[Rhodes22-list] batteries and juice

[Peter Thorn]

GlacierBill, Lou, Jerry, Everyone, Anyone-

I've been thinking about converting Raven into a floating substation.
Here's my reasoning and would appreciate any constructive comments,
knowledge or experiences you might think helpful and be willing to share.
I'm a believer in "measure twice, cut once" and when it comes to boats,
"measure three times..."

Everyone uses their boat a little differently.  We like to use Raven for 3
day trips or longer.  A 6 day trip is better.  9 days would be ultra
luxurious.  Mary Lou and Fred's cruising practice of "every third night" in
a marina (for porta dump, shorepower, showers) seems right.  I like nights
on the hook, bow to the wind.

Using Don Casey's boat electrics book I made the attached Excel worksheet
showing that two group 27 or 31 deep cycle batteries can almost go three
days.   My research uncovered that only 45% of the available amp hours
should be considered because: a) batteries last much if not discharged below
50% capacity and b) it's difficult to charge batteries past about 95% in a
short time.

Thanks for the recent posts on LED cabin lights. They are helpful.  Casey's
energy budget worksheet displays what pigs incandescent cabin lights are.
Are the LEDs bayonets really bright enough to read by?

To start with just a charger, I'm considering a Xantrex tc40 40 amp
three-stage unit. http://store.solar-electric.com/tc-40-.html   It looks
small enough to fit on the port side of the forward battery/water tank
compartment, powerful enough to easily charge two group 31 deep cycles
overnight and it's half the cost of an Analytic Systems comparable charger.
The tc40 has an optional inexpensive voltmeter (about $40).  I am not sure
how this compares with a Link 10.  Do I need a Link 10 *and* a voltmeter?

The idea is to mount the batteries next to each other in the 7" wide space
forward of the water tank on a firmly attached piece of epoxied plywood.
Stan likes weight up front and that will certainly do that.

Raven will only have a house battery (dual).  Is a battery isolation switch
required?  I know the parallel cables must be of equal length.  What's the
downside to no isolation switch?

A friend's Tanzer 26 has a shorepower inlet (outlet?) inside the cockpit
sidepocket.  It keeps the plug end out of the weather and it's also out of
sight.  Has anyone ever seen a Rhodes wired that way?  Can it be done on a
R22 with the fancy secret balcony pocket?

Thanks.

PT