Originally posted by KnuKonceptz:
Originally posted by SteedaSVTââ??¢:
Your not going to be drawing 170ish amps unless your playing extreme volumes...

Upgrade the big 3 and get another battery and you should be all set



Or playing test tones for SPL. Music will never reach levels like that. For extended playing time you may get some peaks, but the real draw is when doing a sweep or a constant low cycle (60 or lower) This varies by the subwoofer's Impedance curve.

As for adding a second battery, no need to connect it to the alternator. Just connect the front battery to the rear battery and then the amps to the rear battery. Just the postive wre needs to be run, ground each battery with the same gauge wire used to connect them.



To expand on this a little, music (even extremely compressed bass heavy material) will have a crest factor on the order of 6dB and typical pop music will be above 10dB. Crest factor is the difference between the peak and average output in a song. Sine waves have a crest factor of 3dB. Seriously clipped sine waves (nearly square waves) have a crest factor approaching 0 dB. To translate these numbers to this discussion we have consider the amp efficiency, power, and voltage.

If crest factor was 0 and you were producing the full 1000w and your amp was 100% efficient, you would get the following:

1000w/13.8v = 72A

Obviously, it's not 100% efficient, and being from 98 with crossfires claim of older technology, I will assume it's a class a/b amp and lets say it has 50% efficiency(typical). meaning that 50% of the energy is disappated as heat.

You substitute 1000w with 2000w because it is wasting 50% on heat and now you have 144A of current draw.

But, you throw a CD with music in the deck with 10dB crest factor and you have your amps properly dialed in, and now your average current draw drops to a paltry 14.4A with an occassional 144A draw. Not exactly the most strenous load on the system. Under harsh, but not untypical conditions (amp clipping, heavily compressed music) your average draw would be on the order of 60-70A. Crank the gains fully and play sine waves and your alternator will hate you.

Avoid batcaps is the general advice I have read.



"If you are flammable and have legs, you are never blocking a fire exit" -Mitch Hedberg