Replacing FLA with LiFePo4 charging question

[ForeverDes]

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..

Sorry Newhaul! I really appreciate your input here, but Adelie has it right. I haven't made the decision yet, although I am leaning very hard for the simple 1 Battery approach I described a few messages ago.

I started this thread to get feedback and opinions on what I need to properly care for LiFePo4 batteries, because obviously the more extra equipment needed, the larger the upfront and per power unit (ah/wh) cost, and therefore could be a major factor in my ultimate decision.

[newhaul]

Originally Posted by ForeverDes

Sorry Newhaul! I really appreciate your input here, but Adelie has it right. I haven't made the decision yet, although I am leaning very hard for the simple 1 Battery approach I described a few messages ago.

I started this thread to get feedback and opinions on what I need to properly care for LiFePo4 batteries, because obviously the more extra equipment needed, the larger the upfront and per power unit (ah/wh) cost, and therefore could be a major factor in my ultimate decision.

Ok thanks for clarifying i owe adelle an apology.

Here is the big picture you actually don't need to change anything.

I would recommend setting your mppt controller to a stop of 13.8v
I suggest a b2b to charge the lfp off of your alternator .
As to the b2b well the only time I would use it is with the alternator putting out power.

[Scubaseas]

Originally Posted by newhaul

Ok thanks for clarifying i owe adelle an apology.

Here is the big picture you actually don't need to change anything.

I would recommend setting your mppt controller to a stop of 13.8v
I suggest a b2b to charge the lfp off of your alternator .
As to the b2b well the only time I would use it is with the alternator putting out power.

Certainly one way to do it. Does the OP not also need some kind of temperature protection/field cut out on the alternator as LiFePo4 can accept more than the alternator can put out leading to alternator overheating? Or can this be done through the b2b with an alternator temp sensor? Would he get more buffering by charging the start battery and using a combiner or b2b charger off that?

[newhaul]

Originally Posted by Scubaseas

Certainly one way to do it. Does the OP not also need some kind of temperature protection/field cut out on the alternator as LiFePo4 can accept more than the alternator can put out leading to alternator overheating? Or can this be done through the b2b with an alternator temp sensor? Would he get more buffering by charging the start battery and using a combiner or b2b charger off that?

That is a good question .

Ok the reasons for a b2b charger is two fold
1) you want ( imo) an fla starting battery to start the engine as well as protect the alternator from an unexpected bms disconnect of charging ckt which will damage the voltage regulator .
A b2b is the buffer it allows for differing charge profiles
For example on my setup it tops at 14v which is still .5v below the max knee of the lfp.
The stock alternator puts out up to 15 volts . Fla doesn't care.

Ok now the protection part my setup.
55 amp alternator and a 40 amp b2b so derated approx 20% = thermal protection for alternator. Allows the internal stock regulator to do its job. Running the charge via my fla start battery to the b2b to the lfp bank.


Sometimes what I think and post don't sound the same as if I'm talking face to face so happy to answer any questions via PM so as to not derail this thread any further .
Rob SV Stephfen Ulysses

[mbartosch]

Originally Posted by ForeverDes

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.

Even ignoring all other factors this is - in my opinion - one of the most important factor for deciding on the technology and choosing LFP in your case.

You mentioned you are living on the hook for months without shore power during summer, mainly using solar as charging source. This is a scenario in which LFP absolutely shines:

- the LiFePO4 battery will store every Joule of energy the solar panels deliver, almost up to the 100 % SoC mark with about 99 % efficiency. This alone would cut it for me in your use case (and from first-hand experience cruising with a LFP bank for prolonged times I know that LFPs are just awesome with solar offshore)
- a LiFePO4 battery loves to stay off low and high SoC levels which is a frequent use case seen when solar output roughly matches average consumption

For me these two reasons alone would be sufficient to prefer using a LFP battery in favor of a FLA battery in this particular use case.

In similar previous threads FLA advocates (typically without own LFP experience) argued that FLAs are just as good as LiFePO4 in this case, provided "your solar is sufficiently sized". This argument only makes sense if solar capacity is so overdimensioned that solar production covers charging losses (due to diminishing charge acceptance when approaching full SoC for a FLA battery) and making sure that the FLA battery gets charged as closely as possible to 100 % SoC every once in a while.

With LFP you get the luxury to either actually allow dimensioning your solar panel area either more or less exactly to your actual average consumption OR having surplus energy (if overdimensioned) you can actually use for something useful beyond the baseline.

[ForeverDes]

Originally Posted by mbartosch

Even ignoring all other factors this is - in my opinion - one of the most important factor for deciding on the technology and choosing LFP in your case.

