. It’s the fact the capacitor adds ESR to the circuit based on the load on the line, which is typically the line which has the largest loads causing the source to drop voltage.
> I don’t think you understand this, large transient spacing has nothing to do with this conversation. It would only be important of the alternator could vary current output in a near instantaneous manner in relation to the load.


Transient spacing is important because it disproves your sentence: "The capacitor adds ESR to the circuit based on the load on the line." The fact of the matter is that, for all intents and purposes, the capacitor adds absolutely nothing to the circuit during the fully charged condition -- which can be approximated as the time between transients. When the cap is fully charged, it does not draw current from the source and therefore doesn't participate in anything. Why is this important? Because, as I explained already, it determines the ceiling of the voltage -- the very thing that you said a capacitor decreases. But as I explained, the capacitor doesn't touch the amplitude of the ceiling if it has an adequate time to recharge (between transients).



> Give me a break, Lumens represent the duty cycle through definition. Duration of the drop has nothing to do with this again. We are limited by our impulse recognition, around 20hz. If we have dimming it’s occurring over a duration longer than 1/20th of a second.


Detection threshold depends on duration. I'm sorry you disagree, but this is well established in the published literature.



> Surrounding luminance does have something to do with our perception, but like I said 200 lumens is around the minimum perceptible change. It only goes up from there.
> 
> Like it or not, I’m right.


I'm afraid "surrounding luminance" has a little more than "something" to do with our perception. It has everything to do with our perception. But that's not really the issue. You cannot give a number like "200 lumens" without accounting for the duration of the pulse or the absolute levels involved.


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## GMo (Aug 9, 2005)

MarkZ said:


> The dimming isn't dictated by the Vdrop across the ESR. It's dictated by the Vdrop across the alternator's ESR. The Vdrop across the ESR is merely the RESULT of that.


You’re making this confusing…
It’s not the ESR of the alternator, it’s the total resistance due to the cycling of the field and the diodes, but that’s what I said. The voltage drop is 2V @ 40amps. The total power lost is 80watts (assuming a time variable). The capacitor must provide a significant amount of power in comparison to 80watts lost from the source. 



MarkZ said:


> Because it's a very awkward way at looking at things. Again, you've failed to illustrate why the capacitor can only have a positive effect if the load resistance is greater than the ESR. What you're talking about appears to be an analysis of the efficiency of the capacitor, which isn't very important to the end product. The cap could be delivering 1A (time averaged) to the load in one instance but dissipate 1000 watts across its ESR, or 1A to the load in another instance but dissipate 1 watt and the end result will be the same: 1A for the load. The alternator, then, will be forced to supply the rest of the current to the load, which would cause the voltage drop across the effective output impedance of the alternator to be the same in both cases. The voltage at the terminals of the headlights would therefore be the same. So the ESR of the capacitor isn't the limiting factor.


ESR effects the LOAD current and the capacitor discharge. The discharge of the capacitor is going to vary with load vs ESR. If the load current is 10A, the discharge of the capacitor is going to be different than if the load current is 20A. If the ESR of the capacitor is .01ohm, than the load current and capacitor discharge is going to be different than if the ESR of the capacitor is .001ohm. 
I’m not discussing efficiency of the capacitor in terms of energy dissipated, its efficiency of the energy transferred through the capacitor and energy dissipated through the load contacting the ESR of the capacitor. 
ESR is added to the circuit directly affecting the load and capacitor discharge.



MarkZ said:


> ANY current the capacitor can provide is of use. I agree that the capacitor's capabilities are greater with lower ESR (assuming it has the capacity to handle long enough transients), but as long as the end result is the same then the ESR is of no importance, and therefore can't be the benchmark with which to judge the effect a capacitor's effect on supply voltage.


The concept of resistance alone, shows that higher resistance means more current dissipated. And more current means greater proportional energy dissipated. 
So the amount of energy the cap can provide changes with ESR, and greater energy is dissipated as load increases.



MarkZ said:


> Transient spacing is important because it disproves your sentence: "The capacitor adds ESR to the circuit based on the load on the line." The fact of the matter is that, for all intents and purposes, the capacitor adds absolutely nothing to the circuit during the fully charged condition -- which can be approximated as the time between transients. When the cap is fully charged, it does not draw current from the source and therefore doesn't participate in anything. Why is this important? Because, as I explained already, it determines the ceiling of the voltage -- the very thing that you said a capacitor decreases. But as I explained, the capacitor doesn't touch the amplitude of the ceiling if it has an adequate time to recharge (between transients).


