Capacitors: What You Need To Know Before Buying.

[old_skool_noma]

So, you just installed your new stereo, but you notice your lights dim when the bass hits?

Or

You're buying parts to build a system and youre worried that your lights will dim because (insert name here) said that you need one?

If you answered yes to either of these questions, a capacitor is not the answer to your problems.

A capacitor acts like a small battery to filter small ripples in your electrical system, it discharges when the input voltage drops below the charged level of the capacitor to keep a constant voltage.

Now you're probably wondering why they wont fix your problem if they do what I just said, right?

Well, here is your answer, a capacitor simply will not support any electrical components placing that much demand on your electrical system. Sure you could get a huge capacitor. The price of one of a capacitor large enough to adequately support that substantial of an electrical system just isn't worth the difference, and you're still not fixing your underlying problem, an inadequate charging system. Once the capacitor is discharged from being over extended from being used improperly, it becomes even more of a strain on your already limping electrical system by trying to recharge.

Now you ask, if a capacitor wont fix my problem, then what will?

Well, there are three steps that you can do to combat your inadequate charging system. Steps 2 and 3 are interchangeable, I would recommend them in the listed order, but it isn't as important as the first.


Step one: upgrade your big three wiring, these wires are:
1. Alternator to Battery (+)
2. Frame to Battery(-)
3. Engine to Frame or Battery (-)

See the following link for more detail.
Big Three Upgrade: How To


Step Two: Higher Output Alternator.
Simply replace your factory alternator with an alternator that put out more amperage. The most common and cost effective is the AD244 from the newer full size trucks.

See the following link for more information about the swap.
AD244 Upgrade: How To


Step Three: Add Another Battery
Just like it says, add another battery, you should use at least the same size wire that you used for your big three, if you have any considerable length of wire to reach the new battery, you need to fuse the wire at each end to help prevent any electrical fires if the insulation should become compromised.

If you are dealing with batteries of different types and or ages, an isolator should also be used to prevent premature battery failure, but this will also cause a half volt drop across the isolator.


This should fix your problems for up to a moderately high powered system (2000-4000 RMS Watts) if it doesn't repeat steps 2 and 3 and necessary.

Now that you've read why you don't need a capacitor, now you can see what they are useful for.
You already know that capacitors filter ripples in your electrical current from the beginning of this tutorial.
There are sound quality benefits to using capacitors as a filter before your amps. The first benefit is if there is an immediate need for a high current draw such as a bass note with a very fast attack, the capacitor can discharge faster to supply the required current, in addition to the current that is already there from your battery and alternator to keep your amplifiers response as fast as it can be.
Secondly it helps keep voltage spikes from reaching your amplifiers.

In conclusion, unless you have extremely fine tuned hearing chances are, you will never miss a capacitor in your system, but, I will not discourage you from getting one, so long as you are using it for the right reasons, if you are trying to fix a voltage problem with it, you are simply trying to put a band aid on a bullet wound, but if you have a strong electrical system and are looking for something to smooth peaks and provide an additional kick if its needed, chances are a capacitor is what you are looking for.


Happy Building,
Brandon

[eriley]

Sticky...

This is perfect, you should only ever use a capacitor to smooth out your bass response, for everything else its just a band-aid.

[Speedy2222]

they said on xtreme 4x4 yesterday that they're used to stop headlights from dimming =-o i sent them an email setting them straight...

[old_skool_noma]

T hate it when TV shows especially give wrong information like that, its mainly just a marketing tool to sell something cheap to manufacture, I would think that the sales stated out using them as I described that they should be, then someone used it for a band aid and it made their dimming less noticeable so they thought it was the cure, so the lower end companies caught wind of this and exploited a lot of sales from people that didn't know any better

[B_Rich]

Very well written old skool noma. I think you'll really reach out to people who are debating this very topic, without sounding like an asshole and making them feel like shit. I hate doing that to people.

