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smokeumtires

Rf Capacitors?

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lightning audio (rockford) makes a 100 farad cap. I have also scene these caps modded to do 100+ buy just adding cells in them. I dont know if you can get your hands on them anymore though. If your over 3k I dont see much of a point in a cap. SNAFU that was the best thing i have ever scene on smd :)


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Cool - no problem. Incidentally, I have one of the old Rockford Fosgate 100 Farad capacitors that I'm not using . . .

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Tony Candela - SMD Sales & Marketing
Email me at [email protected] to learn about becoming an SMD Partner!

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battery cough cough :lol:


Red light rev ya engines..light goes green u take off, petal to the floor.I take it slow but some how seem to catch up with u at he next red.So u think u can do it again.light goes green you stall..i put my foot down just to show u what fast really looks like :)

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Cool - no problem. Incidentally, I have one of the old Rockford Fosgate 100 Farad capacitors that I'm not using . . .

i could put use to it if u want. and lol to Geardropper who bumped this for something retarted <_<:noob:

Edited by emperorjj1

J. Jsig_253411.jpgMy CardomainFINISHED COBALT SS/SC DUAL ALTERNATOR PICS icon_nuts.gif

theres no such thing as too expensive when it comes to upgrades like that, because imo if you are gonna spend to upgrade then do it correctly rather then be a cheap ass ricer

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Yeah, how funny is that. homiewes & Geardropper, thank you for your excellent clarification. The SMD community is indebted to you.

Now, go read page 1.


Tony Candela - SMD Sales & Marketing
Email me at [email protected] to learn about becoming an SMD Partner!

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Holy Cow there's a bunch of mis-information in this thread about caps. Caps work - period. But how? Simple . . . capacitors do TWO things:

1. Store charge

2. Oppose changes in voltage

Now, both of those things sound mighty nice to me. To understand how a cap benefits a car audio system, one has to first understand that there are TWO separate voltage plateaus available in an automobile:

1. Running - With the alternator charging, voltages will typically be from 13.8 to 14.4 VDC

2. Not running - With the alternator IDLE, voltages will typically be from 12.0 to 12.6 VDC

I'll take the higher of the two any day. For UNREGULATED amps, this allows them to draw MORE current therby making more power. For REGULATED amps, this allows them to draw LESS current to make their rated power. Either way, it's a WIN for you. So, how do we ensure the higher of the two?

Again, simple. With the vehicle running, consider the DELTA between what the alternator can make and what the nominal voltage the batteries can provide is. For this example, lets assume 14.4 VDC - 12.6 VDC = 1.8 VDC. When we exceed the current output capability of the alternator, it's voltage output is compromised. In some cases, heavy demands of amplifiers can far exceed the current capability of the alternator, leaving us with only the reserve of current within the battery. But, car batteries weren't intended to power amplifiers . . . they were intended to start cars [battery = Load with vehicle running.] A really fresh car battery can do this for a while, but given that we're exceeding the output capability of the alternator, it's charge isn't getting replenished quickly enough - need about 13.0 VDC minimum to allow charge to flow back into the battery.

A properly sized capacitor will change the rules. With the vehicle running, it stores charge at the higher voltage plateau - 14.4 Volts. As the amplifiers demand current, it will flow from the place of least resistance . . . Ohm's Law tells us that happens to be the place with the highest voltage. That will be in order:

1. The capacitor (closest)

2. The alternator

3. The battery

Ideally, you've selected the correct size capacitor for your system's needs. And . . . that "30F" cap that sells for $59 in a blue velvet box with chrome and a big blue LED readout is just a glorified volt meter These devices have ZERO benefit. There is a reason why quality capacitors cost money, and ours are no exception. These are the facts:

1. A 1 Farad capacitor can store and release 72 Joules (watt*second) of energy at 12 Volts.

2. Said capacitor can charge and discharge hundreds of times faster than an automitive battery of any kind.

3. Capacitors present nearly no load to a properly set up charging system.

4. Automotive batteries require 7 to 10 amps of current EACH to allow charge to flow into them.

5. Capacitors work GREAT for every day street systems.

6. The benefits or capacitors are negated in SPL competitions.

For best results, I recommend locating capacitors within a foot of the amplifier - as in, no more than 12 inches of wire between the capacitor and the amplifier. The further away from the amp they are, the less of a benefit they offer.

