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#1
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when is capacitors used?
I heard that the car battery cannot supply current at a fast enough rate
(because of chemical reaction neccesary) for subwoofers and that a cap is needed. At what power ratings should one start to worry about this? |
#2
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when is capacitors used?
Most of the people here will tell you that you never have to worry
about a cap, since it is useless - I do not completely agree with that though. If you have a power problem, invest your money into a better electrical system (battery/alternator). My opinion is that if your light on the car dim a bit on deep bass tone, a cap will fix this problem. I bought one to fix this and I see no diming anymore; it also look cool. The way you asked the question, it sounds like you do not know if you need one. If you don't know if you need one, you probably don't. Andre. "Johan Wagener" wrote in message ... I heard that the car battery cannot supply current at a fast enough rate (because of chemical reaction neccesary) for subwoofers and that a cap is needed. At what power ratings should one start to worry about this? |
#3
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when is capacitors used?
I heard that the car battery cannot supply current at a fast enough rate
(because of chemical reaction neccesary) You heard wrong. Current due to electron flow moves at the speed of light. for subwoofers and that a cap is needed. At what power ratings should one start to worry about this? You should start to address whether or not a capacitor will help you if your headlights are dimming such that it's become an annoyance to you. When that happens, consider installing capacitors as close to the headlights as possible. Oftentimes it won't be much more money to buy a high output alternator or have yours modified by a shop. This is a much more effective tool to reduce dimming. |
#4
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when is capacitors used?
On Fri, 19 Dec 2003 11:53:52 -0500, "Mark Zarella"
wrote: I heard that the car battery cannot supply current at a fast enough rate (because of chemical reaction neccesary) You heard wrong. Current due to electron flow moves at the speed of light. You're right, Mark, but it is fair to say that a battery might not be able to "supply current at a fast enough rate" in some instances. If you have a large current draw that the alternator cannot keep up with, and the battery has to make up the difference, you can get a significant voltage drop due to the relatively high internal resistance in the battery. (This is why even a "good" battery will often drop down to as low as 9.6V while starting your car.) for subwoofers and that a cap is needed. At what power ratings should one start to worry about this? You should start to address whether or not a capacitor will help you if your headlights are dimming such that it's become an annoyance to you. When that happens, consider installing capacitors as close to the headlights as possible. Oftentimes it won't be much more money to buy a high output alternator or have yours modified by a shop. This is a much more effective tool to reduce dimming. I would go even further and recommend upgrading the wiring to the headlights before trying a capacitor. And I agree, if you can get a new alternator or get your current one rewound for reasonably little money, that's probably the way to go. Scott Gardner |
#5
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when is capacitors used?
I heard that the car battery cannot supply current at a fast enough
rate (because of chemical reaction neccesary) You heard wrong. Current due to electron flow moves at the speed of light. You're right, Mark, but it is fair to say that a battery might not be able to "supply current at a fast enough rate" in some instances. If you have a large current draw that the alternator cannot keep up with, and the battery has to make up the difference, you can get a significant voltage drop due to the relatively high internal resistance in the battery. (This is why even a "good" battery will often drop down to as low as 9.6V while starting your car.) That's correct. All power sources have an output Z. But that's quite different from what he said. Especially in regard to his next comment. for subwoofers and that a cap is needed. At what power ratings should one start to worry about this? You should start to address whether or not a capacitor will help you if your headlights are dimming such that it's become an annoyance to you. When that happens, consider installing capacitors as close to the headlights as possible. Oftentimes it won't be much more money to buy a high output alternator or have yours modified by a shop. This is a much more effective tool to reduce dimming. I would go even further and recommend upgrading the wiring to the headlights before trying a capacitor. I've demonstrated before (in a post to Eddie Runner about 6 months ago - the math is there in a google search) that the headlight wiring makes no difference. |
#6
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when is capacitors used?
