More CAE published CRAP.
Ok, for starters LOOSE the red top. They are for cold or hot starting temperature extremes ONLY. NOT for an overlaoded electrical system.
Secondary batteries on a stock alt and overloaded electrical system DO help with normal driving - somethign CAE wont tell you because they have no experience with it.
Remember you alternator is the highest voltage point in you electical system. It supplies everything with power. Then your system comes online at full power. The alt is now producing it's max output, but it still isnt enough. As a result the voltage will drop until it hits the floating voltage of the battery(s) in your system. (A 12v battery will float at 12.9-13.5volts) Then the battery(s) and alternator work in concert to supply power to your amp. The more batteries you have, the higher the voltage floor (what the alt and battery's combined voltage drops to) will be. The ONLY problem you will see comes when you deplete the battery's charge. At this point you MUST get off of the system and turn it off to let the alt charge the battery(s) back up. Once this is done, you can do it all over again. //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif
This is PRECISELY how I am running 4 zapco 9.0s (~8.8kw) using only 2 batteries and a mere 190 amp alternator. (According to CAE i'd really need a 900 amp alt....LOL)
As long as you allow some recharge time after banging, extra batteries wil do you LOTS of good. Also keep in mind that doing that IS stressing the alternator, so it may die eventually.....
In the ideal world, yes you should get a high output alternator (I highly recommend
http://www.hoalternators.com) but sometimes $$$ issues prevent it.