You mentioned you are living on the hook for months without shore power during summer, mainly using solar as charging source. This is a scenario in which LFP absolutely shines:

- the LiFePO4 battery will store every Joule of energy the solar panels deliver, almost up to the 100 % SoC mark with about 99 % efficiency. This alone would cut it for me in your use case (and from first-hand experience cruising with a LFP bank for prolonged times I know that LFPs are just awesome with solar offshore)
- a LiFePO4 battery loves to stay off low and high SoC levels which is a frequent use case seen when solar output roughly matches average consumption

For me these two reasons alone would be sufficient to prefer using a LFP battery in favor of a FLA battery in this particular use case.

In similar previous threads FLA advocates (typically without own LFP experience) argued that FLAs are just as good as LiFePO4 in this case, provided "your solar is sufficiently sized". This argument only makes sense if solar capacity is so overdimensioned that solar production covers charging losses (due to diminishing charge acceptance when approaching full SoC for a FLA battery) and making sure that the FLA battery gets charged as closely as possible to 100 % SoC every once in a while.

With LFP you get the luxury to either actually allow dimensioning your solar panel area either more or less exactly to your actual average consumption OR having surplus energy (if overdimensioned) you can actually use for something useful beyond the baseline.

You bring up a very good point. My solar array is adequate (and then some) for the energy I actually use, but due to charging losses, the FLA batteries don't take all that in. My panels are rated at 380 watts, and from what I can tell I get about 100ah/day from them.
As to living on the hook, I'm still a landlubber, but my boat spends all its time on a mooring ball, except when I'm sailing it. I sail 2-4 overnights a week usually, so I like to leave the fridge on instead of packing all my cold food back and forth 2x a week. So whether I'm actually on the boat or not, my biggest energy drain is still running.

I'm also pretty well maxed out on solar real estate unless I do something fairly drastic to increase it, so adding enough panels to compensate for charging losses in FLA would be far more expensive than switching the house bank to LiFePo4.

I haven't yet seen any responses here, or data from anywhere, that suggests (with hard data) FLA house batteries are better for my situation in the long or even middling term. I'm watching LiFePo4 prices and sales, and either when I find a good deal or get tired of waiting, I plan to pull the trigger and buy 200AH worth, likely in a single battery with built in bms. I have 2 sources now that I can purchase those (with discounts) for well under $1k each, delivered. Both are generic, so there's more risk than with say, battleborns, but I'm ok with that. I've got 5 months before I will launch, so there's a chance I could find an even better deal by then.

[Adelie]

Originally Posted by newhaul

Ok thanks for clarifying i owe adelle an apology.



Here is the big picture you actually don't need to change anything.



I would recommend setting your mppt controller to a stop of 13.8v

I suggest a b2b to charge the lfp off of your alternator .

As to the b2b well the only time I would use it is with the alternator putting out power.

Don’t worry I’m good. I could see how the title could be interpreted that way.

[mbartosch]

Originally Posted by ForeverDes

You bring up a very good point. My solar array is adequate (and then some) for the energy I actually use, but due to charging losses, the FLA batteries don't take all that in. My panels are rated at 380 watts, and from what I can tell I get about 100ah/day from them.
As to living on the hook, I'm still a landlubber, but my boat spends all its time on a mooring ball, except when I'm sailing it. I sail 2-4 overnights a week usually, so I like to leave the fridge on instead of packing all my cold food back and forth 2x a week. So whether I'm actually on the boat or not, my biggest energy drain is still running.

I'm also pretty well maxed out on solar real estate unless I do something fairly drastic to increase it, so adding enough panels to compensate for charging losses in FLA would be far more expensive than switching the house bank to LiFePo4.

I haven't yet seen any responses here, or data from anywhere, that suggests (with hard data) FLA house batteries are better for my situation in the long or even middling term. I'm watching LiFePo4 prices and sales, and either when I find a good deal or get tired of waiting, I plan to pull the trigger and buy 200AH worth, likely in a single battery with built in bms. I have 2 sources now that I can purchase those (with discounts) for well under $1k each, delivered. Both are generic, so there's more risk than with say, battleborns, but I'm ok with that. I've got 5 months before I will launch, so there's a chance I could find an even better deal by then.

At least for LFP I can provide some hard data from our 2016/2017 cruise. Scroll down to the "2018 Update" heading for an retrospective analysis of our energy management solution. At that time Entropy had 425 Wp solar, a 400 Ah LiFePo4 bank and a Balmar alternator.

[newhaul]

Here is the longest running thread I have been a part of . he beginnings predate my lfp experience by about 5 years .
https://www.cruisersforum.com/forums...nks-65069.html

This is another great one
https://www.cruisersforum.com/forums...ey-201795.html

There are many others on the forum

[feudalkaos]

To answer your questions directly:

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?
This could be reasonable if the MPPT controller is programmed correctly and you feel absolute confidence in its ability to stop charging before it overcharges the Lithium bank. This will also make your other charges a little bit less efficient. The B2B charger is a great tool but it has loss.

