LiFePO4, maybe but..

The recent LiFePO4 poll got me thinking: If I went this route and relocated my battery bank outside of the hot ER, how could I connect the alternator to the new bank location?

We're talking 300A max @12V, a 50' round-trip, and cabling within the ER. That means multiple 4/0 cables each way. I don't like using multiple cables because if every connection isn't perfect and identical.. Can't move the alternator from the engine, can't move the batteries to a closer, cool space..

Go to 24v battery bank. Replace the alternator. Replace the inverter. Get a big 24-12 converter for the 12v loads (or better, keep one large 12v AGM for those loads, charged with a 24v-12v charger). I guess that'd work but additional complexity and $.

..or 24v with a 12v AGM might not work. Could be the case that I'd run out of 12v well before the 24v bank (powering just the inverter) is run down. So put 2 AGMs in rather than 1. So now rather than my current 4 AGMs I have 2 AGMs and LiFePO4 . Getting silly-complex here.

Other ideas?

danderer said:

The recent LiFePO4 poll got me thinking: If I went this route and relocated my battery bank outside of the hot ER, how could I connect the alternator to the new bank location?

We're talking 300A max @12V, a 50' round-trip, and cabling within the ER. That means multiple 4/0 cables each way. I don't like using multiple cables because if every connection isn't perfect and identical.. Can't move the alternator from the engine, can't move the batteries to a closer, cool space..

Go to 24v battery bank. Replace the alternator. Replace the inverter. Get a big 24-12 converter for the 12v loads (or better, keep one large 12v AGM for those loads, charged with a 24v-12v charger). I guess that'd work but additional complexity and $.

..or 24v with a 12v AGM might not work. Could be the case that I'd run out of 12v well before the 24v bank (powering just the inverter) is run down. So put 2 AGMs in rather than 1. So now rather than my current 4 AGMs I have 2 AGMs and LiFePO4 . Getting silly-complex here.

Other ideas?

Click to expand...

Good questions and I don't think there is any simple answer without having someone who really knows their stuff inspecting your existing system and everything's location in person and designing a system for you. This is why getting it right is expensive and time consuming. It is easy to overlook details about your existing system that could cause problems when implementing this technology.

I would imagine that installing buss bars for the new battery system as close as possible to the new bank and then run a charging circuit between the alternator and this house bank. Controlling the alternator's output when charging LiFePO4 is one of most important considerations as they can absorb charge so much faster than other chemistry types that alternators can easily get overheated trying to satisfy the bank. Other battery types have internal resistance within them that slows charging and also protects the alternator, kind of by accident but we have grown accustomed limiting factor always being present and fail to account for it when doing a "drop in" upgrade to LiFePO4. Your alternator probably won't live long trying to continuously supply 300 amps to this new house bank, but whatever safe output you can safely meter it back to while feeding a LiFePO4 bank will still outperform that effective rate of charging your current AGMs.

I find the potential fascinating and hope to see the integration of it for Marine applications mature but I certainly don't claim any level of expertise.

I'd actually measure the maximum charge current from the alternator after it heats up and derates. It may be a lot less than 300A. One 4/0 can handle the current, even in engine spaces, but at 300A there will be unacceptable voltage drop. At 150A it isn't great, but could be compensated for with remote sense. Or course 24V makes it a lot easier.

Another thing to consider is how much charge the LFP can actually take. It sounds like you would have a very large bank, but when I go through this exercise on my sailboat which has a 24V 440AH battery, it is problematic. Conventional wisdom is that you need only 1/2 the size in LFP, in my case 220AH, but that size would not be able to absorb the available current from my Electrodyne alternator. I either have to limit the output, or increase the battery size larger than needed. It would still be a plus though, because the recharge time even at the lowered rate would be quicker than AGMs.

You should check out this group on FB. Many are familiar w/ Rod Collins, he's the admin. A lot of great LFP in there...

