What size LiFEPO4 bank

[john61ct]

Already embedded in my posts above, and most of the many approaches should be pretty self-evident to someone who's been participating at your level.

See if you can come up with at least a partial list, and maybe I'll help fill in any gaps.

What they call "an exercise left for the reader".

Of course not you specifically. if you don't feel like it - no one should feel entitled to the work of fellow volunteers.

Anyone can play, maybe ramblin rod wants to give it a go.

[john61ct]

Originally Posted by Q Xopa

You dont agree LFP is the solution.

And in case you misinterpreted, LFP is definitely **a** solution, and as I stated, an excellent one for those that can afford it.

Maybe "the best" one for those who can drop many thousands without thinking twice.

[ramblinrod]

I do want to address an issue prevalent in this thread.

Not once have I claimed, "FLA is superior to LFP" (or vice versa).

I never would.

As I have always said, each technology has it's advantages and disadvantages.

How their characteristics translate into user benefits depends on the individual use case.

Recently I did state, "FLA is very well suited to solar charging".

It is.

We all know, (at least I have, for a long, long time), that solar charge output typically diminishes during the afternoon until sunset, and if everything is sized properly, will fairly closely match the diminishing FLA charge acceptance, as the bank reaches 100% SOC.

Having a higher charge acceptance rate spec, is no real benefit to the user, if the charge rate is limited by the output of the solar charging system.

On a sunny day, if the FLA bank is around 75% charged by noon, that is awesome. This means, that we have somewhere in the neighbourhood of 6 to 9 hours, to charge it to 100%.

Is the excess solar charging output available (if any) for the rest of the day "wasted"?

Well, there is a big difference between "not needing" to use something existing, and "wasting" it.

Burning fuel to charge LFP, when not required because there is sufficient insolation, could be considered "wasting" fuel.

Notwithstanding, if anyone is concerned about solar charging output going "unused", they may divert excess production to power discretionary electrical loads, and even automate this to heat water, when solar power in excess of that required for battery charging, is available.

Please don't try to pretend that ICE charging LFP is less "wasteful" than solar charging FLA.

[MikeFergie]

One of the boats that I met on a world cruise that convinced me to change to LiFePo4 was a Cantana 43 that had 400 amps hours (12v) fitted and all he had was 2 x 200w panels and his alternators. He had no gen set and still loved the changeover due to not having to worry about being below 50% and not having to charge to 100%.

I think it’s a wrong to assume you need a big gen set to make LiFePo4 work on a boat.

This Catana carried on from my side of Africa all the way down to Cape Town across the Atlantic. All the way down to Cape Horn around Cape Horn Patagonia and then on to Equador. Not sure where it currently is.

[evm1024]

Originally Posted by MikeFergie

One of the boats that I met on a world cruise that convinced me to change to LiFePo4 was a Cantana 43 that had 400 amps hours (12v) fitted and all he had was 2 x 200w panels and his alternators. He had no gen set and still loved the changeover due to not having to worry about being below 50% and not having to charge to 100%.

I think it’s a wrong to assume you need a big gen set to make LiFePo4 work on a boat.

This Catana carried on from my side of Africa all the way down to Cape Town across the Atlantic. All the way down to Cape Horn around Cape Horn Patagonia and then on to Equador. Not sure where it currently is.

Indeed. That really was one of the targets that the graph I posted a few pages back shows. 400 AH LiFePO4, 29 amps of solar and "normal" sun gives you fully charged batteries every day without the heat, smell, vibration, cost, wear and tear on man and machine that ICE brings with it.

Not something you can do with 400 AH of FLA.

[Dockhead]

Originally Posted by john61ct

. . . Although a hybrid setup with just a small LFP bank feeding a DCDC to get the main lead bank to 100% Full, would be one way to do it. Violates KISS though.

We explored this in a long and interesting thread some time ago. Being linked with a lithium bank means lead can always get its finishing charge -- best of both worlds, right? But at the end of the day we understood from the numbers, crunched in a disciplined way, that it's not worth keeping any lead around.