On Sat, 20 Dec 2003 10:17:10 -0500, "Mark Zarella"
wrote: I heard that the car battery cannot supply current at a fast enough rate (because of chemical reaction neccesary) You heard wrong. Current due to electron flow moves at the speed of light. You're right, Mark, but it is fair to say that a battery might not be able to "supply current at a fast enough rate" in some instances. If you have a large current draw that the alternator cannot keep up with, and the battery has to make up the difference, you can get a significant voltage drop due to the relatively high internal resistance in the battery. (This is why even a "good" battery will often drop down to as low as 9.6V while starting your car.) That's correct. All power sources have an output Z. But that's quite different from what he said. Especially in regard to his next comment. for subwoofers and that a cap is needed. At what power ratings should one start to worry about this? You should start to address whether or not a capacitor will help you if your headlights are dimming such that it's become an annoyance to you. When that happens, consider installing capacitors as close to the headlights as possible. Oftentimes it won't be much more money to buy a high output alternator or have yours modified by a shop. This is a much more effective tool to reduce dimming. I would go even further and recommend upgrading the wiring to the headlights before trying a capacitor. I've demonstrated before (in a post to Eddie Runner about 6 months ago - the math is there in a google search) that the headlight wiring makes no difference. True enough. I should have suggested checking the connections and general condition of the wiring rather than using the vague term "upgrading". Ten to fifteen amps of current shouldn't tax the factory wiring, assuming all of the connections are clean. I noticed you suggested placing the capacitors as close to the headlamps as possible. If the headlight wiring makes no difference, than the placement of the caps shouldn't be that critical. If the headlamp wiring is of adequate size that there's not a voltage drop between the battery and the headlamps, then there's no reason to worry about the physical placement of the caps. You could put them in parallel with the battery, at any location in the car, as long as the wiring between the capacitors and headlamps doesn't produce a significant voltage drop with the rated current. I maintain that if placing the caps closer to the headlamps makes a difference, then the existing headlamp wiring has problems. Scott Gardner |
#7
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when is capacitors used?
I would go even further and recommend upgrading the wiring to the
headlights before trying a capacitor. I've demonstrated before (in a post to Eddie Runner about 6 months ago - the math is there in a google search) that the headlight wiring makes no difference. True enough. I should have suggested checking the connections and general condition of the wiring rather than using the vague term "upgrading". Ten to fifteen amps of current shouldn't tax the factory wiring, assuming all of the connections are clean. Dimming isn't a matter of taxing the wiring though. It's the system voltage fluctuation. That's why the resistance of the wire has no bearing on the level of dimming. Just the average power of the headlight output. I noticed you suggested placing the capacitors as close to the headlamps as possible. If the headlight wiring makes no difference, than the placement of the caps shouldn't be that critical. I wouldn't call it critical. If the cap is part of the aesthetics of the installation, then install it wherever. But it's most effective near the device that needs it, as it minimizes the impedance between the cap and the symptomatic device (eg. headlights) while maximizing it elsewhere. Ideally, you'd diode isolate the headlights, but then you have to deal with high current diodes and a diode drop. Placing the cap near the headlights is the second best solution, because the ratio of impedance between cap and headlights and cap and rest of system is maximized in that case, and as a result the currentfrom the cap "preferentially" flows through the headlights. If the headlamp wiring is of adequate size that there's not a voltage drop between the battery and the headlamps, then there's no reason to worry about the physical placement of the caps. But there's always a v drop. The question is how significant it is. Well, if the cap is delivering a large amount of transient current (which is supposedly the point of using them), then the v drop can be substantial. And in fact, it turns out the inductance of the wire may even be more detrimental. You could put them in parallel with the battery, at any location in the car, as long as the wiring between the capacitors and headlamps doesn't produce a significant voltage drop with the rated current. I maintain that if placing the caps closer to the headlamps makes a difference, then the existing headlamp wiring has problems. Neglecting reactance, let's suppose the resistance of the wire from headlight to battery is equal to the resistance of the wire from battery to amp. Then by putting it in parallel with the battery, or even better, on a separate lower impedance wire (right next to the headlights, for instance) the resistance from cap to headlight will be halved (or better). So why does this matter? It's not uncommon for the resistance of the wire from battery to amp to be, say, .01 ohms (about 15ft of 8 gauge, not including connections and imperfections). The resistance from the battery to headlights is probably at least that amount (6ft of 12ga is about .01 ohms). Putting the cap at the amp doubles (at least) the resistance between cap and headlights AND increases the current draw from the cap due to the amp which contributes to the effective v drop due to a faster rate of discharge since the amp draws more current than the headlights. In summary, it's ideal to minimize the resistance between cap and headlights AND maximize resistance between cap and the remainder of the system. Diode isolating the headlights is the extreme of this concept, as the resistance between the cap and the rest of the system approaches infinity. And as I mentioned previously, the inductance of the wire also plays an important role due to the transient nature of the cap discharge, and there's a linear relationship between inductance and wire length - which can get rather long with a typical amplifier power wire. |
#8
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when is capacitors used?
