Capacitor
11-28-2003, 10:06 AM
#21
2000 Watt CAFz'r
Join Date: Jan 2001
Posts: 2,026
Originally posted by Dukk:
. . . Capacitor is still a valid acessory.
Yes dimming is probable.
. . . Capacitor is still a valid acessory.
Yes dimming is probable.
Or, are you going in the principle, that yes dimming is probably, but it will not be as extreme as it would be without a cap.
I still say if all eletrical systems in the car are up to snuff and wiring is sufficient, there is no need for a cap. If there is a need why? What part of the system is doing its part with the release of voltage/amperage that needs the cap to compensate and smooth it out?
11-28-2003, 02:54 PM
#22
Originally posted by Fever:
Very good then.
So again it must be due to the speed of the discharge of the cap compared to the battery/alt system. The cap helps buffer the car system so there is no sudden drain that causes dimming. Regardless of the abundant supply from the 200amp alt.
Any support? Other ideas?
Gene
Very good then.
So again it must be due to the speed of the discharge of the cap compared to the battery/alt system. The cap helps buffer the car system so there is no sudden drain that causes dimming. Regardless of the abundant supply from the 200amp alt.
Any support? Other ideas?
Gene
But the response time is indeed a major factor. If you've ever hooked up a digital multimeter to your fusebox and watched the voltage dance around when sudden or large currents draws occur like when your turn signal is on or the electric fan comes on you will see just how slow the response can be.
11-28-2003, 04:31 PM
#23
Yankee
Join Date: Oct 2003
Posts: 3,599
The capacitor will be the first to react to a system transient, the RC time constant dictates how quickly. I do not know how long a 1 farad cap can provide power to a stereo and an automotive electrical load without help from the alternator (I am guessing much less than a second) but it would vary vehicle to vehicle. The Cap supplies a brief electron supply then it too becomes a load on the system because it wants to charge at the same FAST RC time constant (not slow Maltesechicken) that it discharged at. This is where a capacitor can be a liability once it has shot its initial load it needs to be recharged prior to properly performing its function again. Caps are used in every amps power supply for this reason, to filter DC and supply many joules of energy for the amp. The cap should be close to the amps for the previously mentioned reasons and to act as an extension to their internal caps.
I also disagree that the battery is slow to deliver current, our stereos work pretty well with the car turned off. In this scenario the battery will not be part of the equation till you reach the batteries terminal voltage.
BIG power demand: 1) Cap discharges then 2) alternator slows then 3) battery draw then 4) the engine idle restores the alternator output then the battery goes off line and the cap recharges.
have you ever noticed I have never made a short post
I also disagree that the battery is slow to deliver current, our stereos work pretty well with the car turned off. In this scenario the battery will not be part of the equation till you reach the batteries terminal voltage.
BIG power demand: 1) Cap discharges then 2) alternator slows then 3) battery draw then 4) the engine idle restores the alternator output then the battery goes off line and the cap recharges.
have you ever noticed I have never made a short post
11-29-2003, 10:09 AM
#24
1000 Watt CAFz'r
Join Date: Oct 2003
Posts: 1,783
^^^Yeah I've noticed, and I like it. You presenting well thought out answers that are concisely writen. Keep it up, it's good reading.
Of course you won't make a high post count this way, but that's just silly kids stuff. I'm an aspiring novelist sometimes too.
Adam
Of course you won't make a high post count this way, but that's just silly kids stuff. I'm an aspiring novelist sometimes too.
Adam
11-29-2003, 11:11 AM
#25
Originally posted by JohnVroom:
The capacitor will be the first to react to a system transient, the RC time constant dictates how quickly. I do not know how long a 1 farad cap can provide power to a stereo and an automotive electrical load without help from the alternator (I am guessing much less than a second) but it would vary vehicle to vehicle. The Cap supplies a brief electron supply then it too becomes a load on the system because it wants to charge at the same FAST RC time constant (not slow Maltesechicken) that it discharged at. This is where a capacitor can be a liability once it has shot its initial load it needs to be recharged prior to properly performing its function again. Caps are used in every amps power supply for this reason, to filter DC and supply many joules of energy for the amp. The cap should be close to the amps for the previously mentioned reasons and to act as an extension to their internal caps.
I also disagree that the battery is slow to deliver current, our stereos work pretty well with the car turned off. In this scenario the battery will not be part of the equation till you reach the batteries terminal voltage.
