How do you ever get those Lifepo batteries charged?

[Shanachie]

So I've been reading all of these entertaining lithium threads as I debate what to do for new house batteries.


Generally, I think all of this is way too complicated, suitable more for the engineering geeks than the average sailor who just wants to cruise around. I like simple.



But one thing keeps bothering me: How do you ever get these huge lithium battery banks charged? I see people talking about 400, 600 even 1,000 amp hours, and it staggers me.


I have a 34-foot sailboat with a Yanmar 3gm30 and a 50 amp alternator as well as 320 watts of solar with a Xantrex MPPT. Let's say I put 400 AH of lithium batteries in and a 20-amp DC to DC charger on the start battery.



If I'm motoring on a sunny, calm day, I'll put close to 40 amps an hour into the battery bank. But that's eight hours to a full charge if I had run the bank down for some reason.


It's still three or four hours if it's a more normal overnight discharge.


Under my current 320AH of FLA, I'm generally into float in early afternoon after solar and a bit of motoring. A couple more hours, sure, but I'm topped off well before I drop the hook.


So what am I missing? What's the difference? Is getting fully charged a couple of hours earlier really worth all of the fuss with BMS, balancing cells and all of the rest? Or is it just fun to be an early adapter?



Enlighten me.

[markxengineerin]

One easy to imagine case is rainy climate, for a boat that spends significant time in marinas and doesn't have a ton of room for solar and/or thinks it's ugly. Leave for a trip fully charged, several days out in the wild without solar, top up the huge bank again at next marina.

Everyone's use is different, for mine, I like to have enough solar to see float at least one day each week, and enough battery to bridge 2-3 days of rain. I have not used the alternator or shore power for 4+ months.

[wholybee]

First, many people here make it more complicated than it needs to be. There are only a few concerns you need to deal with, and none are terribly difficult.

Second, I think the large battery capacity for many is for reserve. So, if you can't charge due to rain or clouds for a few days, you are fine, but it might take several days to get it back up again. LFP also charges faster than FLA. It's noticeable.

For others, they have 1000-2000 Watts of solar.

[jordanbigel]

I might be a good case of what you are talking about - I have 1200ah of LifePo, an admittedly huge bank. I don't NEED that much at all, but, with 3 x 400ah batteries I have redundancy. If one fails, I can easily - easily - get by with just 2 of them. Frankly, I could limp along with just 1 of them for some time and just have to run the generator more. I used to have 4 x 8D LA batteries, so I had the space to basically keep a "spare" battery and still save hundreds of lbs of weight.

I do not have tons of solar, just 2 panels equaling about 375watts - I rely on the generator on a daily basis when cruising, the solar provides about half of what we use in a day, on a good day of sunshine.

The other thing which you may be missing is there is no need to fully recharge the bank. I run somewhere between 45% and 75% SOC. Every 2 or 3 months I charge the bank fully to 100% (to allow top balancing) and the rest of the time its just somewhere in the middle. Coming from a world of LA batteries, this may seem hard to accept, but the LifePo bank likes it this way.

[Swift Drift]

I have a similar use pattern to Jordanbigel with a large bank (840 amp hours) minimal solar (200 watts) and rely heavily on my generator. I have 200 amps of shore power charging capability so when the generator is on, charging is “quick.”
As already mentioned, lithiums will charge faster than your FLA bank since the charge will not taper off (if you start adding 50 amps, you will continue to add 50 amps until full).
Basically your question is irrelevant because:
a) a lithium bank (even a very large one) will charge faster than an your current FLA given the same charger capacity.
b) there is no need to charge lithiums to full.

[HeywoodJ]

Originally Posted by Shanachie

...But one thing keeps bothering me: How do you ever get these huge lithium battery banks charged? I see people talking about 400, 600 even 1,000 amp hours, and it staggers me....


Under my current 320AH of FLA, I'm generally into float in early afternoon after solar and a bit of motoring. A couple more hours, sure, but I'm topped off well before I drop the hook....

How long it takes to charge your battery has very little to with its size and very much to do with how much you used from it since the last time you charged. And then a bit more to do with the battery chemistry.

If you install a 400AH LFP battery in place of your 320AH LA battery and have the same usage then the LFP will charge faster than the LA because it doesn’t have the long taper that LA has. How much faster will depend on your charging system.

OTOH, if you’re installing LFP because you want to use a lot more electricity then you have consider an upgrade to your charging system as part of the whole process.

What you would get by replacing your LA with LFP in the sizes you mentioned is a lot more useable reserve capacity (2x +). Yes, that means you will have to charge longer if you use that reserve, but since PSOC (partial state of charge) isn’t a big deal with LFP you can replace that deep drawdown over days (or weeks) of slow charging that is only marginally above your usage. Doing that with LA will lead to the early demise of your batteries.

