it takes too mch effort to hook up ur system to one batt.
and ur starting to another batt.

ur better off to just intall 2 batts and so wen u drive both of em gets charged therefore u will possibly have 2x the ammount of charge.
cos atm the wiring all goes to one batt. and without knowing wat wire is wat ur like lost. and it s abig headache to find out wat goes where.

(and i just came up with an idea)
u could install another batt in ur boot and all ur amp run off tat. as long as that batt is connected to the thing that charged the batt... i 4got wat thats called
these are only ideas though not 100% sure wat it would produce