Del, sounds like it's more of an issue than just the alternator and power, so I'm gonna ask a couple questions to help figure out more.all i have as far as a system goes is 2 memphis M3 15's and a mc1100d and i like to play it loud, but my electrical system wot permit me. my lights dim a lot and my amp wil go into protection after being played loud for a while like 10 minutes, what can i do. i know this question has been asked and prolly answered a few times but i am new to this forum.
The problem with adding a second battery is that your alternator needs to now charge both. That is more draw on th alt. You should keep the cap get a high out put and then you can add the second battery or just **** can the cap and 2nd battery and get a good batcap. I have the power bastards 250 amp alt and it is great. Alot of companies are putting out these new battery caps. and they are doing real wellTrue a cap does replenish quickly, but also get drained just as fast... Do you realize that the reason Kinetik's HC600 (7"L x 3"W x 6.5"H, very small) is referred to as "the Cap Killer"... It will provide over 100 times the amount of power of a 1 farad capacitor... This is why I say "Add another battery for More reserve" and your voltage drop should go away.
Obviously I'm going to have to put up another FAQ ... This time about Caps vs. Batteries