[newhaul]

Originally Posted by Dockhead

We explored this in a long and interesting thread some time ago. Being linked with a lithium bank means lead can always get its finishing charge -- best of both worlds, right? But at the end of the day we understood from the numbers, crunched in a disciplined way, that it's not worth keeping any lead around.

for me a small Fla start battery for the volvo and alternator protection .seems like a good idea and cheap Insurance.

[Dockhead]

Originally Posted by ramblinrod

I do want to address an issue prevalent in this thread.

Not once have I claimed, "FLA is superior to LFP" (or vice versa).

I never would.

As I have always said, each technology has it's advantages and disadvantages.

How their characteristics translate into user benefits depends on the individual use case.

Recently I did state, "FLA is very well suited to solar charging".

It is.

We all know, (at least I have, for a long, long time), that solar charge output typically diminishes during the afternoon until sunset, and if everything is sized properly, will fairly closely match the diminishing FLA charge acceptance, as the bank reaches 100% SOC.

Having a higher charge acceptance rate spec, is no real benefit to the user, if the charge rate is limited by the output of the solar charging system.

On a sunny day, if the FLA bank is around 75% charged by noon, that is awesome. This means, that we have somewhere in the neighbourhood of 6 to 9 hours, to charge it to 100%.

Is the excess solar charging output available (if any) for the rest of the day "wasted"?

Well, there is a big difference between "not needing" to use something existing, and "wasting" it.

Burning fuel to charge LFP, when not required because there is sufficient insolation, could be considered "wasting" fuel.

Notwithstanding, if anyone is concerned about solar charging output going "unused", they may divert excess production to power discretionary electrical loads, and even automate this to heat water, when solar power in excess of that required for battery charging, is available.

Please don't try to pretend that ICE charging LFP is less "wasteful" than solar charging FLA.

I agree with the first part of this post, but the second part is a bizarre non-sequitur. Yes, solar is complementary to lead and considerably makes up for its faults, PROVIDED you have more solar capacity than you need, such that you have done the bulk charging and gotten that out of the way, while there's still a good bit of sun left.


But the choice is not ICE plus lithium vs solar plus lead. You can use solar with lithium just as well as with lead. And lithium has the huge advantages of (a) much greater efficiency* and (b) not needing a finishing charge, which combined means you need much less solar to do the same amount of work. So lithium and solar also are great together, in fact greater than lead and solar.



The absorption charge with lead is inefficient and a PITA. To ensure the health of a lead bank, you need to either run the generator far more than you would otherwise need to, like many hours per day, OR you need so much solar that you can afford to burn power inefficiently -- and SLOWLY -- pumping the last 15% in, at least every couple three days. This absorption charge phase is really the Achille's Heel of lead batteries.



For those who sail from marina to marina on lakes, with an occasional night at anchor, this won't matter. But for those of us who spend months at a time without tying up to a dock, it is a very big deal.




* Let's be clear what we're talking about here: the charge efficiency of lead acid batteries drops to 60% or less, once the SOC is over 80%. From about 90% during the bulk phase (for example, https://www.solar-facts.com/batterie...y-charging.php). Overall efficiency from 50% to 100% is maybe 70% to 80%; up to 90% if you stop charging at the end of the bulk phase (what I do most days off the grid). That means for every kilowatt hour of power you generate or harvest from the sun, you will get maybe 700 watt hours back out of the batteries when you discharge them. With LiFePo4, this number is anywhere from 92% to 99%, depending on who you believe (I think MaineSail measured 92%).



If you are on a catamaran, or a cruising boat which doesn't sail much, and can fit an oversized solar array, capable of producing double the power you use on an average day, then this is not such a big deal, as solar power is pretty cheap. If you can't fit that much solar, or you are using a generator, this is a very big deal.

[ramblinrod]

Originally Posted by MikeFergie

One of the boats that I met on a world cruise that convinced me to change to LiFePo4 was a Cantana 43 that had 400 amps hours (12v) fitted and all he had was 2 x 200w panels and his alternators. He had no gen set and still loved the changeover due to not having to worry about being below 50% and not having to charge to 100%.

