Here is a a prime example of a 12V group 31 battery (Deka/East Penn) that absolutely needs to be installed properly. If not they will leak on one tack and this leakage can quickly ruin the batteries.
Here the batteries are properly installed with the neg post facing PORT and the positive post facing STARBOARD.
I can not stress enough how critical proper orientation is with batteries that have offset fill/vent caps as these do..