BIG power demand: 1) Cap discharges then 2) alternator slows then 3) battery draw then 4) the engine idle restores the alternator output then the battery goes off line and the cap recharges.
have you ever noticed I have never made a short post
The capacitor will be the first to react to a system transient, the RC time constant dictates how quickly. I do not know how long a 1 farad cap can provide power to a stereo and an automotive electrical load without help from the alternator (I am guessing much less than a second) but it would vary vehicle to vehicle. The Cap supplies a brief electron supply then it too becomes a load on the system because it wants to charge at the same FAST RC time constant (not slow Maltesechicken) that it discharged at. This is where a capacitor can be a liability once it has shot its initial load it needs to be recharged prior to properly performing its function again. Caps are used in every amps power supply for this reason, to filter DC and supply many joules of energy for the amp. The cap should be close to the amps for the previously mentioned reasons and to act as an extension to their internal caps.
I also disagree that the battery is slow to deliver current, our stereos work pretty well with the car turned off. In this scenario the battery will not be part of the equation till you reach the batteries terminal voltage.
BIG power demand: 1) Cap discharges then 2) alternator slows then 3) battery draw then 4) the engine idle restores the alternator output then the battery goes off line and the cap recharges.
have you ever noticed I have never made a short post
As to the speed of the charging system, I still maintain that it reacts slower to load changes than a cap can. I see you agree with this but yet disagree that a battery is slow to react. It is 'slower' to react than a cap. We can agree on that. And yes, the big fallacy with a cap is that once it's discharged to help out on a big current transient, it then needs to be charged again. This is why caps IMO are useful only for more 'SQ-oriented' music where the genre of music predominantly is much more transient in nature than say the average SPL guy who likes to listen to 40 Hz test tones on his Big Fat Momma Bass CD. The more capacitance you have, the more of a load it is to charge them but on the other hand the less likely they are to become discharged or close to discharged with transient music.
11-29-2003, 06:33 PM
#26
Yankee
Join Date: Oct 2003
Posts: 3,599
Looks like we agree Sux!
I have done this with an old Perreaux that had huge caps in it and it would play ~80db for 3-10 sec.
KIDS dont do this at home, new car electronics and digital stereo dont like voltage spikes!! This can be expensive.
I have done this with an old Perreaux that had huge caps in it and it would play ~80db for 3-10 sec.
KIDS dont do this at home, new car electronics and digital stereo dont like voltage spikes!! This can be expensive.
11-29-2003, 06:36 PM
#27
Yankee
Join Date: Oct 2003
Posts: 3,599
Looks like we agree Sux! A new CCAB first
I have done this with an old Perreaux that had huge caps in it and it would play ~80db for 3-10 sec.
KIDS dont do this at home, new car electronics and digital stereo dont like voltage spikes!! This can be expensive.
I have done this with an old Perreaux that had huge caps in it and it would play ~80db for 3-10 sec.
KIDS dont do this at home, new car electronics and digital stereo dont like voltage spikes!! This can be expensive.
11-29-2003, 09:45 PM
#28
2000 Watt CAFz'r
Join Date: Jan 2001
Posts: 2,026
Thanks for the informative posts John.
Here are the conclusions that I have come to from reading this.
Since it takes the alternator a few seconds to realize there is a current draw in order to pick up the speed and give more current a cap is a good investment.
Here is something that this post has caused me to ponder. Perhaps the batteries "inability" to deliver current as "quickly" as a cap is connected to its Amperage output. If a battery is only an 80 amp battery it will never be able to deliver more than 80 amps at any given time. So, if you are drawing 100-120, the battery cannot keep up, and since the alternator hasn't yet kicked into full gear, you aren't going to the get the full potential - Just a thought. I could be wrong (and then when you get a better battery this idea no longer applies)
Secondly, I have a question about the whole "capacitor becoming a load on a system." If the system is set up as Dukk's scenario mentions, I don't see why the cap would ever become an additional load. Here's why:
Bass kick - current required, but not enough current is coming from the alt - so the cap kicks in and drains maybe 1/2
Now there is a definite load on the system so the alt goes full gear supply power to the system and charging the cap.
The cap gains maybe 1/4 more before next bass hit, now it is down to 1/4 capacity. But the alt is now going full tilt and doesn't need to pick up lag time. Charges the cap to a little over 3/4 - losses half, the next time gains a little more than before, -bass kick, losses half etc. etc.
Is it not possible in the ideal set up (running test tones exempt) that the charging system should be able to keep up with keeping the cap at least partially charged so it wouldn't become an unbearable load on the system?