[sailorboy1]

Originally Posted by HeywoodJ

How long it takes to charge your battery has very little to with its size and very much to do with how much you used from it since the last time you charged. And then a bit more to do with the battery chemistry.

That is what I was going to write. You use the same power/day no matter size of bank. If you have a big bank and let it run down you have to charge it longer if you what it fully charged. But you don't need to fulling charge it, just keep up with use.

Unlike acid batteries LFP will accept all the power you throw at it till almost fully charged. Acid mean time with accept about 25% capacity till about 85% charged and then take 4 hours to finish, and you have to finish to make batteries last.

It just isn't the same once you get the LFP and it is only complex if you want to turn it into that.

[smj]

Originally Posted by jordanbigel

I might be a good case of what you are talking about - I have 1200ah of LifePo, an admittedly huge bank. I don't NEED that much at all, but, with 3 x 400ah batteries I have redundancy. If one fails, I can easily - easily - get by with just 2 of them. Frankly, I could limp along with just 1 of them for some time and just have to run the generator more. I used to have 4 x 8D LA batteries, so I had the space to basically keep a "spare" battery and still save hundreds of lbs of weight.

I do not have tons of solar, just 2 panels equaling about 375watts - I rely on the generator on a daily basis when cruising, the solar provides about half of what we use in a day, on a good day of sunshine.

The other thing which you may be missing is there is no need to fully recharge the bank. I run somewhere between 45% and 75% SOC. Every 2 or 3 months I charge the bank fully to 100% (to allow top balancing) and the rest of the time its just somewhere in the middle. Coming from a world of LA batteries, this may seem hard to accept, but the LifePo bank likes it this way.

How do you limit your soc to 45%-75%? I’ve heard it’s best not to fully charge daily, but my solar usually has my lithium topped up by early afternoon.

[jordanbigel]

Originally Posted by smj

How do you limit your soc to 45%-75%? I’ve heard it’s best not to fully charge daily, but my solar usually has my lithium topped up by early afternoon.

I use 2 things - 1) a Victron BMV-700 which has a built-in programmable relay. The BMV allows me to program the start/stop point in SOC%. The back of the BMV has terminals and 2) I ran wire from there to a Victron SolidSwitch104 (See: https://www.victronenergy.com/access...olidswitch-104) - this tiny thing is about 2" x 2" and is wired between the ignition wire and the voltage regulator (in my case a Blamar MC-614) the switch takes the relay wire from the BMV and controls when the ignition wire is energized.

SO, if the BMV has the relay open (ie. SOC% has not dropped below charge threshold) then the switch cuts the ignition wire to the voltage regulator. When the SOC% drops below the programmed threshold, the ignition wire is energized which turns on the voltage regulator which in turn instructs the alternator to start bulk phase charging. When the programmed SOC% target has been reached, the BMV opens the relay, causing the SolidSwitch to cut off the ignition wire which therefore turns off the voltage regulator and the alternator.

This may sound complicated so far (and I am sure some here will think it is complicated) but I made it even more complicated by adding an "override" switch into the mix. The override switch allows me to (you guessed it) override the SOC% programmed in the BMV and energizes the voltage regulator regardless of the BMV relay.

This allows me to choose when and if I want to go over the target SOC% programmed in the BMV. For example, if I am motoring a long distance to get to a new anchorage and I plan to remain there for several days, I can charge the bank extra. So, if I have the BMV set to a target SOC% of 70% but I want to get it up to 90% (or maybe I want to do a full 100% charge which is needed periodically to top-balance) I can hit the override and charging will continue until I turn off the override switch again.

Or, if the SOC% is still above the trigger threshold (say I am at 55% SOC but the BMV relay is set to activate at 45% SOC) and therefore the regulator is not being powered - but I want to charge the bank anyway, I hit the override switch.

Note also that the voltage regulator has been programmed with LifePo4 friendly settings, so that if I leave the override switch on, the Balmar charging profile then takes over and goes through the normal 3 stage program which keeps things at absorption long enough for top-balancing to occur. If I do not turn off the override, the voltage regulator eventually goes into float mode - so you need to be deliberate with this and not forget you left it on!

But wait, there's more - to make it even MORE complicated, I also wired my battery bank's BMS HVC signal wire into the mix - this required yet another relay ( I used this guy: https://www.amazon.com/gp/product/B089Q6KLPQ). If you use drop-ins, you can't do this because they do not offer HVC signal warnings. But basically the BMS signal will open a NC (Normally Closed) relay so that if the BMS HVC signals, the ignition is cut off and no charging can occur regardless of the BMV or override switch.

