If your total system power is a 1000 watts RMS or more you will need to:
1. Upgrade the alternator to a high output alternator
2. Upgrade to a heavy duty deep cycle battery
3. Upgrade the "Big 3" - that is to replace the power wire between the battery and alternator, the ground from the battery to the chassis and the ground strap from the engine/tranny to the chassis with at least 2 AWG wire.
Failure to do this will result in you replacing them anyway as the alternator will eventually fail.
A cap is only good so far as the audio system isn't trying to pull too much from the electrical system. A cap doesn't provide more power, it's designed to 'stiffen' the voltage to the amp, nothing esle. If the current isn't there, a cap won't help.
A second battery is never a good idea as it's just an added strain on the alternator unless you plan on running the system with the engine off.
Here is a guide that will calculate what size alternator and power wires you need as well how to set the gain http://www.datafilehost.com/download.php?file=6d26c621
You'll need Microsft Excel to use it.
See my site for more info http://spkrbox1.spaces.live.com
A.A.S. degree in Electronics/Industrial Electronics with 25 years in the mobile audio/consumer electronics field
· 1 decade ago