2MuchRiceMakesMeSick

I agree with Kris about the second battery being more trouble then its worth. Even with a battery isolator its still just another patch. Its best to replace the source which would be the alternator

jimmyblue

iTrader: (11)

To be useful the cap's ESR/ESL just has to be less than
what's feeding it. The alternator electronics are slow
and the bettery chemical process is slower. The wire
from source to the amp in the trunk is also in the picture.
If you know your peak pulse current and the allowable
voltage sag you can figure the required ESR. Say you
want to use 200W and it's a square pulse, 2 ohms makes
it 10 amps immediate step current (P=I^2*R). If you want
to hold 0.5V line sag then ESR has to be 0.05 ohms (R=V/I).
If you insist on cleaner then you have to go lower. How
clean you need depends on the power supply rejection
characteristics of the amplifier.

Paralleling caps drops the ESR and ESL (for low frequency
supplementing of internal bypass caps, you probably don't
care about ESL) as it raises the bulk capacitance. Since
price compresses faster than capacity you could be way
cool and have a whole Frankenstein rack of caps. The
knife switch and Jacob's Ladder would be a bonus

One thing I'd be concerned about is the inrush current,
I guess maybe higher-end setups would have a resistor
and a relay shunt that lets it get up to voltage slow
and then hard connects it? Farads of capacitance
would draw a hell of a spike on key-on.

You guys seen these?

http://www.maxwell.com/ultracapacito...s/modules.html

These guys are really into Mil / industrial markets but
430F worth in a spiffy anodized case would make for
an interesting parking-lot conversation piece.

Firehawk526

iTrader: (1)

I still have my BatCap 400 (10 farad) and it serves me well for extended SQ play during competition, but for SPL, I'd rather spend the money on an upgraded alternator.

1200 watts @ 4ohm BUT capable of 600 watts @4ohm and 1180watts @ 2ohm (bridged)

shortdo99

I have a cap too. Helps greatly alond with a optima battery.

Frost

iTrader: (45)

Just thought I'd point out something I was thinking as I read this.... The process you describe here creates phase-inversion in a signal. This is something to think about if you are using a passive device to limit bass to say, a mid-bass driver. If you didn't know, these 1st order -6db/octave filters are just caps.

The reason I mention this is, you don't want your component sets rolling off in sub territory. Their low signals will be 180deg out of phase with the subs, and will contribute to low output where the 2 ranges overlap; a flat spot.

This is the first time I've even looked at threads in this forum, it's good to see that there are knowledgeable folks around to lend a handle on some of the voodoo.

stealth355tpi

if we are still talkin about who has a cap here or not i have one, a 5 farad that works great. i have about 2000watts rms between a sub amp and int amp. i still lose voltage when stopped at a redlight and the rpms are down but i just turn it down then. i think they can help alot of people. just when i was running a sub amp i fried a battery and alternator. i know the 5 farad is more then i need but i was able to get it for the same price as something smaller. but as said before by the rest of you. it really does help to keep the voltage constant and help with all your lights on at night. i just havent got a chance yet to upgrade my battery and alternator yet to keep the voltage up to see how much i can get out of the system. also if anyone can help me with this problem ive been playing around with for awhile now. im using a rockford fosgate headunit but i can play so much bass that i make it skip. is there anyway i can protect the headunit more from the vibrations to keep it from skipping. its gets old when you try to show off and you kill the music bc the headunit is skipping on you. thanks