Starting Battery

[charles]

C34 MK II year 2000:
I am planning on adding a Starting battery, and I'm looking for suggestions on a good location on a MK II. Also, looking for suggestions for a starting battery.

I'm thinking of the Optima starting battery, 800cca from Jack Rabbit Marine.
I believe my Flyback Charger will handle a third battery. I'm pretty sure the boat came with Exide Nautilus 4D's, which are still OK.
For wiring:
Going to replace the Perko engine "on/Off" Switch with a 4 position switch, just like the main battery switch.Then wire the starting battery to Position # 2 on the new switch, and wire Position number 1 to the Common post on the existing Battery Switch. And move the Starting engine wire to the Common post on the new Starting battery Switch
I think this would allow me all combination of the three batteries.
I think most people just put the two house Batteries to posistion one and the starting Battery to position 2. But then you can't separate the two house batteries.
I can e-mail adiagramif anyone wants to see or inspect it.

Comments Please --
thanks
Charlie
hull #149

[Stu Jackson]

Charlie

You don't want to separate your house batteries.


IS IT BETTER TO HAVE ONE OR TWO BATTERY BANKS FOR HOUSE USE?
(By Nigel Calder - I DIDN’T write this!!!)

The popular arrangement of having two house banks alternated in use needs scrutiny before I go any further.

LIFE CYCLES: As we have seen, the life expectancy of a battery in cycling service is directly related to the depth to which it is discharged at each cycle - the greater the depth of discharge, the shorter the battery’s life.

This relationship between depth of discharge and battery life is NOT linear.  As the depth of discharge increases, a battery’s life expectancy is disproportionately shortened.  A given battery may cycle through 10% of its capacity 2,000 times, 50% of its capacity 300 times and 100% of its capacity around 100 times.

Let’s say, for arguments sake, that a boat has two 200-ah battery banks, alternated from day to day, with a daily load of 80 Ah.  Each bank will be discharged by 40% (80 Ah of one of the two 200 Ah banks) of its capacity before being recharged.  The batteries will fail after 380 cycles, which is 760 days (since each is used every other day).  If the two banks had been wired in parallel, to make a single 400 Ah battery bank, this bank would have been discharged by 20% of capacity every day, with a life expectancy of 800 days, a 5% increase in life expectancy using exactly the same
batteries!

But now let’s double the capacity of the batteries, so that the boat has either two 400
Ah banks, or a single 800 Ah bank, but with the same 80 Ah daily load.  The two separate banks will be cycling through 20% of capacity every other day, resulting in a total life expectancy of 1,600 days.  Doubling the size of the battery banks in relation to the load has produced a 210% increase in life expectancy.  The single 800 Ah bank will be cycling through 10% of capacity every day, resulting in a life expectancy of 2,000
days - a 25% increase in life expectancy over the two (400 Ah) banks, and a 250% increase in life expectancy over the single 400 Ah battery bank!

There are two immediate conclusions to be drawn from these figures:

1.  For a given total battery capacity, wiring the (house) batteries into a single high
capacity bank, rather than having them divided into two alternating banks, will result in a
longer overall life expectancy for the batteries.

2.  All other things being equal, any increase in the overall capacity of a battery bank will produce a disproportionate increase in its life expectancy (through reducing the depth of discharge at each cycle).

FOR BATTERY LONGEVITY, A SINGLE LARGE (HOUSE) BANK, THE LARGER THE BETTER, IS PREFERABLE TO DIVIDED (HOUSE) BANKS.

[casaheck]

Charlie

The dealer from whom we bought our C34 (# 1587) (Carolina Wind, Washington, NC) installed a starting battery just outboard of the hot water heater under the settee.  It fits nicely there and is easily accessible.  The starting battery is an Exide Group 24 (deep cycle).  The starting battery can be used for other purposes than starting, if necessary.

Installation involved building, glassing in, and painting a wood base.  The battery is held in place with a wood bracket (also painted) that is bolted to the base.

- Henry

[c34member]

I also have a 2000 MkII and my installation is identical to Henry and Mercedes'.  Small world.  I have an echo charge off my Freedom 1500 inverter to charge it from shorepower.

[Mark Elkin]

Yorkshire Rose is an early Mk I, but you may still find some useful ideas from my started battery project.  I have lots of pictures and diagrams on my web pages.  Visit http://home.san.rr.com/heysailor/sailing/projects/battery01.html to see what I did.

Mark Elkin
Yorkshire Rose, #133

[tassber2]

I used a 1000amp optima AGM battery.  Has lots of power, holds a charge great and is small enough to place starboard of your hot water heater.  It is wired to switch 2 on my battery selector and I use 4 6v golf cart batteries for my house bank wired to switch 1.  Its a great system.