I like the "repeat steps 2 and 3 as necessary" part

[Deja_Vu969]

Wow...that goes pretty in depth. I don't have anything big enough to drain my system...yet. But that explains a lot more than most threads on here. (that I've read). Thanks

[bubbagt57]

STICKY perfectly done thanks

[therule546]

Very good write-up :-)

I wish someone would do one on making a bracket for 2-3 alts retaining a/c. There is one good thread on here about it, but he didnt show a very good shot of the bracket, and Im scared Id mess it up.

[beandip]

Great write up, should be a sticky.

[B_Rich]

Quote: Originally Posted by therule546

Im scared Id mess it up.

Don't take this the wrong way, but you'll never get anything accomplished in life if you have that attitude toward life.

Just take it slow, think things through, ask yourself what could go wrong, then despite whatever you're thinking now, just go for it.

/thread hijack.

[max1million]

A capacitor is like a battery in that it stores a charge, but (for the size) charge and discharge much faster, and stores less. A large capacitor near amp may help with short current surges (thumping bass) with under sized or improper wiring, but common sizes for capacitors would not help much for more sustained current surges (long bass note).

The longer the wire and smaller the conductor within, the more resistance to the current flow. With heavy current draw the voltage from the battery at the other end of the wire drops. If your connecting a heavy load to fuse block/alternator and the cab/frame, it's at the wrong end of the stock wiring that already has it's load to deal with.

Wire up directly (with fuse) to the battery, or at least to the where the heavy cables end at the starter solenoid and engine block. Wiring up to a second battery does essentially the same thing (directly to the battery), but it is also similar to having a super sized capacitor (and more wire) in between the amplifier and the rest of your electrical system. For moderate power a second battery not really needed. Then if your lights slowly dim down while your running down the road with the stereo cranked, you need higher output alternator, and heavier wiring between it and the battery (or starter solenoid) and well grounded (the case/mounting). For better performance of sound system use a heavier gauge wire. Second battery is sometime also used so you don't discharge the main battery (for starting) while parked by having the second switched out of the electrical system when the engine is not running.

Since audio system draws a surging high current instead of constant, you can actually get away with much smaller then ideal conductor sizes without burning up the wires. That's the same reason (and cost) that battery and jumper cables are not commonly 1/2 inch thick or more of copper conductor.

For reference here is some common constant current ratings (rubber insulation), wire conductor gauge/amps:
14g/15a, 12g/20a, 10g/25a, 8g/35a, 6g/50a, 4g/70a, 2g/90a, 1g/100a, 0g/125a, 00g/150, 000g/175a, 0000g/225a
Yes wire gauge number decreases for larger conductor, more amperage, and less resistance. 1gauge is just over 1/4 inch diameter conductor and 0000 gauge is almost 1/2 inch.

[old_skool_noma]

Thank you to whoever stickied this

[max1million]

Forgot to mention using relay for switching power if you connect stuff that don't shut off by it self. Most large amps have a relay built in hence the 2 positive wires, 1 gets connected to low current switched circuit. Also over fusing risks burning/melting wires if they get shorted, lower slow blow fuse or circuit breaker is better.

[B_Rich]

Quote: Originally Posted by max1million

Forgot to mention using relay for switching power if you connect stuff that don't shut off by it self. Most large amps have a relay built in hence the 2 positive wires, 1 gets connected to low current switched circuit. Also over fusing risks burning/melting wires if they get shorted, lower slow blow fuse or circuit breaker is better.

I hate to burst your bubble, but those are 2 things that 99.99% of car audio installs consist of. A remote wire on the amp and a fused power wire.

I've never seen an amp that doesn't have a remote wire input on it....

