Capacitor Question?

[99gatorbird]

I think do the problem i am having with my voltage meter flickering my friends told me to buy a capacitor. I am running a 500w amp right now to one 12" sub. But i plan to run another amp for the interior speakers soon. Question being will a full farred capacitor be to much for my 500w right now(is there any harm done). I was told a half farred would be good for the 500w, but i assume i will need a full farred for the two amps total of about 1200w. Can i go ahead and purchase the full farred now, since i need a capacitor anyways? Thanks :eek:

[youngcamarokid]

Get a high output alternator instead of a large cap. The problem is the amps are drawing more current than the stock (i'm assuming) alternator can supply. A cap will just suck more current, and you might notice a small difference, but you will still be drawing too much current. Get a higher output alternator for ~$150 (i think...haven't price checked em in a LONG time). You can even install it yourself.

Oh yeah, almost forgot. In case you didn't know, the higher the capacity of the capacitor (in farads), the higher the ability to store electricity. The whole point is for the cap to charge during a time of low bass, and then discharge into the amp during a point of high bass, or high current draw (same thing).

If you still choose to get a capacitor instead of an alternator, the answer to your question is: Theoretically, the higher the capacitance, the better. There is no harm to an amp whatsoever by placing a capacitor in parallel to the power supply.

If you don't mind some rambling of electronics talk, read on to find out why the theory of capacitors is a scam:

Power supplies of amplifiers are called Switch Mode Power Supplies, or SMPS. These power supplies change the DC voltage of 12-14 from your car and turn them into a 12-14V AC signal by "chopping up" the input voltage at a very high frequency. This AC voltage is sent through a transformer to create a higher voltage. The rest of this high voltage is now chopped up and fed through various other components to create the correct DC voltage to the actual amplifier circuit.

So basically, no matter what fluctuation you have in your car's DC supply voltage, you will get the exact same voltage inside the amp, give or take a few mV, which is too insignificant a value to worry about.

My point is: beef up your alternator and reduce the risk of the rest of your electrical systems not function properly from low voltage, instead of spending the same amount of money on a big metal can that still creates the EXACT SAME load on the car's system. The capacitor will actually INCREASE the current load on your car's alternator and supply system, due to the fact that the cap has to get it's electricity to charge somewhere.

Hopefully I've enlightened more than a few people out there, despite my long post.

[ March 27, 2003: Message edited by: youngcamarokid ]</p>

[99gatorbird]

Is a 2 farad to much for me? ebay has some great prices.

[youngcamarokid]

Re-read my above edited post (much more in-depth)

[99gatorbird]

<blockquote>quote:</font><hr>Originally posted by youngcamarokid:
Re-read my above edited post (much more in-depth)<hr></blockquote>

Thanks man i think u have cleared everything up. appreciate your vast knowledge. anyone know any good sites for high output alt's?

[RSFireDog]

for more info on caps, refer to the technical archive. As far as where to get HO alts, try jegs.

[Takumi Fujiwara]

I disagree. I'd say a good capacitor is the answer to your needs. A higher output alternator is not. The Idea of a Cap- is that it stores voltage. A larger Alternater is basicly going to give u more parasidic ( or however thats spelled ) loss. As in its going to use the pulleys to pull harder on the engine to create more power- Which cant be used. Becasue you car has a 12 Volt battery in it which is where the power is really drawn. And the alternator only really takes over when the battery cant keep up. Ud think So get a bigger battery and alternator. well u can do that. If ur windows and regualr car works arent getting enough power. The reason being is that They are consistant power draws. Even notice that about ¼ to ½ second after u start rolling up ur windows the battery indicator raises back up a bit: thats because Theres a voltage regulator on your alternator and only jumps in when the battery can handlge the load, then it goes back to charging the battery.

The problem lies in the regulator and the charging of the battery. The regulator only jumps in when teh battery cant handle it. And if you watch the voltage it drops and raises when the bass hits on most cars. This is because ( for the most part ) the bass is not consistant, and the voltage regualtor isnt ready for teh power draw. give your power a test and get some Drum and Bass- or somethign with consistant Bass for long periods of time, you'll notice ur power doesnt drain as much as a song with spardic hard hits.

SO you get a Cap- because it stores energy when its not needed and supplies when it is. Id recommend the Cap because it meets the function of what is really needed to be done. What a new alternator is doing is keeping your Battery 100% charged ( or as much as it can, ) The right system can out draw any battery and alternator, so Caps are used to overcome this. Because They always have enough power in them to power ur amp and sub ( or component speakers if thats what ur amping ) And if they drop below usually 11 volts depeding on the cap it'll shut off ur amp till tis charged. which wont happen unless the cars off if u get a 1 farad cap ( works for most people ) I just say say, .5 farad 500 watt system, .2 is about a 250 ( I didnt even know ppl had 250watt amps let alone 500 =) ) and 1 farad for 1000 watt. and so on. up to 1000 farad or so =P Email me or IM me if u really want me to explain capacitors. I dont wanna over post.


