capacitor debate keep it clean

3 questions about capacitors, answer them and then debate on...

We will say there is a alternator with 0 gauge power wire to battery, from front battery to 2nd bettery, from 2nd battery to capacitor, from capacitor to amplifier... alternator charging at 14.4v... if you have a equation that needs more numbers, create your own simulated numbers to demonstrate, Resistance/current/power/etc...

1. How does this capacitor work in this circuit? If you know how it works I shouldn't have to add anymore leading words.

2. What are the pros of this capacitor?

3. What are the cons in this capacitor?



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I can't hear you!

1. Capacitors connected in parallel with this circuit will have equal voltage as shown across the power source, or in this case the battery. Batteries have been shown to have very large reserve capacity compared to capacitors. But they also charge and discharge 100's, 1000's, 10,000's times slower than a capacitor does. Which makes the case for the need of a capacitor. Say your voltage drops from 14.4v to 13.0V during a specifiv 5 second 40hz note. And your battery (HYPETHETICALLY for easy numbers) discharges and recharges in 1 second. Now if you add a capacitor that discharges and recharges 100's,1000's, possibly 10,000's times faster than the battery. What is happening is while your battery is STILL discharging, your capacitor has discharged and recharged 1000's of times. This gives you a better AVERAGE voltage with the amperage your alt and battery PROVIDES. Your capacitor can only be as good as the weakest link in your alt, battery, capacitor combination. So if you're dropping down to 10v on a 5sec 40hz note, you don't need a capacitor you need a bigger alt, THEN a bigger battery, THEN a capacitor. If you're dropping to 12.3v you could use a capacitor and a agm battery because your electrical has shown that it can handle the draw from your amps. With a capacitor you are going to have less of a voltage drop because it discharges and recharges faster, allowing that current to your amps to have a better AVERAGE out of the alt, battery capacitor combination you have. So you may only drop to 12.5v instead of 12.3v... capacitors neveeeerrrrr act like a piece of wire just drawing current because it acts as an open circuit, meaning it can't have CURRENT FLOW, it can't ONLY discharge and recharge.

Pros. Better average voltage, release of high currents almost instantneously to amps with big current draws.

Cons. Cheap ones on the market do not help the benefit of them since they are made of cheap material, if you see a 30 farad cap for 70$, just say no. Normally not enough capacitance for system, or way too much is expected of the capacitor.

Can't wait for this debate to start, love learning new things, and peoples opinions.

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I can't hear you!

Batteries do not discharge slower than a capacitor - like capacitors, they supply the demand. (That's if in parallel. See below re individual discharge rates.)

Similarly, capacitors do not charge faster than a battery (assuming burp and shortish overload situations) because BOTH are at the same voltage (as you stated).
For long burps and overloads, it is pointless having a capacitor - they have minimal reserve time (even a 12V 1.2AH battery outlasts a multi-Farad cap).

If the voltage drops from 14.4V to 13.0V for 5 seconds due to an overload (ie, the alternator is of insufficient capacity OR due to cable drops), there is no recharge involved though - ignoring surface charge - the battery is still being charged (since 13.0V is above its nominal fully charge voltage of ~12.7V).
REPEAT - there is no recharging. Both the cap & batt have dropped to 13.0V.
Further to that, the battery's surface charge will be far greater than the cap's capacity. The advice is usually to use headlights for 5-15 minutes to remove surface charge from a battery, or let it rest for 24 hours. That drops its voltage to its "real" fully charged voltage of ~12.7V (in theory, 12.67V). Will a cap last 5-15 minutes with headlights and only drop to 12.7V?



Unless you are going into certain material or chemical issues (which are not relevant to the situations discussed), your comments -cum- assertions are simply invalid - eg:

The cap voltage will be the same voltage as the battery. (I am assuming the cap is parallel to the secondary battery(s) that are next to the amp. The alternator voltage will be higher.)

Charge and recharge IS current flow.
A cap is not an open circuit - it is a cap. (A discharged cap is a instantaneous short circuit when voltage is first applied - hence the need for series resistance to limit the current if the short or high current could damage the supply.)   