"Mark Zarella" wrote in message ...
I heard that the car battery cannot supply current at a fast enough rate (because of chemical reaction neccesary) You heard wrong. Current due to electron flow moves at the speed of light. for subwoofers and that a cap is needed. At what power ratings should one start to worry about this? You should start to address whether or not a capacitor will help you if your headlights are dimming such that it's become an annoyance to you. When that happens, consider installing capacitors as close to the headlights as possible. Oftentimes it won't be much more money to buy a high output alternator or have yours modified by a shop. This is a much more effective tool to reduce dimming. WHAT?!?!?!?!....ok if ur headlights dim.... that means that its not only the headlights that have the shortage issue its everything sitting on this electric circuit...installing a cap near the headlights will only take care of the headlights....not everything else...the car will still be affected by this lov voltage |
#9
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when is capacitors used?
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#10
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when is capacitors used?
WHAT?!?!?!?!....ok if ur headlights dim.... that means that its not
only the headlights that have the shortage issue its everything sitting on this electric circuit...installing a cap near the headlights will only take care of the headlights....not everything else...the car will still be affected by this lov voltage Well, as Mark said, installing the cap near the headlamps gives the headlamps preference when it comes to using the capacitors output, but the rest of the car's electrical system still sees the benefits of the capacitor. Mark and I cordially disagree on this point, though. I think that if there's enough of a voltage drop between the battery and the headlamps such that you need to put the cap near the headlamps, then the headlamp wiring probably needs some attention. It's not the headlight wiring causing the v drop. It's the entire electrical system. So when capacitors provide high current to the devices, the impedance of the wires (and the impedance of the cap itself) are the only limiting factors, and therefore cannot be neglected. This is based on my installs, where the connection between the battery and the cap (if a cap is even needed) is never less than a 4-gauge wire. This means that there's essentially no voltage drop between the cap and the battery, so if there's a voltage drop between my cap in the trunk and the headlamps under the hood, it's a deficiency with the headlamp wiring. This is where you're mistaken. 12 ft of *perfect* 4 gauge wire is .003 ohms. The inductance is even more critical (much more critical in fact), but the effect can be described with just the resistance. Anyway, the resistance of 5 ft of 12 ga for the headlights is about .008 ohms. So if you install the cap at the amplifier terminals, the impedance presented to it from the amp is much smaller than .011 ohms and therefore all of the current is essentially delivered to the amplifier. Installing it near the headlights makes the impedance from cap to headlights much smaller than the ..011 ohms in the other direction. You can model this with a simple voltage divider circuit putting the cap at different nodes. Maybe I'll put up a website later with the simulations. |
#11
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when is capacitors used?
On Sun, 21 Dec 2003 11:14:06 -0500, "Mark Zarella"
wrote: WHAT?!?!?!?!....ok if ur headlights dim.... that means that its not only the headlights that have the shortage issue its everything sitting on this electric circuit...installing a cap near the headlights will only take care of the headlights....not everything else...the car will still be affected by this lov voltage Well, as Mark said, installing the cap near the headlamps gives the headlamps preference when it comes to using the capacitors output, but the rest of the car's electrical system still sees the benefits of the capacitor. Mark and I cordially disagree on this point, though. I think that if there's enough of a voltage drop between the battery and the headlamps such that you need to put the cap near the headlamps, then the headlamp wiring probably needs some attention. It's not the headlight wiring causing the v drop. It's the entire electrical system. So when capacitors provide high current to the devices, the impedance of the wires (and the impedance of the cap itself) are the only limiting factors, and therefore cannot be neglected. This is based on my installs, where the connection between the battery and the cap (if a cap is even needed) is never less than a 4-gauge wire. This means that there's essentially no voltage drop between the cap and the battery, so if there's a voltage drop between my cap in the trunk and the headlamps under the hood, it's a deficiency with the headlamp wiring. This is where you're mistaken. 12 ft of *perfect* 4 gauge wire is .003 ohms. The inductance is even more critical (much more critical in fact), but the effect can be described with just the resistance. Anyway, the resistance of 5 ft of 12 ga for the headlights is about .008 ohms. So if you install the cap at the amplifier terminals, the impedance presented to it from the amp is much smaller than .011 ohms and therefore all of the current is essentially delivered to the amplifier. Installing it near the headlights makes the impedance from cap to headlights much smaller than the .011 ohms in the other direction. You can model this with a simple voltage divider circuit putting the cap at different nodes. Maybe I'll put up a website later with the simulations. With the numbers you're using, 0.003 ohms resistance between the battery and the headlamps, and 0.008 ohms between the cap and the battery, I'd consider that "no voltage drop". In this case, your headlamps would have to draw 300 amps of current before they saw a 1-volt drop between the battery and the headlamps, and they ain't ever going to draw that much. Even putting the cap back in the trunk, and using the combined .011 ohms, the headlamps would have to draw 90 amps before the wiring caused a 1-volt drop. This still isn't going to happen. I still say that if putting the capacitor closer to the headlamps versus back in the trunk with the amps makes a big difference in how effectively it reduces flickering, then there's something wrong with your headlamp wiring. Scott Gardner |
#12
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when is capacitors used?
