Massive voltage drop

[Skarz-1995]

Fist time “larger” build here. Having issues with voltage drop going down into the 11’s. 2 skar zvx 15’s 3k rms total with a taramps smart 5 wired to .5 ohm I got a 320a alt with xs 3400 up front and group 34 agm in back. I did accidentally order cca wire instead of ofc. 3 runs of 2/0 to the bank I figured would suffice only did 1 run from negative. 3/0 ofc going to amp and 2 runs of 3/0 ofc for bank battery ground, grounded to seat bracket I of coarse sanded off paint. Set gains with oscilloscope it doesn’t clip but when the voltage drops it will go into protect or just not give a good note. I guess my next move would be to ground to frame for the bank battery? Idk any help appreciated 

[Joe X]

if you measure the voltage from the front battery negative terminal to the negative terminal of the amp while playing hard and you get more than say 0.1 volts then your ground connection is bad.