i had an isolator in my car for over 4 years with a single yellow top in the trunk. never had a problem keeping it charged (stock 60A, amplifier power anywhere from 800W to 2400W, depending on which install hehe)...never had a problem starting my car...voltage drop was severe at the high power range but that's expected with that size alt [img]smile.gif[/img]
isolators generally do have a voltage drop across them. Some isolators are simply massive diodes, others are more complex...either configuration will create resistance in the path which effectively decreases voltage. I think i read somewhere that average loss is around 0.7V which would be what my Electronics II book said as well (ideal voltage loss across diode). The isolator keeps the stereo from pulling current off the stock battery...regardless of if the key is on or off (it was on mine i know).
key here is to run a large enough gauge wire to the secondary battery so that current flow is not restricted. also, be sure to wire your amps up to the secondary battery and not the stock. Cd player and other signal processors should be fine on the stock since they draw low current.
also, caps should generally be avoided until you have your battery voltage under control by upgrading the alternator. Problem with caps is that on bass heavy music, if your alternator can't supply your amps with enough juice the cap helps keep the voltage constant. That's fine and good IF your alternator can keep up. However, if yuo're already losing voltage that means the alternator is too small to run your amps. The cap will discharge before the alt can recharge it and repeats until the cap has quickly become an ADDITIONAL load on the alternator.
This is exactly why you never see SPL competitors using caps (might see a few 50-100F caps, but that's a different beast
)...the caps drain completely in the first quarter second or less of the bass tone, alt is tryin to run the amps, cap becomes drained and needs recharging, losing power to the cap. But the cap can't recharge because the music is still playing...robbing your amps of current that could have been being supplied by the alternator
wonder if that makes sense...3AM, final design project due monday, lack of sleep all week, lack of food...hope graduation's worth it lol