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Old 19-05-2019, 17:25   #1
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Advice Requested re Conversion to LFP House Bank

I have a Catalina 36 coastal cruising sailboat which is usually on shore power at the slip but otherwise taken for 3 - 7 day trips away from shore power. Iím in the process of planning a conversion from an 8D AGM house bank to a similar sized but larger capacity Lifepo4 battery.

The engine is a new Beta 25 with a 75 amp small case alternator. I assume the existing 20 Amp charger will need to be replaced with a LFP friendly one.

With the increased battery capacity, I am planning on adding an inverter for the TV and microwave, etc. Nothing more demanding than that is planned. I am also planning on adding a flexible 100 W solar panel to the dodger as well.

While off shore, the basic need is to operate the autopilot, electronics, refrigeration and LED lighting.

Even if I purchase a ďdrop inĒ replacement LFP, should I, for safetyís sake have an external BMS installed as well? I would greatly appreciate any advice on how to configure this new system in a cost effective manner.
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Old 19-05-2019, 19:10   #2
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Re: Advice Requested re Conversion to LFP House Bank

This is not a critique of LFP in general, but they seem to be a total waste of money for your application. The reason to spend the money for an LFP bank is for longevity in frequent deep cycling. You do not frequently cycle your bank as an off the grid cruising boat does.

A standard FLA will be by far the most cost effective solution for your usage pattern.

The only reason to install an LFP in a boat with the usage pattern you outline is to have the latest cool toy. Put whatever price on that you think appropriate.
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Old 19-05-2019, 19:12   #3
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Re: Advice Requested re Conversion to LFP House Bank

Can't give you recommendations on which LFP battery get - I'm still in the process of cobbling together a low cost DIY system, but I am sure that's the way to go for the future.
I would suggest two solar panels, not one single. One panel will be frequently shadowed by the boom. Try two 70's or better yet 2x100.
I'd also dump the microwave - LED tvs or music systems don't suck inordinate amounts of power and are pleasant for life.
Microwaves suck tons of power - and suck the joy out of eating food.
I hope you have a propane stove for your cooking.
Musica y cinema es vida buena.
Microwaves, not so much.
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Old 19-05-2019, 19:51   #4
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Re: Advice Requested re Conversion to LFP House Bank

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This is not a critique of LFP in general, but they seem to be a total waste of money for your application. The reason to spend the money for an LFP bank is for longevity in frequent deep cycling. You do not frequently cycle your bank as an off the grid cruising boat does.

A standard FLA will be by far the most cost effective solution for your usage pattern.

The only reason to install an LFP in a boat with the usage pattern you outline is to have the latest cool toy. Put whatever price on that you think appropriate.
FWIW I completely agree with this for the specific reasons so stated. I'd suggest focusing on maximizing solar, investing in stuff like clean LED lights (if not done so already) and lower-power ~entertainment systems.
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Old 19-05-2019, 20:18   #5
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Re: Advice Requested re Conversion to LFP House Bank

But movie watching is so much nicer with popcorn and my microwave makes it in 3 1/2 minutes.
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Old 19-05-2019, 20:21   #6
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Re: Advice Requested re Conversion to LFP House Bank

I agree that based on the OPs use as presented a change of battery chemistries is hardly indicated. I've owned our boat for 21 years and FLAs work just fine for me.


Also, the OP should read the long thread in the electrical section which will answer lots of his questions. A new alternator is also needed to make use of the high acceptance, in addition to the shorepower charger.


I'd ask myself: Why bother? Get rid of ther 8Dsand go golf carts.


Good luck.
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Old 19-05-2019, 20:59   #7
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Re: Advice Requested re Conversion to LFP House Bank

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But movie watching is so much nicer with popcorn and my microwave makes it in 3 1/2 minutes.
It sure is - when I'm at my land home.
At anchor or cruising the islands - all I have are my batteries. I've been at this mode of life for a good part of two years now.
Turning on my microwave off of my inverter and batteries startled me with the amount of current draw. Watching two or three movies until 2-3 am at anchor is not totally unusual.