I think it’s a wrong to assume you need a big gen set to make LiFePo4 work on a boat.

This Catana carried on from my side of Africa all the way down to Cape Town across the Atlantic. All the way down to Cape Horn around Cape Horn Patagonia and then on to Equador. Not sure where it currently is.

Yes, and this really, really depends on the individual. Some people are absolute worry warts over things that are not really that concerning.

On my boat (400 W solar into 300 A-hr FLA), if I wake up at anchor in the morning, and the forecast is for sun, I don't do anything, as I know my bank (which will be above 50%) will be at 100% by sunset.

When I wake up, if the FLA bank is at 75%, I do nothing. If it is sunny, it will charge. If it is not sunny, it may drop to 50% by the next morning.

When I wake up, and the FLA bank is at 50%, and the forecast is for little sun, I will start the engine and use it for the following:

a) Move to another anchorage. (We like to move on overcast days, so we get the maximum number of nice days, relaxing, swimming, swinging at anchor.)

b) Discretionary inverter loads. (Maybe make a loaf of bread).

c) Heat water. (Do some laundry, have a shower.)

d) Charge the batteries.

Typically, by the time all of the other items are addressed, the batteries are up to at least 75%, and I can shut down and let what solar there is, top them up to (or near) 100%. If they don't quite reach there today, they likely will tomorrow.

So the effort is, check the battery monitor in the morning, and make the decision to start the engine or not.

How much do I worry about it?

Zero.

Interestingly, if I changed to LFP, the exact same decision would have to be made, just at a different SOC level, say 30% instead of 50%.

I accept that if I don't get up to 100% SOC (or close) most days, my FLA battery longevity may be reduced somewhat.

But at 1/10th the cost of LFP drop-ins, and with my FLA bank life expectancy of 4 years, and FLA being one of the best recycled products on the planet, and there being no practical recycling program for LFP, and not knowing what the future holds, and how long I'll own any particular boat, I am good with this.

If I was planning a circumnavigation, with very few stops for any length of time, my needs analysis may result in a different outcome.

I'm not in any race to round the world.

YMMV.

[Dockhead]

Originally Posted by newhaul

for me a small Fla start battery for the volvo and alternator protection .seems like a good idea and cheap Insurance.

Sure, if your power system can be set up like that, this can be elegant.


Mine can't, as engine and genset start banks are 12v and completely separated from house, which is 24v. There are pretty easy ways to protect the alternator, without needing to resort to lead batteries, e.g. https://sterling-power.com/products/...tection-device, for £47. Protecting the alternator is a fairly trivial problem.

[Dockhead]

Originally Posted by ramblinrod

. . . But at 1/10th the cost of LFP drop-ins, and with my FLA bank life expectancy of 4 years, . . .

If that were the choice, then I would agree with you completely and I would take lead every day, even with my use case.


But LFP drop-ins are not the only way to implement lithium power. In fact, LFP drop-ins are a ridiculous approach to the design of a lithium power system, purely as a stop gap to bring lithium power to a boat with a lead-oriented electrical system.



It is not that complicated to set up the infrastructure for lithium prismatic cells, which are themselves cheaper than quality lead batteries on a KWh handled basis. it is surprisingly not rocket science, if you dive into it, and once you understand it, you would want similar infrastructure for your lead bank too if you were forced to keep using it -- it's just good common sense to protect the batteries from high and low voltage events and monitor cell balance -- lead batteries would benefit from it just as much as lithium ones do.

[newhaul]

One thing that I want to mention that nobody has said wrt the the charging efficiencies between the differing battery chemistry's

Peukert's law,

[ramblinrod]

Originally Posted by Dockhead

I agree with the first part of this post...

Excellent, thank you.

Yes, solar is complementary to lead...

Excellent, thank you.

and considerably makes up for its faults,

?

Objection your honour, "argumentative", whether the "characteristics" are advantageous, disadvantageous, or neutral remains to be determined.

