LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

[steelwrk1]

Hello hellosailor,

Thanks for your comments but I cannot follow the math in your volts and amps.

I will have the physical layout of ;

One set of 4 only Kyorocera 215 watt solar panels at one location +/-40 feet away from my battery bank
and
A second set of 3 only Kyorocera 215 watt solar panels at one location +/-30 feet away from my battery bank

Solar panel specs taken from a web site;

KD215 - 215 watt solar panel manufactured by Kyocera.

Ratings: Voltage 26.6 VDC; Current 8.09 Amps; Power 215W

Dimenions: Length 59.06" Width 38.98" Depth 1.8"

Weight: 41.0 lbs

Connections: MC4 connectors with flying leads (35.4" and 43.3")



THEY WILL FEED MY 84 ONLY 60 AMP LiFePO4 BATTERIES THAT GIVE ME A HOUSE BANK OF 1260 AMPS

Originally Posted by hellosailor

Pete-
40 feet from the batteries means 80' round trip, and that's how you work voltage drop and cable size. I'd put the panels in series for higher voltage and lower cable loss. so you've got something like 88 volts from the rear, 66 from the three in front, cleanest solution is as Bob suggests two controllers, two separate systems.

TWO CONTROLLERS, I UNDERSTAND YOU HERE

So if I read you right, that's 88 volts @150 amps from the rear, 66 @ 150 from the front, and I'd use the same cable size to make life simpler.

I DO NOT FOLLOW THE MATH BUT UNDERSTAND THE CABLE SIZE PRACTICALITY

88 volts at 150 amps at eighty feet of cable...the Blue Seas calculator says to run 4/0 AWG cable allowing for a 3% voltage loss and running all day, not crossing through engine spaces. You can find loss calculators and wire sizers online, the only real question is how big a loss are you willing to tolerate in the cable (3% is typical) and how much can you afford to spend on the cable. Well, but the time you hit 4/0 cable there's bulk and weight to consider as well.

I HEAR YOU ON THE SIZE AND WEIGHT

And of course, the choice of fully tinned marine cable or cheaper copper, which I think most of us would call unsuitable since it can corrode if not fully tinned.

HERE I AM LEARNING SOMETHING RE THE TINNED WIRE, THANK YOU....I HAVE ALL KINDS OF NEW COPPER WELDING WIRE FROM THE OLD DAYS, BUT NOT TINNED

But that's a starting point that you can shop and budget around.

There's also a pricey option in the Solarstik, which allows you to mount two large panels outboard on a fully rotating mount. They're expensive, but it would cost as much or more to make them yourself. Having the option to angel your panels and track the sun can make a difference of about 10% more power every hour or two, because you'll lose 10% every time the sun shifts that far. There's a very long thread about these things, posted here I think 5 years ago.

NOT REALLY AN OPTION FOR ME, ( CK OUT THE PICTURE OF MY BOAT, BY CLICKING MY PHOTOS UNDERNEATH THE QTY OF POSTS I HAVE MADE)....PERHAPS THE AFT 3 PANELS AT THE DECK LEVEL MOUNTED 6 ' ON TOP OF THE SWIM PLATFORM AREA will be able to be tilted ...BUT THE ONES THAT WILL BE MOUNTED AT THE SAME LEVEL OF MY RADAR WILL FORM BIMINI TYPE SHADED AREAS AND BE TOO HIGH UP TO ADJUST

And there are tools online that tell you how many hours of sunlight you can expect per day by latitude, in temperate places a full day of sunlight may average about five-six hours worth of "noon" full power.

I UNDERSTAND

Your mileage will of course vary, but that's some basics to start with.

Thanks for your comments and explain what I am missing re your math,

Best Regards,
Pete

[ebaugh]

I don't understand the current calculations either. Wired in series, the max current is the same as the max output of a single panel.

Maybe the solar experts can chime in, but I will speculate a little voltage loss is not too significant on the input to the MPPT controller. I'm not sure you need to keep it under 3%, probably under 10% is sufficient? It takes most any input voltage and creates charging current at 12V. Not to mention, the time spent at "Max" output is basically noon on a cloudless day.