https://www.facebook.com/groups/293580215978963

I used to have two banks of LA batteries. When they started dying, I bought LFPs. 4x170 AH, total 680 AH. Large enough to feed my fridge and freezers, plus the house a/c.
As long I am on shore power, the Mastervolt charger/inverter handles everything. Later I realized that to feed the LFPs while underway, I had to charge them from the main engine’s alternator, or run my Perkins generator sometimes, to provide a/c to the house. The LFP bank is big, but it would be deflated after a while.
So, this is what I did. I still had the ProMariner charge controller connected to the alternator to charge the starter batteries. Two new LA 12v. I wired the empty bank connection to two Victron dc/dc chargers 30A each and parallel connected them to the bus bar for the LFP bank. I included a 60A breaker to each Victron. Theoretically I should have 60A total going to the batteries. The Victron chargers have settings for LFP batteries, which you need to manually enable through Bluetooth.
Of course, these chargers will only get current, when the ProMariner decides to provide it. It always charges the starter first. Once it is done, it will feed the other banks. This is when the Victrons come alive and charge. My alternator can do 160A when it is in a good mood, so it should top off the batt bank just fine. I used 3/0 cables. The positive from the ProMariner to the Victron location is long. The negative just plugs into the bus bar close to the Mastervolt and batt bank. Victron requires all wiring to be exact same when you parallel multiple dc/dc units. Those are smaller size, since the Victrons are only a foot away from the bus bar.
Again, this provides current only when the main engine is running and the starter batteries are full.

A 300A engine alternator? What kind is that? If real then use a DC to DC charger to limit current to say 60 amps and then #2 wire should work fine.

David

DavidM said:

A 300A engine alternator? What kind is that? If real then use a DC to DC charger to limit current to say 60 amps and then #2 wire should work fine.

David

Click to expand...

A big honkin' Leece-Neville. 320A I think though I've derated it to 280 based on the installed wiring sizes.

LeoKa said:

So, this is what I did. I still had the ProMariner charge controller connected to the alternator to charge the starter batteries. Two new LA 12v. I wired the empty bank connection to two Victron dc/dc chargers 30A each and parallel connected them to the bus bar for the LFP bank. I included a 60A breaker to each Victron. Theoretically I should have 60A total going to the batteries. The Victron chargers have settings for LFP batteries, which you need to manually enable through Bluetooth.

Click to expand...

Seems to me some type of FLA/Li hybrid like this might be the most reasonable solution. Someone (in this group?) mentioned Calder advocating such a system. Anyone have info on that?

I mentioned it in another thread but instead of an alternator has anyone looked at an actual generator head?

Much less $$ and far simpler than big alts, charge controllers etc.

It was suggested to me by a marine electrician who lives aboard full time "unplugged" that 5kva heads new are around $600.
Have that wired directly into the inverter charger and you effectively have shore power when the engine is running at cruise speed and full charging capabilities.

Set belts and pulleys for cruising rpm and a light from power source on dash that is activated when in the correct rev range.

danderer said:

Seems to me some type of FLA/Li hybrid like this might be the most reasonable solution. Someone (in this group?) mentioned Calder advocating such a system. Anyone have info on that?

Click to expand...

I think it's fine for smaller systems/boats. With larger systems the issue is that you are limiting LFP charge by the capacity of the DC/DC chargers, where the alternator typically has much more charge capacity. So looking at the examples noted in the past couple of posts, 60A of LPF DC/DC charger capacity is a significant bottleneck when you have a 320A alternator.


With bigger systems, it's much better to reverse the alternator and DC/DC charger connections/roles. Connect the 320A alternator directly to the LFP bank, controlled by an external regulator. Then install a small DC/DC charger (20A, for example) from LFP to the start bank to top it up after starting. That way the lower capacity of the DC/DC charger is matched to the lower recharge demand of the start bank, and the higher capacity alternator is full utilized by the LFP bank. One of the big advantages of LFP is the ability to recharge it faster, so don't build a system that slow charges it, build one that fast charges it.


Also keep in mind that one of the big reasons people keep the alternator connected to the start bank rather than direct connect to LFP is so they can use drop-in batteries, punt on the issue of alternator damage in the event of all BMSes disconnecting, and to avoid adding an external alternator regulator. In my opinion, this approach compromises every other aspect of the system, all to avoid addressing these simple issues.


If you add an external alternator regulator, it can properly regulate the alternator for LFP, and can be shut down in a BMS failure event. If you have a system with an external BMS, in a failure situation it can shut off the alternator before disconnecting the batteries. And the alternative with internal BMSes is to use a clapping diode to protect the alternator. These are available from Sterling and Balmar.

twistedtree said:

I think it's fine for smaller systems/boats. With larger systems the issue is that you are limiting LFP charge by the capacity of the DC/DC chargers, where the alternator typically has much more charge capacity. So looking at the examples noted in the past couple of posts, 60A of LPF DC/DC charger capacity is a significant bottleneck when you have a 320A alternator.

Click to expand...