O Edit : Id say only cap ur sub. Since ur speakers draw a more consistant power. but u can defintly do both, but u wont experience the same power kill as u are now with the sub.

[ March 27, 2003: Message edited by: Takumi Fujiwara ]</p>

[MTMike]

<blockquote>quote:</font><hr>Originally posted by Takumi Fujiwara:
I disagree. I'd say a good capacitor is the answer to your needs. A higher output alternator is not. The Idea of a Cap- is that it stores voltage. A larger Alternater is basicly going to give u more parasidic ( or however thats spelled ) loss. As in its going to use the pulleys to pull harder on the engine to create more power- Which cant be used. Becasue you car has a 12 Volt battery in it which is where the power is really drawn. And the alternator only really takes over when the battery cant keep up. Ud think So get a bigger battery and alternator. well u can do that. If ur windows and regualr car works arent getting enough power. The reason being is that They are consistant power draws. Even notice that about ¼ to ½ second after u start rolling up ur windows the battery indicator raises back up a bit: thats because Theres a voltage regulator on your alternator and only jumps in when the battery can handlge the load, then it goes back to charging the battery.

The problem lies in the regulator and the charging of the battery. The regulator only jumps in when teh battery cant handle it. And if you watch the voltage it drops and raises when the bass hits on most cars. This is because ( for the most part ) the bass is not consistant, and the voltage regualtor isnt ready for teh power draw. give your power a test and get some Drum and Bass- or somethign with consistant Bass for long periods of time, you'll notice ur power doesnt drain as much as a song with spardic hard hits.

SO you get a Cap- because it stores energy when its not needed and supplies when it is. Id recommend the Cap because it meets the function of what is really needed to be done. What a new alternator is doing is keeping your Battery 100% charged ( or as much as it can, ) The right system can out draw any battery and alternator, so Caps are used to overcome this. Because They always have enough power in them to power ur amp and sub ( or component speakers if thats what ur amping ) And if they drop below usually 11 volts depeding on the cap it'll shut off ur amp till tis charged. which wont happen unless the cars off if u get a 1 farad cap ( works for most people ) I just say say, .5 farad 500 watt system, .2 is about a 250 ( I didnt even know ppl had 250watt amps let alone 500 =) ) and 1 farad for 1000 watt. and so on. up to 1000 farad or so =P Email me or IM me if u really want me to explain capacitors. I dont wanna over post.


O Edit : Id say only cap ur sub. Since ur speakers draw a more consistant power. but u can defintly do both, but u wont experience the same power kill as u are now with the sub.

[ March 27, 2003: Message edited by: Takumi Fujiwara ]<hr></blockquote>

Think of electricity as a flow of water. Your alternator ultimately is the source. Your battery is your main supply of water, and a capacitor is like an in-line reservior.

If you're pulling more water out of the system than the source can produce, adding a reservior isn't going to solve the problem.

Increasing the rate of flow at the source, will.

Ultimately, an inscreased source flow AND a reservior will be best.

A high-output alternator and a cap is going to be your best plan. No matter how big of a reservior (cap) you put in, if you draw more out (amp/subs) than is put in by the source (alternator) you're still going to have the same problem, and your battery isn't going to charge.

The alternator (which is inappropriately named.... it should be called a generator) does put current into the electirical system too.. it doesn't just charget he battery. Disconnect it sometime and run your car and tell me how your voltmeter guage looks.

Another option would be a dual-battery setup in an auxilary battery configuration. My dad builds isolator/combiners for that exact purpose. You get a deep-cycle battery just for your stereo system and with the isolator/combiner your stereo isn't even on the same circuit as your other battery/main electrical system, but both batteries get charged simultaniously off the same alternator.

-Mike

[youngcamarokid]

<blockquote>quote:</font><hr>Originally posted by MTMike:


The alternator (which is inappropriately named.... it should be called a generator) does put current into the electirical system too..
Mike<hr></blockquote>

First of all, Mike, please recall that the alternator is separate from a generator. Before the times of alternators, generators were put in cars, and they created DC without it having to be rectified. They were obviously extremely inefficient, so they were replaced with alternators around mid-60's or so. The alternators are different in that they provide AC which has to be rectified to DC. No offense Mike, just clearing it up ;)

Mike, you are right. There is no point having a capacitor sucking up power that doesn't exist.