[steelwrk1]

Thanks Bob,

I thought I was beginning to pick it up and was mixed up from the math.
At any rate assembled the rack for the 3 pannels last night and will place it on the boat today some time,then figure out the mounting.
I am concerned about the amount of weight I am putting on the stern ( built the frame from 2 '' x 2 1/2'' x 1/4 '' 6061 T6 aluminum angles that I cut down to 2 x 2 3/8 x 1/ 4 and cut a 5 '' aluminum I beam in half to form a "T" section ,also 1/4 ''thick ) of the boat and may take a run at lightening up the structure, by drilling lots of holes....we'll see. ( added the aluminum slide out dingy lift on the stern,this year as well)
Will also get a solar pro on board before haul out and post what I learn then.

I hoped T1 Terry would have chimed in , but I guess he got busy with "life".

Best Regards,
Pete

ps
going below freezing here real soon, makes the morning coffee soo much better

[goboatingnow]

PS tinned wire is good , untinned is fine

Dave

[JohnInBKK]

All,

I would like to invest in a Solar powered LiFePO4 system to produce approximately 400Ah per day. I have a nice flat pilothouse roof of about 9m2 for a solar field, but could extend to another deck area if need be. I recon - where I will cruise - a 1000Ah - 1200Ah system could do it. Pity Nigel Calder's latest revision doesn't cover the technology (yet).

I got a quote for:

LiFePO4 12V 1000ah Battery Pack solar battery 12v 1000ah, View 12v 1000ah battery, Neutral Product Details from Changchun Mingda Technology Co., Ltd. on Alibaba.com

with the result:

"On behalf of my company, Mingda Technology Co.,Ltd, I am personally coming to you as a prospective supplier of
extremely high quality, high energy density and CE Certified lifepo4 battery.
For LiFePO4 12V 1000ah Battery Pack solar battery 12v 1000ah, unit price is 4639.35USD.
We can accept any kind of payment terms: such TT, L/C, D/P, O/A, West Union etc".

Obviously something got "lost in translation" - I don't think the company understood I was looking for a complete system and not just a battery bank ($5,000 is probably about right for 1,000Ah @12V).

Could anyone recommend a "reputable" Chinese supplier? (no, not an oxymoron - my boat is from a Chinese manufacturer!)

BTW - Excellent thread! Thanks to all!

[hellosailor]

Bob, this wouldn't be the first time I made a math error. That's why I'm not allowed to practice mathematics across an interstate border. Sorry 'bout that. Pete, the bad news is you'll have to run new correct numbers, the good news is, you won't have to buy those whopping heavy cables.

I think you're right about voltage losses not being so critical with an MPPT controller being able to compensate for them, but whether it is a loss of voltage or amperage, isn't any power loss in the cabling still a power loss that can never be regained?

[Singleprop]

is this a solar thread now?

[steelwrk1]

Hello Singleprop,

My bad, you are correct,I went sideways with this total install.

I am learning here and after having installed the 1260 amp 12 volt house bank , and lived on it for a couple of months I feel the aid of solar power is the way to "HELP" recharge, or at least the best way to use a large house bank

The size of the bank is great BUT you must put back in what you take out and that means main engine or generator time for me. Yes I can go a few days but then I have to run the genny longer.

So no more posts about the solar system till its done.

Regards,
Pete

[JohnInBKK]

Agree with you Pete,
If we're on the topic of LiFEPO4s, then we should also look at the charging options and gain/share experience....

[steelwrk1]

Hello All,

Winterizing LiFePO4 Batteries.

We winterize our engines and gen sets to -45 degrees F. Boats gets hauled early Nov and back in the water April/May. It will rarely get this cold but it is possible.

What do you do with your House bank LiFePO4 Batteries. Like my previous gel cells I will remove the positive side going to the boat, so there is no loads , and I will take a look at them in January to see where they are, if I leave them on board.

I have read the following at different places;

-reduce the charge to 40 to 60 % capacity and leave them on board

-remove them and store in heated building at 40 to 60% capacity

-full charge 90 to 95% and leave them on board

-remove them and store in heated building at full charge 90 to 95%


Has any one have " been there done that" experience on this ?

