LiFeYPo4 questions

[Sunking]

PN FWIW sizing requirements for lithium are not much different that than FLA. With FLA minimum autonomy is 5 days, lithium minimum is 3 days to be equal in usable capacity. The big advantage of lithium can be Peukert losses and weight, but weight i snot really an issue for off-grid unless we are talking a boat or RV. Myself personally I would not use lithium a sit is just still too expensive and unproven. The cycle life claims for lithium thus far have proven to be false, and cold weather performance is very poor. Lots of stranded Leaf owners last winter.

[PNjunction]

..The Calb 400ah cells look like they are priced well. The GBS look really nice but expense wise, add up quickly.

Just make sure you are looking at the price of individual cells, and not comparing bare cells to pre-built systems that may or may not have additional bms systems added on.

I looked at my power bill history and maybe this will give you guys a better idea as to what I am running.

You know that going off-grid with battery storage is currently about 10x the cost from the local power company right? So one does this for reasons other than savings. Just wanted to make sure.

Unfortunately, we still do not have any great idea of how much power you need to run, and for how long, to suggest any sort of battery capacity.

Most likely, I would only run my batteries 30-40% down to extend the life unless the community recommends more.

That's a lead-acid mindset. With lifepo4, instead of running from 100-70% SOC, you would actually do better running in a partial-state-of-charge scenario of perhaps 90-60% / 80-50% SOC. Since there is no need to actually charge lifepo4's fully, charging requirements are eased, and if run in a PSOC state, balance - especially in a somewhat low voltage / low current application like a house bank compared to EV use, is a non-issue assuming the cells were charged reasonably close by the distributor.

If I go with Calb 400ah cells, do you guys recommend any certain BMS system? Especially if I add a second 48v 400ah bank in about 6 months to 1 year?

Also take a look at Genasun and Mastervolt, although they concentrate mostly on marine racing.

While I have no personal experience with these guys, the "House Power BMS" from CleanPowerAuto LLC might be suitable. Note that I don't use any bms at all, except for low voltage disconnect, and a high voltage controlled by my charger. Balance under a house-bank scenario is not that big of an issue if you don't run these things wall-to-wall charge/discharge, which we don't by not purposely undersizing our battery. At this point I'm getting off track into the bms issue, which usually ruins good threads.

Truthfully, unless you really know your power requirements, there's not much for us to recommend. What I WILL recommend is that you consult a qualified systems installer / consultant - like that of our own forum host!

[asheville solar]

Just wanted to thank the two of you for the help. I had a chance to look into those EV sites and you are right, the pricing is right in line with what I am getting from China. The Calb 400ah cells look like they are priced well. The GBS look really nice but expense wise, add up quickly.

I looked at my power bill history and maybe this will give you guys a better idea as to what I am running. I do have my workshop located at my house where on occasion I am running 220v heaters and a 220v compressor. However I am not expecting to run this off my battery bank at night. Most of my house now has LED lights in them and is 100% electricity. No gas, electric heat pump, GE hybrid water heater.

Looking at past electrical bills which include this cold winter: 77.3 KWh/day or 2319 KWh/month.

Most likely, I would only run my batteries 30-40% down to extend the life unless the community recommends more.

If I go with Calb 400ah cells, do you guys recommend any certain BMS system? Especially if I add a second 48v 400ah bank in about 6 months to 1 year?

Thanks for the help,
Chris

[PNjunction]

Chris - the good news is that we don't have to deal with China directly like we did 4-5 years ago. These large prismatics, like GBS, CALB, Winston, etc are available from a number of stateside EV and specialty battery outlets. I personally use GBS cells.

One you might want to look at is

Elite Power Solutions in Tempe, AZ. They specialize in the GBS cells, although I have no firsthand experience with them. I got mine from BatterySpace.

That being said, remember that the manufacturers and distributors are catering mostly to the EV market, and may have never heard of "solar insolation hours", nor the generic rule of not sizing your battery bank to go below 50% DOD. Since lifepo4 is usually taken down to 80-90% DOD by EV'ers and is the standard for rated cycle life, they may be grossly underestimating your capacity needs, even if the data you gave them was perfect.

For best results, we normally eschew "growing into" your battery needs, as this usually results in one or more complete rebuilds of most of the existing infrastructure, not to mention generally poor battery operations with batteries of different age and use patterns.

If you can give us an idea of how much power you are using now, or are planning to use, we can figure out probably much more accurately than a battery manufacturer or EV shop can - or if it is even within the range of reality.

Large prismatics like the GBS and CALBS can easily handle 1C of current, with 3C bursts (on average) but of course, your battery would last a little less than an hour, so that kind of pull, even though it can be done, is not realistic for a house-bank. Still good news for huge surge loads.

If you can give us a better idea of how much power you intend to pull, we can see if it can be done - on both the discharge AND solar recharge capability. Perhaps if this was restated in a fresh new thread we can keep a better handle on it.

[inetdog]

Hi Chris and welcome to Solar Panel Talk!

At this point, your questions follow the general topic of this thread, but is it gets too far afield one of the moderators will help you spin it off into a new thread.
Starting your own thread (in ONE place please) is never going to be discouraged, although some of the answers you get may point to existing threads.