[max1million]

bubble, you missed the first sentence and misinterpreted the rest

"...stuff that don't shut off by it self..." or include relay as most amps by example do (you missed those that didn't)

and while (going back to other reply) you can run an audio amp on less then ideal wire gauge, by over fusing (or none) a smaller wire the risk of melting it in unintentional short circuit or other over current condition is greater, and a more reasonable slow blow or breaker may be better in that situation.

hope that clears it up for you

[old_skool_noma]

Quote: Originally Posted by max1million

Forgot to mention using relay for switching power if you connect stuff that don't shut off by it self. Most large amps have a relay built in hence the 2 positive wires, 1 gets connected to low current switched circuit. Also over fusing risks burning/melting wires if they get shorted, lower slow blow fuse or circuit breaker is better.

the reason i said 2 fuses is because if you have a battery in the bed, you need to prevent the wire between the batteries fused at both ends to prevent current from entering the wire from both sides if the insulation is comprised, yes a circuit breaker will work in this situation, but they can trip from vibrations where as a fuse will not

[B_Rich]

Quote: Originally Posted by old_skool_noma

the reason i said 2 fuses is because if you have a battery in the bed, you need to prevent the wire between the batteries fused at both ends to prevent current from entering the wire from both sides if the insulation is comprised, yes a circuit breaker will work in this situation, but they can trip from vibrations where as a fuse will not

I should whip out my super-dee-dooper-awersome drawing

[old_skool_noma]

Quote: Originally Posted by VoRtEcZr243

I should whip out my super-dee-dooper-awersome drawing

be my guest

[max1million]

I apologize for not making abundantly clear in reply #13 that it was a continuation of reply #11, and for the confusion over it's wording. Reply #13 should start:
"I forgot to mention in reply #11 and the following is in reference to it"
I would have preferred being able to edit directly into reply #11 versus a separate reply, while also using the later improved wording.

I suspect that in reply #16 you are refering to "over fusing" as well as the use of a circuit breaker, in reply #13. If so by "over fusing" I refer to using a fuse of higher amperage rating then is recommended. And breakers often slower to react can allow surges while still limiting the average current, thus better then "over fusing" and similar to using a slow blow fuse. I would however agree, reply #16, more protection where needed is better. With that the current ratings in reply #11, for those that would like to know some recommended values, are from a reference which I use.

My only real contradiction of the original post is: There is no need upgrade the stock small wiring when it is just as easy to go to the source (the battery) or at least to the where the heavy gauge wires (cables) that can handle the current end, when either method will generally do.

If however you are upgrading to a 200amp alternator then go ahead and put in 0000 gauge wire or double up on 1 gauge, it should only help. And if you prefer to change "your big three wiring" as per the original post and it's reference, you might also consider same for frame (or engine block or battery - ) to cab body, if intending to use it for a negative connection (grounding point) for everything.

Again I apologize, for any confusion over my input. Would you please point that thing somewhere else.

[eriley]

max what in the **** are you talking about jesus christ i can't understand a thing you are saying.

The only thing I took out of that is you saying you don't need to upgrade the stock small wiring when you can just go to the source (the battery). Which doesn't make any sense, since the source is the alternator. Therefore by upgrading the stock small wiring you are going straight to the source.

[old_skool_noma]

Quote: Originally Posted by max1million

I apologize for not making abundantly clear in reply #13 that it was a continuation of reply #11, and for the confusion over it's wording. Reply #13 should start:
"I forgot to mention in reply #11 and the following is in reference to it"
I would have preferred being able to edit directly into reply #11 versus a separate reply, while also using the later improved wording.

I suspect that in reply #16 you are refering to "over fusing" as well as the use of a circuit breaker, in reply #13. If so by "over fusing" I refer to using a fuse of higher amperage rating then is recommended. And breakers often slower to react can allow surges while still limiting the average current, thus better then "over fusing" and similar to using a slow blow fuse. I would however agree, reply #16, more protection where needed is better. With that the current ratings in reply #11, for those that would like to know some recommended values, are from a reference which I use.

My only real contradiction of the original post is: There is no need upgrade the stock small wiring when it is just as easy to go to the source (the battery) or at least to the where the heavy gauge wires (cables) that can handle the current end, when either method will generally do.