AGAIN, this is only important of the alternator can vary current and voltage in direct relation with the load. That’s impossible. It takes time for the source resistance to return to its normalized amount. Higher load resistance means more energy dissipated on the line, meaning more time for the source resistance to normalize. That combined with a musical load, with load cycle ranging from 20hz to 100khz, means the typical max voltage is lowered.



MarkZ said:


> Detection threshold depends on duration. I'm sorry you disagree, but this is well established in the published literature.
> 
> I'm afraid "surrounding luminance" has a little more than "something" to do with our perception. It has everything to do with our perception. But that's not really the issue. You cannot give a number like "200 lumens" without accounting for the duration of the pulse or the absolute levels involved.


Lumen through definition is energy integrated over time, so duration is part of the definition. Look it up.
Until I see scientific published data that says that our minimum perception isn’t around 200 lumens, that’s what it is.


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## JAG (May 6, 2006)

Hi Guys .... Just thought I would stop back in and say a line :

The cap I used worked PERFECTLY at stopping the dimming headlights , and measured between 14.0 and 14.7 at the cap's outputs on my digital multi-meter while the music was playing


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## MarkZ (Dec 5, 2005)

GMo said:


> You’re making this confusing…
> It’s not the ESR of the alternator, it’s the total resistance due to the cycling of the field and the diodes, but that’s what I said. The voltage drop is 2V @ 40amps. The total power lost is 80watts (assuming a time variable). The capacitor must provide a significant amount of power in comparison to 80watts lost from the source.


Sure. But what I'm trying to point out is that If the voltage drop is 2v as you said, it's not due to the ESR of the capacitor -- it's due to the current through the effective output impedance of the electrical system (ie. alternator/battery, by whatever mechanism you want to attribute it to). As I described, you can have two conditions with capacitors with grossly different ESRs, yet the same Vdrop in the end.



> ESR effects the LOAD current and the capacitor discharge. The discharge of the capacitor is going to vary with load vs ESR. If the load current is 10A, the discharge of the capacitor is going to be different than if the load current is 20A. If the ESR of the capacitor is .01ohm, than the load current and capacitor discharge is going to be different than if the ESR of the capacitor is .001ohm.


Not necessarily. The load current, assuming it's voltage-dependent (as is the case for most car amplifiers), is going to depend on the voltage at its terminals. This voltage depends entirely on the amount of current being drawn from the alternator and the duration of the draw. A capacitor can potentially deliver a portion of the load current thereby decreasing the amount of current drawn from the alternator (and therefore decreasing the voltage dip), but as I described in my last post, this may _or may not_ be affected by the ESR. All that matters is time-averaged current delivery. If, for example, you compared a 1F cap with an ESR of .05 ohms with a 0.1F cap with an ESR of .05 ohms, for most transients the current delivery would be greater with the larger cap. Therefore, the voltage dip would potentially be less severe in the larger cap case, despite the fact that the ESRs are the same for both. Granted, ESR often increases with increasing capacitance, but usually not linearly and also not when capacitors are added in parallel. 



> The concept of resistance alone, shows that higher resistance means more current dissipated. And more current means greater proportional energy dissipated.
> So the amount of energy the cap can provide changes with ESR, and greater energy is dissipated as load increases.


Again, I don't dispute that. I just fail to see how it's important. Your losses could be enormous, but you still could benefit from whatever current the cap can provide.



> AGAIN, this is only important of the alternator can vary current and voltage in direct relation with the load. That’s impossible. It takes time for the source resistance to return to its normalized amount. Higher load resistance means more energy dissipated on the line, meaning more time for the source resistance to normalize. That combined with a musical load, with load cycle ranging from 20hz to 100khz, means the typical max voltage is lowered.


But the load cycle doesn't vary from 20-100k. The switching frequency (or any high frequency, for that matter) is taken care of by the amplifier's filter capacitors. The load cycle is going to depend most on the cycle of the transients, which can be as low as 1Hz -- or even lower for some tracks.



> Lumen through definition is energy integrated over time, so duration is part of the definition. Look it up.