I agree with this and everything else you wrote. In going through this mental exercise I've concluded that for LFP to work the way I'd want it to would require much, much more than just battery replacement. I knew this but am now realizing just how much more it would require.

Every solution will have compromises. 60A of LFP charge is certainly a compromise. However, assuming I mount the LFP batteries in the laz to keep them cooler, there is no practical way to get a large charge to them from the alternator at 12v.

Getting the ER cooler would be a solution but I've already got decent airflow and the reality is that things get heat-soaked and forced ventilation doesn't make that much difference in my ER. Just the nature of the design I suppose.

A 48v LFP bank mounted in the laz could work. Replace the alternator and inverter/charger.

Except this is a 12v boat. Converters aren't a practical answer for things like the windlass. So put a 48v bank in the laz fed by the alternator (and inverter/charger). Keep a 12v AGM bank, fed/charged by the LFP at 60a or so. All draws come from the AGM which are kept topped by the LFP which is charged by the alternator and inverter/charger.

So what have I gained here? Additional capacity and maybe some faster charging. I don't have a capacity problem now (more is always nicer but..) and can charge at 200+a even with the alternator hot.

My conclusion from the exercise is that LFP doesn't make sense in my case. If I want more capacity then a couple solar panels or a couple more AGMs is a more cost-effective approach.

danderer said:

I agree with this and everything else you wrote. In going through this mental exercise I've concluded that for LFP to work the way I'd want it to would require much, much more than just battery replacement. I knew this but am now realizing just how much more it would require.

Every solution will have compromises. 60A of LFP charge is certainly a compromise. However, assuming I mount the LFP batteries in the laz to keep them cooler, there is no practical way to get a large charge to them from the alternator at 12v.

Getting the ER cooler would be a solution but I've already got decent airflow and the reality is that things get heat-soaked and forced ventilation doesn't make that much difference in my ER. Just the nature of the design I suppose.

A 48v LFP bank mounted in the laz could work. Replace the alternator and inverter/charger.

Except this is a 12v boat. Converters aren't a practical answer for things like the windlass. So put a 48v bank in the laz fed by the alternator (and inverter/charger). Keep a 12v AGM bank, fed/charged by the LFP at 60a or so. All draws come from the AGM which are kept topped by the LFP which is charged by the alternator and inverter/charger.

So what have I gained here? Additional capacity and maybe some faster charging. I don't have a capacity problem now (more is always nicer but..) and can charge at 200+a even with the alternator hot.

My conclusion from the exercise is that LFP doesn't make sense in my case. If I want more capacity then a couple solar panels or a couple more AGMs is a more cost-effective approach.

Click to expand...

Well, it's proof that every boat is different.


Re getting high amps to the laz, voltage drop can be accommodated by sensing voltage at the battery rather than the alternator. This can be done in one way or another with all the external regulators that I know about. Sizing cables for ampacity will yield much smaller cables that sizing for voltage drop over a longer distance. I am pushing 400A from ER to laz for charging, for example. Not that this solves all problems, but it might help.

How many years do LiPo last compared to AGM?

Our AGM lasted about two years before we started seeing noticeable reduction in power. At four years they were barely alive. They were properly taken care of and on solar charge from day one.

phillippeterson said:

How many years do LiPo last compared to AGM?

Our AGM lasted about two years before we started seeing noticeable reduction in power. At four years they were barely alive. They were properly taken care of and on solar charge from day one.

Click to expand...

That's an unusually short lifespan for any battery unless they were either in a very high temperature environment or being cycled fairly deeply every day.

twistedtree said:

Sizing cables for ampacity will yield much smaller cables that sizing for voltage drop over a longer distance. I am pushing 400A from ER to laz for charging, for example. Not that this solves all problems, but it might help.

Click to expand...

Never thought of that. Seems like a neat approach. Hmm..

THere are larger cables than 4/0 that could be used to avoid the multi conductor setup.

I have been out of the electrical trade to long to remember the details but many of those cables use the same insulation as the Ancor and similar competition. The only thing missing may be the tinned individual strands.
But I will emphasize "MAY" as I have seen cables like that that were not Ancor and were tinned

If the ends of each wire is dealt with properly that should not be a problem.

It will take sealing well between the lug and the wire insulation, an anticorrosion spray, a darn good crimper and good workmanship.
Those gaps between the insulation and the lug will need to be sealed well.

