Replacing FLA with LiFePo4 charging question

[sailorboy1]

Originally Posted by ForeverDes

Sorry for yet another LiFePo4 thread!



Background info:
I currently have a single 8D FLA house battery of unknown capacity, and what looks like a group 27 dual use (deep cycle/start) FLA starting battery. I'm limited on space to add batteries, but I could fit 4x 6v 225AH deep cycle Sam's club batteries in a 2S2P configuration. It would be a fairly simple install, and I could keep my current charging scheme, which is: a dual battery onboard charger, 380W (2x190W parallel) solar through a 60 amp mppt controller, and a 65amp alternator.

There's a "1-2-both-off" battery selector switch. Solar is wired to the house bank side, alternator wired directly to the start battery, and the on board charger has dual outputs and is wired to each bank.
In the same space as the 4 FLA batteries I was planning to use, I could fit 400ah of LiFePo4 batteries. (2x200ah 12v). They'd use a little less total space, and they weigh less than 1/2 what the FLA batteries do. The LiFePo4 batteries are longer but less tall, and height is my my limiting dimension. I don't currently have an inverter, but I have plans to add a 2000W pure sine wave inverter at some point in the next year or two. My largest load is the portable, 12v, 45w fridge. At 4 amps and a duty cycle of 50% max, that's 50 AH per day. The other loads probably never exceed 20 AH.

I stay on a mooring ball in the summer and store my boat inside, but not heated, in the winter.

I don't know the state of my current batteries, but I know I don't trust them to last through this summer season.

I'm trying to wrap my head around what changes would be required for upgrading the house bank to LiFePo4.

Is it reasonable to disconnect the onboard charger from the house bank, and then use a dc to dc charger from the start battery to the house bank, while leaving the solar wired (through the appropriately programmed mppt controller) directly to the house bank? Or should all charging sources go through the starting bank?

Solar is more than enough to keep up with my modest house loads for several days of use in the summer.

If the above is reasonable, does the battery selector switch need to be removed? I can't imagine a scenario in which combining mixed chemistry banks would be a good idea.

If disconnecting the battery selector is appropriate in this situation, I'd like to use it to "split" my house bank in two as a measure of redundancy. I'd like to leave all house loads connected through the 1-2-both-off switch and use a battery isolator between the mppt controller (and dc to dc charger) and batteries.

What am I missing, and what am I just plain wrong about?

p.s. my goal with LiFePo4 would be a conservative charging scheme, never trying to reach above 85%-90% soc.

I didn't read ANY of the replies so have no idea of the current state of thread drift.

But I feel that for this application/use LFP batteries are just throwing away money.

[Scubaseas]

Originally Posted by ForeverDes

I have a 1960 Atomic Four, and I put in the the electronic ignition module from Indigo Electronics.
(Sorry I misspoke earlier by saying EFI)

No worries, I had figured you had meant ignition. Crane/FAST is a good piece of kit. With the kit and the coil replacement, yes it would be OK to leave the key on but keep in mind the unit may draw 3 to 4 amps just sitting there with the key on. Plus whatever your gauges, alternator and anything else on the Key On circuit will draw power. Optical window electronic ignitions can fry your coil if KOEO if they do not have a dwell cut out feature. I can see why they are keen on adding this to their earlier ignition conversion systems.

While I agree coils should not fry (and they do not when running because dwell does not keep the coil energized 100% of the time like when the KOEO, only about 45 to 55% of the time) when the key is left on but I have seen many a Pertronix unit or coil fried because of the key being left on and the motor not running. Even with either optical triggers or hall triggers. The Module you have now looks to see if the motor is running and cuts the power to the coil if it doesn't see the distributor spinning. Pertronix (earlier versions) were notorious for burning out the coil or the igniter if KOEO.

Sorry to wander off topic. I was just offering to share my experience of being a foreign and domestic master mechanic for over 50 years. Or just consider me some guy on the Interweb. Same difference I suppose.

[ForeverDes]

Originally Posted by sailorboy1

I didn't read ANY of the replies so have no idea of the current state of thread drift.

But I feel that for this application/use LFP batteries are just throwing away money.

I'm not trying to be combative here, but why do you feel that way? Is it the upfront cost difference? The arguably unproven real-world longevity of LiFePo4? Something else?
I understand it's a higher upfront cost, but lifetime costs for LifFePo4 look MUCH better than FLA, so do ah/$ and wh/$.
I'll admit, if I was thinking of spending 10x the cost of FLA upfront I doubt the lifetime costs would be a concern. But I'm only looking at spending 2-4x the cost FLA.
As to longevity, I have specific reason to believe FLA will degrade based on my use, because using only solar and without regular access to shore power I can't count on regularly getting FLA batteries through the absorption phase of charging, which appears to be vital for maintaining their capacity long term. I also have reason to believe for LiFePo4 this is absolutely not a problem, and may even help extend their life.