WHAT?!?!?!?!....ok if ur headlights dim.... that means that its not
only the headlights that have the shortage issue its everything sitting on this electric circuit...installing a cap near the headlights will only take care of the headlights....not everything else...the car will still be affected by this lov voltage Who cares about the rest of the car? What's the fluctuation going to hurt? The only reason the driver even notices that there's a fluctuation is because of dimming. If the fluctuation is so severe that it could potentially cause damage, then more important issues must be addressed. |
#13
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when is capacitors used?
X-No-Archive: Yes
A capacitor is basically a reservior with a very small internal resistance. It is very effective at supplying a very high instantaneous current. It's best placed as close as possible to load requiring high instantaneous current. When there's a demand for more power, electricity comes from a source with smallest impedance. In this case, a low internal resistance capacitor placed within a foot of amplifier rather than from rather high internal resitance battery connected a few feet away. By letting the capacitor supply peak demand, you can reduce the sagging on upstream. Johan Wagener wrote: I heard that the car battery cannot supply current at a fast enough rate (because of chemical reaction neccesary) for subwoofers and that a cap is needed. At what power ratings should one start to worry about this? |
#14
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when is capacitors used?
In article ,
"Johan Wagener" wrote: I heard that the car battery cannot supply current at a fast enough rate (because of chemical reaction neccesary) for subwoofers and that a cap is needed. At what power ratings should one start to worry about this? When the current is high enough to worry, you're in need of more storage than the usual 1 to 3 F cap. Car audio stiffening caps are mostly a gimmick. |
#15
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when is capacitors used?
"Kevin McMurtrie" wrote in message
... In article , "Johan Wagener" wrote: I heard that the car battery cannot supply current at a fast enough rate (because of chemical reaction neccesary) for subwoofers and that a cap is needed. At what power ratings should one start to worry about this? When the current is high enough to worry, you're in need of more storage than the usual 1 to 3 F cap. Car audio stiffening caps are mostly a gimmick. explain who there a gimmick, if you need a big boost of volts for a bass note you'll need the cap then the batt. will never get the power down the line quickly enough. |
#16
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when is capacitors used?
explain who there a gimmick, if you need a big boost of volts for a bass
note you'll need the cap then the batt. will never get the power down the line quickly enough. What do you mean? It moves at the speed of light. |
#17
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when is capacitors used?
"Mark Zarella" wrote in message
... explain who there a gimmick, if you need a big boost of volts for a bass note you'll need the cap then the batt. will never get the power down the line quickly enough. What do you mean? It moves at the speed of light. electricy does not always move at the speed of light, it depends on the medium |
#18
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when is capacitors used?
explain who there a gimmick, if you need a big boost of volts for a
bass note you'll need the cap then the batt. will never get the power down the line quickly enough. What do you mean? It moves at the speed of light. electricy does not always move at the speed of light, it depends on the medium Right. In fact, it never moves at the speed of light. But relatively speaking, it's close enough. So that still doesn't clarify your point. |
#19
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when is capacitors used?
