Wattage and Power System

[stipud]

But now, once again, do you disagree that a cap is a band-aid and that a HO alt is the real way to fix this? Again the cap and batter can fill up with any electrons if the alt doesn't supply it.

I don't think anyone disagrees with that, we're just squabbling over scemantics like we usually do

I will say though, that when playing music the average current draw of a stereo system isn't all that high. If you've got a modern car, you probably have a decent alternator with 125+ amps, so as long as you aren't running high beams, low beams, fog lights, defrosters, seat heaters, A/C, and your stereo at full volume, there's usually no need for an alt upgrade. Sometimes it's extremely expensive and a huge pain in the ass to install (like mine was). Sure though, if your alternator craps out and is already underpowered, then a new alternator is a good idea.

When I built my stereo I put in a 200 amp alt first (since it was broken), then an Optima bluetop, then 0 gauge big 3, then 2 gauge straight into my Ti500.4. Absolute overkill, I know. I still have a 1F cap waiting to go in.

[Pillow]

This is a great thread!

Stipud, what the hell are you running for that much draw!!! Overkill no doubt. You must be Steve Meade in disguise.

[ttocs]

i thought meade ran a couple of alts.

Yes, semantics arn't they fun? I too would agree that with only a 600 watt system that I would put in the amp and see what happens. You will know if you need more power from your system....

At what point would you say a HO alt IS needed? I know my octane needs one as it can drag the system down close to 12 v at night at high volumes, and I do like to jam at night. I think it was rated around 800 watts and I have no idea what the stock ranger alternator is rated at.

[stipud]

At what point would you say a HO alt IS needed? I know my octane needs one as it can drag the system down close to 12 v at night at high volumes, and I do like to jam at night. I think it was rated around 800 watts and I have no idea what the stock ranger alternator is rated at.

When to replace it depends on the user, their musical tastes, and willingness to live with voltage drops and their side effects, etc. For most people, even with kilowatt systems, they won't notice the voltage drop in any other way than headlight dimming. Losers... errr... I mean awesome people like us probably care more about the SQ being lost in the process, and would be more willing to upgrade.

[Eric D]

A lot of you will probably be shocked to read this...

I worked at a car audio shop (Sound Buggy) for five or so years. They were in business from mid 1980s until I think 2004. To my knowledge in that entire time they never installed a high output alternator. It does not mean it did not happen, just in my time I never saw it, and I never saw any photos in the old systems book, or heard any of my co-workers talk about it.

Now, you do have to define high powered system. Back then 500W was a lot, today not so. I had a modified MS1000TA for an installation in my vehicle. By today's standards that is probably not considered high power either. I never had any issues with head light dimming.

My neighbor had my Xenon X600.1 in his system and the headlights would dim so bad you could hardly see them. The difference was my system was adjusted for 0db of gain overlap. His was adjusted for pure square waves at full output.

His amp would actually shut off momentarily when a bass note hit hard then come back on. We put a 1 farad cap in there and the problem went away. The lights would still dim but the amp would not shut off any more. Now I realize this is just one example, but I just don't understand how anyone can argue that the cap did not help in this situation. No cap, and the amp shut off. 1 farad and the amp kept playing through the note.

This is the statement I am going to make and you guys can pick apart or help me refine...

"A capacitor will not reduce the performance of a car stereo system, and in some cases can improve the performance of a car audio system"

[Eric D]

Another point I would like to throw out is this. A lot of headlight dimming or power related problems may (keyword here is may) be solved by actually running a larger amplifier.

When an amp is driven very hard, something in the system is loosing efficiency. Now an amp should play a square wave just as well as a sine wave without affecting it. However, since the distance a speaker cone moves is based on voltage, a severely clipped signal may have a lot of acoustical power with low efficiency.

So a 200W amp for example playing beyond clipping and generating Xdb SPL, may be beaten by a much larger say 500W amp not clipping and playing up to that same Xdb SPL while actually drawing less current from the electrical system of the vehicle. This is really something which needs to be tested to prove, but I have always believed in the idea buying the largest possible amplifier you can afford is better than skimping.