You're trying to look at a highly nonlinear visual system as a linear system. Sorry, but it ain't. JNDs depend strongly on duration of the stimulus in ALL sensory modalities. For example, you recognize that there's a strong dependence of loudness discriminability on duration, right? The same thing is present in the visual system.



> Until I see scientific published data that says that our minimum perception isn’t around 200 lumens, that’s what it is.


Um...you're the one who came up with the 200 lumen number. The burden of proof is on you. But if you're truly interested, I can dig something up for you if you'd like.


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## GMo (Aug 9, 2005)

MarkZ said:


> Sure. But what I'm trying to point out is that If the voltage drop is 2v as you said, it's not due to the ESR of the capacitor -- it's due to the current through the effective output impedance of the electrical system (ie. alternator/battery, by whatever mechanism you want to attribute it to). As I described, you can have two conditions with capacitors with grossly different ESRs, yet the same Vdrop in the end.


Sure, but this was never in question. This was never a discussion about ESR vs capacity. This is a discussion on how a capacitor doesn’t have the capacity to significantly effect the voltage drop, and how ESR decreases the effective energy transfer and how ESR decreases dimming.



MarkZ said:


> Not necessarily. The load current, assuming it's voltage-dependent (as is the case for most car amplifiers), is going to depend on the voltage at its terminals. This voltage depends entirely on the amount of current being drawn from the alternator and the duration of the draw. A capacitor can potentially deliver a portion of the load current thereby decreasing the amount of current drawn from the alternator (and therefore decreasing the voltage dip), but as I described in my last post, this may _or may not_ be affected by the ESR.


ESR directly affects the energy transfer of the capacitor, it’s easily seen through the equivalent ESR model. Through this model, it’s easy to see that the energy transfer affects the load current. ESR effects load current through contact of the capacitor’s leads, in relatively low amounts (energy out of cap vs. load current) during the Vdrop pre-peak, and in relatively high amounts during the transient post-peak.



MarkZ said:


> All that matters is time-averaged current delivery. If, for example, you compared a 1F cap with an ESR of .05 ohms with a 0.1F cap with an ESR of .05 ohms, for most transients the current delivery would be greater with the larger cap. Therefore, the voltage dip would potentially be less severe in the larger cap case, despite the fact that the ESRs are the same for both. Granted, ESR often increases with increasing capacitance, but usually not linearly and also not when capacitors are added in parallel.


But my point isn’t dealing with energy transferred to the circuit by the cap, it’s obviously insignificant as is easily shown with the energy storage equation. It’s that ESR lowers the ability for the capacitor to transfer energy, affects the current at the leads, and increases time period for the voltage to stabilize through the current.



MarkZ said:


> Again, I don't dispute that. I just fail to see how it's important. Your losses could be enormous, but you still could benefit from whatever current the cap can provide.


I absolutely agree that the cap will add energy during the discharge, but as I said it’s going to be insignificant. My point was that on top of the ideal energy transfer being insignificant, the ESR factored energy transfer would be more insignificant. 



MarkZ said:


> But the load cycle doesn't vary from 20-100k. The switching frequency (or any high frequency, for that matter) is taken care of by the amplifier's filter capacitors. The load cycle is going to depend most on the cycle of the transients, which can be as low as 1Hz -- or even lower for some tracks.


Filter capacitors only provide minimal energy in comparison to output power. The load duty is the pulse or set duty of the power supply. A 1HZ overall transient is the post-filtered or post-output combined frequencies, not necessarily load frequency. 




MarkZ said:


> You're trying to look at a highly nonlinear visual system as a linear system. Sorry, but it ain't. JNDs depend strongly on duration of the stimulus in ALL sensory modalities. For example, you recognize that there's a strong dependence of loudness discriminability on duration, right? The same thing is present in the visual system.
> 
> Um...you're the one who came up with the 200 lumen number. The burden of proof is on you. But if you're truly interested, I can dig something up for you if you'd like.


Again this is a discussion on MINIMUM lumen delta perceptible for a car bulb. Sure the number is going to increase per surroundings, per visual problems, per source distribution, and etc, etc etc. 
This is information which was discussed by engineers for the CIE. If you have information or math showing that the minimum perceptible change in lumens for a car bulb is much lower than 200 lumens, feel free to discuss it.


