Amp and Cap Wiring Help

[spoonraker 10+ year member]

Alright MTLHEAD, if you know so much about Caps, could you save me some time and let me know why they're so worthless.... I'm not saying they aren't, but I just don't know one way from the other about them, so maybe if you could fill me in....thanks

let me field this one...

A capacitor is not a battery, not even close. They store electricity, they do not create it. And they can't even store that much. The highest discharge time I've ever seen for a capacitor was 8 seconds at 300amps, which I'll admit, is impressive, however that figure is the equivalent of an amplifiers max power rating, meaning it doesn't matter, because it is never utilized. Heres why :

Basic electrical theory tells us that electricity always flows from the highest electrical potential to the lowest i.e. highest voltage to lowest. In a car you have the alternator and the battery as the power sources. In a normal audio system an amplifier is powered completely by the alternator until it draws more power than the alternator can give out, at which point the alternator drops sharply in voltage and when it drops below 12V (battery voltage) the load begins to be drawn from the battery.

The reason people call capacitors band-aids is because they do benefit your system, but only for a fraction of a second, and ultimately end up doing nothing.

A capacitor will charge to the alternator's voltage, and once again when the bass hits, the alternator will drop volts sharply, however with a capacitor in place, instead of the load immediately jumping to the battery, it jumps to the capacitor since it has the highest voltage at this point. This is when that discharge time comes into place. Even with the super-cap 8 second discharge time, you have to keep in mind the electrical laws we discussed earlier. Once the capacitor drops below 12v it is useless since the load will be drawn from the battery. So with our 8 second complete discharge time super cap, we are only utilizing approximately 15% of that discharge time, meaning that our cap keeps the load off of the battery for a measly 1.2 seconds. Most realistic capacitors have a discharge time considerably less than that and when you factor in how little of that is being used, you realize that if you blink you will miss your capacitor doing anything.

 

[Foote 10+ year member]

let me field this one...
A capacitor is not a battery, not even close. They store electricity, they do not create it. And they can't even store that much. The highest discharge time I've ever seen for a capacitor was 8 seconds at 300amps, which I'll admit, is impressive, however that figure is the equivalent of an amplifiers max power rating, meaning it doesn't matter, because it is never utilized. Heres why :

Basic electrical theory tells us that electricity always flows from the highest electrical potential to the lowest i.e. highest voltage to lowest. In a car you have the alternator and the battery as the power sources. In a normal audio system an amplifier is powered completely by the alternator until it draws more power than the alternator can give out, at which point the alternator drops sharply in voltage and when it drops below 12V (battery voltage) the load begins to be drawn from the battery.

The reason people call capacitors band-aids is because they do benefit your system, but only for a fraction of a second, and ultimately end up doing nothing.

A capacitor will charge to the alternator's voltage, and once again when the bass hits, the alternator will drop volts sharply, however with a capacitor in place, instead of the load immediately jumping to the battery, it jumps to the capacitor since it has the highest voltage at this point. This is when that discharge time comes into place. Even with the super-cap 8 second discharge time, you have to keep in mind the electrical laws we discussed earlier. Once the capacitor drops below 12v it is useless since the load will be drawn from the battery. So with our 8 second complete discharge time super cap, we are only utilizing approximately 15% of that discharge time, meaning that our cap keeps the load off of the battery for a measly 1.2 seconds. Most realistic capacitors have a discharge time considerably less than that and when you factor in how little of that is being used, you realize that if you blink you will miss your capacitor doing anything.

A battery doesnt create power either, it only stores it as well. Also, capacitors discharge waaay faster than any battery. Way. Also, I think your explanation for what a cap does is way off. A capacitor is shooting out quick charges when the bass is hitting to your amp, so that your battery doesnt have to. When your bass isnt hitting, instead of your alt not powering anything much, it is charging the cap for the next bass hit. i dont see how such an application isnt useful. To me it seems very useful. When you arent draining power, the power is being put to good use by saving up in the capacitor for the next drain.

 

[lostdaytomorrow 10+ year member]

A battery doesnt create power either, it only stores it as well. Also, capacitors discharge waaay faster than any battery. Way. Also, I think your explanation for what a cap does is way off. A capacitor is shooting out quick charges when the bass is hitting to your amp, so that your battery doesnt have to. When your bass isnt hitting, instead of your alt not powering anything much, it is charging the cap for the next bass hit. i dont see how such an application isnt useful. To me it seems very useful. When you arent draining power, the power is being put to good use by saving up in the capacitor for the next drain.

Do you realize how charge an average car audio capacitor can store?

Answer: Not very much in terms of how much is needed to help with any sort of electrical strain on the car battery and alternator.

 

[Foote 10+ year member]

Do you realize how charge an average car audio capacitor can store?
Answer: Not very much in terms of how much is needed to help with any sort of electrical strain on the car battery and alternator.

Dont get an average one then. Do you realize how good an average battery is for 3kw+ systems? Exactly? So dont get an "average" capacitor. Go big.

 

[spoonraker 10+ year member]

I think you need to reread my post, let me break this down for you...

Also, capacitors discharge waaay faster than any battery

Yes, that's right. I never said they didn't, not really relevant to anything...

Also, I think your explanation for what a cap does is way off. A capacitor is shooting out quick charges when the bass is hitting to your amp, so that your battery doesnt have to.

Actually that's exactly the same thing I said. When your amp draws lots of power (bass hit) your alternator will give up the load to the cap, the cap will drain and give up the load to the battery. In that order. Also this whole process takes at most 1 second.

i dont see how such an application isnt useful. To me it seems very useful.

It isn't useful because it doesn't save your battery from being drained, it simply just creates a fraction of a second delay from the time the bass hits to the time the battery is drained.

When you arent draining power, the power is being put to good use by saving up in the capacitor for the next drain

This is true, however like I just explained, a capacitor can only hold so much electricity, and that amount is nowhere near enough to power a medium powered audio system for more than a second.

Look if you don't believe me, break out the multimeter. If you are getting voltage drops, a capacitor will not do anything other than delay the drops for the blink of an eye.

I'm not saying a capacitor is bad, they won't hurt anything, however they won't be of any benefit, and they are definitely not a fix for the common problem of not having enough alternator power. Not only that but for the price of an insanely powerful capacitor that might give you a full 1.2 seconds of discharge, you could buy a high output alternator, or a couple deep cycle batteries which would have a much greater impact on your electrical system.

 

[05gliguy 10+ year member]

^^ well said.