Large Power Capacitors Good or Bad???

[PrecisionBoost]

I have to say that I think that large capacitors are important to having a nice clean power supply when installing a decent sized stereo.

There has been a number of discussions about whether they improve the electrical system or create an extra drain on the system.

I know Oz is on the "capacitors are bad" band wagon but I love to argue so lets get down to the details of how they are a waist of time and money.

Just to lay out the ground rules.... anything that looks remotely like an attack on another person will be immediately deleted from this post so everyone (including myself) should keep watch of what they say to one another.

[Efratech]

Ding Ding! Let's get it on! :lmao: :lmao:

(yeh im bored tonight)

[asam]

Well I don't know what to think, so let me show some test results from rockford fosgate......yea I know its kind of partial information.

http://www.rockfordfosgate.com/scripts/ ... MQ**&p_li=

[PrecisionBoost]

Ok.... here is my point of view..... a capacitor is just like a battery... it accepts a charge and it can release a charge.

If you push 1 amp of current into it and then discharge it at a rate of 1 amp it will charge and discharge at exactly the same rate.

A battery will act exactly the same way.

Batteries use a chemical process to charge/discharge

Capacitors store energy via electric fields.

Both batteries and capacitors will have an internal resistance so they will waist power during the charge and discharge cycles.

Batteries have a higher internal resistance and can't charge/discharge as fast as a capacitor

Capacitors are more efficent than batteries when it comes to power storage.

Batteries have the advantage of being able to store thousands of times more energy per square inch compared to capacitors.

When an amplifier hits a bass note the power comes first from the alternator, then the battery.

The dimming of the lights is the voltage of the alternator jumping from around 14.5V down to the nominal battery votage ( say 12.6V )

Alternators can't put out instantanious current, batteries can to a point.

So when a bass note hits it draws power from the alternator and then the battery fills in any extra current required.

Unfortunatly there must be a reasonable difference in voltage between the battery and alternator in order for the alternator to be able to push current into the battery efficently.

Capacitors on the other hand...... they can charge up to exactly the same voltage as the alternator.

This is one of the reasons they are better than batteries ( the other being an efficency issue)

Basicly what happens when you put a capacitor into the circuit is that the alternator charges it up to 14.4V..... and when a bass note hits both the capacitor and alternator put current into the amplifier.

The result is that the voltage drops less than it would in a system that does not have a capacitor.

So instead of going from 14.4V down to 12.6V and back up to 14.4V the capacitor system might go from 14.4V down to 13.5V and back up to 14.4V.

Imagine a system where you have your big battery at 12.6V, a small little battery at 14.4V and the alternator at 14.4V

When the alternator can't put out the "instant"current level the ampifier wants the small 14.4V battery helps out and send current into the amplifier.

When the bass note is finished the 14.4V battery will need to be recharged... which causes a small drain on the alternator.

If the 14.4V battery had not been there the voltage would have dropped to 12.6V and the large battery would have dished out the extra current.

And just like the small 14.4V battery the large 12.6V battery needs to be recharged.

So no matter what happens...... the alternator has to send current out to one of the components (it's a 12.6V battery, a small 14.4V battery or a capacitor.... it makes no difference)

A large capacitor is just like this small battery.... but since it does not use chemical power it is more efficent and wastes less power during each charge/discharge cycle.

So any way you cut it..... the power has to come from somewhere.... and the capacitor will waist less energy than a battery.

[PrecisionBoost]

Now.... on the flip side..... a system with a capacitor will allways draw more power from the alternator.

This is not because of inefficent internal resistance..... it's because the amplifiers are given more "instantanious " power.

Here is an example with a light bulb.....

Light bulb A is cycled between 14.4V and 12.6V on a contnuous basis

Light bulb B is cycled between 14.4V and 13.5V on a continuous basis.

Obviously light bulb B is going to use more power.... no if and's or but's about it.

Just like a light bulb.... if you have a bass note hit and the amplifier only has 12.6V to use it will put less power into the speaker.

Alternatively if the capacitor allows you to feed it 13.5V it will use more power..... but it gets put into the speaker.... making a stronger bass note.

So...... no matter which way you cut it the capacitor based power system will allways draw more power..... but all of this "extra" power is pushed into the audio system.

If you had about 100 farads of capacitance the voltage wouldn't drop below 14.3V..... the capacitors would be able to handle all of the amplifier power needs.

And again.... the amplifier would use about 20% more power and put 20% more power into the subwoofer speaker.

[asam]

If power capacitors didn't do anything then why would competition cars use them. Also why would they be sold by so many companies if they didnt do anything.