Thanks for any comments,
Pete

[Wraith_Mac]

Originally Posted by steelwrk1

So no more posts about the solar system till its done.

Regards,
Pete

Pete,
As far as I am concerned you make as many posts on the methods of charging your LiFePo4 battery as you wish!!

In short it's not a SOLAR thread but a discussion thread for those using LiFePo4 house banks, this would and should include all means used to charge them.

Pete, you are in no way out of line IMO and I for one have appreciated your postings of the issues you need to resolve re. solar charging.
We can all add to our knowledge of charging solutions if we wish to.
Cheers,
Mac

[Maine Sail]

Just an update:

I am finally closing in on 200 cycles on our LiFePO4 battery bank. I have not pushed charging voltage to cell balancing levels and only performed a single top balance on the cells, 192 cycle ago, or last winter. We do have a BMS system but I treat it as an insurance policy and do not use it for cell balancing only for emergency HVC or LVC events.

At high charging voltages the BMS can shunt small amounts of current to other cells in order to keep them in-balance. For EV guys who need every last ounce of energy, and push the voltages into the knee range, a BMS is a good tool to have. For house bank use, which more closely mirrors off-grid, I have decided not to push my charge voltages into the "upper knee range" because I find no use in doing so other than the risk of potential over charging of the cells....

Since July the charge voltage has been limited to 13.8V which puts back in nearly 98% of the bank capacity but has far less risk of over charging and damaging the cells. All of our charge sources are now limited to 13.8V.

During the winter I played with numerous charge voltages and settled on 13.8V to 14.0V and in July decided 13.8V was the perfect balance point on our boat for our use. 14.0V gives a little shorter acceptance taper but at 13.8V the taper to full from bulk is still about 30 minutes. Many, many HOURS less than LA batteries..

In July I also had to current limit our 160A alt to 115A - 120A. This allows the alt to run there indefinitely without exceeding 225F. The temp limiting features of most external regulators reduce the current too deeply for my tastes and the alt goes from full bore to half speed and the over all charging is slower. I played around and around with temp settings but found Balmar's Belt Manager on the MC-614 worked significantly better.

If going Li you will want/need an alt significantly larger than where you actually want your current or it will get VERY, VERY hot and could cook itself. I still have the temp sensor and it is still set for 225 but at the new current limit it has yet to exceed about 220F...

I deem our bank "full" when the current drops to 5A at 13.8V. Pretty simple stuff. I then manually synch the battery monitor and cycle to 80% DOD again.

If this bank was not for experimental purposes, and my own education on Li and cycling use, I would likely cycle only to 60% or 70% DOD... At 5A & 13.8V I shut off solar and the alternator and do not turn them back on until the bank drops to approx 80% DOD.

Here's where the cell balance tested yesterday:

*Resting
*Loaded
*Bulk Charging
*Absorption Charging (Voltage Limited to 13.8V)

I am using my NIST calibrated Fluke for all measurements to keep everything the same.

Unloaded resting (five days) @ 74% SOC - Cell temps 49F:

Cell #1 = 3.362V
Cell #2 = 3.361V
Cell #3 = 3.361V
Cell #4 = 3.361V

Loaded @ a -17.4A average load @ 72% SOC - Cell temps 49F

Cell #1 = 3.313V
Cell #2 = 3.314V
Cell #3 = 3.314V
Cell #4 = 3.313V


Charging @ 121A 13.72V - Cell temps 49F

Cell #1 = 3.431V
Cell #2 = 3.430V
Cell #3 = 3.429V
Cell #4 = 3.430V

Charging @ 36A - 38A (current dropping quickly) 13.80V (regulator voltage limiting) - Cell temps 49F

Cell #1 = 3.452V
Cell #2 = 3.452V
Cell #3 = 3.453V
Cell #4 = 3.452V

Not half bad for 192 cycles, approx 70% of them to 80% DOD, and no cell balancing since the initial top balance 192 cycles ago.