I have used them my systems for a very long time . . . since about 1986.

dont take this as sarcasim any way snafu.

I will be soon running 2 amps for my subs. 3000wrms by 1 @ 1 ohm each. They will be ran daily at around 15.5 volts at around .7 ohms.

My amps will put out 4500wrms by 1 @ 1 16.5 volts.

I will soon have a irragi alt and voltage regulator whenever he gets back to me, just waiting on Dom.

Ive also seen one of my amps draw over 450 amps at ruffly .75-1 ohm.

So are you telling me that running a big capacitor will benifit me more then lets say 4 Powermaster 3100s or 4 kinetik hc2400s?

All I know is anything below 12.5 volts I am at risk of frying mosfets when the amps are ran at 1 ohm.

You really didn't give me much information to go off of . . .

- Your amps are obviously unregulated as they can produce more power with higher input voltage . . . maybe T3ks?

- What topology are they? (Class D?, bd?, A/B?) OR, what are their efficiency ratings?

- How much current at 14.4 volts are you paying Dom for?

Some simple math with your 3,000 watt Class D example at 14.4 VDC on sine waves would be:

3,000 / .75 = 4,000 watts Input required x 2 = 8,000 watts input

8,000 / 14.4 = 555 amps of current

Let's say your amps require 17 feet of power wire between them and the batteries and another 5 foot between them and the frame (chassis won't cut it here) for their grounds. To get 555 amps of current to your amps at 14.4 VDC, you'd need:

Big Wire:

- 1/0 AWG wire has .0001 ohms resistance per foot - 22 foot of it will have .0022 ohms of total resistance

- 555 amps through 22 foot of 1/0 . . . 555 x .0022 = 1.22 Volts drop in the cable alone

- 4 runs of 1/0 AWG . . . 555 x .00055 = .30 Volts drop in the wire - mo' better

BEEFY Alts:

- 300 amps at 14.7 volts . . . remember, we lost 3 tenths of a volt in our four runs of 1/0 AWG . . .

- 2 required

Now, if we add batteries, these need 7 to 10 amps of current each to allow charge to flow into them . . . I'm not seeing the benefit with the car running. But, if you wanted to jam this system with the key off then you'd need 'em for sure. Look at the AH rating on the battery you're shopping for. On music, these two amps would require roughly half of the current they require on sines . . . let's say these batteries had a 65 AH rating.

555 / 2 = 277.5 Amps

277.5 Amps / 65 AH = 4.3

So, you'd need 4 to 5 batteries to play this system wide open on music for ONE hour. After one hour, nominal battery voltage would be somewhere around 10.5 to 11 VDC.

And . . . these 4 batteries would require 40 amps of current to allow them to be charged with the vehicle running . . . better get Dom to up those alts to 350 amp models . . .

Ain't nuthin' free . . . Incidentally, this is a case where capacitance just can't cut it. The amount of capacitance a system this size would require would make it cost prohibitive, but if you could swing it, two of our 100 Farad caps of old would certainly help.

Now - where you're getting 16 volts DC you'll have to share . . .

best info I've seen on caps in a while, most ppl on these forums hate on caps, but they have a purpose.

But on a side note, I take it you imply that caps aren't useful for comps. In the division I'm running in, we're limited to 2 batts plus stock, but unlimited caps. I'm considering running two D3100s plus the the spp1200 under the hood. So my question is, if I'm running 4-5k with a 200 amp alt, would lets say a 40 farad cap be helpful? I want to get the most out of it lol. I've done my own research, but I'm always looking for others intelligent input.

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get this, http://www.sonicelectronix.com/item_38795_Kinetik-HC600B-KHC600B.html?from=857-141-701

it ways as much as a capaciter but its a battery. plain simple perfect for what you need

If that's a response to my post, you need to read it again.

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