What size LiFEPO4 bank

[ramblinrod]

Originally Posted by jbinbi

I currently have 420ah bank, with 580 W of solar and 2 80A Hitachi alt. On sunny days, with a hour of motoring I can put 100-200As back into the battery bank, though I am conservative and try to keep to using 120A a day. Refrig, navs. All LED lighting.

I would like to up these numbers, knowing I can use 150 to 200A a day, and be able to put that back in. Would be ok if maybe have to run the engine an extra hour.

Was looking at getting 600 Ah of Trojans, but now thinking of Li.

What size bank Li should I be looking at if I want to be able to use 200A a day.

Assuming the 2 80A alternators, how much can I put back in to a Li bank in what time? Can I get 150 A in in an hour or so?

After looking at this thread in more detail, I suggest looking at your use case more deeply.

If you day sail / marina hop, and can recharge on shore power overnight at least every second night, switching to LFP will be little advantage, other than reducing house bank weight.

If you anchor out 24/7/365, then LFP could be an advantage if your charge sources can take advantage of the higher acceptance rate.

(Note that if you sell the boat in less than 6-10 years, it will be the next owner that realizes the financial benefit of the life charge cycles.)

[Gripfast]

I would like the page of that member and service provider.

[newhaul]

Originally Posted by Gripfast

I would like the page of that member and service provider.

I assume you are referring to mainesail .
https://marinehowto.com/

[jbinbi]

Originally Posted by ramblinrod

After looking at this thread in more detail, I suggest looking at your use case more deeply.

If you day sail / marina hop, and can recharge on shore power overnight at least every second night, switching to LFP will be little advantage, other than reducing house bank weight.

If you anchor out 24/7/365, then LFP could be an advantage if your charge sources can take advantage of the higher acceptance rate.

(Note that if you sell the boat in less than 6-10 years, it will be the next owner that realizes the financial benefit of the life charge cycles.)

I do 'marina hop' (never heard that term but like it), but rarely at a dock. Cats don't easily get dock space. Normally at a mooring.

But usually have to motor into the harbor and out, which adds at least 30 min if not more. With 2x alternators. Stock charger is only 40A, but currently have no generator.

If it is a rainy day and we absolutely have to go somewhere, we normally wind up motoring more. If a rainy day and we are at a mooring, that is when we drain lots more battery as no solar output, no engine as well. But if I can burn 1 gal to run the engines in neutral for 100 Ahs to be put back in, no big deal either.

I need new batteries, I can just get 4 trojans to replace the 3 120 Ah Exides, maybe even 6 and get to 600 Ah. Would be WAY LESS expensive than LiFePO, but not nearly as sexy....And 1 hour of motoring will not put in 150 Ah, though the first hour probably gets quite a bit in there if I am at 50% SOC.

[newhaul]

Originally Posted by jbinbi

I do 'marina hop' (never heard that term but like it), but rarely at a dock. Cats don't easily get dock space. Normally at a mooring.

But usually have to motor into the harbor and out, which adds at least 30 min if not more. With 2x alternators. Stock charger is only 40A, but currently have no generator.

If it is a rainy day and we absolutely have to go somewhere, we normally wind up motoring more. If a rainy day and we are at a mooring, that is when we drain lots more battery as no solar output, no engine as well. But if I can burn 1 gal to run the engines in neutral for 100 Ahs to be put back in, no big deal either.
.

this is exactly the reason for changing one alternator to a 200 amp or even a 240 amp unit with external regulation to 160 amp ( 200 amp unit) or about 200 amp ( for the 240 amp unit )
derating is to protect the alternator . Otherwise Lfp will take everything they can produce . They will overheat and get fried .

[john61ct]

Originally Posted by Delfin

My data comes from the cycle testing done by Lithionics, and I would be surprised if any other manufacturer would have significantly different results. In your specific example of going from 80% to 70%, Lithionics shows about 100 more cycles, not a 50% increase in usable cycles as you imagine

It varies not only by manufacturer, but also by all the other use-case-specific variables that determine longevity, particularly average discharge rate and temperature.

This is a Winston chart

But again, you will never see the same delta unless you precisely copied the conditions of the test protocol that produced this chart.

Even then, note that would be impossible, since straight from the mouth of a horse at Lithionics, that chart was produced for marketing purposes, and is based on "modeling extrapolation" I doubt many are tying up the testing hardware for the many years required to get actual hard data.

I also did qualify with an **example** statement, using **might get**, since there will never be a simple generalization formula to quantify the relationship between these variables.

In any case, the main point I was making, was refuting the common myth that you'll still get optimum lifespan out of LFP no matter how deep your average discharge.

Specifically responding to this:

Originally Posted by makobuilders

And I've seen the specs on many lithiums that claim very good lifespan taken down all the way to 100%

[john61ct]

Another general chart

https://www.ev-power.eu/blog/LiFePO4...ed-on-DOD.html

Note the logarithmic scale, so the 70-80% delta is in fact pretty close to a 50% gain.

[ssmoot]

Originally Posted by Delfin

If you wish to listen to those with actual practical experience with these batteries, or better yet, the manufacturers that do the kind of testing the U.S. military requires, like Lithionics

Lithionics doesn't make cells. I'd be curious to know what the actual manufacturer's data sheet says.

[Delfin]

Originally Posted by ssmoot

Lithionics doesn't make cells. I'd be curious to know what the actual manufacturer's data sheet says.

They assemble them after matching impedance. They do their own testing as they have to stand behind performance expectations in sales to the gummit.

