voltage issue

I have a 2002 grand marquis, Big 3 completeted, 200 amp alternator, kicker zx1500.1, 3 Rockford t1 12s, ppi black ice 800.4, kinetik 1400 in the back. The problem that I am having is that my front battery is constant at 14.4 volts with the car on. My rear battery however drops to below 10 volts. I have the battery wired up front + to back + and the rear battery grounded to the chassis. At this point im not sure what other steps I could take to have the rear battery match the voltage of the front batteryLife is what u make of it so make the best of it

Also I meant to add that it is with the car on and music playingLife is what u make of it so make the best of it

If you have the two batteries connected in parallel, then what you describe is impossible unless you have large resistance in your interconnecting power cable causing it to drop 4 volts. What gauge is the cable (and it is fused)?Support the12volt.com

Read voltage at every junction between the 2 batteries. Input to the front fuse holder, output of the front fuse holder, input to the rear fuse holder, then output of the rear fuse holder.

^^ What they said. Measure voltage around all of the fuse holders like he said to eliminate that as a possibility. If that doesn't reveal anything, you could also try running a direct ground cable between batteries. So run a wire from rear battery - to chassis (like you have now) and then run another wire from that same point on the chassis near the rear battery up to the front battery -.

Thanks. I went through and found the issue. The connection on the line from the front fuse wasn't fully connected there (bad soldering) and the on the second battery before the fuse. Took some time but I found it. Thanks so much for the help. 1 more just random general question. Do u guys think that 2 T0D215s from rockford would get me more spl then the 09 model t1s that I currently have? I know I have enough trunk space box wise, but I haven't heard the T0s. But they look pretty beasty. Just want to know what u guys think.