If however you are upgrading to a 200amp alternator then go ahead and put in 0000 gauge wire or double up on 1 gauge, it should only help. And if you prefer to change "your big three wiring" as per the original post and it's reference, you might also consider same for frame (or engine block or battery - ) to cab body, if intending to use it for a negative connection (grounding point) for everything.

Again I apologize, for any confusion over my input. Would you please point that thing somewhere else.

you must be vastly confused on the way the automotive charging system works, the battery has to get its power from somewhere, that would be the alternator, the factory 8 ga wire isnt big enough to support much more than the factory electrical system, this is why we upgrade the wire going from the alternator to battery, block to frame and the battery to frame (big three).
8 ga wire is only rated for 40 amps, even the factory alternator puts out 90 so they were going cheap from the factory, so if you upgrade to a higher output alternator you will need even heavier wire.

also 0000 wire is very few and far between in mobile installations and is for the most part impractical to most members on this forum. 0 ga or at most 2/0 is the largest nearly anyone would need.

[max1million]

Not confused and yes I do understand the charging system, electrical in general, as well as some internal electronic circuits. And I have done plenty of wiring including home and auto not to mention other, as well as building regulated power supplies and simple low power audio amps.

Alternator to battery, it depends on how much of the alternator's output is actually run constantly though the wire to the battery. 20 amp charge (commonly under 10 amps shortly after starting), plus 20 amps average for a moderate amplifier (about 300 watt continuous, more for peak or max) equals 40. If other accessories are connected at alternator (such as head lights, constant current when on) that current doesn't go through this wire when running, it's drawn off the alternator directly. With no alternator output (not running) the lights would draw through this wire but the amplifier would would not. The wire is also generally where it has airflow cooling it, not packed in insulation in a wall or under carpeting. Less average current plus cooling you can push the specs a bit. If it's just the current surges (the thump thump causing flashing lights) you need worry about, then connecting directly to the battery may take care of that. Some current from battery and some current from alternator output, recharging in between surges.

The alternator's negative is the case mounted to the engine, and the negative engine block to battery is generally sufficient as that also handles the high current discharge of the starter, even though under spec for the starter as is battery to starter. If your not using the frame as a wire then battery to frame makes no difference as long as it handles OEM that's connected to frame. Same goes for cab. Block to frame and battery to frame is just double excess.

I agree 0000 gauge is a bit excessive, but it was an example using recommend ratings for a constant 200 amp (plus 25 instead of minus). Unless your actually drawing a constant 200 amp you don't need alternator or wiring to handle it, but it wouldn't hurt. OEM alternators come in various amperage ratings, even as low as 35 amp. If alternator is putting out enough to charge the battery with all accessories including stereo on then it's enough, maybe just barely but enough. If your head lights are slowly dimming going down the road (not to be confused with flashing), and vehicle won't start after you shut it off, as said before you need to fix or upgrade the charging system, cause it's not enough output to handle all. Otherwise the battery can handle the surges.

My first choice is to connect to (and with) what will handle the current surges, then upgrade the rest as needed or desired, to better handle the average current. You can do however you like.

[greatdane68]

Great thread!!! This is the very reason that I run a capacitor in my stereos. That, and they're good for troubleshooting if you get one with a digital gauge on it.

[danssoslow]

Capacitors are also less prone to be scrutinized by the police. That "I use that bat to test my tires" crap only works with truck drivers.

[old_skool_noma]

Quote: Originally Posted by danssoslow

Capacitors are also less prone to be scrutinized by the police. That "I use that bat to test my tires" crap only works with truck drivers.

never heard of that before, but okay, i guess, dan is the man so ill jump on the band wagon

[Speedy2222]

here's some cap history for you guys.. basically the origin long read but good
and i didn't write this lol

caps dont do shiznit, especially a 1 farad..read an enjoy

After studying a little history on large 1 Farad capacitors in car audio, you'd be amazed that they even sell at all. How useful are they? What do they really do? Will a Cap 'improve' my sound quality? Will it Prevent my lights from dimming? Will it audibly affect my audio system in any way?

