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#1
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Capacitor, how to find out what size?
Im anticipating that I will need a capacitor with my current setup. I
havent finished the install yet but I think more power will be needed. How do you know what size cap to get? Is there a formula or something? Ive also heard that its possible to get too large a cap. Any truch to this? and or can a cap too big damage the amp(s) Thx |
#2
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Capacitor, how to find out what size?
"http://www.mobileaudio.com/rac-faq/rac-faq_2.html#SEC21"
-- Mark that was easy... wrote in message ... Im anticipating that I will need a capacitor with my current setup. I havent finished the install yet but I think more power will be needed. How do you know what size cap to get? Is there a formula or something? Ive also heard that its possible to get too large a cap. Any truch to this? and or can a cap too big damage the amp(s) Thx |
#4
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Capacitor, how to find out what size?
On Wed, 10 Mar 2004 21:04:16 -0500, thelizman
wrote: wrote: Im anticipating that I will need a capacitor with my current setup. You won't. I havent finished the install yet but I think more power will be needed. How do you know what size cap to get? Is there a formula or something? Many shops will tell you 1 fd / 1000 watts. Then they'll sell you one. The latter should cast suspicion on the former. Ive also heard that its possible to get too large a cap. Any truch to this? and or can a cap too big damage the amp(s) No. It won't. But it doesn't matter - you won't need a cap anyway. -- thelizman "I didn't steal the FAQ either" So what's your course of action when a customer complains about flickering or dimming headlamps/dash lights, but he's not having any battery charging problems? Do you tell him to "suck it up and live with it", or do you sell him a high-capacity alternator or lower-ESR battery that he doesn't really need? I don't believe capacitors will make your system "louder", "cleaner", or "hit harder", but I have seen small capacitors fix lighting problems when the charging system was otherwise adequate. Scott Gardner |
#5
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Capacitor, how to find out what size?
With the 100 bucks I would spend on a cap, I'd rather buy a new higher
power alternator. Just my 2 cents. ....which may or may not be more effective in the light dimming department than the cap. |
#6
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Capacitor, how to find out what size?
"Scott Gardner" wrote in message ... On Wed, 10 Mar 2004 21:04:16 -0500, thelizman wrote: wrote: Im anticipating that I will need a capacitor with my current setup. You won't. I havent finished the install yet but I think more power will be needed. How do you know what size cap to get? Is there a formula or something? Many shops will tell you 1 fd / 1000 watts. Then they'll sell you one. The latter should cast suspicion on the former. Ive also heard that its possible to get too large a cap. Any truch to this? and or can a cap too big damage the amp(s) No. It won't. But it doesn't matter - you won't need a cap anyway. -- thelizman "I didn't steal the FAQ either" So what's your course of action when a customer complains about flickering or dimming headlamps/dash lights, but he's not having any battery charging problems? Do you tell him to "suck it up and live with it", or do you sell him a high-capacity alternator or lower-ESR battery that he doesn't really need? I don't believe capacitors will make your system "louder", "cleaner", or "hit harder", but I have seen small capacitors fix lighting problems when the charging system was otherwise adequate. Scott Gardner With the 100 bucks I would spend on a cap, I'd rather buy a new higher power alternator. Just my 2 cents. --Viktor |
#7
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Capacitor, how to find out what size?
MZ wrote:
With the 100 bucks I would spend on a cap, I'd rather buy a new higher power alternator. Just my 2 cents. ...which may or may not be more effective in the light dimming department than the cap. Agreed. I thought I would need a cap for my system but ended up being able to get a new alt and double the amperage for less than the 'reccomended' size cap i would 'have' to buy. EFFENDI |
#8
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Capacitor, how to find out what size?
On Thu, 11 Mar 2004 09:21:24 GMT, EFFENDI
wrote: MZ wrote: With the 100 bucks I would spend on a cap, I'd rather buy a new higher power alternator. Just my 2 cents. ...which may or may not be more effective in the light dimming department than the cap. Agreed. I thought I would need a cap for my system but ended up being able to get a new alt and double the amperage for less than the 'reccomended' size cap i would 'have' to buy. EFFENDI I guess a lot of it depends on your car, too. For my car, $100 won't even buy a stock-replacement 60A alternator. $120 will get you an 85A aftermarket replacement, but that's as high as it goes unless you get into custom brackets and the like. Scott Gardner |
#9
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Capacitor, how to find out what size?
