The truth about caps

[ChinoCharles]

No, I didn't get it yet. That was meant to be a question but after reading it I can see why it wasn't viewed as such.

I'm running 1400 watts. Headlights dim quite a bit when the sub is angry. A cap is enough to solve my dimming issues, right?

[goku87]

Before you start complaining, if you want to fight the numbers, do the math yourself. Everythying you need is on the wikipedia site.

Anyway, my two cents is:
CAPS WON'T HELP

ONE:

Breifly, the time constant = RC, where R would be the woofer impedance, and C would be the capacitance of the cap. It takes 5tc to completely discharge a capacitor (99%), likewise it takes 5tc to completely charge (99%). In theory, a capacitor seems like a nice alternative to a voltage source, but the fact that the charge and discharge rates of a capacitor are exponential, it hurts more than it helps, and here's some numbers for you to ponder:

With a subwoofer impedance at 4 ohms, a 2 farad capacitor, and an initial charge of 14v (im being generous) it will take 2.69 seconds to drain the cap to 10v, a very poor operating voltage and an obvious dim of lights would occur. Likewise, it would take 2.69 seconds to return the capacitor to full charge (again, only 99% of source voltage). I have never heard any music that alternated between bass on/bass off equally that could give a capacitor the chance to recharge. If there is any bass whatsoever, there will be a current draw, and the capacitor will not be charged to its full capacity. In this regard, not only is the amplifier pulling power from the alternator, but also the capacitor, to try and maintain the system voltage. It is adding an extra current draw, and if your system is already maxed out to the point of dimming lights, fork over the extra money for a new battery. The capacitor is just going to fry your alt and you will have ended up spending money on a cap+alt which is more than a battery.

TWO:

Capacitors realistically can't completely charge all the way due to the nature of how they work. They just slowly get closer to the max. What this means that even if you weren't maxing out your stereo, the voltage would still drop because the capacitor is pulling extra electrons out of the system to help charge it to get it closer to maximum capacity (which will be 99% after 5tc). This can be seen in voltage rectifiers where AC is converted to DC. Capacitors are used to help remove the ripple, but the higher number of capacitors there are, the lower the voltage drops.

THREE:

For those of you who say they work because they are in computers and stuff, you should know their use is mainly for time keeping in the millions of multivibrators in your computer.

Okay, I'm done.

[blktiger60]

I believe standard alternators have room for modifications. You could take your stock alt to a pal who knows eletrical componants and have him/her wind a few more wires around it.
I don't know the specifics for the alt in the Yaris, so this may not be the case with it.
Personally, I would go with an alt with more output as oposed to a cap.

[bzinn 1]

If you look at a properly installes system running big ampage a cap can do some good but really is not needed.Been to several meets and talked to many competitors and less than half use them.They do have a place,to lower the spike to the alternator and it can help,but not really needed if you build it right........I am pushing over 1000w to my system and headlights have never dimmed,if they dim a person might not have large enough power supply wire to the amps, and it is gettign resistance,which can definatly cause issues.

They do have a place but I have never needed one.....but I always upgrade everything to work together.

[goku87]

Originally Posted by PK198105

you're only about half right. first off the capacitor in a sound system setup is only used to smooth the voltage out and prevent major dips in voltage. that's why we use high capacitance values in audio setup so your RC is high (ie enough time to prevent voltage dips)

But the fact I was getting at is even though the time constant is high, the current draw is relatively just as high, negating any "big value" advantage it has. It's just not worth it. The math doesn't lie.

Originally Posted by PK198105

second caps in computers are used first to prevent voltage spikes as all computers need a stable power so that the data doesn't get corrupted with missed volatges (a binary 1 is between 3.3V and 5V, if no caps were used this value would not always be consistent and therefore data corruption would exist). Also the caps in computers are used to debounce the signal (a condition that occurs when a switch is throw, the correct voltage value is not instant and it will take a certain time before it settles). Capacitors don't "create" timing they are there to ensure that there is no time delay/drift. Now caps inside the chips are part of the timing

The useage you are talking about is the same thing I was talking about in the voltage regulators the paragraph above the computer one.