[Eric D]

Thought of a good example... let's say you have a 500w amp playing a -0dB bass note for 1 second. For the sake of simplifying the argument, the amp is 50% efficient, so it requires 1000w to produce its rated power. 1000w at 14v is 1000/14=71.42 amps. This means to power the bass note for one second requires 71.42 coulombs of energy. If you were drawing only from a 1 farad capacitor (14 coulombs at 14v), with no external charge, it would be drained completely flat in 14/71.42 =0.196 seconds. Now this is assuming the amplifier would even run below 10v or so. If you assume that the amp turns off when the voltage sags below 10v, then you only have 4 coulombs of power available, which means it would be drained to 10v in 4/71.42 = 0.056 seconds.

So for powering an amp, a capacitor is utterly useless. But for filtering microscopic ripple in D/C there is nothing better.

Stipud, I think your math here is good, but I think there may be a bit more to the story. I know I don't have the math to fully explain this, but I am going to do my best to use what logic I have. I also notice you mention "no external charge" but that has to be considered. A cap is not a battery, that is for certain.

You have three sources for energy in your stereo, the alternator, the battery and the capacitor.

The alternator has a maximum quantity of current it can deliver, it is say 75A for a common one (maybe there are larger, I really don't keep up on it).

The battery is capable of the most current, maybe 1000A for a short period of time.

The cap is capable of very little storage, but delivers it nearly instantly.

When a bass note hits, the cap starts to drain before the battery, but the battery is still feeding it, and it is feeding it based on the size of the power wire and its own internal current limitations.

This is either a calculus problem or even a differential equation involving a formula for the current flow into the cap vs the current flow out of the cap. Now if an amp shuts down at say 10V of input voltage, the cap will delay the time for the voltage to drop to 10V vs without the cap. This delay is significant enough to keep the amp on in many cases.

A larger alternator will delay the drop from 14.4V down to 12.6V at the battery. So it will improve the chain as well.

A larger battery or more batteries might only help if the power wire is large enough, which generally is one of the biggest issues the person is starting with, too small a power wire.

I know you guys like to make the point a cap is great for filtering DC ripple, but I don't think a single car audio salesman would sell one based on that point. They probably would not even understand that point. They sell them as a Band-Aid to someone with other installation issues, and if the Band-Aid stops the bleeding, the customer is happy.

[Eric D]

Ok, I know I really need to just stop posting for a bit, but you guys have me really thinking about this.

I now have 200A of 13.8V DC in my basement. Why not test the cap theory?

Can all of us, cap haters and lovers alike come up with a test to prove this out? I would think so.

I can run an amp with a 16ft set of 8ga wires and see what it takes to make it shut down. Then add a cap and see if it helps. Then step up to 4ga and see if that helps.

I have a lot of different equipment to work with. I would think we could come up with a pretty scientific way to check this out.

I also have my 40A power supply which we could play with to represent a very weak electrical system (like in a small KIA or Ford Festiva for example)

[audiophyle_247]

There have been several scientifically approached tests done on Caps, quick google search will find plenty for ya.

Salesmen, as well as many other people, see the cap power terminals and think to themselves something along the lines of this..
"Hmmn, looks like a tiny battery, has terminals on it like a battery, it MUST be a battery!"

The Car battery is 12v, the Alternator is what puts out 14v. It has been established that a cap does not store energy like a battery, which is obvious because lights still dim after installing them. Until the voltage drops below 12v, the battery isnt really doing anything, so adding more batteries wont do much unless you are constantly dipping below 12v. The alt puts out only so many amps, and when you exceed that the voltage drops almost instantly. A cap will never fix that, and Stipuds math pretty clearly shows how minimal their effect is. The only thing you can do is upgrade the 14v source, which leaves you only one option.


I have installed quite a few HO Alts for customers, but most forgo the HO Alt because the steep price tag involved is harder to deal with than the occasional "dimming headlights". lol

[dBincognito]

It has been established that a cap does not store energy

When was that established ?