I made this (crude) diagram for my own use while I was designing this setup, I am not sure if this will help you (or anyone) but here it is anyway. I put these components on a small piece of wood and then attached it to the wall next to the voltage regulator and ran the various wires to it and to the regulator. Works like a charm.

Note: For my bank, my solar is so small compared to the bank size, I have never reached full charge using solar and frankly I dont see how it could - I have on my ToDo list to wire the solar MPPT controllers into this circuit so the BMV can also control the solar, but for now that is not happening. The point is this same technique can be used to control and alternator (voltage regulator) or solar controllers, or the AC battery charger (I also have my Victron Multiplus charger wired into this system as well, though it is not indicated on this diagram which only address the voltage regulator control part of things). So when I am at the dock on shore power, the BMV also controls SOC% by turning on and off the MultiPlus's shore power input.

[smj]

Thanks Jordanbigel, you’ve given me plenty to think about!

[CaptainRivet]

Originally Posted by Shanachie

So I've been reading all of these entertaining lithium threads as I debate what to do for new house batteries.


Generally, I think all of this is way too complicated, suitable more for the engineering geeks than the average sailor who just wants to cruise around. I like simple.



But one thing keeps bothering me: How do you ever get these huge lithium battery banks charged? I see people talking about 400, 600 even 1,000 amp hours, and it staggers me.


I have a 34-foot sailboat with a Yanmar 3gm30 and a 50 amp alternator as well as 320 watts of solar with a Xantrex MPPT. Let's say I put 400 AH of lithium batteries in and a 20-amp DC to DC charger on the start battery.



If I'm motoring on a sunny, calm day, I'll put close to 40 amps an hour into the battery bank. But that's eight hours to a full charge if I had run the bank down for some reason.


It's still three or four hours if it's a more normal overnight discharge.


Under my current 320AH of FLA, I'm generally into float in early afternoon after solar and a bit of motoring. A couple more hours, sure, but I'm topped off well before I drop the hook.


So what am I missing? What's the difference? Is getting fully charged a couple of hours earlier really worth all of the fuss with BMS, balancing cells and all of the rest? Or is it just fun to be an early adapter?



Enlighten me.

If you are in float with you 320AH FLA in early afternoon now, then 320AH LFP would be full at noon
the charge efficency of FLA is bad, around 50% and LFP has 94-98% efficency means the double amount of charge really ends up in your battery.
And you won't need 400AH LFP as 320AH FLA gives you a usable capacity of 120-140AH means a 150AH LFP bank is equivalent to what you have now.
Put 200AH LFP on your 34 footer and you are happy and get that fully charged.


its not complicated especially small systems like yours, just don't get dropins. 4 good cells plus BMS,a shut off relay, a DC2DC charger for the alternator, switch the profil from your MPPT to Lithium and thats it if your installation with FLA was proper before.


it gets complicated on world circum boats especially cats with multiple backups with 2 alternators, 1000AH bank, 6kw inverters, 2500W solar, wind generator and 12/24V system....
and as others said I don't need 1000AH, mostly around 200AH per day and rest is reserve for a bad week of rain and because I have a full electric galley and sometimes draw 6kw so the bank gets discharged with a much lower current per cell=less stress. Got cheaper LFP cells but therefore more so I have more avaliable capacity, 3 bunnies at the same time...

if the bank is really down I need couple of days full sunshine till its full again. But LFP doesn't need to be full compared to FLA, its actually much more happy if its between 40-60% SOC.

So alternatively i (seldomly, last year 5 times) use a 3500W mobile gas gen via 24V/180A shorepower charger, 1 hour is enough for a day. I only have 2x30A DC2DC for the alternators, enough for everything thats permanently on.

[Shanachie]

After reading more lithium battery threads, I've decided that most sailors with these batteries are electronics nerds/ trend-setters who thoroughly enjoy building increasingly complicated systems.



Not that there's anything wrong with that!


As someone who only wants the lights to turn on and the diesel to start at appropriate times, I think golf cart batteries with solar will fill my needs quite nicely.


Simple is reassuring to me. When the lights don't turn on, I want to be able to trace the problem quickly. Sorting through the complicated setups of lithium lovers isn't attractive.

[BlueH2Obound]

Charging is no problem with the right solar or whatever. As mentioned above, you won't believe how much more rapidly LiFePO4 batteries will charge when compared to FLA or AGM batteries, so with LiFePO4, the time you DO have solar, or run your engine/alternator, or run your generator will be utilized much more efficiently than before you changed to LiFePO4! You'll love the change!

[Loredo]

1680AH LFP bank, no solar, only alternator / generator / marina charging here. For me the most important thing with the LFP batteries is not having to charge them completly every time. With the AGM's I had prior that was a major inconvenience.