Originally Posted by camelll

Well 2 years and my alternator is still working fine and so is my cap.

The word of the day for you is credulous.

Originally Posted by camelll

You know for someone who thought that there glowshift gauges were causing there battery to completely drain, and you even claim to work with electronics. I can see why you think this way about caps.

The only reason I thought that was because that was the only modification I did to my yaris, and I just happened to have a factory battery that failed about the same time.

Originally Posted by camelll

If you think that all a cap does in your computer is just time keeping then remove them and see if your computer turns on!

I said:

This can be seen in voltage rectifiers where AC is converted to DC. Capacitors are used to help remove the ripple, but the higher number of capacitors there are, the lower the voltage drops.

...you should know their use is mainly for time keeping in the millions of multivibrators in your computer.

So basically, even though I didn't say that was the only purpose was for timing, lets pretend I did. You told me to remove them and see if my computer turned on. That would prove nothing since IF they were still only timing, the computer still wouldn't run since there would be no timing for any processes to take place. Nice try though.

[sqcomp]

Hey Taln! I'm baaaaack!

Keep your caps. Keep your second batteries. I'm running with a better solution for the Yaris.

Alternator side ground finish point:



Alternator to frame ground finish:



Alternator ground start point:



Tranny to frame 0 gauge ground wire with nice compression fittings:



Tranny and frame ground points (this is take from under the car looking up):



Battery to frame ground:



Instead of trying to force more water through a small hose...make the hose larger and have the water flow easier. Work smarter not harder!

[goku87]

Originally Posted by camelll

Well I have a better word PROOF, 2 + years of the alternator and cap operating as they are intended would be proof or evidence. My lights not dimming after the install of the cap, again that would be proof or evidence.

Being gullible would believing that caps do not work. So do you think that caps work in every application they are used for except car audio? If you believe that then credulous would be a word for you!

Find yourself a nice 40hz sine wave and make your system play it. Check the voltage of your system with the capacitor, then disconnect it, and check again.

[fuji]

SQcomp,

Can you post bigger pictures of your mod? It looks like a really good idea.

[sqcomp]

For some reason these imageshack pics won't let you supersize them...

They're all on the cellphone so I have them regardless. I'll try to figure it out after work today.

"Big 3" upgrade. Helps the juice flow. It's like using Lance Armstrong's lungs when cycling.

Oh and the caps "work". They work as they're intended to...for short bursts of stored potential. They DO NOT create energy. They store it. Hmm? Just like a battery...and what does an alternator charge? Yes kiddies...the batteries.

If you're system is sort of making it, but just needs a little boost every once in a while. Get a cap. Most of you don't know when that threshold of just enough or too much is. You just throw 15 amplifiers in there and toss a cap and another battery in and say, "look! I'm a super genius!"

Have fun with that...Mr. Super Genius.

The less work my Alty has to do, the better. You stick with what works for you...I know I do.

[goku87]

Originally Posted by camelll

Are you saying that caps work in every application except for car audio? That is what I want you to answer.

Depends on what you mean by "work." If by "work" you mean they give you extra power when you need it for those extra hits, then no. I say they don't work according to the math behind it. If by "work" you mean they make the voltage more stable at a lower voltage, thereby making less available power available to the amp to begin with, then yes, in this sense they will "work."

I'm not trying to say anyone is right or wrong. I'm only stating my opinion and supporting it with facts in the hope others will understand it just as others are doing.

[sqcomp]

A cap as a noise filter is one thing. A cap as a solution to not having enough juice? Like I said before, if the alternator is just shy of making it on it's own power...it will work.

Now, if your alternator is consistantly working to it's max, it will only produce so much power and will eventually fail. It's like if you keep running your engine at redline...it will die soon enough.

Yes, a cap does NOT make power. It is like a battery, it stores it and releases it (albeit faster). Putting a band aid on a gushing wound is not the solution.

Yup...the photobucket pics are a smidge bigger...