so i showed my friend my sx12 and hes like why dont u have a cap and i told him that it would put strain on my stock alternator and he was like no it wouldnt and so i was wondering if someone could explain to me how this works so i can tell him
a cap is basically a teeny tiny battery that works really quick. It charges quick and discharges in a fraction of a second. Meaning something HAS to charge it - and that would be your alternator.
IF you have a good, strong alternator a cap isn't going to hurt anything. At the same time it isn't going to help anything unless you feel reducing V peaks and increasing V sags (slightly) is an improvement. There is no audible difference, and only on a rare occasion will they provide much help for dimming headlights.
Cap is like an AC filter in your car. It will smooth out AC ripples, as well as release power at a much faster rate than your alternator/battery. The problem usually occurs when it gets drained faster than it can recharge, as in long bass notes.