And a cap is not an open circuit (through it) for AC voltage. IE - it acts like a filter making the voltage smoother.
But the battery also exhibits cap-like behavior. (Some circuits even model the battery as a very large capacitance.)


There is no debate per se in the above.
The inferences drawn are simply incorrect. How can a cap recharge and discharge from the same voltage? It recharges when its rail voltage is higher than itself. It discharges when the rail is lower (ie, the water and bucket model). That's no different than a battery.

As to discharge rates, I don't know where that comes from.
The only truth to that is that a capacitor discharges (ie - its voltage decays) much faster than a battery because it has nowhere near the same capacity - ie, capacitance. (That does depend on sizes, but if a 9V battery keeps a lamp lit longer than a 1F cap...)
Ergo, why use a cap?


You may see several articles that show how a small battery (eg, 12V 1.2AH) has far greater capacity than a 1F or larger cap.
Hence the argument with a battery and cap in parallel becomes - for greater capacity - a battery with a small battery in parallel.
That then becomes 2 equal batteries - or a larger battery - for even more capacity.


The main desire for capacitors would be to replace batteries as caps do not have inefficiency (well, maybe 1% compared to ~30% recharge inefficiency for a battery).
But to replace an automotive battery would require a trailer load of capacitors.
Apart from the cost involved, it is simply not worthwhile. Cars burn far less fuel for the battery's 30% inefficiency than towing a heavy trailer around.

Another reason for caps might be because secondary batteries are undesirable or can't be located near the amps, but that is not relevant in your case.


Unfortunately I have lost the link to the original article, but have a look as Richard Clark's article as reproduced at https://forum.realmofexcursion.com/accessories-electrical/17919-why-you-dont-need-capacitor.html

FYI - Ignore any mention elsewhere re "placing more load" on the alternator. The reality is quite the opposite - bigger batteries (and caps) LESSEN the load on the alternator - not that an alternator should care, though undersized batteries else alternators can cause noticeable lifespan issues.
Also, despite people saying otherwise, ripple on a DC supply is AC. In this case, ripple etc is an AC voltage offset by 12VDC (or "AC with a 12VDC bias").

There is no debate.  Caps do what they do, and Oldspark has detailed that nicely.  They are not a panacea for needing additional ampacity: only a larger alternator will give you that with the engine running.  But they function just like, well, capacitors.

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" The advice is usually to use headlights for 5-15 minutes to remove surface charge from a battery, or let it rest for 24 hours. That drops its voltage to its "real" fully charged voltage of ~12.7V (in theory, 12.67V). Will a cap last 5-15 minutes with headlights and only drop to 12.7V?"

do this in a GM vehicle and your car probably wont start without a jump box... just saying.

the reason you need a cap is because car audio companies sell them and sales and marketing teams will tell you anything to convince you that you need one. just like most people believe that a higher wattage sub woofer WILL be louder, its all about making money and capacitors are great money makers because that 10 farad cap that costs you $300 probably cost $20 to make.

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But old spark then you should know that capacitor DO NOT have to fully discharge in order to recharge... and NO how can you say it acts like current flow??? The current changes at an EXPONENTIAL rate when charging and discharging in a capacitor. That is not what current FLOW is. The capacitor gives out bursts of energy MANY thousands of times faster than a battery which makes it LOOK like current flow at the amp. But it simply isn't.

Since you want to talk metaphors I.e. lol let's look at your light bulbs in your home, I know its AC but capacitors act the same way in both, simply discharging and recharging. Anyway our home lights are set at 60hz, meaning it has 60 ON/OFF cycles per second. But to the human eye it looks like the light bulb is ON. That's the same way it looks to a amp. This is true, I've done a lab on it, and experiment, with results and a lab report AND graphs of the capacitors discharge and charge rates with different wave forms.

I don't understand how you think capacitors and batteries charge at the same rate...?

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I can't hear you!

