Dry camping - battery usage - very simple question

[freewill2008]

For a starting point, assume the less-than-new batteries still have
75% of their original 85AH capacity. The total capacity of the 4
batteries would be (4 X 85 X .75) = 255 AH. A good rule of thumb
says that only a 50% discharge should be allowed (voltage at 50%
would be almost exactly 12), so the real available power is 255/2 ~
128 AH. Because the Cat will require about this much power to crank,
there would little reserve power for the coach interior. (Note that
with 4 fresh golf cart batteries - the original BB design, these
numbers would roughly double.)

Suppose the bus were equipped with a separate battery to crank the
Cat (a split battery system). In this case, there should be about
128/6 or 22 hours of battery available for "sleep condition" with the
existing batteries.

These are all "bench racing" numbers. Differing conditions and
interpretations could lead to a bit of change to the bottom line, but
this covers the general idea when the same batteries are used for
automotive and house systems.

Bob Griesel '84 FC31 WLII WA


--- In WanderlodgeForum@yahoogroups.com, "hippieforever3"
wrote:
>
> I'm still struggling with trying to figure out if my batteries are
> trashed or somehow I have an inordinately high current drain.
>
> The facts;
> 4 - 12volt - 85ah marine deep cycle batteries in parallel
> Batteries have been fully charged w/ external charger to 14.5+volts
> current drain with almost everything off (sleep condition) = 6amps
> measured with a good quality clamp ammeter
>
> Question
> How long should healthy batteries be able to maintain cranking
voltage?
>
> Regards,
> GPSGary
>