caps - what do they do or what do they supposedly do?

[davidfre21 5,000+ posts]

people always saying not to get one, but i never new what they caccualy do so this is why i started this thread. and if nothign why are they so popular?

ive heard 2 things about them and wonder if they are true?

1) They stop dimming of headlights

2) They alow u to run ur sub longer with out ur engine started with out killing ur bat?

thx

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[DBfan187 5,000+ posts]

people always saying not to get one, but i never new what they caccualy do so this is why i started this thread. and if nothign why are they so popular?
ive heard 2 things about them and wonder if they are true?

1) They stop dimming of headlights

2) They alow u to run ur sub longer with out ur engine started with out killing ur bat?

thx

To supply power to your amp and release it when the amp demands it! //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

 

[geolemon 10+ year member]

Caps aren't useless...

But often misunderstood.

So then they don't do what people expect, and they say "Oh, they are useless" //content.invisioncic.com/y282845/emoticons/rolleyes.gif.c1fef805e9d1464d377451cd5bc18bfb.gif

Or else they cite that ridiculous test that RC did... showing full minutes on the X-axis, so the waveforms looked to be identical, cap vs. no cap. //content.invisioncic.com/y282845/emoticons/rolleyes.gif.c1fef805e9d1464d377451cd5bc18bfb.gif

At any rate, understand what capacitors do.

They store a charge. They can be charged up to any voltage up to their maximum voltage level (usually 20v). They store lighting fast, and discharge lightning fast, and don't suffer any damage from that lightning fast behavior.

Now, understand what batteries do.

They store voltage. They try to maintain a constant 12v, although that will drop somewhat as the battery becomes discharged... but never to 0v. In fact, the very act of charging and discharging a battery is harmful, if it discharges more than just a bit. Trying to draw current quickly can damage a battery. Batteries also respond relatively slowly to demands for energy, for current... deep cycle batteries being the slowest (hence why they aren't recommended for a car audio application typically).

And your alternator is a voltage source, that's capable of generating a certain amount of energy... a certain amount of current, when regulated to 14.4v.

When you exceed that current capability, there's no problem... all that happens is that the additional current is drawn from your battery until the current demand goes back down.

If it's because the bass just hit a big note, the alternator provides what current it can, the battery provides the rest. In order for this to happen, the car's voltage level drops from the 14.4v of the alternator to the 12v of the battery.

You might notice your lights dim in your car when this happens, since lights are naturally more bright on 14.4v than they are on 12v.

The capacitor is a great addition to a power supply system, because they do help augment the amp when this transition occurs.

Bear in mind, the battery is slow to respond to begin discharging. Yes, it's only milli-seconds.. but that's dramatically slow in the scope of electrons that are moving at the speed of light! //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

The capacitor discharges lightning fast, helping supply the current the amp needs at a minimum until the so-brief, and slight voltage drop due to the battery's slow response has passed, if not being able to supply almost the whole additional current to cover the peak itself.

It helps smooth out the response of your car's electrical system, and can help with your light dimming situation, which can seem more extreme without capacitors installed.

The real trick setup is not just installing one in the rear of the car near your amps, but also up front, by the battery, to help it get a "head start" if you will, when the demand for voltage is there. //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

But the most important thing is fundamental...

Make sure your main power wiring is up to snuff, if not "overkill".

Upgrade the "magic 3" underhood, and make sure all the connections are well made, bare metal on metal (paint is an insulator).

 

[80_Cutlass_mn 10+ year member]

Wow....im speechless. This is by far the easiest and most understandable full description of what a cap can, cant do and when they can be used. Thanx Geolemon. I think this deserves a sticky //content.invisioncic.com/y282845/emoticons/idea.gif.5acb6a39a9b92425414c316dda202bad.gif//content.invisioncic.com/y282845/emoticons/fyi.gif.9f1f679348da7204ce960cfc74bca8e0.gif :stuck: :thumbsup

 

[Sharp_Shoota 10+ year member]

Yeh it makes sense to put it closes to the battery since the cap provides current faster than the battery, but it looks a lot cooler in the boot with the system. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[maylar 10+ year member]

Batteries also respond relatively slowly to demands for energy, for current... Bear in mind, the battery is slow to respond to begin discharging. Yes, it's only milli-seconds.. but that's dramatically slow in the scope of electrons that are moving at the speed of light!

Bullshit. Someone show me the Physics that says the electrons in a battery flow slower than the speed of light and I'll buy him a beer.
Capacitors are used in car audio because

(1) They look cool

(2) Under certain conditions they can actually help reduce headlight dimming

(3) Manufacturers push them on unknowledgeable people.

Under ALL circumstances, lowering the impedance of your charging system (heavy duty alternator, fatter wires, etc) will do much more than a capacitor. That's why "cap" is a dirty word around here.

 

[Radar 10+ year member]

Bullshit. Someone show me the Physics that says the electrons in a battery flow slower than the speed of light and I'll buy him a beer.

From Radar's Physics Edit:1 Copywrite 12/16/2003

P. 203 sect 1 "Electrons in a battery flow slower than the speed of light"

I like Budlight

 

[taylor 10+ year member]

agreed, i can take some quotes right from my work modules form electrical school to prove it.