"...PROVIDED you have more solar capacity than you need..."

Objection, if the solar capacity is adequate to fully charge the bank most days, it is by very definition, "right-sized".

But the choice is not ICE plus lithium vs solar plus lead. You can use solar with lithium just as well as with lead.

Objection, nobody has claimed otherwise.

And lithium has the huge advantages...

Objection, the amount of advantage or disadvantage, if any, remains to be determined.

To ensure the health of a lead bank, you need to either run the generator far more than you would otherwise need to...

Objection, irrelevant to anyone using renewable energy as a charging source.

OR you need so much solar that you can afford to burn power inefficiently....

Objection, the alternative, if one does not use solar, they are burning and wasting fossil fuels, causing air pollution, noise pollution, and emitting known carcinogens into the environment, when they could be charging with solar, a "renewable" energy source.

This absorption charge phase is really the Achille's Heel of lead batteries.

Objection, argumentative.

For those who sail from marina to marina on lakes, with an occasional night at anchor, this won't matter. But for those of us who spend months at a time without tying up to a dock, it is a very big deal.

Objection, the individual use case must be evaluated. Many who sit at a dock all the time, choose to run a generator, the instant they unhook. Conversely, many who spend months a time at anchor, will be well served with a properly sized FLA bank and solar.

* Let's be clear what we're talking about here:

Yes, please...

the charge efficiency of lead acid batteries drops to 60% or less, once the SOC is over 80%. From about 90% during the bulk phase (for example, https://www.solar-facts.com/batterie...y-charging.php).

Objection. So what?

This make virtually no difference to the boater. Fully charged at the end of the day, is fully charged at the end of the day. If the solar charging system is "right-sized" for the FLA bank, the batteries will be charged, the beer will be cold, and no partially burned organic compounds will be spewed into the atmosphere.

If you are on a catamaran, or a cruising boat which doesn't sail much, and can fit an oversized solar array...

Objection, "right-sized".

[newhaul]

Originally Posted by ramblinrod

But at 1/10th the cost of LFP drop-ins, and with my FLA bank life expectancy of 4 years, and FLA being one of the best recycled products on the planet, and there being no practical recycling program for LFP, and not knowing what the future holds, and how long I'll own any particular boat, I am good with this.

I would love to see the actual numbers on this .

Especially considering 1) the actual size difference in ah that is needed on hand to effectively do the same work.
2) the brand and cost of each brand and type of battery .


I have done the numbers and quality for quality at most its 2 to 1 difference between Lfp " drop ins " and Fla " drop ins " . Working ah for working ah.

And that difference is made up in the lower maintenance of Lfp. Jmho.

[newhaul]

Originally Posted by ramblinrod

Excellent, thank you.



Excellent, thank you.

?

Objection your honour, "argumentative", whether the "characteristics" are advantageous, disadvantageous, or neutral remains to be determined.



Objection, if the solar capacity is adequate to fully charge the bank most days, it is by very definition, "right-sized".



Objection, nobody has claimed otherwise.



Objection, the amount of advantage or disadvantage, if any, remains to be determined.



Objection, irrelevant to anyone using renewable energy as a charging source.



Objection, the alternative, if one does not use solar, they are burning and wasting fossil fuels, causing air pollution, noise pollution, and emitting known carcinogens into the environment, when they could be charging with solar, a "renewable" energy source.



Objection, argumentative.



Objection, the individual use case must be evaluated. Many who sit at a dock all the time, choose to run a generator, the instant they unhook. Conversely, many who spend months a time at anchor, will be well served with a properly sized FLA bank and solar.



Yes, please...



Objection. So what?

This make virtually no difference to the boater. Fully charged at the end of the day, is fully charged at the end of the day. If the solar charging system is "right-sized" for the FLA bank, the batteries will be charged, the beer will be cold, and no partially burned organic compounds will be spewed into the atmosphere.



Objection, "right-sized".

argumentative cherry picking .

You should really quote the whole statement that you object to or have an alternative opinion for .