Before you get the truth to any of the above questions, chances are, you've probably spent $100 or more on one of these devices. However, let's study a little history regarding this issue.

A long time ago, in a land far away, 2 elves...Ok, Richard Clark & Wayne Harris (Carsound magazine and the inventor of DB Drag, respectively) separately came up with a solution to preventing their lights from dimming.

WHO WERE THESE GUYZ?

As you may know, Richard Clark is one of the founders of autosound2000 Tech Briefs, Carsound magazine, and a published author of the industry of mobile electronics. In SQ competitions, he posted a record of 1234 1st place finishes, and only ended up NOT 1st in his first event. I've heard that he had minor system problems, but judging by his record, he must have corrected it. (evidently, he needed a Capacitor )

Wayne Harris was previously a leader at Rockford Fosgate in their development. Later, in his free time, he created the organization we call DB DRAG. Wayne was the first SQ World Champion from the organization we know as IASCA (International AutoSound Challenge Association).

Both of these gurus are both legends, and considered the leading experts in the field. During their competition days, both guyz came up with a way to assist in the prevention of voltage drops. In SQ competitions, the look of your system is actually more important than the sound, and having your lights NOT dim under high playing levels is a competitive advantage.

As you may know, amplifiers are made up a bank of little capacitors, resistors, etc. What has been common engineering knowledge is that capacitors store energy, and more or bigger ones assist in balancing the power supply.

Wayne came up with the idea of putting several dozen 'little' (approx 100uF) capacitors on a circuit board to 'extend' the power supplies storage. At about the same time, or shortly afterward, Richard came up with the idea of one huge mondo capacitor (I believe it was 800,000uF or 0.8F) to do the job.

Eventually, Richard won. The large cylindrical tubes won over the complicated 48 caps strapped to a circuit board. However, what did this really accomplish? Let's start here:

WHAT IS A CAPACITOR?

Basically, capacitors are an energy storage device. Large, 1 Farad or more
capacitors store energy (electrons) between their plates. Capacitors differ
from batteries because batteries store energy in the form of chemical
energy--and rely on acid and lead plates, as the place of storage. For a more detailed
description of a capacitor, go here:

http://www.eatel.net/~amptech/elecdisc/caraudio.htm

Then on the right hand side, scroll down to CAPACITOR. Keep in mind the use
of capacitors in an audio system.

WHY DO PEOPLE BUY CAPACITORS?

The number 1 reason would have to be because their lights dim when their
system is playing HARD. In car audio, we are told that a capacitor is
designed to prevent the voltage drop associated with your lights dimming.
The number2 reason is that it is rumored to 'improve' sound quality or
'stiffen' the power supply/source.

WHY DO MY LIGHTS DIM?

Headlights brightness is in direct proportion to the source voltage. For
instance, if your car is running, system voltage is ~12.5 -14.4 VOLTS. Your
lights will be much brighter than when your car is turned off--where battery
voltage is ~12V. Most car alternators put out between 75 to 120 amps of
current. When this current draw threshold of the charging system is
exceeded, system voltage will drop as power demands are now shared by the
alternator and the storage devices (battery & cap). We are using battery
reserves beyond this point until the demand lessens

When playing your system really hard. Your lights dim because your
alternator can't keep up it's charging voltage (around 13.5V) and therefore,
demand exceeds output. When this happens, your electronic devices are
dipping into the power storage of the battery. Since the battery stores
power at ~ 12-12.5V, there is a 1.3 to 1.8V drop in voltage available. This
in turn is why your lights dim down.

HOW MUCH POWER DOES A CAPACITOR STORE?

1 Farad = 100 joules or 100W/second
850cca battery = ~2,200,000 farads

For storage purposes, you'd need ~2,200 1 Farad capacitors to equal the energy of your battery.