I asked them whose cells that used, but they wouldn't tell me. Their test data is published on there website.

[ramblinrod]

Originally Posted by john61ct

It varies not only by manufacturer, but also by all the other use-case-specific variables that determine longevity, particularly average discharge rate and temperature.

This is a Winston chart

But again, you will never see the same delta unless you precisely copied the conditions of the test protocol that produced this chart.

Even then, note that would be impossible, since straight from the mouth of a horse at Lithionics, that chart was produced for marketing purposes, and is based on "modeling extrapolation" I doubt many are tying up the testing hardware for the many years required to get actual hard data.

I also did qualify with an **example** statement, using **might get**, since there will never be a simple generalization formula to quantify the relationship between these variables.

In any case, the main point I was making, was refuting the common myth that you'll still get optimum lifespan out of LFP no matter how deep your average discharge.

Specifically responding to this:

Thank you for this chart.

It confirms what I have been saying all along; that if one sizes the FLA bank right, and treats it right, it is difficult to financially justify LFP. The other advantages, reduced sag, higher acceptance, lower weight could be justification IF the user can actually benefit from these characteristics.

[evm1024]

Originally Posted by john61ct

SNIP %<
This is a Winston chart

SNIP%<

This is NOT a Winston chart. Tineye shows the first scan in 2015 on:

https://planeetta.wordpress.com/page/10/ Gaia - Ainoa kotimme

You will note that the word Winston is absent along with many other changes.The Gaia site appears to credit (my translation is not so good) Iron Edison - https://ironedison.com/

Whether Iron Edison originated this graphic or not it appears to be purely a SALES tool and does not reflect data from any specific controlled test. I am not saying anything about the data represented on the graph. I am saying that we have no idea of the source of the data and thus it cannot be confirmed. GIGO if you draw any conclusions from it.

Who knows where it came from originally - it is no longer on Iron Edison's site.

That graph is more what you'd call 'guidelines' than actual rules....

[Delfin]

Originally Posted by evm1024

This is NOT a Winston chart. Tineye shows the first scan in 2015 on:

https://planeetta.wordpress.com/page/10/ Gaia - Ainoa kotimme

You will note that the word Winston is absent along with many other changes.The Gaia site appears to credit (my translation is not so good) Iron Edison - https://ironedison.com/

Whether Iron Edison originated this graphic or not it appears to be purely a SALES tool and does not reflect data from any specific controlled test. I am not saying anything about the data represented on the graph. I am saying that we have no idea of the source of the data and thus it cannot be confirmed. GIGO if you draw any conclusions from it.

Who knows where it came from originally - it is no longer on Iron Edison's site.

That graph is more what you'd call 'guidelines' than actual rules....

Below is Lithionics cycle life projection. Rate of discharge is a factor with the slower rates of discharge increasing cycle life above what is shown here.

[Delfin]

Originally Posted by ramblinrod

Thank you for this chart.

It confirms what I have been saying all along; that if one sizes the FLA bank right, and treats it right, it is difficult to financially justify LFP. The other advantages, reduced sag, higher acceptance, lower weight could be justification IF the user can actually benefit from these characteristics.

If you get a chance to spend some time cruising with Lithium vs. LA you might understand why Lithium is so favored by those who actually use them for that purpose. Put another way, is listening to your genset for 1 hour vs. 4 worth buying a battery that will last 7-10x longer than LA?

[ramblinrod]

Originally Posted by Delfin

If you get a chance to spend some time cruising with Lithium vs. LA you might understand why Lithium is so favored by those who actually use them for that purpose. Put another way, is listening to your genset for 1 hour vs. 4 worth buying a battery that will last 7-10x longer than LA?

I consult many boaters (professionally) on marine electrical system upgrades.

For FLA vs LFP pros and cons analysis, we really have to look at the use case.

FLA may be the best choice for a boat that is connected to shore power most nights or has reasonably conservative electrical energy demands, would always prefer to use renewable energy charging sources, has a finite upgrade budget for the electrical system, they don’t really know how long they will own it before moving up, down, across, or out of boating, and doesn’t get their self esteem from how much they pay for something, or how “cool” others think owning something makes them.

LFP may be a logical choice for a boater with heavy electrical energy consumption demands, is rarely on shore power, has no desire for using renewable energy charging sources, has very deep pockets, and will not sell the boat for at least 15 years.


Everyone else likely falls somewhere in between, and it will take much more careful use case analysis to determine which solution is “best” for them.

[newhaul]

Originally Posted by ramblinrod

I consult many boaters (professionally) on marine electrical system upgrades.

For FLA vs LFP pros and cons analysis, we really have to look at the use case.

FLA may be the best choice for a boat that is connected to shore power most nights or has reasonably conservative electrical energy demands, would always prefer to use renewable energy charging sources, has a finite upgrade budget for the electrical system, they don’t really know how long they will own it before moving up, down, across, or out of boating, and doesn’t get their self esteem from how much they pay for something, or how “cool” others think owning something makes them.

LFP may be a logical choice for a boater with heavy electrical energy consumption demands, is rarely on shore power, has no desire for using renewable energy charging sources, has very deep pockets, and will not sell the boat for at least 15 years.


Everyone else likely falls somewhere in between, and it will take much more careful use case analysis to determine which solution is “best” for them.

so what you are saying is that I wasted 250 bucks on my Lfp bank ( 100ah) that has been performing wonderfully purely off grid charging on solar and wind ( renewable sources no ice used ) for the last year being a liveaboard At 48° north +/- ?

Doing the same with Fla would have required almost double the ah capacity. Or about the same money.