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## MarkZ (Dec 5, 2005)

GMo said:


> Sure, but this was never in question. This was never a discussion about ESR vs capacity. This is a discussion on how a capacitor doesn’t have the capacity to significantly effect the voltage drop, and how ESR decreases the effective energy transfer and how ESR decreases dimming.


ESR does really put a damper on how much energy the capacitor can deliver. We don't disagree on that. We appear to disagree on the relationship between ESR and dimming. It's my stance that increasing ESR potentially decreases the amount of current the capacitor can provide to the load (but, as I explained previously, this depends on other factors such as the length of the transient and the capacitance of the cap). And that this decrease in current delivery REDUCES its ability to fight dimming. It sounds to me like you're saying that an INCREASE in ESR further enhances its ability to fight dimming, based on your line "how ESR decreases dimming." Higher ESR's aren't going to help keep the headlights from dimming.



> ESR directly affects the energy transfer of the capacitor, it’s easily seen through the equivalent ESR model. Through this model, it’s easy to see that the energy transfer affects the load current. ESR effects load current through contact of the capacitor’s leads, in relatively low amounts (energy out of cap vs. load current) during the Vdrop pre-peak, and in relatively high amounts during the transient post-peak.


It "affects" it, yes -- all else being equal. But reread my post again. I said that it's the voltage drop across the alternator's effective output impedance that determines the amount of dimming, NOT the ESR of the cap. It's all about how much energy the capacitor can deliver, and ESR is only one of several factors that determines that.



> But my point isn’t dealing with energy transferred to the circuit by the cap, it’s obviously insignificant as is easily shown with the energy storage equation.


I don't think it's "obviously insignificant" at all. By what other mechanism do you think the decrease in dimming is occurring?



> Filter capacitors only provide minimal energy in comparison to output power. The load duty is the pulse or set duty of the power supply. A 1HZ overall transient is the post-filtered or post-output combined frequencies, not necessarily load frequency.


Filter capacitors can provide all the energy to the very fast pulses that the SMPS draws upon, on a per-pulse basis. If the switching frequency is 30kHz, then each pulse is going to be on the order of 10 microseconds, depending on the duty cycle. That's not much energy in there. The filter capacitors will do as their name implies, and filter that high frequency just as any LPF would do. The prime obstacle is their ESL, which is probably not a whole lot higher than the ESL of the circuit along the main power line, from PS to amp terminals right down the line. Altogether, the current delivered along the big power wire to the amp is not pulsed because it never sees that high frequency load variation -- thanks to the filter caps.



> Again this is a discussion on MINIMUM lumen delta perceptible for a car bulb. Sure the number is going to increase per surroundings, per visual problems, per source distribution, and etc, etc etc.
> This is information which was discussed by engineers for the CIE. If you have information or math showing that the minimum perceptible change in lumens for a car bulb is much lower than 200 lumens, feel free to discuss it.


Your delta is not constant for all absolute levels of illumination. To use an extreme example to illustrate the point, you're more likely to detect a change of 200 lumens in a dim bulb than you are observing the same change of 200 lumens if you're staring at the sun. To use an electrical analogy, in both cases you've got the same amplitude of AC, but they're riding on two completely different DC levels. This is a property unique to the visual system, as the same phenomenon does not hold true for a photometer (measurement noise notwithstanding).


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## GMo (Aug 9, 2005)

MarkZ said:


> ESR does really put a damper on how much energy the capacitor can deliver. We don't disagree on that. We appear to disagree on the relationship between ESR and dimming. It's my stance that increasing ESR potentially decreases the amount of current the capacitor can provide to the load (but, as I explained previously, this depends on other factors such as the length of the transient and the capacitance of the cap). And that this decrease in current delivery REDUCES its ability to fight dimming. It sounds to me like you're saying that an INCREASE in ESR further enhances its ability to fight dimming, based on your line "how ESR decreases dimming." Higher ESR's aren't going to help keep the headlights from dimming.


???? You’re confused
ESR decreases a capacitor’s ability to transfer energy. It also, decreases the capacitor’s ability to store charge. The energy a capacitor delivers is already insignificant to dimming, the fact is that dimming isn’t alleviated from the energy transfer into the circuit. Energy into the circuit from a cap isn’t going to be significant enough to prevent an alternator from cycling to a full field. 



