At 07:36 PM 7/29/2002, John Brush wrote:
>Car batteries have no chance of surviving such an application, as you say,
>but decent deep cycle, not marine, batteries are used in this manner all
>the time. I'm pretty sure that is what the original poster was asking
>about.
>
>If the batteries are not exactly matched, and they never will be,
>equalization charge cycles will bring them close enough to where it
>doesn't matter.

Routine method in golf carts AFAIK.  Big six-volt honkers in permanent
series-parallel circuit.

Recent thought re marine battery banks is that it's better to have one
massive one plus a small starting battery rather than two smaller ones --
at least if you are instrumented to be able to determine state-of-charge
without having to let the battery sit 24 hours and then measure
open-circuit voltage.  Major reason is that Peukert effect dictates that
for a given current draw, a battery (bank) of capacity 2X will give more
than twice the capacity of two banks of capacity X.  The higher the drain
the more advantage you get.

Wiring should be done so the positive feed comes from one battery, and the
negative from the other.  This helps ensure that each battery is drained
equally.

david

--
David Beierl - Providence, RI
  http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"