You might need at least 2 batts. And a ho alt would be necessary for daily to keep them charged. And some 0awg wire and fuses. Takes more than just another batt to make power the proper way man.
I've been having this problem for a while. I tried grounding the rca's on my hu but the noise is still there. Once playing music at high volumes it becomes unnoticeable but its there. Get annoying but I couldn't find a solution so I just left it.