My first car had 2 - 6 volt batteries, positive ground, hooked together in series, in a compartment under a piece of carpet, behind the two front seats.(only 2 seats)
It also had several cam screw type latches that went around the perimeter of the battery cover that were a royal pain in the a$$ to line up and latch or un latch. The batteries hung doun under the car and were exposed to road grime, water splashing, and being hit by rocks an debris. The batteries were such a pain that I changed them over to one 12 volt set in the trunk in front of the rear wheel well on the passanger side so as to balance the drivers weight. Worked like a charm and makes me wonder why they did not do that to begin with.
I loved that car, but hated the battery arrangement and ALL of the electrical wiring arrangement. And so began the discvery and life long process of changing things that I do not like in cars or boats or tractors, or houses. I generally end up re-wiring everything.
Can you guess what kind of car it was? 4 cyl rear wheel drive. Not American made.