Work must be done by an external influence to move charge between the conductors in a capacitor. When the external influence is removed, the charge separation persists and energy is stored in the electric field. If charge is later allowed to return to its equilibrium position, the energy is released. The work done in establishing the electric field, and hence the amount of energy stored.

The current through a component in an electric circuit is defined as the rate of change of the charge q (t ) that has passed through it. Physical charges cannot pass through the dielectric layer of a capacitor, but rather build up in equal and opposite quantities on the electrodes : as each electron accumulates on the negative plate, one leaves the positive plate. Thus the accumulated charge on the electrodes is equal to the integral of the current, as well as being proportional to the voltage.

How do they not hold a charge ?

[Eric D]

You can not make the statement "A cap will never fix that", referring to voltage drop, when indeed it does reduce voltage drop. That is the whole point of it.

A cap will not necessarily end head light dimming, but if it reduces it and allows an amplifier to stay above the threshold where it shuts down, the cap has solved the problem.

I would guess 95% of the time people get into this argument not understanding what a cap is and how it works. If you don't know this, you cannot be in this argument. This goes for both sides. Plenty of people think caps are great but still don't know what they are doing and how they work.

[ttocs]

You have three sources for energy in your stereo, the alternator, the battery and the capacitor.
.

I disagree. You have one SOURCE for energy(the alt) you have two storage devices for it. Do not confuse the two. Again you can dig a lake, but unless the it rains, you can't fill it.

Now again, your solution for your neighbor would have had to be considered a big big band-aid. IF the amp is shutting off and the headlights are that dim then that car NEEDS a HO alt. Putting an additional storage device will help the amp, but the charging system is still over taxed even with the band-aid. What happens when you put a band-aid over a wound that needs stiches? You end up with a bunch of bloody band-aids and a really good scar.

I just follow one simple rule, do it right, do it once.

[ttocs]

Ok, I know I really need to just stop posting for a bit, but you guys have me really thinking about this.

I now have 200A of 13.8V DC in my basement. Why not test the cap theory?

Can all of us, cap haters and lovers alike come up with a test to prove this out? I would think so.

I can run an amp with a 16ft set of 8ga wires and see what it takes to make it shut down. Then add a cap and see if it helps. Then step up to 4ga and see if that helps.

I have a lot of different equipment to work with. I would think we could come up with a pretty scientific way to check this out.

I also have my 40A power supply which we could play with to represent a very weak electrical system (like in a small KIA or Ford Festiva for example)

If you are going to run a test, I want to to stress your power supply to its max, and then add your cap. Now I want you to keep that thing cranked for as long as it takes to find out how long it will take for your power supply to fail? If you are taxing it with or with out a cap, it will sooner or later fail. Now at that Point I would recomend taking that money you saved on not installing a cap, and buy yourself a power supply that can handle the load. At the point you installed a HO alt, a cap is really really not much to consider then. I have a 200A in my mustang and I am just waiting for my trucks to die to upgrade it.

[ttocs]

You can not make the statement "A cap will never fix that", referring to voltage drop, when indeed it does reduce voltage drop. That is the whole point of it.

A cap will not necessarily end head light dimming, but if it reduces it and allows an amplifier to stay above the threshold where it shuts down, the cap has solved the problem.

I would guess 95% of the time people get into this argument not understanding what a cap is and how it works. If you don't know this, you cannot be in this argument. This goes for both sides. Plenty of people think caps are great but still don't know what they are doing and how they work.

A cap MAY fix minor voltage dips, keep your music playing and MAY even improve SQ(I would love to see the study on that). IT will not help anything in the chargin system.

do it right, do it once and you will save your time and often because of that money too. How much time have you guys spend aquiriring a cap and the mounting stuff, finding a good location for it and the ground, and finally charging it only to find that there is still a bigger problem?

wow, I thought this wa over yesterday when I went to sleep .............

[stipud]

Stipud, I think your math here is good, but I think there may be a bit more to the story. I know I don't have the math to fully explain this, but I am going to do my best to use what logic I have. I also notice you mention "no external charge" but that has to be considered. A cap is not a battery, that is for certain.