"Johan Wagener" wrote in message
... I heard that the car battery cannot supply current at a fast enough rate (because of chemical reaction neccesary) for subwoofers and that a cap is needed. At what power ratings should one start to worry about this? some people don't realize that if you have a fully regulated amp, you get little to no benefits. if it's un-or-semi regulated you may/can see some benefits |
#20
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when is capacitors used?
At what power ratings should one start to worry about this?
some people don't realize that if you have a fully regulated amp, you get little to no benefits. if it's un-or-semi regulated you may/can see some benefits How do you figure? Headlight dimming would be more pronounced if anything for a fully regulated amp. |
#21
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when is capacitors used?
Just to add alittle to the Headlight dimming and the cap issue. Take the
cars charging system. Simulations lack Time Lag for the Regulator to pick up on a Voltage fluctuation. Not to mention that the Cars electrical system is run buy the alt when running. WHen demads are high enough the Alt cannot keep up and we have Voltage sag, which inturn drops the enitire voltage of the charging system. Seeing that almost all electrical components are in parallel with the Alt and battery. That fluctuation will be felt throughout the electrical system. So those that say if a 50A draw causes a 1V flucuation at the amp that sag will be produced throughout the entire system. Not to mention that most auto manufactures do not use the best techniques for wiring Headlights. Their are reasons why wpoplw rewire Headlights with Bigger Ga. Wire, Relay's and use the Head light switch wiring for Relay activation. -- 1991 Tornado Red Corrado, CCA Member # 6645 Stereo is a continuous W.I.P. There are two parts to wisdom: 1) Having a lot to say, and 2) Not saying it. |
#22
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when is capacitors used?
Just to add alittle to the Headlight dimming and the cap issue. Take the
cars charging system. Simulations lack Time Lag for the Regulator to pick up on a Voltage fluctuation. Not if you make the current draw frequency low enough. You could even attempt to simulate the PWM action by putting a high frequency in the low freq envelope. But it's unnecessary for our purposes. Not to mention that the Cars electrical system is run buy the alt when running. That's easily simulated. Just raise the voltage and modify the output Z. Or if you want to get really fancy, put a second source in parallel. WHen demads are high enough the Alt cannot keep up and we have Voltage sag, which inturn drops the enitire voltage of the charging system. Seeing that almost all electrical components are in parallel with the Alt and battery. That fluctuation will be felt throughout the electrical system. So those that say if a 50A draw causes a 1V flucuation at the amp that sag will be produced throughout the entire system. Correct. The fluctuation is the result of the output impedance of the source. Not to mention that most auto manufactures do not use the best techniques for wiring Headlights. Their are reasons why wpoplw rewire Headlights with Bigger Ga. Wire, Relay's and use the Head light switch wiring for Relay activation. Right. Many manufacturers run the headlight power all the way to the dash, through the switches, and back again. People often modify the circuit so this wire drives a relay. This is done to improve the total output of the headlights. But it actually does not improve the flickering! |
#23
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when is capacitors used?
"Mark Zarella" wrote in message
... At what power ratings should one start to worry about this? some people don't realize that if you have a fully regulated amp, you get little to no benefits. if it's un-or-semi regulated you may/can see some benefits How do you figure? Headlight dimming would be more pronounced if anything for a fully regulated amp. no it wouldn't, fully reg. amps put less strain on elec. systems then un-reg. amps. |
#24
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when is capacitors used?
How do you figure? Headlight dimming would be more pronounced if
anything for a fully regulated amp. no it wouldn't, fully reg. amps put less strain on elec. systems then un-reg. amps. No, the dimming would be more pronounced because the regulated amp would draw more current than the unregulated counterpart. That is, in order to compensate for the drop in input voltage, excess current is drawn in the regulated amp. In an unregulated amp, the current drawn is directly proportional to the supply voltage. As a result, dimming increases with more regulation. |
#25
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when is capacitors used?
"Mark Zarella" wrote in message
... How do you figure? Headlight dimming would be more pronounced if anything for a fully regulated amp. no it wouldn't, fully reg. amps put less strain on elec. systems then un-reg. amps. No, the dimming would be more pronounced because the regulated amp would draw more current than the unregulated counterpart. That is, in order to compensate for the drop in input voltage, excess current is drawn in the regulated amp. In an unregulated amp, the current drawn is directly proportional to the supply voltage. As a result, dimming increases with more regulation. no it's less pronounced the amp will change the rail voltage to compensate for lost power. |
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