The way I look at it, its like water being poured into a glass and the glass empties in spurts, but the stead flow of the charging system keeps the glass reasonably full. Perhaps, even with a testtone running, the glass can be half empty, and all of the water being poured in goes straight through keeping an even keel. Or does my theory fall short in that in the chain of service, the cap gets served (filled) first and the rest of the system comes second?
John, I'm into writting on-line short stories too [img]smile.gif[/img] . Where has Dukk gone? I thought he wanted this discussion going for his own reading pleasure?
Anyway, posting to learn . . .
Ryan
Here are the conclusions that I have come to from reading this.
Since it takes the alternator a few seconds to realize there is a current draw in order to pick up the speed and give more current a cap is a good investment.
Here is something that this post has caused me to ponder. Perhaps the batteries "inability" to deliver current as "quickly" as a cap is connected to its Amperage output. If a battery is only an 80 amp battery it will never be able to deliver more than 80 amps at any given time. So, if you are drawing 100-120, the battery cannot keep up, and since the alternator hasn't yet kicked into full gear, you aren't going to the get the full potential - Just a thought. I could be wrong (and then when you get a better battery this idea no longer applies)
Secondly, I have a question about the whole "capacitor becoming a load on a system." If the system is set up as Dukk's scenario mentions, I don't see why the cap would ever become an additional load. Here's why:
Bass kick - current required, but not enough current is coming from the alt - so the cap kicks in and drains maybe 1/2
Now there is a definite load on the system so the alt goes full gear supply power to the system and charging the cap.
The cap gains maybe 1/4 more before next bass hit, now it is down to 1/4 capacity. But the alt is now going full tilt and doesn't need to pick up lag time. Charges the cap to a little over 3/4 - losses half, the next time gains a little more than before, -bass kick, losses half etc. etc.
Is it not possible in the ideal set up (running test tones exempt) that the charging system should be able to keep up with keeping the cap at least partially charged so it wouldn't become an unbearable load on the system?
The way I look at it, its like water being poured into a glass and the glass empties in spurts, but the stead flow of the charging system keeps the glass reasonably full. Perhaps, even with a testtone running, the glass can be half empty, and all of the water being poured in goes straight through keeping an even keel. Or does my theory fall short in that in the chain of service, the cap gets served (filled) first and the rest of the system comes second?
John, I'm into writting on-line short stories too [img]smile.gif[/img] . Where has Dukk gone? I thought he wanted this discussion going for his own reading pleasure?
Anyway, posting to learn . . .
Ryan
11-30-2003, 06:59 PM
#29
Yankee
Join Date: Oct 2003
Posts: 3,599
A capacitor is a fully passive component, it can operate only at the highest terminal voltage applied to it. Once it is charged at say 14 volts it has 1 farad of potential energy stored. As power is drawn from the cap the terminal voltage of the cap will drop and the cap is no longer carrying a full farad of charge, now it is at a lower potential (lower voltage) lets say 12.75 volts, and has less energy in storage (.5 farads). This is your partially filled glass analogy but... The cap is now perfectly happy to stay at this charge indefinitely unless the active components (battery, load, or alternator) tell it to either (1) perform more work and lower its terminal voltage (empty the glass more) or (2) the alternator raises terminal voltage (lets assume 14 volts) the 12.75 terminal voltage of the capacitor will act as a load and demand electrons to recharge immediately (this glass demands to be filled first or at least in parallel with the amps capacitor bank).
In other words, yes it still has energy stored in it, but it is only usable when the system voltage is less than the caps voltage. A capacitor is by definition a device that opposes a change in system voltage.
In other words, yes it still has energy stored in it, but it is only usable when the system voltage is less than the caps voltage. A capacitor is by definition a device that opposes a change in system voltage.
11-30-2003, 07:49 PM
#30
Yankee
Join Date: Oct 2003
Posts: 3,599
A capacitor, in this application, will negate some voltage transients but on big severe transients it will minimize the severity (max voltage drop and max voltage overshoot or limiting x axis excursions) but it will lengthen the recovery time (longer y axis) by adding a dynamic that opposes x axis correction and could set up a little voltage ‘ringing’ rather than voltage dampening in dynamic situations. This sounds bad but it isn’t that significant, we are talking about fractions of a second. Remember putting a cap next to the amp is essentially beefing up the amps power supply. Bear in mind I think a cap is a good idea, I can not quantify if it improves the sound of a system, nor can I say it is a must, but it does seem to be a good idea in any significantly sized system. They show well (they look cool), they are fun to discharge with screwdrivers, they make dealers money, and they provide an electrical service … everyone wins.
