[Chuck v]

Dexter,

Lead acid batteries don't behave very well when connected in parallel, particularly if they are different sizes or even different manufacturing dates/condition if they are the same size and brand. The issue comes from the characteristic of the lead acid cell being a very low impedance when fully charged but a higher impedance when discharged. This causes a discharged battery to not charge very well when in parallel, but the least charged cells charge first when all are in series.

If you look at electric vehicle arrangements, you will see that the batteries are almost always in series, and the operating voltages are often 48 volts or higher. When I had my cabin running on solar power, it was a 24 volt system with very large cells all in series.

My coach uses 6 volt golf cart style batteries in a series/parallel combination to power the 2000 watt inverter -- not the ideal, but a workable solution that uses commonly available battery sizes. Just remember that you should replace all the batteries at the same time and with the same manufacturer, size and if possible date code.

Chuck