I would tend to agree that the 100 bucks or so would be better spent on
upgrading the alternator, however, in my case, GM didnt spare an inch cramming the LS1 into the firhawks engine compartment. There literaly is no room for a larger alternator. |
#10
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Capacitor, how to find out what size?
...which may or may not be more effective in the light dimming
department than the cap. Agreed. I thought I would need a cap for my system but ended up being able to get a new alt and double the amperage for less than the 'reccomended' size cap i would 'have' to buy. That's not really the point I was making. I was suggesting that in some cases a cap is actually more effective. High output alternators often suffer from the same limitations that a stock alternator suffers from when idling. |
#11
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Capacitor, how to find out what size?
Where do you shop, $100 for a higher power alternator?
With the 100 bucks I would spend on a cap, I'd rather buy a new higher power alternator. Just my 2 cents. --Viktor |
#12
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Capacitor, how to find out what size?
What makes you think that you need a larger alternator in size for more output? The case size does not need to change. In article , " wrote: I would tend to agree that the 100 bucks or so would be better spent on upgrading the alternator, however, in my case, GM didnt spare an inch cramming the LS1 into the firhawks engine compartment. There literaly is no room for a larger alternator. |
#13
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Capacitor, how to find out what size?
Yup.
That's not really the point I was making. I was suggesting that in some cases a cap is actually more effective. High output alternators often suffer from the same limitations that a stock alternator suffers from when idling. |
#14
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Capacitor, how to find out what size?
That all depends on what was meant as "higher power". I know I can get
either a new slightly more powerful alternator or get my current alternator rewound to a higher rating (say about 95 amp or 100 amp) for around $100 for my Contour. It may not be a 200+ amp alt, but it'd be "higher power" than my stock 80-85 amp. Brandonb Captain Howdy wrote: Where do you shop, $100 for a higher power alternator? With the 100 bucks I would spend on a cap, I'd rather buy a new higher power alternator. Just my 2 cents. --Viktor |
#15
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Capacitor, how to find out what size?
That's not really the point I was making. I was suggesting that in some
cases a cap is actually more effective. High output alternators often suffer from the same limitations that a stock alternator suffers from when idling. MZ, at the same RPM a higher power alternator will produce more current than a lower power alternator. Not always! In fact, some produce less current than the stock at idle. If you have enough power coming from the alternator there will be less problems with lights dimming since the alternator will be producing enough current to power both your system and lights at same time. That's right. But sometimes (certainly not always) a capacitor will contribute more towards reducing dimming than an alt. It depends entirely on how bad off your electrical system is in relation to the power demands of the vehicle, as well as the type of music and listening habits of the user. Most of the time you need more power only for the bass. The tweeters and midranges dont need as much power. If you have xover's then the subs and tweeters for example won't be running at the same time, so it's safe to assume that you can get alternator to cover your subs and other accessories. If you don't have xover's then you have to get alternator that will cover all speakers running at the same time (e.g. tweeters+midranges). I'm not following this paragraph. The alternator (and capacitor) affects all aspects of the electrical system. Of course, if all you have is a 100 dollar bill, spend it on cap. It won't give you more power, it will cover the surge power needed for bass. It can deliver a sufficient amount of current in a short enough period of time to have a noticeable effect on headlight dimming at all rpms. And MZ, please tell both sides of story when making a point. It's easier to understand why they should or shouldn't choose one over other (new alt/cap, etc.) I believe I have told both sides of the story. Check the FAQ. |
#16
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Capacitor, how to find out what size?