Why that large of a battery bank? Firstly, I simply used the spaces occupied by the old AGM bank. Most importantly, even if I let them sit at say 50% SOC I still have plenty of power reserve without harming the batteries.

What's not to like?

[MWGDVC]

Shanachie,
I am with you regarding the desire for things to just work.
My goal for my electrical system was for the power to be available when we wanted to use it, without constant fiddling, or worrying. In short, a system that took care of itself. We got the boat to sail and explore, not be powerplant managers.
I do not like anything requiring phones, apps, and bluetooth to use, program, monitor or control.
Being a cheapskate I tend to keep using something as long as it works, and phones will not function after a very short time due to “improvements” leading to an older phone being unable to run the updated programs.
All of my equipment aboard uses wires between components.
I needed to replace my very old Trojan golf cart house battery bank a little over a year ago, so I went down the rabbit hole of battery technology. I chose LiFePo for the following reasons;
My house battery space is in an uncomfortable space to access, so checking battery water was difficult due to the ability to get a clear view of the cells. +1 lithium.
My companionway ladder is steep and nearly a 6’ climb to the cockpit, making lugging 4 75 Lb. batteries out to clean them a bit of a chore. Lithium 25Lbs. each. Another win for LiFePo. (though they haven’t needed removal for any reason since installation)
As I understand the characteristics of LiFePo, they are like a competitive eater, consuming all that they can cram down their throat quickly, until capacity is reached.
Lithium will accept a high charge rate as long as a charge source is available, or until full. This seems to mesh well with solar charging characteristics, on sunny days lots of power available for a few hours.
As FLA batteries get full, their internal resistance increases, slowing the rate of charge. This causes the solar available time to run out before full charge is achieved. And a regular full charge is required for the longevity of FLA batteries.
Lithium seems to let you keep most all the Watts you harvest or produce, 100W in, 98W added. FLA seems to not let you keep as much of what you produce, seems like 100W in, 60W added.
Another benefit of this battery chemistry is the voltage remains high through most of the discharge cycle. Lights stay bright, autopilot is happier, in fact, all electrics/electronics aboard are happier.
Perhaps the most attractive features of lithium is the power available for use. My old 450 AH bank was limited to 50% of capacity discharge (225AH). Seldom did the bank get to 100% state of charge on solar alone, usually around 85-90% state of charge, the remainder being supplied by an alternate charge source such as alternator, generator or shore power. Realistically given the age of my old house bank, we had perhaps 150AH available for use daily.
Regarding the aging of batteries, the manufacturers of lithium claim 3000 cycles v/s 300 for FLA. Time will tell what the real world lifespan will be...
I replaced with 300 AH of lithium and the worries of power management went away. Running the fridge in the heat of summer, along with anchor lights, fans, and such lights and appliances as we would like for normal life, the batteries are still at 75-80% SOC at first light. Our 640W solar array has us reaching 100% by between 10:00 and 11:00 AM (if sunny at 35 degrees N). I have adjusted the solar controllers down now to stop charging at 70% while on the dock. Every few weeks I will turn on the shore power charger for a little while, allowing the batteries to reach 100% SOC to allow the batteries to balance themselves. No big deal. Much easier than checking battery water. Once set up, a LiFePo house bank is truly a set it and forget it system.
I think the terms “game changing” or “life changing” are overused, but this upgrade has greatly improved our life aboard experiences.
No longer do we need to worry if something gets left on , within reason of course.
The one mistake I have discovered in my equipment choices was the size of my DC-DC charger. I chose Renogy’s 60A. 60A uses 75A to produce 60A. That current draw causes my alternator to run hotter than I like. (Balmar 120A, external regulator) but fortunately the Renogy has a ½ power option, so I alternator charge the house bank at 30A, drawing a sustainable 38A.
I do use an AGM starting battery, as this chemistry battery, as I understand it, is better suited for the high current, short duration load of the starter and windlass.




For your current use, 320 AH of FLA means around 90-100AH usable. 2X100AH lithium would double your useable capacity, reduce weight aboard by 50 Lbs. and charge far more quickly on solar.
Realistically you are probably harvesting 72AH per day from solar in Tampa.
In addition, if you used a 20A DC-DC, which is as large as I would go with a 50A rated alternator, you would replenish the house bank by 10% of capacity per hour motoring.
You don’t have to take out a second mortgage to make this upgrade, I paid just over $3.00 per Amp hour for 12VLiFePo batteries.
Get a battery monitor if you don’t already have one. It is like a fuel level gauge for your batteries.
DC-DC converter that you can set for lithium charging.
Set your shore power charger for lithium. (I found the shore power charger unnecessary after switching, did not use it at all.)
Set your MPPT solar controller for lithium, wire it up and go.
Sorry for the lengthy post,
Mike