Why Capacitors Do NOT Work

[2fnloud]

I am so tired of reading post or recommendations that "adding a capacitor" will fix your electrical woes. That I am starting this thread to post links to provide proof that capacitors are a waste of money.

link 1 BCAE

You will need to scroll down the right bar to #46 where capacitors are the topic covered but below is some verbage taken from the topic

"The dips in voltage are smaller. If the capacitor does its job, the added voltage (less voltage drop means higher voltage available to the amplifier) would give you more power output, especially with amps with unregulated power supplies. You probably noticed that I said 'supposed_to_do' earlier. This is because there has been some discussion as to whether a capacitor is a help or a hinderence when it comes to keeping the voltage at a higher level than without it. Of course, if you ask someone that's spent more than $100 on a capacitor if it helped, they'll tell you that it has. Why on earth would someone 'fess up' to wasting that much money on 'snake oil'. I've yet to see a capacitor make an audible difference."


Link 2:

Link 3

Link 4

I like link for the best, a person runs his system with four different power supply configurations:

1. No rear batteries, no capacitor
2. No Rear Battery, 1 Capacitor.
3. Both Batteries, No Capacitor
4. Both Batteries, 1 Capacitor

Then lists the SPL output and voltage drop that each configuration produced.


And with that I rest my case, people save your money, if voltage issues are your concern with your 3s, please look into:

1.) The biggest battery you can fit in the stock location
2.) Larger Alternator
3.) "Big 3" wire upgrade
4.) A grounding upgrade kit (like BigTyla's)

I normally would not recommend number four, but I have read on the forums how his kit and probably kit has improved the car's votages.

Alan, if you find this useful please sticky.

[CoreyB]

All a capacitor does is move a source of voltage closer to the amp. It will help with short draws of power but will not sustane a constant draw. If your system causes your headlights to dim when bass hits in your music a capacitor will help reduce this.

[DrGonzo]

A capacitor is another load on the overall electrical system. if the system itself is not stable to begin with than adding a capacitor will do nothing more than make the issue worse. You must be able to supply the necessary voltage to the system to begin with. A capacitor is used only to stabilize instances of sharp voltage drops. These sharp voltage drops are from the sharp bass hits and the amplifier not having an ample voltage regulator to compensate for it's power or the amplifier being pushed past it's design limits. A capacitor is not a battery. It does store a charge but when it discharges it has nothing left until it recharges. So if you have a cap, that first hit will get full power but than after that you have to wait till the cap recharges which could be as long as 120 mil seconds depending on the cap.

Lights dimming is due to voltage drops either from the primary power source or bad grounding. Installing a deep cycle battery is the first stage. Upgrading your wiring and grounds would be the second stage. The final stage would be installing a high output alternator. After that I would look into adding an additional deep cycle battery and voltage regulator to regulate the charge of the dual batteries and decrease the charge system load. If you have two batteries and no regulator you are putting a major strain on the charging system.

[CoreyB]

You are partialy correct IMO. A capacitor does in fact store a charge and will absorb sudden voltage drops. Most capacitors charge way faster than 120 secs more to the tune of miliseconds. Having your lights dim during a bass hit doesnt mean you have a problem with your charging system just that it wasnt designed to produce the sudden current draws of the amp. While adding batteries would be a better solution than capacitors, capacitors do help greatly.

From Wiki

Energy storageA capacitor can store electric energy when disconnected from its charging circuit, so it can be used like a temporary battery. Capacitors are commonly used in electronic devices to maintain power supply while batteries are being changed. (This prevents loss of information in volatile memory.)

Conventional capacitors provide less than 360 joules per kilogram of energy density, while capacitors using developing technologies could provide more than 2.52 kilojoules per kilogram.[22]

In car audio systems, large capacitors store energy for the amplifier to use on demand. Also for a flash tube a capacitor is used to hold the high voltage

[DrGonzo]

Oops I meant to say mil seconds. original post updated!

I did say that it does store a charge but not like that of a battery. It is a fast cycle discharge so it depletes then recharges in cycles. Depending on how fast the cap can cycle means how much additional readily available amperage you will have.

