Car audio system - 2 550 watt amplifiers, 2 10" subs, 2 250 watt 6x9s, 1 .5 farad capacitor, upgraded battery and alternator. After installing the capacitor according to the manufacturer's wiring diagram, I find that the car battery is draining while parked with the system turned off. The amps are powering off, the only apparent cause is the recently added capacitor. After removing the cap from the system, the battery drain appears to have stopped. Is this normal for a capacitor to drain the battery under these conditions, or could it be malfunctioning?

 

You can test it if you have a multimeter. First, pull it out of the system and touch the two ends together to fully discharge it (or put a wire or something across it to not get shocked)

If the multimeter has different settings for different Ohms, set it to it's highest setting (>10k)

Then connect the multimeter to the capacitor, and make sure that polarity is correct if it an electrolytic. The Ohms will shoot down near 0 then continue to rise until overload as the capacitor is charged by battery of the multimeter. It might stop at a fairly high value if it has a dielectric leak. This might be necessary for the capacitor for some reason, I'm not too knowledgeable about specifics, just know that some do this, and it essentially means that the capacitor has a fairly high resistance I think. This might cause some battery power loss if it is shorted somewhere in the system to ground, but adding the capacitor shouldn't reveal this issue.

If the capacitor is bad, then it will go to 0 and stay at 0, but it could also be broken somewhere on the inside and just show overload, that is, and open circuit.

I think this is all correct, but I do only have 3 years of college on this subject so as far as real world reasons for these issues, I'm not too knowledgeable.