As for LFP being just something to be cutting edge and unnecessary in your circumstances, don't listening to them, lad, for there be danger.
LFP weighs about 1/3 of lead. I just help a friend move about 600 AHrs of AGM's into his boat via dinghy.
Spare your back, legs, arms - they are pretty expensive to fix, and parts are hard to come buy.
Get the LFP.
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Old 20-05-2019, 09:55   #8
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Re: Advice Requested re Conversion to LFP House Bank

I appreciate the responses!

The immediate short term cost effectiveness may not make sense to some, but the long term benefits of decreased weight, double the real storage capacity, double the life span, and half the recharge time, in my view will be cost effective in the long term. And that’s not to mention the added convenience of inverter power and greater capacity offshore. My current 8D AGM is near its end so that’s why I’m at the decision point now.

I have read a large number of threads on LFP related technology installations but none, so far, have clearly pointed me in the direction I need to go. My central questions remain as before... If I purchase a “drop in replacement” LFP should I still install a BMS in addition? Should I go with a charger/inverter or separate units? How important is a larger alternator vs drag on the engine? Does anyone have specific hardware that they strongly recommend, or warnings regarding products to stay away from?

I’m hopeful that others who have successfully made the conversion on a similar scale will offer some good advice. Thank you, everyone, in advance.
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Old 20-05-2019, 10:49   #9
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Re: Advice Requested re Conversion to LFP House Bank

You never stated the amount of storage you are seeking.
As for your existing 75A alternator, assuming it is run on a single V-belt, I don't see any reason to change it, especially if you provide adequate solar panel charging. You will probably see more belt stretching, dusting and belt breakage due to the LFP much higher acceptance rates, so get plenty of spare belts and become proficient at checking, adjusting and replacing them. I think the wider use of LFP will drive marine engine makers to switch all but the smallest engines to serpentine toothed belt drive instead of v-belt.
Get an integrated inverter/charger (with LFP charging profile obviously). Easier to wire.
If your drop in LFP battery already has its own BMS, why add another? If you put your own cells together, you will ned a BMS.
Finally, add at least one, preferably two digital voltmeters readily visible (I like red colored ones) so you can easily see what your system voltage is at any time.
Welcome to spinal liberation - your body will thank you profusely.
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Old 20-05-2019, 12:15   #10
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Re: Advice Requested re Conversion to LFP House Bank

Thank you AndyEss. I'm considering a 300 AH 8D size LFP replacement for my aging 8D AGM. My 75 A alternator is on a serpentine belt drive thankfully, but will I need a new alternator control unit?
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Old 20-05-2019, 12:28   #11
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Re: Advice Requested re Conversion to LFP House Bank

My experience so far with bare-bones DIY LFP (except 24v/200ah and I've changed prices for 12v components):
12v 400ah CALB LFP: $2100 ("smart" LFP cells with integrated BMS costs much more $ per ah capacity while making you a slave to that BMS)
LFP-friendly alternator voltage regulator: $375
BMS: $450
Quality marine-grade inverter/charger/control panel: $1,500-2,000+ (Victron, Xantrex, Maservolt, Magnum; skip the generic inverters)
Probably new smart monitoring, wiring, voltage cut-out devices: few to many hundreds of dollars (or more)

Minimum $5k, likely north of $6k if you do everything yourself. I don't get the weight savings idea for a short-range/few days cruiser (in terms of sailing performance) while you can pay someone ~$50 to lift batteries in/out of the boat. If you do remove the lead battery system components, I'd suggest documenting everything well and keeping the components you remove. Should you decide to change boats in the future, you can re-install the lead stuff while moving your LFP system to the new boat (assuming it didn't have one).

FWIW I don't like the common Chinese inverters that I see many people using (look the same but carry different brand names). One too many accounts of those things smoking/smelling under operation or suffering from ~infant mortality when placed into operation. Not saying the big-name inverter chargers are per se superior, but from my perspective more of a known entity while otherwise typically available with other components to make a more congruous power system.

