Jimbo

What's the downside to testing it with a cap first? If it works then leave it alone.

Aaron

The important thing to remember about the cap is that it is there to hold the voltage at the right level (bulk capacitance) and provide current on demand as the custom system requires; but, the alternator will still need to provide pretty good current because you will need to recharge the cap. The current draw depends also on the music played and the amount current needed by the amp to drive the speakers. A cap will provide that burst of current that the amp will demand, and it will put less stress on your batter/alternator. Also, don't disregard subterFUSE's comment on I drive going bezerk. Current transients and voltage spikes caused by fast current pulls have been known to create voltage spikes that many traditional automotive electronic units (body control module, engine control module, etc.) are afraid of, so there is no telling what I drive willl do. Just be careful is all we are trying to say. Find out if the CCC runs from battery or ignition (I believe its battery). See if a tech(or you) can get ahold of a scope and some probes and get a plot plot of the battery voltage and current at the CCC module or I-Drive module under worst case music conditions to see if you may have a potential problem. BMW and many others do design for their audio systems and take these factors into account...so should you.

04r1belgium

Well, actually, you have to put a 100A fuse inline with the positive to the amp, meaning in normal operating conditions it will never come close to 100A.

If you take basic electricity laws in account: P=E*I ----> If the amp is kicking out let's say 500W (which is hella loud) that would mean a current draw of 500/13.8=36A Now let's say I *really* want to thump a little, which would only be short time for impressing someone and I run 800W through the sub, this would mean 800/13.8=58A.

Even with voltage drops, I don't think I will ever be pulling anything close to 100A.

I'm not competing in SPL or dB-drag, I just want a full bass out of my install, and that means I will mostly be using the amp at 50% of it's power at most. But that is the area where the amp will be putting out clean power without distortion or clipping.

Anyway, we'll see how the Idrive reacts.... If the E60 can not handle a serious aftermarket install the way a 10.000$ Skoda can, there's something really wrong and it will have to go.

subterFUSE

Neither did I. I competed in SOUND Q, 1000+ watts class.

I was running 1400 watts to three JL Audio 10W6 subs.... but that was more for headroom than anything. Amp gains were run quite low. The other amp was 4 x 100 Watts, running 2 sets of Dynaudio component speakers ( a system 220 MKII, and a system 240 MKII) I was never operating the system at full tilt. Regardless, the current draw was very high. The amps alone were a lot of current, but then add in the extra processing.... and it was a nightmare.

I had to have a 200 Amp Circuit Breaker, which we installed in the engine compartment next to the Optima Yellow Top battery.

My biggest problem was that even with the 15 farads of capacitance I had, the amps wanted more. If I ran the system hard, the amps would actually take power away from the other components, like the active crossover (Precision Power FRX-456). This sometimes made the crossover power light flicker some, and the processing would get sloppy.

All I meant by my comments was.... it's always best to err on the side of assuming you need more power and more capacitance. You can NEVER have too much of either.... but too little, and you've got problems.

Personally, I am afraid of the iDrive's potentially adverse reations to power supply fluctuations. This is why I will probably never touch the audio system in that car. For me, it's all or nothing with audio. Either I change out EVERYTHING or I do nothing.