Scott Gardner wrote:
So what's your course of action when a customer complains about flickering or dimming headlamps/dash lights, but he's not having any battery charging problems? Bull****. If their stock electrical system can't supply the current to keep lights from dimming, then they are having charging problems. They need to upgrade their ground paths (hint: that stock 10 gauge to the fender isn't helpting), sometimes the alternator, but the last thing you should think about adding to an otherwise healthy electrical system is a cap. Caps really only become necessary on large multi-amp systems. Do you tell him to "suck it up and live with it", or do you sell him a high-capacity alternator or lower-ESR battery that he doesn't really need? There's the keyword: "sell". There's more money to be made selling people caps and batteries than a few feet of heavy gauge wire. -- thelizman "I didn't steal the FAQ either" Before you ask a question, check the FAQs for this newsgroup at http://www.mobileaudio.com/rac-faq. It contains over a decade and a half of knowledge. teamROCS Car Audio Forums http://www.teamrocs.com/caraudio/ teamROCS Car Audio News http://www.teamrocs.com/news/ "It's about the music, stupid" This post is Copyright (C) 2004. Reproduction of its content anywhere other than usenet without the express written permission of the author is forbidden. |
#17
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Capacitor, how to find out what size?
wrote:
I would tend to agree that the 100 bucks or so would be better spent on upgrading the alternator, however, in my case, GM didnt spare an inch cramming the LS1 into the firhawks engine compartment. There literaly is no room for a larger alternator. Please quote the text of the message to which you are replying when responding to a message here. -- thelizman "I didn't steal the FAQ either" Before you ask a question, check the FAQs for this newsgroup at http://www.mobileaudio.com/rac-faq. It contains over a decade and a half of knowledge. teamROCS Car Audio Forums http://www.teamrocs.com/caraudio/ teamROCS Car Audio News http://www.teamrocs.com/news/ "It's about the music, stupid" This post is Copyright (C) 2004. Reproduction of its content anywhere other than usenet without the express written permission of the author is forbidden. |
#18
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Capacitor, how to find out what size?
"Captain Howdy" wrote in message news Where do you shop, $100 for a higher power alternator? With the 100 bucks I would spend on a cap, I'd rather buy a new higher power alternator. Just my 2 cents. --Viktor What I meant was spend those $100 toward a new alternator. I never said you'll find an alternator for $100. That won't even buy you stock one, even rebuilt stock for most vehicles. --Viktor |
#19
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Capacitor, how to find out what size?
"MZ" wrote in message news ...which may or may not be more effective in the light dimming department than the cap. Agreed. I thought I would need a cap for my system but ended up being able to get a new alt and double the amperage for less than the 'reccomended' size cap i would 'have' to buy. That's not really the point I was making. I was suggesting that in some cases a cap is actually more effective. High output alternators often suffer from the same limitations that a stock alternator suffers from when idling. MZ, at the same RPM a higher power alternator will produce more current than a lower power alternator. If you have enough power coming from the alternator there will be less problems with lights dimming since the alternator will be producing enough current to power both your system and lights at same time. Most of the time you need more power only for the bass. The tweeters and midranges dont need as much power. If you have xover's then the subs and tweeters for example won't be running at the same time, so it's safe to assume that you can get alternator to cover your subs and other accessories. If you don't have xover's then you have to get alternator that will cover all speakers running at the same time (e.g. tweeters+midranges). Of course, if all you have is a 100 dollar bill, spend it on cap. It won't give you more power, it will cover the surge power needed for bass. And MZ, please tell both sides of story when making a point. It's easier to understand why they should or shouldn't choose one over other (new alt/cap, etc.) --Viktor |
#20
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Capacitor, how to find out what size?
On Thu, 11 Mar 2004 22:55:30 -0500, thelizman
wrote: Scott Gardner wrote: So what's your course of action when a customer complains about flickering or dimming headlamps/dash lights, but he's not having any battery charging problems? Bull****. If their stock electrical system can't supply the current to keep lights from dimming, then they are having charging problems. I disagree. Alternators only need to be able to keep up with the *average* current demands of the car's electrical system, and as you've pointed out in another thread, average current draw can often be surprisingly low. If you can drive around all day with the headlamps on and the stereo cranked up without draining your battery, then the alternator is obviously keeping up with the average current demand, even if you get some flickering of the dash lights or headlamps during short periods of peak demand. Rather than replacing the alternator with a higher-capacity model, one or more small, well-placed capacitors can stop the dimming problem. However, I think we both agree that the sound quality/SPL level won't be affected. I think that upgraded alternators are often recommended when they're not needed, although I agree that capacitors are needlessly installed MUCH more often. Scott Gardner |
#21
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Capacitor, how to find out what size?