Due to its impedence (ESR & ESL), a cap's energy is only 50% available. What's worse, is that in order for a 1 Farad cap to discharge, first the alternator output must have maxed out, and the voltage must have dropped around 1.5 volts. But I thought a cap was supposed to prevent that (voltage drop)!!!!!????? Yep, you got the point.


IF A BATTERY = 2,200 CAPS, THEN WHY BUY A (PUNY) CAP?

My question exactly. Marketing is the reason why people buy caps. In many cases, upgrading wiring will help your system get the maximum transfer of current. Once that has been reached, adding a capacitor may have a minor effect on your system. 50W over the course of a second is not a lot of power considering an amplifier may draw 2000W to put out 1400 watts. Let's look at the situation from a resources standpoint.

Alternator 80 amps
Car accessories (minus stereo) 40 amps
A large Car Audio system (DRAWS ) ~200 amps AT FULL OUTPUT

In this case, you have 240 amps of draw, but only 80 amps of current from the alternator. In your case, you need 160 amps x 12 volts or or let's say 1920 watts of energy. Since a cap stores 50W, how much of a difference do you think it's going to make? A cap is basically a peashooter. W+e need a Howitzer cannon here, to do the job well.

Also, Once a cap is discharged, where does it get it's power from? The alternator, which is already overloaded. Once a cap is discharged, it's worthless. Like SWEZ says, ・.The cap already shot its wad, an does limp til recharged・ I知 not so certain I will allow him to babysit my kids, but you get the drift. (I never said it quiet like that... and oh...I'm great with kids!)

SO, WHAT IS A CAPACITOR GOOD FOR?

1. Audio Jewelry- impress chicks with large cylindrical shiny thingy
2. Extra weight in winter time
3. A very POOR... BUT expensive distribution block
4. A projectile in the event of a crash
5. Rolling pin--for cooking purposes
6. A neat thing to tell your friend, "..Hey man, lick the top of this..


Please do not try # 6. New hairstyles are always refreshing, but if you are wearing railroad tracks across your teeth, you might have one big filling after it痴 over.

HOW CAN CAPACITORS IMPROVE SOUND QUALITY?

They can't. Sound quality is not dependant upon the presence of large bulky 1 Farad capacitors. How many 1 Farad Capacitors do you think the Boston Pops, Aerosmith, or Snoop dog use in the recording studio?

IN A NUTSHELL.......

When Richard, our fearless inventor, became World renown for winning every competition under the sun, people began copying what he did. Soon, every 'serious' competitor had a 'stiffening' capacitor--not to be confused with the 'loosening' capacitor.

WHY?

In the late 80s, people began sticking out their tongue when dunking the basketball because Michael Jordan did. Did sticking out your tongue improve your dunking ability? Same here with adding a capacitor to your electrical system.

STILL A GLUTTON FOR MORE PUNISHMENT?

Here's the Original Cap Debate.

http://www.carsound.com/ubb/Archives...-1-000307.html

Phoenix Gold's marketing guru had just posted information on how their Powercore (basically the Alumapro CAP15 in a Phoenix shell) had both stabilized their voltage and improved the sound quality. Richard called him on it (all in another post) and the marketing geek was unable to quantify any of the conditions that resulted in the voltage being HELD at 14.2V and the 'improved' sound quality.

Please do not read every stinking post as valid. There are a lot of people that have had the efficacy of capacitors inbred to their minds, and were not (and still not) convinced in the futility of a 1 Farad storage device.

In a final note, Richard relayed a quote regarding battcaps ( www.battcap.net ) as, "..The audio industry is the only place i know of where you can publish specs that show your product is useless and still be able to sell them------and whats worse is that technically ignorant people will argue against the math!!!!!!!..............RC.." when referring to the product. This also relates to most digital readout capacitors, and I wish my Archie Bunker skills could have said it better myself.