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post #71 of 138 Old 4 Weeks Ago
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Re: Realistic expectations for my house batteries

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Two Group 27's is a small bank, and implies that your electric propulsion needs are modest. For a larger need, high charge acceptance rates becomes important because one needs to put a lot of current back into the batteries before next use. Or one needs longer times between usage to achieve full charge.
Those two group 27 batteries are just for my 12 volt house bank. I also have four 8A4D AGM batteries for my Electric Propulsion bank. It has it's own charging systems which includes solar, wind and my Honda 2000 generator. Also I can use 120 volts AC if I'm at a dock which is rarely.

One nice thing about having the 10KW Electric Propulsion bank in addition to my house bank is I can tap into if needed while at anchor. Which I do from time to time. I use my 1600 watt 48 volt inverter to use my bread maker. Nothing like the smell and having fresh bread when you wake up in the morning at anchor.

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Re: Realistic expectations for my house batteries

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Those two group 27 batteries are just for my 12 volt house bank. I also have four 8A4D AGM batteries for my Electric Propulsion bank. It has it's own charging systems which includes solar, wind and my Honda 2000 generator. Also I can use 120 volts AC if I'm at a dock which is rarely.
Ah, that makes more sense. I was thinking you had a trolling motor or something similar! I now see I missed that in your original post, and conflated your house bank with your propulsion bank.

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Re: Realistic expectations for my house batteries

Bored, can’t sleep. Just looked up prices of Lithium batteries, GC2. The cheapest I saw was over $2,000 per batterie. So I would be looking at about $10,000 for my house bank of 4 GC2 batteries? Really? What am I doing wrong?

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Re: Realistic expectations for my house batteries

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Originally Posted by MastUndSchotbruch View Post
....We CRAVE weight, the keel of my boat is a blob of lead that is literally heavier than the rest of the boat.

Why don't we build a keel out of the cheapest, heaviest lead acid batteries and all go electric? .......
I don't know about craving weight, but keel boats certainly have tons of weight intentionally added for ballast. I get the desire to swap it for something with dual purpose. I think there are two limitations for adding batteries to the keel. Nothing on a boat is actually waterproof, including the hull. We all get some sort of leak eventually. Further, no two keels are alike. This would make manufacturing efficiency very difficult and very expensive.

It would be nice to see an effective long range electric solution, but it's not in the cards with current technology. Actually, most of the advancements in both batteries and charging (solar/wind) have been in manufacturing efficiency, not storage capability. The energy density, therefore storage of potential energy, of carbon based fuels can't be beat so far.


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Re: Realistic expectations for my house batteries

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Bored, can’t sleep. Just looked up prices of Lithium batteries, GC2. The cheapest I saw was over $2,000 per batterie. So I would be looking at about $10,000 for my house bank of 4 GC2 batteries? Really? What am I doing wrong?
I'm not sure where you are looking, but there is hardly a typical group size on the site linked below that is near that price level. Not many sailboats use 8Ds. Maybe your battery size is the unusual variable and there is a near match that is more affordable.

I currently have 4x Group 31 Gel batteries at approx 100ah each, which cost approx $475 each. That was a total of $1,900 for 200ah of usable capacity (50% of total capacity).

If I were to upgrade to lithium, the attached shows Group 31 lithiumPO batteries at $1,050 each and the same 100ah total capacity in each. However, you can run a LifePO battery down to 20% SOC, so that's 100x4x80% or 320ah of usable capacity for $4,200.

At least for this brand, lithium is twice the cost, but one gets 50% more usable capacity, superior charging profile (ie much less generator/engine time or faster renewable charging) and they weigh about a third of what the Gels weigh.

It would be cheaper to add even more weight and batteries, but for those who are space or weight constrained or value the faster charge rate, lithium has value.

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Re: Realistic expectations for my house batteries

GC2 batteries are “Golf Cart” batteries.

I did a little more looking and found some Lithium as low as $1,100.

Batteries Plus sell lead acid GC2 batteries for $110 - $130.

So look at it this way, if I get 3 years from a set of batteries I get 30 years of battery per pocket book charge.

The lithium batteries would have to last 30 years to be equal.

That’s probably being a bit facetious and I’m sure there are other advantageous BUT...

HOLY COW THATS A LOT OF MONEY!

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Re: Realistic expectations for my house batteries

Comparing the cost of LFP to FLA is a bit of apples and oranges, although they both store energy. A better comparison would be to gel or agm, because at least then you will be comparing physical and operating features like no maintenance, etc.

Consider one aspect of the cost of LFP to be similar to the cost of a watermaker - it is almost always cheaper, even in the long run, to buy and jug water than to get a watermaker. But people cruising still fork over thousands for a watermaker by the droves for very good reasons other than cost. LFP has the same rationale from a general overhead viewpoint, ignoring the details of why.

Not included in most cost comparisons is that it takes less solar and less fuel to recharge LFP.

Replacing batteries often can be inconvenient and expensive. We had to replace a GC house bank in Panama once. Battery prices for flooded golf cart batteries there cost 75% of what our equivalent capacity LFP bank cost. AGM prices in Panama were 3x that, so much more than LFP. And we had to interrupt our cruise to go back to Panama to get them. We had to buy a simple, common automotive start battery in the Bahamas. That one cost $200 - I can't imagine what a house bank of reasonable batteries would cost there, but it would surely be more than a LFP bank.

If money is the sole, or overriding, consideration, then flooded golf cart batteries can't be beat. If one is not cruising or living full-time off grid, then LFP doesn't make as much sense.

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Re: Realistic expectations for my house batteries

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Originally Posted by hpeer View Post
GC2 batteries are “Golf Cart” batteries.

I did a little more looking and found some Lithium as low as $1,100.

Batteries Plus sell lead acid GC2 batteries for $110 - $130.

So look at it this way, if I get 3 years from a set of batteries I get 30 years of battery per pocket book charge.

The lithium batteries would have to last 30 years to be equal.

That’s probably being a bit facetious and I’m sure there are other advantageous BUT...

HOLY COW THATS A LOT OF MONEY!
No I don't think you are wrong in your skepticism on a Lithium conversion. Even if the 2000 charge cycles of Lithium batteries holds up. I won't live long enough to see if they actually do. It's been said most cruising boats spend 90% on their time at anchor. I certainly do. I head some place and hang out anywhere from a few days to a week. Since I do have a SAILBOAT usually my boats EP bank just needs a little top off. Solar and wind maintain it after that even if I do tap into it's energy from time to time.

Another thing you need to add to the costs of Lithium is the Battery Charger and the BMS (Battery Management System) needed to protect the cells from over/under charging. When I converted 11 years ago to EP I bought a second backup AGM battery charger (which I have never needed) so I've got a little more invested if I were to change now too. Personally the complexity needed to maintain a Lithium Battery bank scares me. AGM'S are easy to understand and figure out without additional circuitry needed to maintain them. What can I say I'm just a KISS (Keep It Simple Sailor)

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Last edited by mbianka; 4 Weeks Ago at 08:10 AM.
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Re: Realistic expectations for my house batteries

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Um, some of us don't crave weight - just the opposite. Others who can handle weight don't want it in the places batteries are usually stored. In fact, you might be the only person I've heard of that craves more weight on their boat.

Mark
Really? Wouldn't a heavier keel improve pretty much every monohull's performance? Am I the only one who likes better sailing quality?
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Re: Realistic expectations for my house batteries

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If one were designing a boat from the ground up that would make sense..

Yes, of course. I am not starting to hollow out my keel and putting in batteries.
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