Yeah Optimas aren't great for car audio. May I ask if this "big boat walmart battery" is a sealed agm? I think I know what battery he is talking about, and if so, its just a normal lead acid. On a ranger theres room under the hoot for 2 more batteries, so all is good there. My problem is, my ranger has a 95amp alternater, so i will need to upgrade that. I already get my voltage gauge dropping with just 2 jensen 12's and a 250w amp, or just my headlights and fog lights (The fogs are 150w HID variety. They were free and BRIGHT) That's pretty sweet you have extra space under the hood for batts I'm jealous. Yeah just don't put a normal acid batt inside the cabin, sealed agm is fine. Heres the engine compartment. If you look on the lower left corner, theres room right there for one, and I cant remember where I could put a third. lol And since this is a car audio forum, two more pics. One is my BIG audio for my truck Yes, I can scare people shitless And the other is a BIG piston