How many amp hours can I fit? - Page 3 - SailNet Community
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post #21 of 43 Old 02-19-2009
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MaineSail,

Just checking

I know that you are very knowledgable in this area, and I'm not, so thought that maybe I was missing something.

I still have trouble with P=U*I
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post #22 of 43 Old 02-19-2009
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A question. What do you guys do about charging these large battery banks? I have a 100 amp alternator on my main and after a long night on the hook I takes about 6 hrs of running to recharge 2 8ds along with running the fridge thru the inverter.
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post #23 of 43 Old 02-19-2009 Thread Starter
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Jorgenl - We're buying them direct from Mastervolt in Ft. Lauderdale. They stock them in Baltimore. They just dropped the price to $550 each for me, including shipping, since someone else also ordered some and they can split the shipping charges.

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post #24 of 43 Old 02-19-2009
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Valiente-
Using individual 2v cells and bolting them up is in fact the worldwide standard for the batteries used in electric fork lifts and other industrial applications. It is the only way to assemble a huge battery and still have a way for one or two men to lift the pieces by hand, and it is a proven economy since individual cells can be (and are) replaced if one cell fails.
When you think about it, it has the same number of failure points as any 12v battery which has been assembled--and then sealed out of reach in a case. But, with individual cells you can at least access the connections.

Of course, you can't ust hop down to the local chandlery to buy the cells, or get warranty service on them. But there's a fork lift battery supplier in just about every commercial port in the world.
You make good points. I am in the unenviable position of once having known nothing about battery options and being unable to make the right choice, and now knowing a great deal about battery options and still not feeling I can make the right choice...

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post #25 of 43 Old 02-19-2009
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A question. What do you guys do about charging these large battery banks? I have a 100 amp alternator on my main and after a long night on the hook I takes about 6 hrs of running to recharge 2 8ds along with running the fridge thru the inverter.
Good grief, why would you run the fridge through the inverter? Inverters are inefficient things and I consider them appropriate for small stuff, like a bunch of adapter bricks or a small LCD screen, and/or brief stuff like five minutes of microwaving.

You sound like a great candidate for wind and solar, if not a genset. An alternator from a diesel is hard to make efficient. But an AC fridge is brutal on a boat without that kind of "energy depth".

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post #26 of 43 Old 02-19-2009
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Good grief, why would you run the fridge through the inverter? Inverters are inefficient things and I consider them appropriate for small stuff, like a bunch of adapter bricks or a small LCD screen, and/or brief stuff like five minutes of microwaving.

You sound like a great candidate for wind and solar, if not a genset. An alternator from a diesel is hard to make efficient. But an AC fridge is brutal on a boat without that kind of "energy depth".
Well the boat came with a 110v fridge. A 12v or propane is on the list you know the list with all the $$$ signs. How much actual efficently is lost through the inverter?
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post #27 of 43 Old 02-19-2009
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How much actual efficently is lost through the inverter?

It depends on what you are doing but 10% is a bare minimum. With some items that internally are DC but that actually plug into AC the inefficiencies can exceed 30% or more.

See this: Inverter Inefficiencies (LINK)

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post #28 of 43 Old 02-19-2009
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Great link. thanks. So it looks as though the larger the inverter the greater the loss
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post #29 of 43 Old 02-19-2009
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Valiente-
If the battery makers ever got together and sang the same song, and anyone could get "one truth" about which ones really last best, perform best, etc., etc., ... It might be possible to make easier choices.

But hey, if you think batteries are confusing try shopping for a mattress. Or tires. Or a mail-order bride.(VBG)

Even when Consumer Reports does their lab comparisons for car SLI batteries, the results mean nothing a fast year later as all the makers fiddle with their products and all the brands change their sources or re-spec the products.

So you start with tape measure and a "want" and then do the best you can. And whatever you buy--you still don't know if the batteries are "any good" unless the entire charge system and use pattern (cycling) is optimized as well.

Somewhere along the line most folks say "Oh, * it, its time to go sailing!" instead.
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post #30 of 43 Old 02-19-2009
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Well, this is what is driving me back from the brink of a big investment in slim, sealed AGMs to comtemplating a load of truck-sized 8D lead-acids that will require me to carry around a hygrometer and a couple of jugs of distilled water.

At least I am familiar with the technology and the maintenance isn't particularly daunting.

I am lucky (well, I planned it that way, really) in having the sort of boat where I can carry weight like batteries low, cool (outside of the engine compartment) and can keep them accessible from above. So I don't really require the "forget about 'em" advantages of AGM like some do. But I do plan on having four 8Ds or the equivalent and I want short cable runs tying everything together, because I want to have a lot of reserve capacity in order to avoid using the diesel to charge, so this means some framing, carpentry and planning is required.

And a tape measure.

Maybe I should look anew at the Surrettes. Easier on the back.

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