If there's something else I've missed, I'd love to hear it. I'm not convinced LiFePo4 is my best option here, but so far all the research I've done seems to point in that direction.

[newhaul]

Side note for everyone in this situation or considering it in the near future .
Lfp prices are falling rapidly
Mind you these numbers are from the ev market but will apply to us similarly
That figure now stands at roughly $137 per kilowatt-hour, and likely to plunge to about $100 per kilowatt-hour in the next couple of years,
It was well over $1100 per kwh 10 years ago.

This is just about battery costs not the rest of your specific setup wrt charge sources

[ForeverDes]

Originally Posted by Scubaseas

No worries, I had figured you had meant ignition. Crane/FAST is a good piece of kit. With the kit and the coil replacement, yes it would be OK to leave the key on but keep in mind the unit may draw 3 to 4 amps just sitting there with the key on. Plus whatever your gauges, alternator and anything else on the Key On circuit will draw power. Optical window electronic ignitions can fry your coil if KOEO if they do not have a dwell cut out feature. I can see why they are keen on adding this to their earlier ignition conversion systems.

While I agree coils should not fry (and they do not when running because dwell does not keep the coil energized 100% of the time like when the KOEO, only about 45 to 55% of the time) when the key is left on but I have seen many a Pertronix unit or coil fried because of the key being left on and the motor not running. Even with either optical triggers or hall triggers. The Module you have now looks to see if the motor is running and cuts the power to the coil if it doesn't see the distributor spinning. Pertronix (earlier versions) were notorious for burning out the coil or the igniter if KOEO.

Sorry to wander off topic. I was just offering to share my experience of being a foreign and domestic master mechanic for over 50 years. Or just consider me some guy on the Interweb. Same difference I suppose.

Hey we are all just some guy (or gal, or person) on the internet. I appreciate your chiming in though, and experience from any source is always welcome. Since accidentally frying the coil last year I've gotten into the habit of removing the keys from the ignition anytime I turn the boat off. A habit I hope to continue!
I'm not 100% sure if the unit I have has a dwell cut off or not. It is an optical unit with a shortened dwell, iirc. I just recall from conversing with Indigo before purchase that leaving the key on would not fry the coil, and I believe it was stated that the logic unit doesn't even energize the coil unless the rotor (or, in this case, shutter) is spinning.

[newhaul]

Originally Posted by sailorboy1

I didn't read ANY of the replies so have no idea of the current state of thread drift.

But I feel that for this application/use LFP batteries are just throwing away money.

Actually don with his diy idea the real upfront cost difference is negligible. ( pricing based on trojan t105's) but lifetime wh cost is much lower with the lfp in his setup profile.

[ForeverDes]

Originally Posted by newhaul

Side note for everyone in this situation or considering it in the near future .
Lfp prices are falling rapidly
Mind you these numbers are from the ev market but will apply to us similarly
That figure now stands at roughly $137 per kilowatt-hour, and likely to plunge to about $100 per kilowatt-hour in the next couple of years,
It was well over $1100 per kwh 10 years ago.

This is just about battery costs not the rest of your specific setup wrt charge sources

That's an excellent point and part of the reason waiting to do any changes for even a single season would be great for me.

It also brings me to another point, that I may be overthinking this whole thing in terms of charging sources.

The least expensive way for me to dip my toes in the water, as it were, would be to put in a single 200ah LiFePo4 battery charged from solar and nothing else. I'd basically hook my current battery cables to the new battery and change the charge profile on my mppt controller. The cost for this would be about 1.8x replacing with FLA, give me 2/3 the rated usable capacity of FLA, and save me about #250 of weight.

[sailorboy1]

I feel thinking "lifgetime" beyond 4-5 years for the OP is crazy. A much much much less expensive battery will serve his needs for years.

The goal isn't to have the best battery, longest life battery, coolest battery, smallest battery, lightest battery for most people. It is to have the least expensive battery to meet the boats means with a reason life. Reasonable in this case, 2 6V GC2 probably cost $250 and works out to $50/YEAR or less.

[ForeverDes]

Originally Posted by sailorboy1

I feel thinking "lifgetime" beyond 4-5 years for the OP is crazy. A much much much less expensive battery will serve his needs for years.

The goal isn't to have the best battery, longest life battery, coolest battery, smallest battery, lightest battery for most people. It is to have the least expensive battery to meet the boats means with a reason life. Reasonable in this case, 2 6V GC2 probably cost $250 and works out to $50/YEAR or less.

