Is a Capacitor worth it?

[SomeGuyDude 10+ year member]

understandable if you own a POS but if you own a nice quality piece whats the point

Because we're adding to the overall load. Consider us "car overclockers". If you start adding amps, you're gonna need help keeping the electrical flow steady.

Again, I don't think caps (from what I've read) have much use for the vast majority of customers, as in those who lack power and think a cap will patch up voltage drops, but in the right application they do have a benefit.

 

[Stalin-ohaulic]

Because we're adding to the overall load. Consider us "car overclockers". If you start adding amps, you're gonna need help keeping the electrical flow steady.
Again, I don't think caps (from what I've read) have much use for the vast majority of customers, as in those who lack power and think a cap will patch up voltage drops, but in the right application they do have a benefit.

AMEN!

 

[PaulD 10+ year member]

Please explain how a lead-acid battery is subject to changes in frequency.

It is being charged by a device (alternator) that puts out rectified AC that is still fairly noisy, so the battery "sees" DC coming from the alt riding on a smoothed out AC wave (ripple).

The other problem most people do not mention is that the amp's power supply does not draw "DC" from the amp. The Dc to DC PWM power supply draws power at like 60 KHz and and puts it thru a torroid so it can raise the voltage quite a bit. It turns out that under this system, the inductance of the power wire is more important than the resistance to a certain degree - obviously you can't run an amp fused for 100 amps with an 18 Ga wire. A senior engineering guy from Blaupunkt wrote an article about this some time ago.

The real use for a cap in a system is for filtering. It can also supply peak power for transients in an SQ system. They are useless for SPL systems playing sine wave tones with virtually no dynamics because the power will be depleted too quickly. They are just a marketing scheme for companies and retailers to make money on.

 

[midnightg35x 10+ year member]

I may have missed it (this thread has gotten quite lengthy) but what cap(s) are you using and where do you have it located?

I have a single Lanzar 1.5F cap that I bought off of here. It it rated at 20VDC, 24V surge with

Because we're adding to the overall load. Consider us "car overclockers". If you start adding amps, you're gonna need help keeping the electrical flow steady.
Again, I don't think caps (from what I've read) have much use for the vast majority of customers, as in those who lack power and think a cap will patch up voltage drops, but in the right application they do have a benefit.

x2^200! I think I've tried saying that at least twice in this thread alone.

 

[midnightg35x 10+ year member]

The other problem most people do not mention is that the amp's power supply does not draw "DC" from the amp. The Dc to DC PWM power supply draws power at like 60 KHz and and puts it thru a torroid so it can raise the voltage quite a bit. It turns out that under this system, the inductance of the power wire is more important than the resistance to a certain degree - obviously you can't run an amp fused for 100 amps with an 18 Ga wire. A senior engineering guy from Blaupunkt wrote an article about this some time ago.

I'm not quite sure this is all correct. Did you mean the amp's power supply does not draw "DC" from the battery? Even so, if that's the case, the DC to DC SMPS (Switchmode Power Supply) still draws DC from the battery. The PWM controller pulses the gates of the power supply fets which generates a 30-60kHz square wave on their outputs which then gets boosted by the toroids. The drains of the FET's are connected to the 12V line. All good SMPS's have *gasp* larger capacitors (C3 and C4 in the schematic below) on the 12V line before the FET's to filter out the 30-60kHz square wave so the battery only sees a DC draw. I would be interested to read that article from Blaupunkt if you can find it.

Here is a great reference for SMPS design (figure 2): http://sound.westhost.com/project89.htm

As far as inductance goes, larger diameter wire will have smaller inductance (as well as resistance), so in that regard, the bigger the better! 1/0 everywhere! //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[WHATJUSTHAPPENd 10+ year member]

Ah, ya I got turned around by those diagrams that were posted. He has the internal resistance decreasing as the batt is drained, when in reality its the opposite. Somehow I got reversed too lol. Thanks for correcting that.
But the arguement is still the same. His diagram, is wrong.

1. The batt resistances are backwords.

2. The first diagram assumes the alt can power a dynamic load which is not true.

No wrong. I'm not talking about the Impedance of the battery, I'm talking about the Batteries current draw from the alternator relative to the draw of the car's other electronics. The Battery's Impedance is a measure of how much current the battery can deliver. (this value will raise with age, lowering the efficiency of the battery.)

Simply put, when the battery has discharged to a certain point, The battery will draw power instead of sending it all to the other electronics.

 

[WHATJUSTHAPPENd 10+ year member]

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Thats why systems encounter a curve with a peak over time when a sign wave is played over them as the volume is raised. Up to a certain point discharging the battery will lead to less power being delivered to the amp (more than the original output of the Alt.)

 

[smoka 10+ year member]

Well the problem there is with semantics. You really weren't wrong on the esr of the batt. It's not really esr as defined by a capacitor. ESR is sort of used inappropriately on batteries because if you measure the batts' resistance it will be 0 but it obviously has some. This is why people refer to a batt or an amplifier or any device connected that has resistance that can't be measured through conventional methods as having esr. I think sometimes when the cap argument is going down, people only think about a super long, heavy bass note. In that case, sure it makes a cap worthless if the alt cannot keep up. If you're listening to transient music and have a strong electrical system, the cap will clean the power up. There is really no debating this. It's what I've said the whole time and it's true. Also, I don't have some internet degree in electronics. I know these things and then when someone challenges me I just go find it. I think by now you know I'm not in here lying and blowing smoke.

I appreciate you responding in a mature manner. Nobody is perfect (especially not me). I agree with you on the caps arguement. You know quite a bit about electronics, but none of us can know possibly everything. I look forward to arguing with you in the future, hopefully without all the name calling //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[smoka 10+ year member]

Simply put, when the battery has discharged to a certain point, The battery will draw power instead of sending it all to the other electronics.

Not really. Its power draw will be proportionate to its resistance. Same as everything else in the vehicle. Thats why you would turn everything off if you want to charge the batt quickly.

 

[PaulD 10+ year member]

I look forward to arguing with you in the future, hopefully without all the name calling //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

good grief, this wouldn't be ca.com without all the name calling and other juvenile behavior //content.invisioncic.com/y282845/emoticons/laugh.gif.48439b2acf2cfca21620f01e7f77d1e4.gif