I have the battery under the hood and I have a second agm battery behind the driver's seat. A friend grounded it to the alternator. The amps turn on and play, but I get wicked popping noise sometimes pushing pause or when it's under heavy load at 27hz or lower. I believe it to need abetter ground in the back. I realize that drilling through floor board and running the 0 gauge to the frame would be best scenario, bit truthfully I don't want to do that. Any ideas for grounding a battery in the rear driver's floor board? Thank you very much for any suggestions or links ahead of time. This has been happening for a while, and when it happens, it comes through 4 twelves behind your head and scares the @&$# out of you. I'm actually scared of my own system at this point. Also forgot to mention, 0 gauge running from alternator to rear battery positive, bass amp is a ct sound 2200.1 with 0 gauge running power and ground to the rear battery.