And car companies now just push 300 and 400$ batteries onto everyone. Trust me if money was an issue then they are WINNING right now

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I can't hear you!

rfhvhtoo wrote:

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And car companies now just push 300 and 400$ batteries onto everyone. Trust me if money was an issue then they are WINNING right now

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yeah but the battery costs more to make than the capacitor thus there is more profit from a $300 capacitor than a $300 battery


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soundnsecurity wrote:

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rfhvhtoo wrote:

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And car companies now just push 300 and 400$ batteries onto everyone. Trust me if money was an issue then they are WINNING right now

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yeah but the battery costs more to make than the capacitor thus there is more profit from a $300 capacitor than a $300 battery

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Its hard to even find a 300$ capacitor, 300$ for 1 battery, and you NORMALLY need 2 (one in the engine bay and one in the trunk to try an reach ideal performance) is average. And nooo, there is less profit in capacitors because they can last 10+ years. Batteries have to be bought again and again and again, AND recycled. Its a win win situation for audio companies. Because you will never see a battery outlast a capacitor in ideal conditions.

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I can't hear you!

If current flow is not involved in a capacitor, the WHAT is being charged?
I suggest you find out how a capacitor works.


Nor does a battery fully discharge. But a battery discharging 0.01V or 0.1V still has FAR more capacity than a cap.

Exponential is irrelevant. They both follow Ohms Law etc wry supply and demand.

My car battery is 13 years old. Most of it is recyclable, and a far higher percentage than a cap.


What parts of a cap are recycled - the electrolyte?
That argument is another AGAINST using a cap.


And a cap up front is irrelevant. You are talking about the rear or remote performance - ie, holding up the voltage. (ie, the front cap is wasted.)


Alas I have to go.
And I forgot AGM protection using caps, but you have multiple AGMs as I recall.


PS - are you saying a cap outlasts a battery wrt charge? If it doesn't, then what are you asking? Do the calcs!

oldspark wrote:

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If current flow is not involved in a capacitor, the WHAT is being charged?
I suggest you find out how a capacitor works.

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Please tell me you know what's charging and how its charging, and explain.

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I can't hear you!

The news tonight said that GM introduced a hybrid vehicle with capacitors and no batteries. That will NEVER be a headline on any news carrier.

i am an idiot wrote:

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The news tonight said that GM introduced a hybrid vehicle with capacitors and no batteries. That will NEVER be a headline on any news carrier.

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You're right because capacitors need a power source... that's elementary

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I can't hear you!

So in a hybrid vehicle, the batteries are the power source?

Yes it has a potential difference, meaning it has a voltage, if it has a current running through it, it has power, and the power is not being absorbed, so it is being DISSIPATED into the circuit which mean it is a SOURCE of power...

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I can't hear you!

Those must be magic batteries. I always thought that a battery had to be charged by an external source. If these capacitors are so good, why do we have to have a battery?

i am an idiot wrote:

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Those must be magic batteries. I always thought that a battery had to be charged by an external source. If these capacitors are so good, why do we have to have a battery?

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Batteries do not have to be charged by an external source while being used if it has an initial charge... answered.

. Capacitors show the potential difference that is across its terminals, which has to be an outside voltage source. ANY voltage source, does not have to be a BATTERY. But usually is unless you're in a lab with simlating voltage sources like I am... capacitors only react to what is in the circuit, if you have a circuit with no battery aka no potential difference then the capacitor will not show a potential difference, meaning 0v... but again, it can be ANY voltage source, not only a battery... answered

Now I have a question id like answered.... since you think batterues have to be charged by an outside voltage source, why is it that after use and a theoretical voltage drop of say 1 volt, does the battery RISE (key word) back up to its resting voltage? Without external charging... please explain sir


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I can't hear you!

From what you're saying, wouldn't it just stay at whatever voltage it has dropped down to without an external source?

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I can't hear you!

rfhvhtoo - you need to read batteryfaq.org-carfaq.
I recommend downloading as per Section 19 (printing ).

rfhvhtoo wrote:

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Batteries do not have to be charged by an external source while being used if it has an initial charge...