Scott Gardner wrote:
So what's your course of action when a customer complains about flickering or dimming headlamps/dash lights, but he's not having any battery charging problems? Do you tell him to "suck it up and live with it", or do you sell him a high-capacity alternator or lower-ESR battery that he doesn't really need? The dealer would of course try to sell a cap but for the rest of the world, understanding that a small light flickering is a non-issue and move on seem like the sensible choice to do. My 0.02 -- Eric (Dero) Desrochers Hiroshima 45, Tchernobyl 86, Windows 95 |
#22
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Capacitor, how to find out what size?
"electricked" no_emails_please wrote in message
... "Scott Gardner" wrote in message ... On Wed, 10 Mar 2004 21:04:16 -0500, thelizman wrote: Scott Gardner With the 100 bucks I would spend on a cap, I'd rather buy a new higher power alternator. Just my 2 cents. --Viktor I dont' know of a higher power alt you can get for $100 unless you get the factory upgraded amp. unless a lower ESR batt. is in the plans a cap is very cost effective. |
#23
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Capacitor, how to find out what size?
"electricked" no_emails_please wrote in message
... "Captain Howdy" wrote in message news Just my 2 cents. --Viktor What I meant was spend those $100 toward a new alternator. I never said you'll find an alternator for $100. That won't even buy you stock one, even rebuilt stock for most vehicles. --Viktor slight problem, you still need the power at idle where the lights usually dim. for some aftermarket alts. they actually put out less power at idle which will make the problem worse not better. |
#24
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Capacitor, how to find out what size?
Eric Desrochers wrote:
The dealer would of course try to sell a cap but for the rest of the world, understanding that a small light flickering is a non-issue and move on seem like the sensible choice to do. My 0.02 Here's some change: That light flickering is a symptom of unstable voltage. Ripples in voltage can damage digital electronics, cause malfunctions, and other problems. Ignoring this is not a sensible thing at all. -- thelizman "I didn't steal the FAQ either" Before you ask a question, check the FAQs for this newsgroup at http://www.mobileaudio.com/rac-faq. It contains over a decade and a half of knowledge. teamROCS Car Audio Forums http://www.teamrocs.com/caraudio/ teamROCS Car Audio News http://www.teamrocs.com/news/ "It's about the music, stupid" This post is Copyright (C) 2004. Reproduction of its content anywhere other than usenet without the express written permission of the author is forbidden. |
#25
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Capacitor, how to find out what size?
Tha Ghee wrote:
slight problem, you still need the power at idle where the lights usually dim. for some aftermarket alts. they actually put out less power at idle which will make the problem worse not better. That's why cars have batteries. If you have flicker at idle, it's because your power and ground wires at the battery and alternator are insufficient are insufficient. -- thelizman "I didn't steal the FAQ either" Before you ask a question, check the FAQs for this newsgroup at http://www.mobileaudio.com/rac-faq. It contains over a decade and a half of knowledge. teamROCS Car Audio Forums http://www.teamrocs.com/caraudio/ teamROCS Car Audio News http://www.teamrocs.com/news/ "It's about the music, stupid" This post is Copyright (C) 2004. Reproduction of its content anywhere other than usenet without the express written permission of the author is forbidden. |
#26
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Capacitor, how to find out what size?
thelizman wrote:
Eric Desrochers wrote: The dealer would of course try to sell a cap but for the rest of the world, understanding that a small light flickering is a non-issue and move on seem like the sensible choice to do. My 0.02 Here's some change: That light flickering is a symptom of unstable voltage. Ripples in voltage can damage digital electronics, cause malfunctions, and other problems. Ignoring this is not a sensible thing at all. From my Alpine CDA-9815 HU user manual : Nominal voltage : 14.4 (11-16 volts permissible) Looks like they can take quite a variation after all! Sensible circuits should have filtred and regulated power supplies and I bet it's the case in quality equipment. -- Eric (Dero) Desrochers Hiroshima 45, Tchernobyl 86, Windows 95 |
#27
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Capacitor, how to find out what size?
