isolating farad capacitor

Geepers, the alleged experts on this site seem so anti-cap. Why is that? Perhaps they some vested interest in the truth, or NOT ripping people off? Again - I like this site. But I still have to get used to people agreeing WITH me....! Now a few short pedantic comments: - voltage can appear to "increase" with a capacitor, but that is a fault of the measuring system (ie, averaging and not true-RMS measurements etc). - as a capacitor is like a (parallel voltage) smoothing device (as an inductor is a series current "smoother"), and as it tends to decrease the dip depth, it also decreases the peaks. A diode feeding a (parallel) capacitor is like a sample-&-hold circuit (the diode prevents discharge back into the source) which used to hold the peak voltage (which could be well over 16V for a 12V vehicle) for heading by a hi-impedance voltmeter. But a load is NOT a high impedance - a voltmeter may be over 10MR (Mega-Ohms); a headlight may be 2R, and an audio amp under 0.1R. Do the math - the capacitor hold-up time is similar to its time constant or proportional to t=RC (=2x8F = 16 secs for headlight; 0.8 secs for an amp etc - not that t=RC is the formula used; I'm just demonstrating the relatively short hold up time, and rebuffing related pro-cap claims). - lamp of resistive charging of a cap is good to see since it indicates a low internal cap resistance. A discharged cap has infinite inrush current. Luckily internal resistance usually limits it to less than infinity. But the current can be so high as to destroy the capacitor or other circuits, hence why some require pre-charging. (Huge caps of several Farads that don't require precharging are either of robust construction and don't care about other circuitry, else they have relatively high internal resistance. I have long questioned how the latter is removed once in operation!) In a previous 8F discussion, I pointed out how a cheap $35 battery had many times the hold-up time of an 8F capacitor. Alas it stopped short of dynamic (AC) analysis, but that too shows the battery's superiority (low cap & battery ESRs become negligible wrt to load impedances for high-power SMPT amps etc, and alternator sub-transient response (albethe alternator too far from the amp for that benefit). Keeping in mind that most with such HUGE amps will utilise a second battery to ensure preservation of the cranking battery, the above factors are solved by an additional large capacity AGM battery mounted with the amps. The original vehicle battery remains.... The AGM battery is only connected whilst the alternator is charging.... The AGM's surface charge provides more "Farads" than the largest capacitors.... And when cap would have discharged to the battery voltage (say 12.7V or less) and therefore been useless/negligible, the AGM takes over as a "generator" of electricity providing thousands of equivalent "Farads" of energy. Alas I have only scraped the surface - there is lots more. But for now....

For roughly $300, you could have right around a 220A fix. Caps really do nothing except provide one more physical connection between amplifier and battery. For a cap to be efficient, it needs to be WAY larger than 8F. Word of advice, get a high output alternator. It's the 220A fix I mentioned at the beginning of my reply. I used 220 amps as an example. Your application might warrant a different size alternator. Ohms law is a great tool to use for figuring out what size alternator you will need. This is the ONLY way you will get a "bump-up." Good luck in your endeavors sir....