MarkZ said:


> It "affects" it, yes -- all else being equal. But reread my post again. I said that it's the voltage drop across the alternator's effective output impedance that determines the amount of dimming, NOT the ESR of the cap. It's all about how much energy the capacitor can deliver, and ESR is only one of several factors that determines that.
> 
> I don't think it's "obviously insignificant" at all. By what other mechanism do you think the decrease in dimming is occurring?


The alternator’s total resistance is causing the dimming, and for a cap to alleviate the dimming it needs to prevent the alternator to cycle to a full field, or to near that. 
Mark- the total energy out of a 10 farad capacitor with a 2V drop is 20watts, without factoring in ESR. A 10A average load isn’t causing the alternator to cycle to a full field, neither is 20A, neither is 30A. The average load must be proportional to the alternator’s max output for a significant amount of time. The voltage regulator has a set point of time which it uses before cycling the field, and the field takes time to cycle. 
What’s causing the voltage drop to increase over the time integration is the ESR. ESR is also decreasing load current due to its metal/leads. 



MarkZ said:


> Filter capacitors can provide all the energy to the very fast pulses that the SMPS draws upon, on a per-pulse basis. If the switching frequency is 30kHz, then each pulse is going to be on the order of 10 microseconds, depending on the duty cycle. That's not much energy in there. The filter capacitors will do as their name implies, and filter that high frequency just as any LPF would do. The prime obstacle is their ESL, which is probably not a whole lot higher than the ESL of the circuit along the main power line, from PS to amp terminals right down the line. Altogether, the current delivered along the big power wire to the amp is not pulsed because it never sees that high frequency load variation -- thanks to the filter caps.


The filter capacitors are meant to filter ripple, typically on a 30V rail the ripple is around 2V-3V. That’s low energy compared to power output. 
Load current is pulsed with a PWM power supply. Filter capacitors have pulsed output and pulsed input. The load is going to be pulsed and can be in and above the switching range I mentioned. There’s no way around it.


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## Guest (Dec 10, 2006)

I still can't quote on this forum without my 'puter locking up 

GMo ... Mark is not confused. But you have made a couple statements that are absolutely false :

"ESR decreases a capacitor's ability to transfer energy. It also, decreases the capacitor's ability to store charge."

The first part is true, the second part is absolutely false. To demonstrate, imagine first an ideal capacitor of capacitance C, charged to a voltage V. The total charge sotred is, of course, Q = C*V. And the total energy stored is E=0.5*C*V^2. Now add a resistance in series with the capacitor, to include ESR. If the capacitor is charged to a voltage of V, even in the presence of ESR, the total charge ... and energy ... stored will be exactly the same. And of course, the presence of ESR will _not_ cause the capacitor to "leak" or lose charge. Conclusion : ESR has absolutely NO impact on stored charge, only the energy dissipated in the discharging (or charging) process.

"The total energy out of a 10 farad capacitor with a 2V drop is 20 watts, without factoring in ESR."

Again, absolutely false. You have erroneously equated energy and power. If all you know is the capacitance and voltage drop, you can only state the energy lost from the capacitor ... _not_ the power. To determine power you have to include the element of time ... power is the _rate_ of energy transfer.


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## GMo (Aug 9, 2005)

werewolf said:


> I still can't quote on this forum without my 'puter locking up
> 
> GMo ... Mark is not confused. But you have made a couple statements that are absolutely false :
> 
> ...


I never disagreed with this. 
In my statement, werewolf, I say it decreases its ABILITY to store charge, not it’s total charge capacity. I’m referring to its efficiency/rate.



werewolf said:


> "The total energy out of a 10 farad capacitor with a 2V drop is 20 watts, without factoring in ESR."
> 
> Again, absolutely false. You have erroneously equated energy and power. If all you know is the capacitance and voltage drop, you can only state the energy lost from the capacitor ... _not_ the power. To determine power you have to include the element of time ... power is the _rate_ of energy transfer.


Yes, I realize that. In the scheme of this discussion, I felt it was more appropriate and easier to leave time as an undefined variable, and merely suggest that this process of transferring energy happens over an unspecified time period.


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## Guest (Dec 18, 2006)

If we leave time as an "undefined variable", it is equally "true" to state that the total energy out of a 10 Farad capacitor with a 2V drop is 1000 watts.

How might that equally "true" statement change your argument?


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