Well articulated John, thanks.

 

Unless you look at the word sideways, like I do, you might want to swap around the x and y axis on my previous post. Time is typically the horizontal axis.

 

Are you sure that if it is charged at X voltage but then voltage goes down to Y, that it cannot retain it's full capacitance at Y voltage, after being given a period to recharge itself back up at Y voltage? What happens if a cap is charged at 12v (engine off) and then the car is started and the voltage rises to 13.8-14.4v? I would think that virtually anybody who has ever installed and charged a cap has done so with the engine off so if the cap is only as good as the voltage applied to it during charging, then there should be no problem when the car is running because the voltage then is higher. So you are saying that if a cap is totally depleted when engine running, that it cannot possibly go back to say 1 farad when the engine is turned off and voltage drops to 12v? I'm not sure if I agree with that.

 

Doesnt your cap have a little orange wire going to it?

 

The cap at rest with a potential of 12 volts can give a mighty good kick, and as you charge an uncharged cap it draws a nice arc. It would be less impressive if the voltage delta was only a volt or two but it would still be a good tank of electrons. This is where I was wrongish I was speaking of relative(delta) voltage not absolute.
During the afore mentioned transient the max voltage delta was a drop from 14 volts to 12.75. Granted it still is fully charged at 12 volts (my wording was not precise, some would say wrong) it just can’t do any work until there is a voltage differential for it to work into. Voltage (keeping the water analogy) is pressure, current is water flow, wire gauge is pipe size, resistance is head loss (caused by piping and elevation) and work performed by the water, the capacitor is akin to a small pressurized tank of water, and the alternator/battery is the water pump.

Farad - [n] the capacitance of a capacitor that has an equal and opposite charge of 1 coulomb on each plate and a voltage difference of 1 volt between the plates

Coulomb - a unit of electrical charge equal to the amount of charge transferred by a current of 1 ampere in 1 second

 

Nope. None of the ones I own or have owned have ever had anything but two terminals on them for the primary power and ground wire.

 

Without the remote turn on it would be on all the time even when you turn the engine off! snicker

 

^Which is fine/should be fine considering it should stay charged just like a battery for a finitely long time like a battery until it is discharged/eaten.

 

Eating batteries and drinking electrolyte no wonder you are painting toilet bowls and exploring alternative meats

 

The capacitor is an interesting topic (that could almost be sarcasm too), it is the 'pride of ownership piece'. Many manufacturers badge them (I am certain FEW make them) with pretty lights and wild paint schemes and chrome. Kids with thumpin cars don’t make the cut if they don’t have a couple Farads in the trunk. Show cars have capacitors prominently displayed, I mean it can’t be a good system if it doesn’t have a big ol capacitor.
The capacitor is arguably the least important piece of the power supply setup. A good battery, a BA alternator, a clean ground connection, correctly sized wiring and fuses, and a properly designed amplifier are all much more important. But it is one of the most talked about items in this and other forums and some canonize them and others vilify them.
But it comes down to what Dukk said earlier “the Capacitor is still a valid accessory” and even a necessary part of a moderately powerful stereo and ohhhhh yeah don’t they look pretty.