That's exactly why I excluded the charging system, because the actual "in practice" equation is way too complex for discussion, even if we oversimplified it. That's why capacitors have fallen prey to a lot of pseudoscience, because their effects on dynamic music are not as easily demonstrated through scientific or mathematical terms.

I agree with you that a capacitor would delay the voltage drop, the question is "by how long?", and "how effectively?". I have demonstrated that a cap on its own is drained in a fraction of a second, but when you have an alternator and battery to support it, that time will definitely increase. Assuming the voltage drops were very brief, it may even be enough to bridge, or at least smooth out the edges of the gap. In your friend's case it was just enough to keep the amplifier going, which is an undeniable anecdote that the bandaid situation CAN work.

However, a farad capacitor does lose 1 volt for every coulomb it releases. In this case, you would only get 2 coulombs of power until hitting 12v, where the battery would take over. Because this is such a small amount of potential energy served by the capacitor, I would rather spend the money on upgrading the battery. A better battery can keep the voltage from sagging below 12v, which in my opinion is more important to an undercharged system than reducing 14v sag for a split second. With an upgraded battery, your voltage would drop to 12v quicker, but it would plateau there, while with an upgraded capacitor and a poor battery, you would drop from 14v less quickly, but could easily fall below 12v, causing more serious side effects.

So while I agree with your points about how capacitors can and do help, I think their price makes it a less convincing upgrade compared to things like wiring or the battery. So I agree with ttocs side of the argument as well. Using a capacitor can assist many setups, but there are also other things that one should consider upgrading first. But assuming you just had a capacitor lying around, I wouldn't hesitate to install it, even as a bandaid.

I am not sure if your bench test will illustrate the same issues that a car has, for example the A/C ripple may not be as big of a problem. Since you have an oscilloscope you might want to have a look at the D/C in your car, to see if we can illustrate the ripple filtering as well. To me this is the main purpose of a capacitor, and while it can be used to reduce voltage drop for a split second, that's not the ideal situation to use it in. For this purpose I would look at multifarad capacitors or batcaps, which are less effective at ripple filtering but more effective at storing power. However, before getting to that point I would prefer upgrading the rest of the system. Of course everyone's situation is different and there's never a sure answer to anything.

[VW337]

dammit, i like how i say that in the 3rd post...no one ever listens to Brian!

I saw but wanted to expand it a little.

[Eric D]

ttocs,

You are pretty much dead wrong here. You really need to do some research before trying to argue about this. You don't fully understand how these electrical devices are working. I am not trying to make this a personal attack, but it is becoming frustrating to argue with you when you don't understand a lot what myself and others are talking about.

Your reasoning is also pretty messed up that my neighbor needed a HO alternator to run a 600W amp. There are literally thousands of people out there who have even bigger amplifiers with factory alternators and they are getting by just fine.

Upgrading the alternator is the very last thing anyone should do. Not only are the alternators very expensive, but installing them is more involved and the risk of damaging something else is not worth the effort for the average person.

I take it you are an alternator salesman because you sure sound like one?

Stipud,

I think you and I are pretty much on the same page, but I feel the time a cap will "bridge or smooth out" the gap is longer than you do. And at this point there is not a really good way to prove either of us right.

I know one thing all of you may be missing the boat on is how much capacitance someone needs. I have not specified what I recommend, but you guys may be assuming some quantity which is probably very low. There are huge caps on the market, 250 farad or more, and the time they will fill in gaps is way more significant than you guys are considering.

[Phoenixcolt]

So....uhhhh....big 3 to start...right?

[ttocs]

UH, stipud said he agreed with me so I am not sure how you are on the same page as him and I am wrong .

I am not familiar with your car but my alts are both right on top of the motor. Undo the belt, two mounting bolts, the power wire and disconnect the regulator. Disconnect the ground of course but total time for me was 45 mins. Your right that it is more expensive but this is one of the cases where literally you have to pay to play. A 600w amp CAN deplete a stock alt depending on the brand of amp and the type of car requiring an alt. Doing the right thing is not normally the cheapest or the easiest route.