I can assure you that it has not been easy to get to 192 cycles, lots of tally-marks in my note book, some of them missing DOD etc. but 192 tally marks. Many of these cycles were done in my shop at .25 "C" or 100A loads and the rest were done on the boat often with the help of a ceramic disc heater to accelerate testing and DOD.

I did a lot of invoicing on-board this summer rather than in my home office as it allowed me to turn on a 100A load while doing it and get some more cycles in. Unfortunately I don't feel the 100A loads are representative of normal use on boats, but none the less, I used it to accelerate the cycles. I wanted 200 by the time I haul for the season and I may just barely make it, though could be shy by a few too.

Essentially we've simply been turning off all charge sources and letting the bank draw down to 80% DOD before even considering to re-charge. Even at 80% DOD with our average loads we don't seem to drop below 13V as a bank voltage or roughly 3.25V per cell. At average house loads of less than 10A the voltage barely moves at all throughout the 100% to 20% capacity range. Voltage is a horrible indicator of DOD at average house loads below 10A on a 400Ah LiFePO4 bank. Yesterday I was sitting there drawing nearly 14A running the Espar, inverter, stereo and a bunch of electronics. The loaded bank voltage was still 13.26V and held steady the entire three hours I ran that load.. I find this pretty darn good for cells that were at 49F...

I also took the opportunity to measure the internal resistance yesterday with my Argus analyzer. This is the same tool and same measurement I took when the cells were brand new so I had a baseline to work from. I don't suspect this tool is 100% accurate for measuring the internal resistance on Li so I am using it to track changes....

When new, 192 cycles ago, the internal resistance using the Argus was 0.58 mΩ and yesterday it was 0.57 mΩ. The CCA measured by the Argus was 5213CCA when new and Yesterday it was 5337......Seems odd that I have seen improvements but the tool used was the same. Battery temps were similar as I took the original measurements in my unheated garage so probably around 50F - 55F when new and 49F yesterday....

I just left a boat this morning with a three year old bank of golf cart batteries and the internal resistance was 7.6 mΩ........ Quite a difference.

One observation I have noted over the years is that with lead acid batteries, and coastal cruising boats, the actual cycles to 50% DOD are pretty minimal before the banks are dead and replaced.

When I poll my own customers, new and old, on how many overnights and trips they take per year it gives me a good understanding of cycle life. I think it is pretty safe to say that the average coastal cruiser barely sees 130-150 cycles, over 4-5 years, before the banks are dead. I do have many customers I have extended to 7-8 years, but this was at added expense to get the batteries to last that long. Still even at 7-8 years many of them have barely broken 200 cycles.

Heck many customers I pick up do as little as 15-20 cycles per year. I often find a 1 week cruise and a hand full of Fri/Sat weekends. In less than one year I have already completed 192 cycles on this technology and most to 80% DOD not the 50% of lead acid.

Charging to 13.8V is working exceptionally well, despite the Chinese manufacturer suggesting 14.6V + is safe... The cell balance has not budged at all in 192 cycles and we are getting 98% of the rated capacity at 13.8V so why push harder.......

I was planning on yearly top balances but I may just push it longer to see how long it takes to need a top balance.

Just some more musings...

[FlyingCloud1937]

Originally Posted by Maine Sail

Just an update:

I am finally closing in on 200 cycles on our LiFePO4 battery bank. I have not pushed charging voltage to cell balancing levels and only performed a single top balance on the cells, 192 cycle ago, or last winter. We do have a BMS system but I treat it as an insurance policy and do not use it for cell balancing only for emergency HVC or LVC events.

At high charging voltages the BMS can shunt small amounts of current to other cells in order to keep them in-balance. For EV guys who need every last ounce of energy, and push the voltages into the knee range, a BMS is a good tool to have. For house bank use, which more closely mirrors off-grid, I have decided not to push my charge voltages into the "upper knee range" because I find no use in doing so other than the risk of potential over charging of the cells....

Since July the charge voltage has been limited to 13.8V which puts back in nearly 98% of the bank capacity but has far less risk of over charging and damaging the cells. All of our charge sources are now limited to 13.8V.

