6 volts are the best to use for RV duty (wired in series). No battery performs at it's best wired in parallel with another matching battery because as they age, the difference in voltage between the two produces a constant current flow between them resulting in a constant charging situation as one discharges the other. Golf cart batteries are capable of lasting a LONG time but, forgotten under the steps, don't get taken care of like they should. They need to be checked for water on a regular basis and the tops and terminals kept clean. People always used to talk about how setting a battery on concrete would 'draw the electricity out of it'. That's not exactly true, but, sitting on a cold surface will discharge a battery. As batteries charge, they 'boil off' electrolyte. If you remove the cap of a charging battery, you will see it bubbling. The fumes will vent out of the battery and some will condense on the top of it. Over a period of time, it builds up and, if the battery is colder than surrounding air (which sitting on concrete overnight generally causes this condition since the concrete will be at earth temperature), moisture can condense as dew on the battery top. When this happens, the combination dirt/moisture/electrolyte becomes a conductor and the battery will discharge across it's top. Using a digital meter, you can measure the voltage by putting the negative lead on the negative battery post and touching the positive lead to the crud. You will read a voltage! This is why it is so important to keep the tops of your batteries clean! The harder you use them, the more condensed electrolyte is formed and, un-maintained, the faster they will self-discharge across the dirty top. Any battery only has so many charge/discharge cycles until the electrodes get 'worn out' so minimizing the charging/discharging by keeping the tops clean is vital for getting the most out of batteries. I'd bet most of you reading this will find the tops of their batteries dirty if you go out and pull the step..