Ask around at actual electrical distributor and/or electrical wiring specialty houses. You may have to dig around. Any one supplying robotics cable may be able to help as they need high flexibility, heat resistance, and lots of these machines use lots of power.

And as T.T. mentions some of the Vdrop can be taken into account by the use of the controller/regulator remote sensing function.


It is just a suggestion.

phillippeterson said:

How many years do LiPo last compared to AGM?

Our AGM lasted about two years before we started seeing noticeable reduction in power. At four years they were barely alive. They were properly taken care of and on solar charge from day one.

Click to expand...

Something is wrong in your setup or operations. Properly cared for good quality AGM batteries will last 8-10 years. I'm on 15 years now on one boat and yes they need to be replaced but are still functioning. If you discharge them deeply every day for 3 years, then yeah, they might be done, and you are an excellent candidate for LFP.

DDW said:

Something is wrong in your setup or operations. Properly cared for good quality AGM batteries will last 8-10 years. I'm on 15 years now on one boat and yes they need to be replaced but are still functioning. If you discharge them deeply every day for 3 years, then yeah, they might be done, and you are an excellent candidate for LFP.

Click to expand...

Well, we discharged ours 25% of total or 50% of usable - 180ah out of 840ah @ 24v bank
2500 watts of solar had them fully charged by lunchtime
On rainy days, always got a big headstart with genset
Maggoted after 5 years of full time use.

Everything on the interwebs points to AGM having between 500 to 1000 cycles

Lifepo4 between 3000 and 6000 cycles

Simi 60 said:

Well, we discharged ours 25% of total or 50% of usable - 180ah out of 840ah @ 24v bank
2500 watts of solar had them fully charged by lunchtime
On rainy days, always got a big headstart with genset
Maggoted after 5 years of full time use.

Everything on the interwebs points to AGM having between 500 to 1000 cycles

Lifepo4 between 3000 and 6000 cycles

Click to expand...

Victron rates their LFPs at 2,500 cycles using an 80% range of use. My guess this is a tested metric, not the untested marketing hype of other suppliers.

Simi 60 said:

I mentioned it in another thread but instead of an alternator has anyone looked at an actual generator head?

Much less $$ and far simpler than big alts, charge controllers etc.

It was suggested to me by a marine electrician who lives aboard full time "unplugged" that 5kva heads new are around $600.
Have that wired directly into the inverter charger and you effectively have shore power when the engine is running at cruise speed and full charging capabilities.

Set belts and pulleys for cruising rpm and a light from power source on dash that is activated when in the correct rev range.

Click to expand...

Did you get any feedback on this? Initial thoughts are that it's an easy way to gain considerable recharge capacity with minimal marginal cost, effort, spares, maintenance etc.

In what other threads has this been discussed?

catalinajack said:

Victron rates their LFPs at 2,500 cycles using an 80% range of use. My guess this is a tested metric, not the untested marketing hype of other suppliers.

Click to expand...

Victron are but one supplier

The oft touted Battleborn say 3000 to 5000

How long do Battle Born Batteries last? As an update to this video, our batteries come with a 10-year warranty (8-year full replacement manufacturer's defect warranty and 2 years prorated). They are designed to last 3000 – 5000 cycles, at which point the battery will still hold 75 to 80% of its energy capacity.

Click to expand...

Regardless, even at the lower end of the scale they are still far better than AGM in so many ways

danderer said:

The recent LiFePO4 poll got me thinking: If I went this route and relocated my battery bank outside of the hot ER, how could I connect the alternator to the new bank location?

We're talking 300A max @12V, a 50' round-trip, and cabling within the ER. That means multiple 4/0 cables each way. I don't like using multiple cables because if every connection isn't perfect and identical.. Can't move the alternator from the engine, can't move the batteries to a closer, cool space..

Go to 24v battery bank. Replace the alternator. Replace the inverter. Get a big 24-12 converter for the 12v loads (or better, keep one large 12v AGM for those loads, charged with a 24v-12v charger). I guess that'd work but additional complexity and $.

..or 24v with a 12v AGM might not work. Could be the case that I'd run out of 12v well before the 24v bank (powering just the inverter) is run down. So put 2 AGMs in rather than 1. So now rather than my current 4 AGMs I have 2 AGMs and LiFePO4 . Getting silly-complex here.

Other ideas?

Click to expand...

If your objective is move the LFP to a cooler place (nice, but not mandatory) perhaps consider just venting cool air over the LFP in the ER. I simply put a piece of $5.00 foam board insulation to provide a bit of a barrier to heat from the CAT located 36 inches away, and put a pancake fan blowing outside air through 3" pvc pipe onto the top of my LFP batteries. They stay quite cool.

