Why a Capacitor will never help your stereo...

[v6maro]

All I know is when my base hit, by volt meter went into the red. Now, it barely dips. All I know is that it DOES what it is supposed to do.
'nuff said
-Steve

[OneQuickV6]

For anyone REALLY interested and bored to read that HUGE, LONG thread, why not take an intro EE class, and they'll help you out, and show you more than you ever even wanted to know about this stuff. If caps are worthless, why did Edison and other great minds deal with them, and devote so much time to producing strong ones that hold so much charge??? In EE I learned to think of electricity as plumbing and water flow. Small pipes = resistance (in Ohms), water flow = Current (in amperes), and a resevoir or damn = capacity or back-up for flow problems when river runs low (in Farads). This way of looking and thinking about this stuff may help clarify some of it for some people. Hope I helped more than hurt.

[predator5100]

Well havign 4 years of electrical the capacitor will help and does provide good energy storage. If your amp is pulling all of the 12 volts 300 farards you desereve to go death. It helps keep the life of your battery and alowws the amp to hit harder. Think about it your car battery is 12-15 volts now think about it if i have a battery which i'm constantly struggly to keep charged it sucks it's life away granted the capacitor is the same way but it helps

[Dominic]

I agree in that if you occassionally have small voltage drops - a capacitor will help.

If you can suck a consistent amount of current (say 50+Amps continuous...) your alternator will never keep up at idle, and the capacitor will simply *get in the way*.

Capacitors are only helpful when you can supply the current, you just can't get it there fast enough to prevent a voltage drop - otherwise, don't bother.

[chas]

a cap can help and you are not wasting your money if you buy one. since most amps have this rms versus peak problem (you dont run peak all the time) you can see a benefit if your rms current draw isnt exceeding what you charging system can supply.

caps usually have a very low internal resistance. they charge/discharge quickly. (we would call them batteries otherwise). i dont understand the arguement in the carsound post. the voltage across the cap wont drop to less than the voltage across its terminals. yes, the cap will draw power when it recharges but (hopefully) the amp at this point doesnt need as much power.

if caps dont work this way, why would they be used in the backside of power supplies? they average out the 60hz wavefrom into a flat line. the caps provide the power about 1/4-1/3 of the time.

i should mention i dont understand the mention of ohm's law in the other post. i dont think you can just simply use ohm's law to analyze this problem at an instant in time. the cap's behavior is governed by 1/rc where R is the resistance of the total inductive load on the cap (car and amp). the cap will discharge at this rate to the voltage across its terminals (it will also charge at this rate).

[ April 09, 2002: Message edited by: chas ]</p>

[Backfire]

<blockquote>quote:</font><hr> if caps dont work this way, why would they be used in the backside of power supplies? they average out the 60hz wavefrom into a flat line. the caps provide the power about 1/4-1/3 of the time. <hr></blockquote>

I am pretty sure there is more to an AC/DC converter than a few caps, but either way, that usage illustrates the argument against cap usage. If the power supply, or alt, is capable of providing the necessary power, but a large quick current draw causes a voltage dip, a capacitor will aid in minimizing voltage spikes by acting as a temporary energy source. However, if you put a load on the power supply, which is beyond its limits, the capacitor will do nothing, and the power supply will either burn up or blow a fuse. A capacitor does not change the power rating of the electical system. The cap will not prevent alternator failure in situations of constant abuse.

[DEE97GTP]

<blockquote>quote:</font><hr>Originally posted by ChameleonGreen:


This is another incorrect statement. A capacitor is NOT a battery at all nor is it remotely like one. A battery creates power through chemical reactions. A capacitor actually stores an active electric charge within it's guts. Kind of like holding a lightning bolt until you need that charge. The rest of that paragraph is correct though.<hr></blockquote>

Your taking the post too literal, I said think of it like a battery. Actually, if you want to get technical, a battery acts alot like a huge capacitor. A battery does not create power, it stores/converts it from chemical energy to electrical, much like a generator/alternator converts mechanical to electrical. You can't get any more out of it than you put in. Actually, you put more in than you can get out of it. Some energy is lost as heat when you charge and discharge the battery, due to its internal resistance.

I agree with the other statements in the following posts.

Oh, and ohms law always applies in some for or another.

The primary role of capacitors in industry is using them as filters. That is basically what your are doing when you add these big caps, your are filtering out the voltage spikes and dips.

The water analogy is the best physical representation for electricity. :D

DEE

[xdamxincx]

hmmm...some very good testimonials..and debates....
but from personal experience from competing in car stereo with my car for 2 years now ..
my 15 ferad cap has allowed me to continuosly abuse my system with the stock alternator with more than one amp and two 12's and components..
but in my spl truck i didn't use caps because i had several batteries...
but after each run i would charge all my batteries before another pass..

so most theory stated here is beleivable..but not always true...caps do help to a certain extent....

[ April 11, 2002: Message edited by: xdamxincx ]</p>

[chas]

a capacitor is not a battery -- atleast electrically. however you could make the analog to a rechargeable battery (however, the capactior, when fully charged, ideally, looks like an open circuit)

an ac/dc convertor (non switching) is just a transtormer, a couple diodes, and some caps. most power supplies have voltage regulators but that's not really ac to dc conversion.

if you are using a cap to filter something you place it in series, not in parallel.

i would not use ohm's law to analyze this problem since its not static. the original poster picked a hypothetical situation to analyze. would the configuration ever realize this condition?