Battery hook up for subs

its kinda drainin my battery now at night my lights flicker, so i wanna put a extra battery in the trunk, how do i go about hooking that up ?

get a battery isolator and run a power wire from the alternator to the extra bat. Ground the extra bat to the frame. Although a higher output alternator and better battery would be the best bet.

thanks bro

Get a yellow top optima battery, that will help.