Capacitors

Ok, here goes my stupid question. Now I do know quite a bit about electronics. I studied 2 yrs at a technical school, no degree cause I didn't take all the electives and the upper level math.  So, what purpose do these big caps serve in power supply for your audio system. Basically a cap blocks DC, passes AC, can be used as a filter, etc. But how could it possibly boost your supply amperage or voltage, either of  which being low can cause dim lights, etc. Help an old guy out. I used to wire em to the nearest hot wire, and what amps? AND WE USED TO WALK 10 MILES TO SCHOOL IN THE SNOW!!!! 

they cant. they can drop/equal out the voltage. "Southside is right on, a cap is NEVER the way to solve the problem of your alternator not being able to keep up with system demand. A stiffening capacitor is designed to help an amplifier maintain power output by dampening the small voltage ripples caused by demand spikes when your system is operating near peak output. A capacitor WILL NOT, under any circumstances, increase your system voltage nor increase system current capacity beyond what the alternator can supply. In every case, if you are installing a system that will demand more amps from your alternator than it can produce, you need to upgrade the alternator. Would a capacitor help your system? Maybe. Is it necessary? No." quoting dyohn(if you have a problem with me doing so dyohn, please tell me). hes much better at explaining things than i could ever. i read an in depth answer somewhere on this board but dont have time to find it. just use the handy search link and you will find what you are looking for

bullman96 wrote: A capacitor WILL NOT, under any circumstances, increase your system voltage nor increase system current capacity beyond what the alternator can supply. In every case, if you are installing a system that will demand more amps from your alternator than it can produce, you need to upgrade the alternator.

Most of what you said, I agree with, except this part. While it is true that a cap is NOT MAGIC, it isn't a pit of free energy, it CAN very much so, increase the instantaneous current capability of your power source. The VERY purpose of the capacitor is to be there to fill in the ripple, as you said, but that voltage ripple is filled in by the capacitor providing CURRENT. A capacitor CAN, AND DOES provide current, even though the OVERALL average power consumed by the system can never exceed the maximum continuous power available from the alternator. When the cap is discharged, it will pull a current gulp from the ultimate energy source (the alternator) but that current gulp is self limited by the internal resistance of the capacitor. Also, the energy supplied by the capacitor can NEVER exceed the storage capacity OF the capacitor, in Joules, or one watt for one second. A 1F cap, charged to 12 volts, can supply 1 amp for 12 seconds, or 12 amps for 1 second, or 12000 amps for one millisecond. It is ALL the SAME AMOUNT OF ENERGY stored and released - 12 Joules. The ultimate current capability is limited by the ESR or equivalent series resistance, and the lower the specified ESR, the more current it can suppy, just for a shorter period.It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

I agree with DYohn-a lot of sales people are telling all people buying systems that they need to buy a cap. When in reality if they are getting a big system they need to upgrade the electrical system in the vehicle. Instead of telling them that and the customer asking "Well how much is that and can your installers do it?" and the salesman saying "No." they just throw the "Magic caps" in your face thinking, leaving the customer under the impression that this will fix the dimming light problem.~The Rookie~

Rookie of the year that is...

Don't let the smoke out of your equiptment..it doesn't go back in.

Thanks for all the input guys. You pretty much reinforced what I believed myself. The cap is basically a filter, cleaning up the ripple left over from the alternator rectiifcation, as well as a very short term boost in the event of a supply voltage drop or spike for that matter. In other words, a good clean DC.