[MTMike]

<blockquote>quote:</font><hr>Originally posted by youngcamarokid:


First of all, Mike, please recall that the alternator is separate from a generator. Before the times of alternators, generators were put in cars, and they created DC without it having to be rectified. They were obviously extremely inefficient, so they were replaced with alternators around mid-60's or so. The alternators are different in that they provide AC which has to be rectified to DC. No offense Mike, just clearing it up ;)

Mike, you are right. There is no point having a capacitor sucking up power that doesn't exist.<hr></blockquote>

You are correct.... however, an Alternator creates Alternating Current. The current from the alternator is converted to DC by the rectifier diode circuit, which is built into the 'alternator' unit. So wouldn't the whole unit still be considered a generator because the net result was DC? [img]smile.gif[/img]

[RSFireDog]

<blockquote>quote:</font><hr>Originally posted by MTMike:


You are correct.... however, an Alternator creates Alternating Current. The current from the alternator is converted to DC by the rectifier diode circuit, which is built into the 'alternator' unit. So wouldn't the whole unit still be considered a generator because the net result was DC? [img]smile.gif[/img] <hr></blockquote>

The process of rectifying the AC current into DC current is handled inside the alternator by something more complex than a rectifying diode. A diode is a "solid state" device that allows current to flow in one direction only without any moving parts. It relies on the different electrical properties of the materials it is made of to act as a one-way valve for current. By arranging diodes so that current from each of the three stator wires is only allowed to pass in one direction, and by connecting the three outputs together, you get a very smooth and stable DC output without any moving parts. (This arrangement is typically manufactured as a single part and is referred to as the diode pack or diode trio.) This lack of moving parts makes the alternator not only very reliable - but also comparatively inexpensive to build and repair.

Also, the key different between an alternator and a generator is what spins and what is fixed. On a generator windings of wire (the armature) spin inside a fixed magnetic field. On an alternator, a magnetic field is spun inside of windings of wire called a stator to generate the electricity. This allows the wires to be directly and easily connected to their outputs without the need for sliding contacts to carry the relatively high output current. The magnetic field is still generated via electro magnets mounted on a rotor, and the relatively small field current that powers them is supplied to the rotor by two small brushes that each ride on a separate and continuous slip rings. These smooth slip rings (unlike the comparatively rough contacts on a commutator in a generator) and the fact that the relatively heavy windings are fixed instead of rotating allows the alternator to be spun to much higher speeds. This allows it to reach it's maximum output sooner and to be spun fast enough at engine idle speeds to produce enough electricity to power most (if not all) of the needs of the car without relying on the battery.

Not to sound all scientific on you mike ;)

[youngcamarokid]

<blockquote>quote:</font><hr>Originally posted by RSFireDog:


The process of rectifying the AC current into DC current is handled inside the alternator by something more complex than a rectifying diode. A diode is a "solid state" device that allows current to flow in one direction only without any moving parts. It relies on the different electrical properties of the materials it is made of to act as a one-way valve for current. By arranging diodes so that current from each of the three stator wires is only allowed to pass in one direction, and by connecting the three outputs together, you get a very smooth and stable DC output without any moving parts. (This arrangement is typically manufactured as a single part and is referred to as the diode pack or diode trio.) This lack of moving parts makes the alternator not only very reliable - but also comparatively inexpensive to build and repair.

<hr></blockquote>

Actually, this isn't entirely accurate.....

Running the AC signal through the diodes gives you a positive-only waveform. It's still an alternating current wave, but it's positive-only, as the diodes have limited the current to positive. This wave has twice the original frequency. It's then run through a regulator that creates the constant current feed from the positive only wave.

;)

[Takumi Fujiwara]

::yawn:: K, since we are going to pretend we are in a lame physics class- think of your alternator as a water damn 100 feet high and 100 miles deep full of water. And your a man standing at the bottom of it with a glass of water trying to just slightly open the damn 3 times a day for glasses of water. wow that sounds like fun. The alternator is the damn full of water, the damn is hard to open dificult to control. so waht you do is you get your house piped for city water as ur car does for its electrical, and you get the cute little water boy to supply ur house with a pureflow water despencer or something like it for drinking water. They are usually slow flowing, just think of it more like only drinkin in shot glasses thought. Omg, I dont even care. [img]graemlins/burnout.gif[/img] later.

[Christian]

DAMN!

[MTMike]

<blockquote>quote:</font><hr>Originally posted by Takumi Fujiwara:
::yawn:: K, since we are going to pretend we are in a lame physics class- think of your alternator as a water damn 100 feet high and 100 miles deep full of water. And your a man standing at the bottom of it with a glass of water trying to just slightly open the damn 3 times a day for glasses of water. wow that sounds like fun. The alternator is the damn full of water, the damn is hard to open dificult to control. so waht you do is you get your house piped for city water as ur car does for its electrical, and you get the cute little water boy to supply ur house with a pureflow water despencer or something like it for drinking water. They are usually slow flowing, just think of it more like only drinkin in shot glasses thought. Omg, I dont even care. [img]graemlins/burnout.gif[/img] later.<hr></blockquote>

WTF was that all about? LOL ;)

RSFireDogg..... I'm aware of all of that. My dad's an EE and I've worked along side him for numerous years. I was simplifying mine down when I posted because I didn't feel like typing all that you did. [img]smile.gif[/img]

Y'all are right though, technically the alternator is an alternator, but it has the rectificaton circuit built into it. The ultimate outcome is still DC generation.

-Mike