 

[80_Cutlass_mn 10+ year member]

agreed, i can take some quotes right from my work modules form electrical school to prove it.

Im kinda confused here. Who exactly were you agreeing with in this matter. Radar, or Maylar. //content.invisioncic.com/y282845/emoticons/confused.gif.e820e0216602db4765798ac39d28caa9.gif

 

[geolemon 10+ year member]

Bullshit. Someone show me the Physics that says the electrons in a battery flow slower than the speed of light and I'll buy him a beer.
Capacitors are used in car audio because

(1) They look cool

(2) Under certain conditions they can actually help reduce headlight dimming

(3) Manufacturers push them on unknowledgeable people.

Under ALL circumstances, lowering the impedance of your charging system (heavy duty alternator, fatter wires, etc) will do much more than a capacitor. That's why "cap" is a dirty word around here.

I don't do "bullshit".

I also don't do reading comprehension seminars...

I suggest you revisit my words to see where you went wrong. I never said that electrons flowed slower or faster.

I said that batteries are slower to respond to discharge, and are also proportionally slower to charge. That's not a function of electron speed.

Capacitors have lightning fast discharge times, and proportionally lightning fast charge times.

I'll give you one large difference (related to their speed, charge and discharge) - ESR.

They indeed have very different properties... they do very different jobs.

You seem to be confused on that.

By the virtue of your post above, you seem to think that alternators, batteries, capacitors all do the same job, as sources of electricity. Very interesting. //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

I think that I should let you dispute the points of my post - as you find issue - and then we'll address them one by one, to see what is "bullshit". //content.invisioncic.com/y282845/emoticons/laugh.gif.48439b2acf2cfca21620f01e7f77d1e4.gif

I particularly like your edjumicated statements like "Manufacturers push them on unknowledgeable people." //content.invisioncic.com/y282845/emoticons/rolleyes.gif.c1fef805e9d1464d377451cd5bc18bfb.gif

Look, as regards your overly-bold and off-base statements...

Fundamentally, Capacitors and Batteries are very different items.

Here are a few links to get you back on track:

The first sentence says it all.

Why do you need a power cap? (this site isn't even a car audio topic, if you needed a less biased source... yet it's the same problem, and the same solution that you claim is "bullshit" //content.invisioncic.com/y282845/emoticons/rolleyes.gif.c1fef805e9d1464d377451cd5bc18bfb.gif )

Even though it's not the electrons that are flowing slower, that wasn't ever the statement or the issue... the response of the component, the amount of current allowed to flow over time is the issue, comparing a battery to a capacitor.

So I would take that beer now, except I don't drink (maybe you've had too many yourself).

Maybe you can shed some of those unedjumicated myths that you cling to (my doubts are that you even understand where they came from - do you? //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif).

 

[taylor 10+ year member]

i was agreeing with RADAR.....also to everyone who says caps are useless, you do realize that almost every electronic device uses large banks of capcitors.....

 

[davidfre21 5,000+ posts]

wow this thread really does answer like everything about caps, thx a lot

ps.

make this thread sticky mods, to hopely end the rest of cap threads

 

[slick rick 10+ year member]

so if i have headlight dimming problems, would an optima battery or cap do the trick?

 

[tommyk90 5,000+ posts]

Well, either way i dont have room for one, so i say screw the cap and i'm just gonna get a bigger alt, new battery, and upgrade the "big 3".

 

[geolemon 10+ year member]

so if i have headlight dimming problems, would an optima battery or cap do the trick?

You'll have to describe your problems, and possibly monitor your voltage.

Headlight dimming, by itself, after all, isn't a problem at all. //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

It simply happens when all electrical demands in your car have exceeded your alternator's total current capability, at whatever RPM your engine is currently operating at. This isn't harmful, the battery will simply supply whatever excess current is required... generally, this isn't a large amount of current, and the battery charges it back up in an equal amount of time.

When this happens though, in order for the battery to supply that small amount of current, the car's voltage level will need to drop from the 14.4v of the alternator to the 12v of the battery.

Simply put... light bulbs are brighter on 14.4v than they are on 12v.

Replacing your 12v battery with another 12v battery won't change a thing.. because your headlights will still be just as dim on that 12v.. regardless of what battery is supplying it. //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

There is the transitional period to consider... that instant in time where the voltage does initially drop, and the battery is instantaniously called upon to provide the current being demanded!

If you had a "slow" battery (such as a deep-cycle battery - it's thicker plates that allow it's "deep cycle" abuse also hinder it's performance), you might actually see your lights seem to dim a bit easier, or more even.

A faster battery (plain-old standard battery) is faster.

Augmenting your electrical system with a capacitor (either up front by the battery, to augment current demands at those transition times, or directly at the device creating the large demands - such as your amplifier) will in the very same way augment this.

It won't stop the dimming, but it can help, as the cap will charge to nearly 14v levels, and will discharge during those transients from 14v down to the 12v level of the battery - and by that time, the battery is supplying current on it's own. //content.invisioncic.com/y282845/emoticons/cool.gif.3bcaf8f141236c00f8044d07150e34f7.gif