I'm using a 1-Farad cap and a optima yellow top. It has really curbed the voltage drop. When my cars hitting the hardest the voltage never drops below 13.4 at the cap.

[PrecisionBoost]

So it's a choice....

1) Use a large bank of capacitors and use more power.... but put 98% of that extra power into your subwoofer amplifier

2) Don't use a capacitor bank and your system will put out less total power when averaged over a period of time.

[PrecisionBoost]

When my cars hitting the hardest the voltage never drops below 13.4 at the cap.

You should try capturing the voltage at the amplifier input with a digital storage Oscilloscope ( measures the exact voltage about 20 million times a second)

Even with large capacitors you still see dramatic differences in voltage levels as bass notes hit.

It's unfortunate that capacitors can't store as much power as a battery.

If you put a 14.4V battery in there it would quickly discharge down to 13 to 13.5V due to the fact that there needs to be a differencial between output voltage and charging voltage.

In a lead acid battery the difference is about 1.2V (don't quote me on that.... I don't have my electrochemistry book handy)

So in order to have a "healthy" charging system the alternator must put out somewhere in the range of 1.2 to 1.5 volts more than the battery sits at when fully charged.

The only other device that is capable of storing charge is an inductor but they aren't as efficent as a capactor and they tend to leak power if they aren't charged/discharged at a regular rate.

[PrecisionBoost]

Next part of this topic......

Electronic systems like the ignition coil also use more power when a capacitor is installed..... but it also means that they put more of that power into the spark.... which results in more efficent burning of the fuel.

Imagine spark plug #1 firing off 14.4V and then all of a sudden spark plug #3 only has 12.6V to draw from (due to a large instantanious current draw of a subwoofer amplifier)

Spark #3 is going to put out 20% less power than spark #1

The ECU has power regulators to keep the voltage steady at 5V so large spikes in the power supply (due to stereo systems) won't affect them much.

Basicly the light bulbs and the ignition system are the only parts that will be affected by bass notes hitting.

[PrecisionBoost]

Just for the hell of it...... next time I get some time on the Dyno I will add a 1.5 farad capacitor right at the ignition module to see if any further power can be made.

Installing large gauge power wire all over the engine ensures that the voltages don't fluctuate from point to point...... so when all parts of the engine have exactly the same refference voltage levels the car gains power due to less "internal resistance" between different areas of the vehicle.

Capacitors would further extend this so that all "ripple" is removed from the power system.

The larger the capacitors the less "ripple" you will see if measured with an Oscilliscope (which shows the voltage on a video screen )

[andy11]

If caps don't work, then I guess we should start pulling them out of virtually every DC power supply made. (Hopefully someone understands where I'm going here...) If cap's weren't so damn expensive, you could virtually eliminate voltage fluctuation by wiring 3 or 4 large caps in parallel.

[AcingTeam]

Jerry!! Jerry!! Jerry!! Jerry!!

[TheGreatAndPowerfulOz]

Here is my half a cent.

"Capacitors are bad" when installed on an electrical system that is inadequately wired.
The majority of people (and an alarming amount of car stereo shops) will install a cap as a quick way to hide headlight dimming, yet do nothing to resolve the cause of the dimming, whcih is wiring that is too thin and an inefficient battery.

I will agree that for sound quality, IF and WHEN the electrical system has been upgraded, it will help even out the voltage drops that can cause the more power intensive portions of music to play at the levels at which they were intended. This is because the recharging of the cap is aided by the upgraded wiring.

Trying to run a stereo system that draws (for example) 2,000 watts RMS with stock, thin wiring under the hood and 10ga power cable from the battery to the amplifiers, WILL make the lights dim and greatly reduce the output of the entire stereo system, while stressing the voltage regulator in the alternator. Many people think that a cap is the answer and add one. When they see the lights not dimming as much, they think the cap fixed it.

Caps, when used improperly are detrimental to a system, but when used properly, can be helpful, even though it is only a slight amount which is to help even the voltage.


Erfinder, have you looked into a product called a BatCap? I have not researched them, but from what I have read on a forum, they are a combination of fast charge/discharge battery and capacitor.
A quick check on Yahoo found the link: http://www.batcap.net/index1.htm

Cliff

[kinkyllama]

Before i had my cap my amp sucked up so much energy sometimes my car wouldnt run.. then i installed a cap and its fine now.. but how much longer before my alternator has had enough?


I dont have the problem anymore cuz i had to take one of my subs out but one day i plan on putting a single sub equalr or greater power than the two i had.. but when i do that i plan on upgrading all the wires and all that junk

[PrecisionBoost]

Jerry!! Jerry!! Jerry!! Jerry!!

Who is Jerry??