During the winter I played with numerous charge voltages and settled on 13.8V to 14.0V and in July decided 13.8V was the perfect balance point on our boat for our use. 14.0V gives a little shorter acceptance taper but at 13.8V the taper to full from bulk is still about 30 minutes. Many, many HOURS less than LA batteries..

In July I also had to current limit our 160A alt to 115A - 120A. This allows the alt to run there indefinitely without exceeding 225F. The temp limiting features of most external regulators reduce the current too deeply for my tastes and the alt goes from full bore to half speed and the over all charging is slower. I played around and around with temp settings but found Balmar's Belt Manager on the MC-614 worked significantly better.

If going Li you will want/need an alt significantly larger than where you actually want your current or it will get VERY, VERY hot and could cook itself. I still have the temp sensor and it is still set for 225 but at the new current limit it has yet to exceed about 220F...

I deem our bank "full" when the current drops to 5A at 13.8V. Pretty simple stuff. I then manually synch the battery monitor and cycle to 80% DOD again.

If this bank was not for experimental purposes, and my own education on Li and cycling use, I would likely cycle only to 60% or 70% DOD... At 5A & 13.8V I shut off solar and the alternator and do not turn them back on until the bank drops to approx 80% DOD.

Here's where the cell balance tested yesterday:

*Resting
*Loaded
*Bulk Charging
*Absorption Charging (Voltage Limited to 13.8V)

I am using my NIST calibrated Fluke for all measurements to keep everything the same.

Unloaded resting (five days) @ 74% SOC - Cell temps 49F:

Cell #1 = 3.362V
Cell #2 = 3.361V
Cell #3 = 3.361V
Cell #4 = 3.361V

Loaded @ a -17.4A average load @ 72% SOC - Cell temps 49F

Cell #1 = 3.313V
Cell #2 = 3.314V
Cell #3 = 3.314V
Cell #4 = 3.313V


Charging @ 121A 13.72V - Cell temps 49F

Cell #1 = 3.431V
Cell #2 = 3.430V
Cell #3 = 3.429V
Cell #4 = 3.430V

Charging @ 36A - 38A (current dropping quickly) 13.80V (regulator voltage limiting) - Cell temps 49F

Cell #1 = 3.452V
Cell #2 = 3.452V
Cell #3 = 3.453V
Cell #4 = 3.452V

Not half bad for 192 cycles, approx 70% of them to 80% DOD, and no cell balancing since the initial top balance 192 cycles ago.

I can assure you that it has not been easy to get to 192 cycles, lots of tally-marks in my note book, some of them missing DOD etc. but 192 tally marks. Many of these cycles were done in my shop at .25 "C" or 100A loads and the rest were done on the boat often with the help of a ceramic disc heater to accelerate testing and DOD.

I did a lot of invoicing on-board this summer rather than in my home office as it allowed me to turn on a 100A load while doing it and get some more cycles in. Unfortunately I don't feel the 100A loads are representative of normal use on boats, but none the less, I used it to accelerate the cycles. I wanted 200 by the time I haul for the season and I may just barely make it, though could be shy by a few too.

Essentially we've simply been turning off all charge sources and letting the bank draw down to 80% DOD before even considering to re-charge. Even at 80% DOD with our average loads we don't seem to drop below 13V as a bank voltage or roughly 3.25V per cell. At average house loads of less than 10A the voltage barely moves at all throughout the 100% to 20% capacity range. Voltage is a horrible indicator of DOD at average house loads below 10A on a 400Ah LiFePO4 bank. Yesterday I was sitting there drawing nearly 14A running the Espar, inverter, stereo and a bunch of electronics. The loaded bank voltage was still 13.26V and held steady the entire three hours I ran that load.. I find this pretty darn good for cells that were at 49F...

I also took the opportunity to measure the internal resistance yesterday with my Argus analyzer. This is the same tool and same measurement I took when the cells were brand new so I had a baseline to work from. I don't suspect this tool is 100% accurate for measuring the internal resistance on Li so I am using it to track changes....