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Yes, provided it has enough capacity (as with a capacitor).
But then you need to recharge it to recover its initial state of charge - again, no different from a capacitor except for its ~30% inefficiency.

rfhvhtoo wrote:

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You're right because capacitors need a power source... that's elementary   

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Same as batteries, except for their initial "dry" charge.
Batteries just like capacitors do not "self recharge" - that's elementary.

rfhvhtoo wrote:

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why is it that after use and a theoretical voltage drop of say 1 volt, does the battery RISE (key word) back up to its resting voltage? Without external charging...

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That's call self recovery, but it never recovers to the original voltage since a discharge has occurred.


Your other statements are common electrical/electronic theory - eg:
Every component has whatever voltage it has across it whether it be a power source (capacitor, inductor, battery, generator, PV cell...) or a load (capacitor, inductor, battery, generator, PV cell...).
Every component responds to what is in the circuit. But we can accurately model that - eg, V=I, Frequency is proportional to RC, C=Q/V.


And getting back to much earlier fundamental issues:
A capacitor is charged by charge.
The flow of charge is current.

Watch the animation "DC does flow thru a capacitor" about 3 screens down on talkingelectronics-Page03.

Then maybe try antonine-education.co.uk-Capacitor_1 - note for example: "The capacitor does NOT conduct electricity. The flow of ac is due to the charge and discharge of the capacitor.".   
...and the two flash animations about 3/4 down in splung.com's Capacitance of a Capacitor.

@ rfhvhtoo:I cant take it anymore... What does your name stand for/mean...? Acronym...? Maybe its simple and i just do not see it... TY

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M.E.C.P & First-Class
Go slow and drink lots of water...Procrastinators' Unite...Tomorrow!

Oldspark, I'm the one that said capacitors charge and discharge... you stated earlier that its a current flow... please explain this..

The idea of a capacitor is not to have a large reserve... batteries can recover, (what is this recovery process doing to the battery? Its not called recovering, its called charging, as long as the potential difference between terminals is increasing then the battery is CHARGING because it is not DISCHARGING) and please will you just explain yourself and site your sources, stop sending me other places because you have nothing to support your argument. Its a DEBATE not a "I can't answer this question just go and read this"

As batteries are able to self recover, capacitors CANNOT, why? Because its 2 plates with a dielectric in between them! Nooooo current flow!! Do the CALCS!!! (Aka you're wrong, your statement is false)

Now I know you like to break things into quotations, so if you could please respond to the 3 statements I have included above.

RFHVHTOO- rockford fosgate hit very hard too, I've had it since aol was the fastest at 56kbps so before making up good screennames were cool lol

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I can't hear you!

" and please will you just explain yourself and site your sources, stop sending me other places because you have nothing to support your argument. Its a DEBATE not a "I can't answer this question just go and read this" "

and what are your sources? if you are correct then why cant you do the calculations and post them?

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soundnsecurity wrote:

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" and please will you just explain yourself and site your sources, stop sending me other places because you have nothing to support your argument. Its a DEBATE not a "I can't answer this question just go and read this" "

and what are your sources? if you are correct then why cant you do the calculations and post them?

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My resources is myself, I'm citing my own research in a lab at the university of florida, I don't need an article to TELL me how these work, I've seen it with my own eyes, with instruments much more accurate than a hand held oscilloscope, capacble of measurements to the nano second.

If you can't understand the concept, you can't understand the equation.

Equations are being thrown in the air left and right but no one is explaining anything. Except basic physics. Y'all HAVE NOT mentioned the word joules yet! In one of the equations! Which are ESSENTIAL to capacitors.

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I can't hear you!

using yourself as a source can only work if you submit research and observations to everybody else for peer review so that your observations and conclusions drawn from those observations can be agreed upon by everybody else. just saying "trust me" isnt good enough in any debate. until you can support your argument with some sort of evidence then this is a pointless exercise.

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My

soundnsecurity wrote:

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using yourself as a source can only work if you submit research and observations to everybody else for peer review so that your observations and conclusions drawn from those observations can be agreed upon by everybody else. just saying "trust me" isnt good enough in any debate. until you can support your argument with some sort of evidence then this is a pointless exercise.