[Eric D]

UH, stipud said he agreed with me so I am not sure how you are on the same page as him and I am wrong .

I am not familiar with your car but my alts are both right on top of the motor. Undo the belt, two mounting bolts, the power wire and disconnect the regulator. Disconnect the ground of course but total time for me was 45 mins. Your right that it is more expensive but this is one of the cases where literally you have to pay to play. A 600w amp CAN deplete a stock alt depending on the brand of amp and the type of car requiring an alt. Doing the right thing is not normally the cheapest or the easiest route.

I guess you are actually right after all. Apparently those thousands of people out there with 1000W+ systems and factory alternators are just getting really lucky.

[ttocs]

not lucky, but it is a matter of time. stuff breaks when you run it hard.

[Eric D]

not lucky, but it is a matter of time. stuff breaks when you run it hard.

Who cares? Amps break if you run them hard. Decks break over time if you have a bass heavy system. Batteries fail. What is your point?

[ttocs]

not lucky, but it is a matter of time. stuff breaks when you run it hard.

Who cares? Amps break if you run them hard. Decks break over time if you have a bass heavy system. Batteries fail. What is your point?

That the cap prevents none of this, what is it good for other then the possible sq that most of probably can't hear after years of solid pg power?

And I hope I am not ruffling your or any others feathers, I learned from the coulumb lesson and find this interesting.

I also have too much time on my hands being disabled.............

[Jacampb2]

I've done this before, but I can't help myself.

Simply put, the textbook definition of a capacitor is a component that resists a change in voltage. How much change they can resist, depends on several factors, but they do resist change. This is why they work to smooth rectified DC. They charge during the high voltage periods and discharge during the low. Rectified DC always has pulses in it left over from the AC peaks. Capacitors help smooth it out by nearly instantaneously charging to the high peak and nearly instantaneously discharging during the low dips. With correctly sized smoothing capacitance, what you end up with is an average of the highs and lows after the caps. It does work, and that is why there are smoothing capacitors in nearly any rectified DC supply.

Here's the rub though. Every wire has voltage drop, you can minimize it, but every conductor known has resistance. The more current flow through said conductor, means more voltage drop. So, when the amp hits hard, there is voltage drop at the load end of the conductor, your battery and alternator may see significantly less voltage drop on their end, ESPECIALLY in the case of undersized power/ground wires. A capacitor at the load end of the line will try to do the same job it does in any other smoothing application, it will resist the change in voltage (the voltage drop) and help maintain and average somewhere between the high and low voltage peaks. This works perfectly well if the current draw does not exceed what the source is capable of supplying. If the source cannot maintain the current necessary, you will end up with a somewhat smoothed but still declining voltage at the load end of the line. This only will happen during very heavy loading, during normal program material, the cap should be able to do it's job quite nicely.

And the rest of what I have to yap about... When you rectify single phase AC, like that found in your average home, with no filtering (smoothing) caps, you end up with something closer to pulsed DC then true DC-- see the picture below.

A car alternator actually produced 3 phase AC. When 3 phase is rectified it produces a very close representation of true DC w/ no filtering. This is simply because 3 phase is 3 AC waveforms each 120° out of phase with the next, the resultant rectification means that most of the wave forms overlap and have very shallow peaks and valleys. The battery will do a decent job of filtering the remaining AC artifacts. It would be interesting to see on a scope. I would be willing to do it, but not until we have warmer weather again, I am not dragging my bench top scope out to the car in this crap!

Anyhow, I'm done. Take it as you like, I think if you take the time to research it, you will find the information is accurate.

Later,
Jason

[Eric D]

This one of many things a capacitor does.

The amount it fills in is based on a lot of variables, such as the power wire size, the capacitor size, and the current draw of the amplifiers.

It will never fill in the dip completely, that is impossible.

In case it does not make sense, the red line is the voltage at the amplifiers power input terminals. The dip is caused by a high energy portion of a music track.