slight problem, you still need the power at idle where the lights
usually dim. for some aftermarket alts. they actually put out less power at idle which will make the problem worse not better. That's why cars have batteries. If you have flicker at idle, it's because your power and ground wires at the battery and alternator are insufficient are insufficient. At idle, your alternator is still producing ~14v. So a 1.5 volt drop down to battery voltage can still produce a noticable dimming effect. Most alts deliver relatively little current at idle, so it's often not difficult to get that 1.5v drop. Depending on the severity of the situation, a cap can often alleviate the dimming effect rather substantially. The power and ground wires at the battery and alt, as well as the general "health" of the battery and alt should always be checked out first though. |
#28
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Capacitor, how to find out what size?
Here's some change: That light flickering is a symptom of unstable
voltage. Ripples in voltage can damage digital electronics, cause malfunctions, and other problems. Ignoring this is not a sensible thing at all. The fluctuation every time you start your car is more severe than the dimming associated with the audio system. Hell, Eddie Runner calls the dimming a feature... |
#29
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Capacitor, how to find out what size?
Eric Desrochers wrote:
From my Alpine CDA-9815 HU user manual : Nominal voltage : 14.4 (11-16 volts permissible) "Permissible". The word "permissible" in no way negates the fact that some malfunction may occur. If you're so include, put a voltage regulator on your headunits ground path, and limit it to 11 volts. Call me when you learn better. And how do you go from a cars ECM to your Alpine headunit? Are you familiar with the term "non sequiter"? -- thelizman "I didn't steal the FAQ either" Before you ask a question, check the FAQs for this newsgroup at http://www.mobileaudio.com/rac-faq. It contains over a decade and a half of knowledge. teamROCS Car Audio Forums http://www.teamrocs.com/caraudio/ teamROCS Car Audio News http://www.teamrocs.com/news/ "It's about the music, stupid" This post is Copyright (C) 2004. Reproduction of its content anywhere other than usenet without the express written permission of the author is forbidden. |
#30
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Capacitor, how to find out what size?
MZ wrote:
The fluctuation every time you start your car is more severe than the dimming associated with the audio system. Sorry Mark, but no. When starting, ECMs operate in open loop mode, which requires very little current and voltage. -- thelizman "I didn't steal the FAQ either" Before you ask a question, check the FAQs for this newsgroup at http://www.mobileaudio.com/rac-faq. It contains over a decade and a half of knowledge. teamROCS Car Audio Forums http://www.teamrocs.com/caraudio/ teamROCS Car Audio News http://www.teamrocs.com/news/ "It's about the music, stupid" This post is Copyright (C) 2004. Reproduction of its content anywhere other than usenet without the express written permission of the author is forbidden. |
#31
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Capacitor, how to find out what size?
thelizman wrote:
Eric Desrochers wrote: From my Alpine CDA-9815 HU user manual : Nominal voltage : 14.4 (11-16 volts permissible) "Permissible". The word "permissible" in no way negates the fact that some malfunction may occur. If you're so include, put a voltage regulator on your headunits ground path, and limit it to 11 volts. Don't have to, there's one inside the deck. Call me when you learn better. OK. And how do you go from a cars ECM to your Alpine headunit? The only ECMs I know of are those my sat TV provider send to diseable hacked receivers. Are you familiar with the term "non sequiter"? I'm affraid I'm not. Must be a language barrier thing. Regards, -- Eric (Dero) Desrochers Hiroshima 45, Tchernobyl 86, Windows 95 |
#32
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Capacitor, how to find out what size?