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you have no information standing in this debate, so your opinion is invalid... until you come up with an argument, or an idea. Please post away. The research that I'm stating isn't based on my research alone its in THE TEXTBOOKS, would you like to read it? Ill send you a ebook. What I'm talking about is only the basics of understanding capacitors, research shouldn't even be needed in this process its only the CONCEPT. What I'm stating as my research is the labs I've done to validate these concepts.

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I can't hear you!

rfhvhtoo, did you look at the links I posted?
If you did, hopefully it should not take much for you too realise how false YOUR claims are.

I've already said that it is charge - ie, current - that charges a battery. Please google for how a capacitor works, or review those links.

So a capacitor is NOT to have a large reserve? Thank you - you have just agreed with why we continuously state that caps are useless for 12V audio supply purposes (as compared to a battery (excluding AGM protection and "remote" voltage smoothing).
I guess that's why audio forums say you only need 0.5F and not 1F or 10F etc.
Mind you, I thought the usual desire for a power cap was to MAINTAIN the amp's voltage - ie, have sufficient capacity to "ride through" a burp or 5-second high demand that the alternator can't supply.   


Again, battery self recovery is NOT recharging. There is absolutely ZERO recharging involved. It is merely stabilisation of its chemicals that increase its internal voltage. (So too is "surface charge" though that does involve its "excess" current or rather, its additional surface charge.)
A battery can only recharge with an external source.


So capacitors do not involve current flow? I beats me why power capacitors (for mains/AC use) are "specified" for different currents (based on their hold up time with 50Hz or 60Hz with or an acceptable voltage sag).
But in that case, what do they involve - voltage with no current - ie, no power? Good - you have just shown why caps are useless.
I guess that link showing the LED lighting with a series capacitance is false, as are other sites and books and the theory and equations that confer the same.
I must find out why my ciruits work if the current isn't flowing thru the series (and un-paralleled) cap - maybe it's flowing thru the cap's plastic insulating cover, or arcing thru the air. Or maybe you have discovered a tunneling-capacitor!   


You want to compare Joules? Calculate the Joules in a 1F cap and compare that to a battery. What was it? - a typical car battery has 10,000,000 times the Joules of a 1F cap? (Another 12volter supplied the correct figures the last time I posted similar.)
Start by replying with the number of Joules for a 1F capacitor discharging fro 14.4V to 12.6V - or similar figures of your choosing.


If have explained to the best I can without spending time rethinking my explanations so that you might understand easier. But I won't detail or repeat basic knowledge and tutorials that are so available on the web and elsewhere. That's a waste of my time.
It's a different matter if someone needs clarification to some site's or source's meaning.


However, it seems this thread has come to a natural ending since you have not provided info sources. Ergo, we are all operating from "opinion" (excluding the links and their links).

My opinion is based on a reasonable understanding of electronic and electric theory, and having debunked various crap; having done what others have claimed is impossible; and revolutionised certain industry practices, equipment specifications, and designs by coming up with novel alternatives or, again, showing how wrong or false certain "accepted" practices were.
Others here may be similar, but certainly have decades of experience as well as a history dealing with issues like this. A quick read of this site should make their expertise obvious - many times solving what other industry "experts" and equipment/vehicle originators can't.


BTW - when you quote sources, don't quote floridaspl unless its from one of the few that do offer correct information. Same for other car-audio forums except for the few reputable "source" forums.
[If Tommy thinks this is a headspin, check out what those forums (and Yahoo Answers) etc write. OMG!]   


If you want to discuss REAL problems you are having, we'll take it from there and determine where they are occurring.


If you really want to solve the problem, the break away from the present moronic amplifiers. Split its PSU and move that to the battery/alternator, then run its smaller cables (maybe +ve, GND, and -ve) to the amp.
Honestly, an industry that maximises input current (by sticking to 12V) and carries that over long heavy conductors, and uses 1-Ohm loads instead of 4 or 8 Ohm etc...

OK, this is getting nasty, like I assumed it would.  Locked.

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