On BMS: I'm in the camp that doesn't like the LFP cells with integrated BMS. For starters you pay more per ah, then you and your other components are a slave to nuances of the BMS unique to that cell system. I'm ignorant to what's new/best on the market...mostly because it's a lot more money and I didn't read into it. YMMV.
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Old 20-05-2019, 12:52   #12
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Re: Advice Requested re Conversion to LFP House Bank

Quote:
Originally Posted by AndyEss View Post
You never stated the amount of storage you are seeking.
As for your existing 75A alternator, assuming it is run on a single V-belt, I don't see any reason to change it, especially if you provide adequate solar panel charging. You will probably see more belt stretching, dusting and belt breakage due to the LFP much higher acceptance rates, so get plenty of spare belts and become proficient at checking, adjusting and replacing them. I think the wider use of LFP will drive marine engine makers to switch all but the smallest engines to serpentine toothed belt drive instead of v-belt.
Get an integrated inverter/charger (with LFP charging profile obviously). Easier to wire.
If your drop in LFP battery already has its own BMS, why add another? If you put your own cells together, you will ned a BMS.
Finally, add at least one, preferably two digital voltmeters readily visible (I like red colored ones) so you can easily see what your system voltage is at any time.
Welcome to spinal liberation - your body will thank you profusely.
I went seperate Inverters and chargers. 2x 3kW 24V Victron Inverters and Sterling Procharge chargers.

My thinking was if one combined unit fell over I have both functions out. Its working fine for me, but from what I have seen most people do the combined units, lots of Victrons, and are happy with the combined units. Honestly I dont think it matters much.

My way is extra expense, room and complexity so realistically probably isnt worth it.

I also have Victron 4 x Mppt 15/75s and a Sterling B2B. I have provably gone a bit overboard here.

Alternators. Hmmm, these can really lighten your wallet. Going to the popular marine elec suppliers and getting off the shelf High output marine alternators is not for the financially timid.

I went the 'school bus' style alternator option. I got large case Delco 28si's 24V 110A at under $400 ea. I have also splurged for a 2nd hand Serpentine pulley kit, off CF. Ive also had to play around fabricating some pullies and brakets so if your not up for some DIY then probably not the best option.

Others have different views but going to the expense and trouble of doing an LFP install I dont see skimping on increased charging rate when the motor is on doesnt really make much sense to me.

I have a lot of the components ready for LFP but havent quite got to that point myself.

Still considering my options here.

This all comes down to a lot of personal preferences and which aspects are important to you. There are obviously so many iterations possible.

You can bet the more people you ask the more varied replies you'll get.
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Old 20-05-2019, 15:35   #13
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Re: Advice Requested re Conversion to LFP House Bank

I personally agree on separating charging and inverters.

Allows for the bank to separately be isolated from charge buss vs loads, HVC keeps loads powered, LVC allows charging.
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Old 20-05-2019, 15:59   #14
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Re: Advice Requested re Conversion to LFP House Bank

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Thank you AndyEss. I'm considering a 300 AH 8D size LFP replacement for my aging 8D AGM. My 75 A alternator is on a serpentine belt drive thankfully, but will I need a new alternator control unit?
You need a controller that is either programmed for LFP or can be operator-adjusted to properly charge LFP. That is, you must have the correct charge voltages.
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Old 20-05-2019, 17:11   #15
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Re: Advice Requested re Conversion to LFP House Bank

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I personally agree on separating charging and inverters.

Allows for the bank to separately be isolated from charge buss vs loads, HVC keeps loads powered, LVC allows charging.
Yes, a little off track but I have to admit I have a bus bar fetish and gone a bit crazy with them.

As John has mentioned I have one each pos and neg for both charge souces and loads. A seperate set for switched and unswitched loads.

Apart from helping keep everything neat they make fault finding a breeze.

I also have seperate sub fuse panels in the seperate boat zones, bus bars for the mast connections, etc. This makes expansions or changing stuff around and disconnecting masts so much more straight forward.
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