"thelizman" wrote in message
... Tha Ghee wrote: slight problem, you still need the power at idle where the lights usually dim. for some aftermarket alts. they actually put out less power at idle which will make the problem worse not better. That's why cars have batteries. If you have flicker at idle, it's because your power and ground wires at the battery and alternator are insufficient are insufficient. -- thelizman "I didn't steal the FAQ either" Before you ask a question, check the FAQs for this newsgroup at http://www.mobileaudio.com/rac-faq. It contains over a decade and a half of knowledge. teamROCS Car Audio Forums http://www.teamrocs.com/caraudio/ teamROCS Car Audio News http://www.teamrocs.com/news/ "It's about the music, stupid" This post is Copyright (C) 2004. Reproduction of its content anywhere other than usenet without the express written permission of the author is forbidden. if your batt. is weak which most times it is, it doesn't matter, what the alt or wires are like. if your going with a aftermarket alt. it may not work any better. |
#33
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Capacitor, how to find out what size?
"thelizman" wrote in message
... Eric Desrochers wrote: The dealer would of course try to sell a cap but for the rest of the world, understanding that a small light flickering is a non-issue and move on seem like the sensible choice to do. My 0.02 Here's some change: That light flickering is a symptom of unstable voltage. Ripples in voltage can damage digital electronics, cause malfunctions, and other problems. Ignoring this is not a sensible thing at all. -- thelizman "I didn't steal the FAQ either" Before you ask a question, check the FAQs for this newsgroup at http://www.mobileaudio.com/rac-faq. It contains over a decade and a half of knowledge. teamROCS Car Audio Forums http://www.teamrocs.com/caraudio/ teamROCS Car Audio News http://www.teamrocs.com/news/ "It's about the music, stupid" This post is Copyright (C) 2004. Reproduction of its content anywhere other than usenet without the express written permission of the author is forbidden. how can there be ripples in DC voltage?? |
#34
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Capacitor, how to find out what size?
"thelizman" wrote in message
... MZ wrote: The fluctuation every time you start your car is more severe than the dimming associated with the audio system. Sorry Mark, but no. When starting, ECMs operate in open loop mode, which requires very little current and voltage. -- thelizman "I didn't steal the FAQ either" Before you ask a question, check the FAQs for this newsgroup at http://www.mobileaudio.com/rac-faq. It contains over a decade and a half of knowledge. teamROCS Car Audio Forums http://www.teamrocs.com/caraudio/ teamROCS Car Audio News http://www.teamrocs.com/news/ "It's about the music, stupid" This post is Copyright (C) 2004. Reproduction of its content anywhere other than usenet without the express written permission of the author is forbidden. no Mark is correct here, the fluctuation is greatest at startup of the car and audio system. this is why most things break when you turn them off, like light bulbs. |
#35
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Capacitor, how to find out what size?
how can there be ripples in DC voltage??
Because there's an AC component that derives from the alternator or transient current draws. |
#36
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Capacitor, how to find out what size?
Tha Ghee wrote:
if your batt. is weak which most times it is, You're average car battery can put out more power than half a dozen alternators. -- thelizman "I didn't steal the FAQ either" Before you ask a question, check the FAQs for this newsgroup at http://www.mobileaudio.com/rac-faq. It contains over a decade and a half of knowledge. teamROCS Car Audio Forums http://www.teamrocs.com/caraudio/ teamROCS Car Audio News http://www.teamrocs.com/news/ "It's about the music, stupid" This post is Copyright (C) 2004. Reproduction of its content anywhere other than usenet without the express written permission of the author is forbidden. |
#37
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Capacitor, how to find out what size?
Tha Ghee wrote:
how can there be ripples in DC voltage?? ....proof that there is such a thing as a "stupid question". -- thelizman "I didn't steal the FAQ either" Before you ask a question, check the FAQs for this newsgroup at http://www.mobileaudio.com/rac-faq. It contains over a decade and a half of knowledge. teamROCS Car Audio Forums http://www.teamrocs.com/caraudio/ teamROCS Car Audio News http://www.teamrocs.com/news/ "It's about the music, stupid" This post is Copyright (C) 2004. Reproduction of its content anywhere other than usenet without the express written permission of the author is forbidden. |
#38
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Capacitor, how to find out what size?