When I ran DB drag comps years ago we never used caps. It was all batteries, wires and massive alternators. In our Pro Class S-10 we were running 2 Ohio generators rated a 300amps 14.5v each, 4 optima yellow tops and 00awg wire throughout. This was feeding 3 US Amps 4000D's pumping out almost 9000 watts to 6 15" Cerwin Vega Strokers. We hit 171.3 DB, I think it was back in 2002. Remember now this was Pro Class. I have never seen a need for a cap and anyone running Pro audio would not be using them either.

[CoreyB]

Ahh I see. You are talking crazy audio. I am talking about you typical car with a 1000W amp and a couple 10s or 12s.

[DrGonzo]

LOL Yeah I used to be into the whole "Go Big or Go Home". Now I have 1 10" and a Memphis amp and thats it really.

But in the end the logic still applies. Someone running a 1000w+ amp should really look into getting a good deep cycle battery and maybe a Mechman alternator. if they are having consistent issues with power draw then the supplied voltage/amperage from the Alternator is not high enough and could cause issues with other various Sensors/computers/electronics beyond the headlight dimming issues.

[Black_Sunshine]

It really does depend on the system and amp draw. A decade ago when I had a small system running maybe 300W RMS, a 1 Farad cap kept the lights from dimming to the bass. This was on my sohc with a lower output alternator than the typical dohc alt as well. My little brother currently is running in the neighborhood of 400W w/ no cap and no issue with the lights. He also has HID's which requires much less current, so that is probably another reason why there's no problems. When I was running my 1000W setup, I had a 3 farad cap until I upgraded to a mechman and an additional battery. Like you guys have said, when it gets to 1000W+, caps just don't cut it.

[BigBoris]

After looking at the links, that test was done using the wrong size cap he was using a JBL A1201GTi rated at 1200WRMS with a peak 2400W and should have had at least a 2.5 Farad minimum, I would have recommended a 3 farad cap. Those test results are inconclusive do to the wrong size cap. Most people get a 1 Farad cap thinking its good enough but what they don't realize is that it won't help unless it's larger then what is needed. So where I am getting 2 amps pushing 1000Wats each I will be running one 4 to 6 farad cap. 6 Farad will be the best choice if you want it to stop diming. Now you might be saying it's over kill but then again the whole point is to stabilize the power and clean it up. Caps do two things, one being it cleans the power going to the amps to reduce noise and two stabilize the power to the amps. Another thing to keep in mind is that most amps don't regulate the power they draw so they may sometimes draw more power than needed. This is why I would say it's best to add at least 0.5 farads to the required size. Example: 1000W amp only needs 1 farad but to be more effective you should have at least a 1.5 farad cap.

Side note; RMS is usually half of the peak Watts. So 1000WRMS is roughly 2000W Peak.

I used to install car audio systems professionally and when you have more then one amp drawing more then 1500 watts you should use two caps one per amp. I have installed in a Chevy Tahoe on the stock alternator and two Optima batterys 6 rockford fosgate amps at 2500WATTS each pushing 6 JL Audio W-7, I had to use 3 10Farad rockford fosgate Caps to stabalize the power correctly. The lights didnt dim at all and in fact he came back around 8 months later to have a larger system installed in his Chevy Avalanche. This was in 2005/2006 so by now the caps have gotten better in quality.

[reallyxxxxxxloud]

All I can do is laugh at the BS in this thread!!!

WTF will a deep cycle do other than let you play for longer without destroying your battery... ? A deep cycle has a huge ESR over a Lead Acid battery. Maybe you guys should learn some basics before trying to teach some of these guys that are trying to learn!!! Upgrade to as big a lead acid as you can as its the fastest discharge battery there is until you go to thin cell technology like Kole or Batcap and lead acid is the cheaper option. You only want a deep cycle if you run the car stereo long periods of time without charge other than that why bother.

And then theres the CAP, caps have gotten better over the years but they are still a waste of time. Yes they will smoothen the supply but will also steal from the amps as they deplete. If you listen to slow bass beats you may be fine but hard fast hitting bass you will accomplish nothing as it will discharge and recharge while the bass is happening (basically it starves the amp on recharge). And any amp if playing music only plays 20% of its RMS rating, as its music (complex waves) not fn puretones!!!

If its dimming get a bigger battery and upgrade your wiring...

A cap to me is just a bandage... You might of covered up the school sore but it will always be there. Fix the system - fix the problem.

Alternators aren't really needed to be upgraded either if your system is just music listening, unless the alt is something below 110amp... Then maybe!!!