Why not two 12 volt batteries

captpar wrote:
Need to replace my 4 6 volt batteries,was thinking why 4 6 volt and not 2 12 volt. Reasons?

Simple, two 12 volt batteries will have approximately 1/2 the amperage capacity of four 6 volt batteries. Remember for batteries connected in series you add the voltage but not the amperage capacity. For batteries connected in parallel you add the amperage capacity but the voltage remains the same.

If you had four 6 volt batteries they were connected in a series-parallel fashion. That is , you had two six volt batteries in series connected in parallel with two more 6 volt batteries that are connected in series. The replacement by only two 12 volt batteries connected in parallel will result in substantially fewer amp-hours available. Yes, with batteries, size matters. Think of each group or "bank" of batteries described above; the four 6's have a lot more bulk than the two 12's.