I've noticed a large amount of people running extra batteries, high power applications, and drawing large amounts of current when they don't have enough general knowledge to run a couple hundred watts.
This kid is dealing with what is supposed to be a dedicated battery, but he didn't hook it up. He wants to replace the big 3 with 8awg... thats stock, or close to stock, in most cars. Obviously he doesn't understand the big 3.
No one should run more than 600 or so watts unless they have a thorough understanding of what exactly is going on with there electrical system