What I'm reading is he's running 4 ohms... and plans to run 2 ohms... If you've got voltage drop at 4ohms I don't think you need batteries, you just straight up need wiring, big 3, and an alt... My battery is over 6 years old and my dad believes it has/is developing a dead cell and it's a standard starting battery.
I'm running:
200Amp alt
big 3 in monster 1/0
main power run in monster 1/0
4 guage off distribution block to SAE-1000D
8 guage off distribution block to 50x4 Pioneer Premier amp
I run full tilt basically all the time [my system has been set with an o-scope]
Never drop below 13.4 driving and never dropped below 11.9 idle playing anything including "Trap Instrumental" done by decaf which play at 25hz