GoneDiving said:

Did you get any feedback on this? Initial thoughts are that it's an easy way to gain considerable recharge capacity with minimal marginal cost, effort, spares, maintenance etc.

In what other threads has this been discussed?

Click to expand...

Nope, it's like it doesn't exist

I mentioned it here, even put up a link to a 2nd hand, but in England, Australian made or badged Dunlite 3kva alt


https://www.trawlerforum.com/forums/s3/changing-house-bank-battery-types-62392-3.html#post1082471

Simi 60 said:

Victron are but one supplier

The oft touted Battleborn say 3000 to 5000


Regardless, even at the lower end of the scale they are still far better than AGM in so many ways

Click to expand...

Battleborn and others simply give a range with no information on how those numbers relate to range of use analogous to depth of discharge for lead acid batteries. Methinks there is, indeed, some marketing hype in those numbers. It seems likely to me that Victron has reached their numbers by actually testing (who knows for certain?) but all the others? My guess is that they have tested their products but do not publish thier results because, if they did, LFP might not appear as cost-effective as most naively assume. What are they hiding? Is it wise to blindly accept 3,000-5,000 cycles not knowing how those numbers were derived?

Yes, LFP compare well to AGM but not so much as against flooded batteries and not so much using Victron's numbers. I ask you this. Wouldn't Victron sell more batteries by not revealing cycle numbers far less than the "others". Also, consider that Victron arrived at their 2,500 cycle number using an 80% range, more cycles for a lesser a range. That means a 100ah LFP has an effective capacity of 80ah. How do you guys factor that into the cost effectiveness of LFP?

Difficult to find empirical research comparing LFP to FLA/AGM, but this research paper does compare some commercial battery chemistries and shows LFP to be 2500-10,000 cycles. Interestingly, the LFP batteries outlasted the study so a subsequent research paper is needed.

https://iopscience.iop.org/article/10.1149/1945-7111/abae37

Screen shot of chart in above paper. Shows wide scatter of battery life, but clearly shows ~2700 cycles for LFP as minimum, with a decent grouping in the 4000 range, and a large grouping that will land well outside the 5000cycle range of the study.

Peter

catalinajack said:

Battleborn and others simply give a range with no information on how those numbers relate to range of use analogous to depth of discharge for lead acid batteries. Methinks there is, indeed, some marketing hype in those numbers. It seems likely to me that Victron has reached their numbers by actually testing (who knows for certain?) but all the others? My guess is that they have tested their products but do not publish thier results because, if they did, LFP might not appear as cost-effective as most naively assume. What are they hiding? Is it wise to blindly accept 3,000-5,000 cycles not knowing how those numbers were derived?

Yes, LFP compare well to AGM but not so much as against flooded batteries and not so much using Victron's numbers. I ask you this. Wouldn't Victron sell more batteries by not revealing cycle numbers far less than the "others". Also, consider that Victron arrived at their 2,500 cycle number using an 80% range, more cycles for a lesser a range. That means a 100ah LFP has an effective capacity of 80ah. How do you guys factor that into the cost effectiveness of LFP?

Click to expand...

The 2500 cycle number has been demonstrated repeatedly in research studies of LFP over the past 20 years. But all those studies are hammering the batteries compared to typical house battery use. They typically charge at 1C or higher (full recharge in 1 hr), charge to the absolute max allowed charge level, then discharge at 1C or more to the lowest possible discharge level. This is because all the research is motivated by EV and other portable applications where charge/discharge rates are high, and extracting the most possible energy from the battery is the goal.


Now compare to a house battery application. It would be frightening if a boat ever tried to do a full recharge or discharge in 1hr. On a boat, a rapid charge might be 1/2 or 1/3 that rate, and discharges are more like 8-24 hrs, if not longer. And the operating SOC range for a house battery does not fully discharge, nor fully charge the batteries. The things that reduce LFP life are over discharging, over charging, very fast charging because it causes heating of the cells, and very fast discharge also because of heating. House bank use avoids all of these life-shortening behaviors.



The research all shows that house bank usage causes much less "wear" on LFP and yields greater cycle life. But honestly, nobody really knows how much, because it takes years, if not decades to actually test it. If a representative charge/discharge cycle takes 24 hrs, then it will take about 7 years to reach the 2500 cycles that everyone is confident can be achieved. Nobody has done this, or at least nobody that I have come across in any of the research. So all the life expectancy numbers are based on modeling and projections. I'm certain Victron and other vendors have not done this testing. Any such long term tests would be a big deal in the industry and headline news.