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.
I have two separate main disconnect switches but my house and starter banks are totally independent and only a B2B charger combines them. For what it is worth, apparently it is fairly common and not really an issue to mix FLA and Lithium banks.

What am I missing, and what am I just plain wrong about?
I am not sure what batteries you are considering, drop in LiFePO4 or build your own. In either case, the BMS is very important. I opted to build my own because most of the drop in batteries have a BMS but no ability to signal charging sources to stop charging. This could lead to them fully outputting when the batter disconnects. This is typically very bad for the charger and for the other electronics in the system. This can cause major voltage spikes.

Here are a few links that helped me a lot when designing my Lithium system for our boat.

Lithium battery systems | Nordkyn Design

https://marinehowto.com/lifepo4-batteries-on-boats/

Our system:
I built a 12V 400Ah bank from 100Ah Sinopoly cells with an Orion Jr 2 BMS.

Ultimately, I decided to error on the side of more safe and less likely to damage anything.

The negative side of the bank goes to a series of current shunts for each of my charging sources. This allows me to know how much charge each source is providing independently.

The positive side of the bank has a large fuse that leads to the main battery disconnect switch. From there it goes to a main buss where I then connect (with fuses) the various power meters I have.

The positive buss is connected to a Tyco latching relay which then connects to the Load buss. This Tyco relay is controlled by the Orion BMS for load disconnect (low voltage, low SOC).

The Load buss has all of the load devices connected to it like my main house panel and my inverter/charger.

Since the inverter/charger is both a load and a charging source I had to add come up with a means to disconnect it on high voltage as well. I did not want to disconnect the output side while charging and risk destroying the charger so I added a large relay to the AC side of the inverter/charger. When the batteries are full this relay opens the shore power connection to the inverter/charger which stops it from being able to produce a charge. This also forces the inverter to start inverting power from the batteries to the AC system which is an advantage for Lithium batteries since they never like to sit at full charge. This makes sure that when I hit a full charge (set at 95% using the BMS) they immediately start discharging and cannot start charging again until they are below 90%.

I connected from the main buss to my Victron MPPT solar charger through a breaker. I then added another Tyco latching relay between the solar panels and the solar charger. This relay is controlled by the BMS high charge output. When the batteries are full the relay opens and stops the Victron solar charger from getting power from the panels which safely stops it from being able to charge.

For my alternator, I still have my original Hitachi internally regulated version that came with my Yanmar. It isn't the best but seems to work. To be sure I didn't overwork and destroy it I kept it connected only to a FLA starter battery. To tap into the power from it I added a Sterling B2B charger that consumes power from the start battery to charge the Lithium house bank. It has an internal disconnect system which I used to stop it from charging. I connected an output from the Orion BMS to signal to the Sterling when to stop.

The Tyco latching relays could not be controlled directly by the Orion Jr BMS because the BMS has continuous outputs and the Tyco's need pulsed outputs. To deal with this I built a small converter circuit. I opted for the latching relays because they use no power in either state once latched.

[DegoRed]

Originally Posted by AMX

Don't Waste Your Money On Batteries - The Shocking Truth I Discovered When Testing RV Batteries
Much Cheaper batteries than Battleborn straight from China
https://diysolarforum.com/

Man that was such a great video, thanks for posting it up, so much data to digest. Your data kind or confirmed what I had already been thinking, but never had any real data, just my gut feeling. LFP is getting so cheap that it makes no sense to not replace old batteries with it LFP over LA.

Will just dropped a new video about EVE batteries everyone has been ordering, been temped to order a set to play with for a while now, hard to argue with $400 +/- for 280ah.

https://www.youtube.com/watch?v=3U4ZfQ_IToI

[newhaul]

Someone answer this question.
Why does everyone always want to over complicate everything with this and that?

90% of installs are way over complicated needlessly.
Or is it me being to kiss on everything ?

[feudalkaos]

Originally Posted by newhaul

Someone answer this question.
Why does everyone always want to over complicate everything with this and that?

90% of installs are way over complicated needlessly.

If you don't mind my asking, what is your level of expertise with electrical engineering?

I am just wondering from what reference point you are coming when you suggest something is overly complicated. Are you an engineer?

I do not specifically agree that "90% of installs are way over complicated needlessly."

I do believe some installs are overly engineered and some under engineered. In both cases they may work but not always as efficiently as possible and more importantly not always safely. I would always error on the side of over engineered for safety.