Tha Ghee wrote:
no Mark is correct here, the fluctuation is greatest at startup of the car and audio system. You don't read engrish very well do you? this is why most things break when you turn them off, like light bulbs. Light bulbs break when you turn them on. They break because over time the filament loses mass as it is vapor deposited on the cool surface of the inside of the bulb. When enough material vaporizes, the filament can no longer handle the current passing through it. -- thelizman "I didn't steal the FAQ either" Before you ask a question, check the FAQs for this newsgroup at http://www.mobileaudio.com/rac-faq. It contains over a decade and a half of knowledge. teamROCS Car Audio Forums http://www.teamrocs.com/caraudio/ teamROCS Car Audio News http://www.teamrocs.com/news/ "It's about the music, stupid" This post is Copyright (C) 2004. Reproduction of its content anywhere other than usenet without the express written permission of the author is forbidden. |
#39
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CAFacitor Myths (was " Capacitor, how to find out what size?")
geolemon wrote:
ONLY if the -average- current draw exceeds your alternator's capabilities do you have a -charging- problem... That's oversimplified - and wrong. If the cables are corroded, the biggest alternator in the world won't charge. If the connections are corroded, the same. The alternator can supply the needs of a stock electrical system and not give a hint of a charging problem. Its when multi-amp systems go in that the deficiencies are borne out. Even smallish amplifiers can yield peak current demands which will exceed even a large alternator's supply capabilities... "Peak" does not equal "average". Even a large amplifier - on average - doesn't drain more than a couple of amps of current, and transients "peaks" only last a fraction of a second. These peak current draws are buffered by the amplifiers internal capacitor banks, and recharge demand is handled by the cars battery, because alternators simply don't react fast enough. And when that happens, the voltage drops to the 12v level of the battery so that it can kick in the few extra amperes that the alternator can't for those brief moments in time... That's wrong, way wrong. Voltage plays no role in which componant supplies current. The battery and alternator always share the total load of the cars electrical system. When current demands exceed that of the alternators output capability, the battery (which has many times the reserve of any alternator) shoulders a greater share of the load. Voltage doesn't make any difference - the voltage doesn't even need to drop for this to occur. Your light bulbs dim simply because light bulbs are brighter on 14.4v than they are on 12v... that's not a sign of a charging problem. Again, you ignore current. I'd like to see you light a household light bulb with 10 AA batteries, and see how bright it gets. The dimming is because of a lack of current. The dropoff in voltage is a symptom, not a cause. The capacitor smooths the transition from alternator to battery, There is no "transition". quite dramatically even.. the results can be seen in greatly reduced headlight dimming, as there's a nice [relatively] slow transition down to 12v now, rather than a temporary, sudden slam to even below 12v every time there is a large transient peak. This may come as a newsflash, but there are capacitors built into amplifier power supplies, and generally they supply sufficient charge for normal operation. Also, there is a lag time for caps too, and it is a function of the load across the capacitors terminals. That is why manufacturers recommend you locate the caps closest to the amps. The amount of charge stored in a capacitor is huge. There's a reason the directions advise you to charge the cap through a resistor with the engine running. You're not going to drain a 1 or 1/2 farad cap so that it can't deliver at least 12 volts with a car audio system. Another downside on an alternator (besides the high expense, possibility of it being largely ineffective without setting your idle speed north of 2000RPM, There's no need to idle up. A quality alternator is rated for output at idle. Otherwise, you can just slap a larger pulley on the alternator. and installation considerations that have been mentioned) is the fact that a bigger alternator is a bigger drag on your engine... and it's a bigger drag all the time, not just when you need it. Wrong. An alternator only requires more torque when the demand placed on it increases. A larger alternator is more difficult to spin, inherently. Bigger rotor, larger magnetic forces... they can really impact your car's performance, robbing horsepower. Most aftermarket alternators are no larger in size than their stock componants. The difference is in the number of turns in the coil, and the increase in mass of the windings in negligable. This is anywhere from "noticable" to "really bad", depending on what kind of car you have... with most cars nowadays, you can feel a HP loss just from switching on your air conditioning... I wouldn't want that kind of loss on a permanent basis, much less one that was even potentially worse... Hope you never turn your air conditioner on. Particularly when you consider that no matter how large of an alternator I am able to buy, I'll likely still be able to produce a transient burst large enough to temporarily exceed the amperage of the alternator. Which is what the battery is for. And even then, that transient burst won't matter much in the grand scheme of things... Then why are you telling this guy to buy a cap? You are full of information. MIS information. -- thelizman "I didn't steal the FAQ either" Before you ask a question, check the FAQs for this newsgroup at http://www.mobileaudio.com/rac-faq. It contains over a decade and a half of knowledge. teamROCS Car Audio Forums http://www.teamrocs.com/caraudio/ teamROCS Car Audio News http://www.teamrocs.com/news/ "It's about the music, stupid" This post is Copyright (C) 2004. Reproduction of its content anywhere other than usenet without the express written permission of the author is forbidden. |
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Capacitor, how to find out what size?