So although nobody really knows how long house batteries will last, everyone is confident they will last at least 2500 cycles, so that's why you see that as a warranty number from many vendors. And some are more aggressive gambling on 3000 or some higher number. But it's really moot anyway because who counts cycles, and what constitutes a "cycle".


What IS clear is that LFP lasts 2.5 to 5 times longer than lead, worst case. And everyone expects it to be a lot longer, with some more optimistic than others. Personally I'm figuring on 3000-5000 cycles, but we will have to check back in 10 years to see how that's going....

mvweebles said:

Difficult to find empirical research comparing LFP to FLA/AGM, but this research paper does compare some commercial battery chemistries and shows LFP to be 2500-10,000 cycles. Interestingly, the LFP batteries outlasted the study so a subsequent research paper is needed.

https://iopscience.iop.org/article/10.1149/1945-7111/abae37

Screen shot of chart in above paper. Shows wide scatter of battery life, but clearly shows ~2700 cycles for LFP as minimum, with a decent grouping in the 4000 range, and a large grouping that will land well outside the 5000cycle range of the study.

Peter View attachment 126841

Click to expand...

I'm reading this now. It looks like the most relevant research to date, and much more than I have seen before. Thanks for posting...

To your point TT - here is the AGM cycle lifespan from Rolls battery. Treated nicely within the 50% DoD range, they have about 1200 cycles. And these are some of the best batteries in the business. Worst case compare is 2:1 LFP to AGM. Most likely case is at least 4:1-5:1.

I've also attached the chart from Trojan for their T-105. Shows around 1200 cycles at 50% DoD (redline in second chart). Not bad, but still a laggard compared to LFP.

I went LFP for several reasons, cycle life being a biggie, but if that had been the only benefit, doubt I would have pulled the trigger. I have a pop-top camper van that we off-grid in. I replaced 2xGC2 (6V Costco Interstate FLA) batteries with 2x105AH LFP (Lion - BattleBorne competitor). The voltage drop across the FLAs was a severe limitation - would not support a 1200W draw from a microwave without causing an under-voltage drop at the Inverter. With the LFPs, no sweat. Granted most boats in our class would have at least six 6V batteries so you wouldn't see the voltage drop, but it's there. And its a limitation. Add-in I could move the LFP batteries into a relatively obscure place on my boat instead of taking valuabe ER space, and it was a no-brainer.

AGM Discharge Characteristics : Technical Support

https://www.trojanbattery.com/deep-cycle-flooded/signature-line-flooded-2/

Well, that's the best study so far on life span and the associated factors. Here are a few takeaways for LFP:


- To answer one question that has come up, lifespan is based on Ah throughput i.e. the product of cycle count and DOD, not simply cycle count. So all the reported data is based on Equivalent Full Charge cycles (EFC). This is true with lead batteries too, and is the basis for DOD vs cycle count curves.


- The biggest factor for LFP is heat. At 15C and 25C lifespan was virtually the same. But at 35C it clearly drops off. That said, at 2500 EFC, the lower temp batteries still had 95% of their initial capacity, where the 35C battery still had a little below 90%.


- The DOD operating range has virtually no effect of battery life. This disproves a common belief that the DOD range matter a lot.


- Charge/discharge rate has little impact on life span until you get above 2C. This shows charge/discharge rates to be less of a factor than commonly thought.


The bottom line, as I see it, is that LFP is even more stable and robust than previously thought. And if you extrapolate the data out to a point where capacity has degraded to 80% of the initial capacity, 6000 equivalent full charge cycles appears quite reasonable.

TT - Thanks for the analysis. I pulled the citation off Wikipedia's references for LiFePO4 batteries. Much of the data was above my head.

35C - the temp that lifespan drops off - is 95F and easily within range of many engine rooms in all but northerly temperatures. A recent TF thread was somewhat ambivalent on ER blowers. My takeaway is that if you're running LFP batteries are in the ER, keep it as cool as possible.

As mentioned, I moved my batteries to my lazarette mostly to free-up ER space as I was not aware of the temp issues. Concurrently moved my inverter there too (Magna 3.1kw). I guess I lucked out.

Thanks again TT. You picked-up more than I ever would have in that artice.

Peter