It is certainly possible to cut corners like not using a BMS and relying only on your charge controller or not handling load disconnects properly. These things may not immediately introduce a problem but over a long enough period of time the risk compounds. Other corners can be cut also but at what cost. Why create needless risk.

That is like saying a seatbelt is needless in a car because you have never had an accident. Maybe a seat belt only saves your life once in a million times of driving but that once is enough to make them worth it.

You may notice that presently the ABYC does not have specifications published for handling LiFePO4 batteries. This is because they have not yet finished researching the risks and the research they have done has mostly shown they are high risk items like any battery. The biggest difficulty is that LiFePO4 batteries are not drop in replacements for FLA no matter what anyone tells you. The system needs to be reconfigured to properly deal with how LiFePO4s charge and discharge.

To the OP, when dealing with electrical systems I would seriously consider getting advice from electrical engineers familiar with the application. A lot of people know enough about electrical systems to make them "work" but not enough to make them work safely and correctly. This forum is a great source of information but be sure you understand the qualifications of the advice given.

[walkabout08]

Originally Posted by tkeithlu

ForeverDes, I really like your goal, and your thinking in reaching it. Too many boaters (I won't call them cruisers) don't think a thing about redundancy. They essentially have no Plan B.

My only remaining question (like unto CarlF) is going to Lithium. I did a purchase price versus amp/hour calculation awhile back for another thread, and found that installing a lithium house bank of the same amp/hrs as a flooded bank cost ten times as much. Are you going to eat up ten replacements of your flooded bank in the time you destroy one bank of lithium, or do you have another reason (weight?) to make the change?

Not sure I agree with LiFe being ten times the cost of FLA. My 225 Amp FLA banks are Trojan 6V FLA in series and they are good for maybe 100 aH actual power. Cost me last summer about $375 for the pair. A pair of LiFe batteries will run around $1800 and provide 175 aH of actual power. According to the ensuing arithmatic that's about 5 times the cost of my FLA, for almost twice the electricity.

[newhaul]

Originally Posted by feudalkaos

If you don't mind my asking, what is your level of expertise with electrical engineering?

I am just wondering from what reference point you are coming when you suggest something is overly complicated. Are you an engineer?

I do not specifically agree that "90% of installs are way over complicated needlessly."

I do believe some installs are overly engineered and some under engineered. In both cases they may work but not always as efficiently as possible and more importantly not always safely. I would always error on the side of over engineered for safety.

It is certainly possible to cut corners like not using a BMS and relying only on your charge controller or not handling load disconnects properly. These things may not immediately introduce a problem but over a long enough period of time the risk compounds. Other corners can be cut also but at what cost. Why create needless risk.

That is like saying a seatbelt is needless in a car because you have never had an accident. Maybe a seat belt only saves your life once in a million times of driving but that once is enough to make them worth it.

You may notice that presently the ABYC does not have specifications published for handling LiFePO4 batteries. This is because they have not yet finished researching the risks and the research they have done has mostly shown they are high risk items like any battery. The biggest difficulty is that LiFePO4 batteries are not drop in replacements for FLA no matter what anyone tells you. The system needs to be reconfigured to properly deal with how LiFePO4s charge and discharge.

To the OP, when dealing with electrical systems I would seriously consider getting advice from electrical engineers familiar with the application. A lot of people know enough about electrical systems to make them "work" but not enough to make them work safely and correctly. This forum is a great source of information but be sure you understand the qualifications of the advice given.

Ok here it is my system 250ah cells in 1p4s a 200 amp in and out Daly bms with active top balancing for 12v nom. 200 watts solar running through a fully programmable pwm controller set to 13.8v stop.
A 55 amp alternator hooked to a 550cca flas start battery running a 40amp b2b to charge lfp if needed set to 14.1. V cut off. I also have a 2500 watt diesel generator and a 100 amp automotive type battery charger ( if i ever need it) so far have not needed it) BTW the charger has a 14.6 volt cutoff . ( as they all do now days ) which is the top balance point for lfp cells ( 3.56 volts per cell)

I am a retired us navy engineer.
So to summarize my setup i have lfp house and fla start solar charges my house daily if needed I have a 55 amp alternator and a 40 amp b2b as a safety system to protect the alternator. A battery monitor similar to the sg200 if I am using the shorepower charger I will be keeping an eye on the voltage . Have yet to need shore charger.

As to your system and many others running g an inverter charger when your battery is charged it is just a pass through for 120v or 240v depending on your system .
The cutoff voltage is 14.6volts or 29.2 with 24 volt systems. Which is at the top balance point of lfp .

Did I miss anything?

Oh yeah I'm also retired from my own marine repair business and used to install complete off grid systems . Both on boats and on land