When new, 192 cycles ago, the internal resistance using the Argus was 0.58 mΩ and yesterday it was 0.57 mΩ. The CCA measured by the Argus was 5213CCA when new and Yesterday it was 5337......Seems odd that I have seen improvements but the tool used was the same. Battery temps were similar as I took the original measurements in my unheated garage so probably around 50F - 55F when new and 49F yesterday....

I just left a boat this morning with a three year old bank of golf cart batteries and the internal resistance was 7.6 mΩ........ Quite a difference.

One observation I have noted over the years is that with lead acid batteries, and coastal cruising boats, the actual cycles to 50% DOD are pretty minimal before the banks are dead and replaced.

When I poll my own customers, new and old, on how many overnights and trips they take per year it gives me a good understanding of cycle life. I think it is pretty safe to say that the average coastal cruiser barely sees 130-150 cycles, over 4-5 years, before the banks are dead. I do have many customers I have extended to 7-8 years, but this was at added expense to get the batteries to last that long. Still even at 7-8 years many of them have barely broken 200 cycles.

Heck many customers I pick up do as little as 15-20 cycles per year. I often find a 1 week cruise and a hand full of Fri/Sat weekends. In less than one year I have already completed 192 cycles on this technology and most to 80% DOD not the 50% of lead acid.

Charging to 13.8V is working exceptionally well, despite the Chinese manufacturer suggesting 14.6V + is safe... The cell balance has not budged at all in 192 cycles and we are getting 98% of the rated capacity at 13.8V so why push harder.......

I was planning on yearly top balances but I may just push it longer to see how long it takes to need a top balance.

Just some more musings...

Excellent Study "Main",

Have you established a criteria for installing on customer boats yet? I would be interested in your thoughts.

It seems very few of my customers can keep from murdering their lead acid banks.

Lloyd

[dlentz]

Originally Posted by Maine Sail

Just an update:

I am finally closing in on 200 cycles on our LiFePO4 battery bank. I have not pushed charging voltage to cell balancing levels and only performed a single top balance on the cells, 192 cycle ago, or last winter. We do have a BMS system but I treat it as an insurance policy and do not use it for cell balancing only for emergency HVC or LVC events.

Just some more musings...

Thank you Maine, nice work.
I also am seeing similar results, although I'm not documenting it as well as you are. I'm also charging to 13.8v, however I'm "floating" at 13.2v. It's a rare occasion that a charge source cycles back into absorption for me at those settings even with refer running. My cycles will consist of more, but much lower DoD, or minicycles, so lifespan will be interesting. I do run my 150A 12V DC generator at 13.9V to reduce run time though. Its always monitored when running and at 13.9V it's not very high anyway. That .1V really does increase the amps going in though.
My balance is running from 5mv across the cells while under load to 50mv when nearing 13.8 on the pack. It's not changing, I would suspect I didn't top balance as accurately as you might have. I initially charged each cell to 3.7V and when the acceptance rate drop to +/- 1% (7 amps on my 700A cells) I called it good. While in theory it'd be nice to have all of the cells identical, I'm thinking as long as one cell isn't going too high while charging, there's little to no harm with slight imbalances. (I hope that doesn't cause a big stir.)
Again thanks for your work, it's providing real world House Bank data that doesn't exist.
Dwain

[Maine Sail]

Originally Posted by FlyingCloud1937

Excellent Study "Main",

Have you established a criteria for installing on customer boats yet? I would be interested in your thoughts.

It seems very few of my customers can keep from murdering their lead acid banks.

Lloyd

Lloyd,

I have my ideas for how I would do it for a customer but until I have a "standard" behind me that I can say I wired & designed it to I am not currently doing this for customers unless "factory made" as in Genasun, Mastervolt etc....

I am on the ABYC discussion list for Li but it has been very quiet. I believe it will come up at the meetings in Feb and will likely first be addressed in a TIR before a standard. Charlie J. has been braver than I and has built a few banks with good success but I am not willing to poke my head in until I have a standard or at least a technical information report to fall back on.

My customers also kill LA batts, most often due to chronic under charging due to being on moorings. Through education I can often get them to better understand, and thus extend life, but not always...