6 Volt, reserve vs weight - SailNet Community

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  #1  
Old 05-06-2003
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6 Volt, reserve vs weight

Am I fooling myself here? Would I be better off with a 4 battery bank than running two 6 volts battieries? My boat is set up for live aboard and I would LOVE to be able to run the refrigerator even when I am away from shore power. It is my only major draw but there is anyways the other small items like running lights, radio, and maybe a reading light. help which way should I go????
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Old 05-06-2003
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6 Volt, reserve vs weight

The answer lies in how much room do you have for batteries and what type? i.e. group 27/group24 or golf cart batteries?

Two 6v golf cart batteries will typically have more reserve power i.e. amp hours of current than two of the other types.
Figure out how many batteries of each type you could install, then add up the amp hour rating of that battery combo.

Batteries in parallel combine the total amphour rating of all the batteries. i.e. two 12 volt batteries rated at 90 amp hours each will give you 12 v and 180 amphours.

Batteries in series combine the total voltage of the batteries. i.e. two 6v batteries in series give 12v and the amp hour rating of one battery.

fairwinds,
Jim
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Old 05-06-2003
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6 Volt, reserve vs weight

I have space to go either way. I am still concerned about the weight. The golf cart battiers are HEAVY and some day I am going to put a new saildrive where I just ripped out the OMC. Damn those batteries are huge. Some 20" tall. The engine compartment is the only space I have that can handle anything that big. I need to find a 12 Volt with the same kinda reserve as a 6 Volt.
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Old 05-07-2003
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6 Volt, reserve vs weight

Don''t know what type of golf cart batteries you have seen, but the ones in my boat are not much heavier than the group 27 batteries (12v) that I replaced, yet they have about a 45 amp hour greater capacity.

Looking at the West Marine catalog, I see GC2 batteries (i.e. golf cart) are rated at 215ah (mine are 225ah) and are 10.25 x 7.125 x 10.8" and weigh 63.5 lbs. The group 27 batteries (12v) are rated at 90 ah and are 12.5 x 6.75 x 9.4" and weigh 53 lbs.

So a pair of the 6v batteries weigh 20 lbs more and give you 35 ah more capacity than a pair of the 12 volters.

Is that what you had in mind?

Jim

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Old 05-07-2003
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6 Volt, reserve vs weight

I was looking at West Marine too but I was looking at the 8L16 @113 lbs 370 ah
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Old 05-07-2003
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6 Volt, reserve vs weight

Four GC2''s would give you 430Ah at 252 lbs which should be enough capacity and not too heavy.

I''ve heard the figure of 100 Ah per day as a rough rule of thumb for a boat with refrigeration. Of course there are many variables, but that is probably a good estimate.

Don''t know how closely you watch your nickles, but I bought by golf cart batteries at Sam''s club for around $45 each. Some told me they were cheap and wouldn''t last but got 4 1/2 years service out of a pair. Of course they were floating on the charger most of the time and not used a lot in a full cruising enviornment which might make a difference.

430Ah would give you the capacity to keep in that 50 to 80% charge range that seems to be the optimum level for battery life and shorter charge time.
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