Originally Posted by sailorboy1

I feel thinking "lifgetime" beyond 4-5 years for the OP is crazy. A much much much less expensive battery will serve his needs for years.

The goal isn't to have the best battery, longest life battery, coolest battery, smallest battery, lightest battery for most people. It is to have the least expensive battery to meet the boats means with a reason life. Reasonable in this case, 2 6V GC2 probably cost $250 and works out to $50/YEAR or less.

Well that's one place we absolutely do disagree.
My goal isn't to have the absolute cheapest battery that will possibly work. It's to have the best battery that I can for my scenario.
You are correct, two 6 volt batteries would be the cheapest thing I could get. I'd have at most one day worth of capacity out of them. I know because that's all I could fit on my former boat, and any day that was cloudy I was on a energy deficit.
Three 6 volt batteries would be worthless, so that leaves four, which will cost at least $500 and probably a bit more. (Core charge, taxes)
I really doubt they would last for 5 years. Two years, yes. Three? Maybe. More than that? I doubt it. At least not at a decent percentage of their original capacity.
Three years of the $500 cost per year is about $170. Assuming a 5-year lifespan, cost per year for the LiFePo4 is $175.
And perhaps you'll think that a 3-year lifespan is way too conservative for FLA batteries. Keep in mind, I'll spend 5 months a year with absolutely no access to shore power. Without a larger solar array, generator, or significant other charging source, FLA batteries will not go through a complete discharge/charge cycle before starting over. I cannot find a single source that says this is good for FLA batteries, and most I've seen consider it a death sentence for them.

[newhaul]

Originally Posted by ForeverDes

That's an excellent point and part of the reason waiting to do any changes for even a single season would be great for me.

It also brings me to another point, that I may be overthinking this whole thing in terms of charging sources.

The least expensive way for me to dip my toes in the water, as it were, would be to put in a single 200ah LiFePo4 battery charged from solar and nothing else. I'd basically hook my current battery cables to the new battery and change the charge profile on my mppt controller. The cost for this would be about 1.8x replacing with FLA, give me 2/3 the rated usable capacity of FLA, and save me about #250 of weight.

That is a good way to think about it and all things being otherwuse equal you will not need as much battery storage power as you think . Most dsys with your current solar your lfp will be fully charged by mid day and the vessel will be running off the " excess " power the solar generates for the rest of the daylight hours.
Remember to throw out everything you know about caring for fla batteries . None of it will apply to lfp.

[sailorboy1]

Well I can recognize when what I write is only being read as looking for a food source to argue about and not really what I wrote at all.

So since I wouldn't know about off grid battery use having only done it for 6 years once I will just subscribe and place thread on igrue.

OP get whatever batteries you what. There is no reason to have started a thread asking as it is your boat do whatever you want. You know what you wanted to do at the start!

[newhaul]

Originally Posted by sailorboy1

Well I can recognize when what I write is only being read as looking for a food source to argue about and not really what I wrote at all.

So since I wouldn't know about off grid battery use having only done it for 6 years once I will just subscribe and place thread on igrue.

OP get whatever batteries you what. There is no reason to have started a thread asking as it is your boat do whatever you want. You know what you wanted to do at the start!

Don don't take this the wrong way but read the title it says he has already made the decision to change to lfp and wants input on how to properly care for the chemistry.

Now yes using walmart/ sams club gc2 batteries is the cheap upfront option but when used in a PSOC situation they will be lucky to last 2 seasons . Then your buying them again.
Twice and you are at yhecost of a 250ah lfp setup that will last at a minimum 10 years. And there is a lot less maintance.

[Adelie]

Originally Posted by sailorboy1

...

OP get whatever batteries you what. There is no reason to have started a thread asking as it is your boat do whatever you want. You know what you wanted to do at the start!

If there was no reason for this thread why have your repeatedly posted in it?

Yes, the battery choice is his, he's looking for advice about how to make the choice and why.

[Adelie]

Originally Posted by newhaul

Don don't take this the wrong way but read the title it says he has already made the decision to change to lfp and wants input on how to properly care for the chemistry.
.....

I don't see the title as indicating he's made the decision. It can read that way and it can be read as having a question about what would be involved in changing battery types.

And the first post makes he clear that he's considering 2 options and hasn't decided yet..

[newhaul]

Originally Posted by Adelie

I don't see the title as indicating he's made the decision. It can read that way and it can be read as having a question about what would be involved in changing battery types.

And the first post makes he clear that he's considering 2 options and hasn't decided yet..

Read the title of the thread

" replacing fla with LiFePo4, charging question."

In other words he has made the decision to change and wants to know how to change / setup his charging sources for the new chemistry.