thelizman wrote:
*Scott Gardner wrote: So what's your course of action when a customer complains about flickering or dimming headlamps/dash lights, but he's not havin any battery charging problems? Bull****. If their stock electrical system can't supply the curren to keep lights from dimming, then they are having charging problems They need to upgrade their ground paths (hint: that stock 10 gauge to the fender isn't helpting), sometimes the alternator, but the last thin you should think about adding to an otherwise healthy electrical syste is a cap...* ONLY if the -average- current draw exceeds your alternator' capabilities do you have a -charging- problem... Even smallish amplifiers can yield peak current demands which wil exceed even a large alternator's supply capabilities... And when that happens, the voltage drops to the 12v level of th battery so that it can kick in the few extra amperes that th alternator can't for those brief moments in time... Your light bulbs dim simply because light bulbs are brighter on 14.4 than they are on 12v... that's not a sign of a charging problem. Bear in mind, there's a time element involved... the time that it take the voltage level to drop down to the 12v level of the battery... an then another time element related to the ramp-up time of the battery as batteries are relatively slow devices to begin giving up charge. there's a rise time... during which voltage will actually continue t drop below 12v. Yes, it's less than a second, this transition... But that's what's nice about a capacitor. It charges up to the 14.4v level of the alternator, and begin supplying charge immediately when the voltage falls even slightly belo that. There's virtually no ramp-up time, a capacitor is able to begin givin up charge virtually instantaniously... And before the capacitor has discharged completely, the battery will b in the equation, able to support the alternator as required, fo however that massive transient or bass-tone lingers. The capacitor smooths the transition from alternator to battery, quit dramatically even.. the results can be seen in greatly reduce headlight dimming, as there's a nice [relatively] slow transition dow to 12v now, rather than a temporary, sudden slam to even below 12 every time there is a large transient peak. thelizman wrote: * Do you tell him to "suck it up and live with it", or do you sell him a high-capacity alternator o lower-ESR battery that he doesn't really need? There's the keyword: "sell". There's more money to be made selling people caps and batteries than a few feet of heavy gauge wire. * Another downside on an alternator (besides the high expense possibility of it being largely ineffective without setting your idl speed north of 2000RPM, and installation considerations that have bee mentioned) is the fact that a bigger alternator is a bigger drag o your engine... and it's a bigger drag all the time, not just when yo need it. A larger alternator is more difficult to spin, inherently. Bigge rotor, larger magnetic forces... they can really impact your car' performance, robbing horsepower. This is anywhere from "noticable" to "really bad", depending on wha kind of car you have... with most cars nowadays, you can feel a HP los just from switching on your air conditioning... I wouldn't want tha kind of loss on a permanent basis, much less one that was eve potentially worse... Particularly when you consider that no matter how large of a alternator I am able to buy, I'll likely still be able to produce transient burst large enough to temporarily exceed the amperage of th alternator. And even then, that transient burst won't matter much in the gran scheme of things... As long as my -average- current draw hasn't exceeded the alternator' capabilities, my battery voltage won't drop below 12v over the cours of my drive... there won't be a -charging- problem - geolemo ----------------------------------------------------------------------- CarAudioForum.com - Usenet Gateway w/over one million posts online! View this thread: http://www.caraudioforum.com/showthr...hreadid=180302 |
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