An LiFePO4 battery bank should be able to handle a discharge current much larger than .2C, although for a correspondingly limited time. Computer battery packs are often discharged at C/2 or higher (to the disappointment of their owners.) The serious restrictions will come on the charging rate, which will depend on the intelligence of the charger, but can be higher than C with the right algorithm and monitoring or .2C with a relatively dumb charger.

[asheville solar]

Acquiring LiFePo4 battery bank and need help

Hello,
I am new to this forum and my name is Chris. I do apologize if I should have started a new thread. I am currently acquiring all the components for a residential 10Kw solar array system. Most likely I will be using Outback's Radian "A" series hybrid inverters for a battery bank. I have contacted numerous chinese suppliers of LiFePo4 batteries and had a couple of questions on the specs one would want for a normal residential home LiFePo4 battery bank since they will build them to your specs.

After speaking to Outback, the Radian system I will be getting will need at least a 400ah battery bank system. Since I ultimately want a 48v system, I have decided to just start with that size and work my way up over the years with amp hour capacity.

Can anyone tell me what discharge rate I would want with a 48v 400ah battery bank? 20A (0.2C)?
max discharge rate?
Any other helpful info would be appreciated.

I am new to this world and trying to learn the language if you will.

Thanks for the help,
Chris

[Spooner]

Actually that is wrong. As long as you know how LFP batteries charge, you can custom-set most of the higher quality controllers to very adequately charge an LFP pack. But you have to know what you are doing. I use a simple Schneider/ Xantrex C12 for my smaller stuff, but the voltages are tweaked properly. Others like just a few messages above, are successfully using Pb based controllers, and while they may not be exactly ideal, they can be made to work, again if you know how to properly set them.

Right now, I'd like to keep your project under one thread to make it easier to track your progress, rather than splitting up the details into this one - if that's ok.

ok I guess I'll only use the other one. I was just trying to drum up as much advice as I could get.

[PNjunction]

Actually that is wrong. As long as you know how LFP batteries charge, you can custom-set most of the higher quality controllers to very adequately charge an LFP pack. But you have to know what you are doing. I use a simple Schneider/ Xantrex C12 for my smaller stuff, but the voltages are tweaked properly. Others like just a few messages above, are successfully using Pb based controllers, and while they may not be exactly ideal, they can be made to work, again if you know how to properly set them.

Right now, I'd like to keep your project under one thread to make it easier to track your progress, rather than splitting up the details into this one - if that's ok.

[Spooner]

Not going to work. LFP batteries are not compatible with charge controllers made for lead acid.

Thank you for letting me know! that was one of my major concerns. what small light weight portable versatile powerful awesome charge controller would you suggest?

[Mike90250]

Almost anything will get fried sitting on the dash of a closed car.
The panel would, I suspect, have been perfectly happy sitting outside the car in the direct sun.

It's a coleman panel, sitting on top of the battery box of a dump trailer (outside, in the sun & dust). Battery is for the electric brakes if it breaks away from the tow vehicle.

[inetdog]

The small dashboard PV I had on it, got sunburn. really needed to be behind a sheet of glass indoors, the plastic frame and wire insulation is all toasted. And pulling the battery was too much pain. Easier to run an extension cord out to it 1x a month. If I remembered.

Almost anything will get fried sitting on the dash of a closed car.
The panel would, I suspect, have been perfectly happy sitting outside the car in the direct sun.

[PNjunction]

The Morningstar TS-60 MPPT is working wonderfully with four 300W panels (1,200w total). I have the custom settings on the Morningstar at 28v, and the cells are very happy.

Nice - 3.5v per cell. Plenty of headroom, and still get rated 80% capacity overall before going well into the discharge knee. Now I just need to work on getting a vessel to house my cells properly.

I have the BMS protecting the cells, that incorporate 2 pole and single pole relays for the Warning HVC and LVC (28.4v and 23.2v), as well as the protection HVC at 28.8v. I have redundancy relays on the HVC to assure full isolation.

Sounds reasonable. Those voltages indicate to me that you are not driving them into an unnecessary balance routine, and the major safeguards are the high and low voltage disconnects. Personally, I'd change the LVD to 25v, but to each his own.

I have gone down to 90% DOD several times, and the LifePO4 are more then happy and will to give a bit more before the sun came up for the panels and Morningstar to get things topped off !

One thing that may be saving you here is that once you go below about 80% DOD, when you recharge, you should do so at a lower than normal charge current until about 3.2v per cell is reached, and then full current can be applied. Many people don't take this into consideration, but fortunately for solar, this is being performed prior to the start of the major solar-insolation hours, so it is doing this nicely behind your back.

I'm with ya' on the happiness factor!

[Hkalan]

Hello,

I am using CALB 3.2v 400Ah cells (8 in series) for a 25.6v House bank as I live totally off-grid on my Bertram 46.6 Flybridge Motor Yacht.

The Morningstar TS-60 MPPT is working wonderfully with four 300W panels (1,200w total). I have the custom settings on the Morningstar at 28v, and the cells are very happy.

I have the BMS protecting the cells, that incorporate 2 pole and single pole relays for the Warning HVC and LVC (28.4v and 23.2v), as well as the protection HVC at 28.8v. I have redundancy relays on the HVC to assure full isolation.

Even with the 24v alternator on the port engine, I have the emergency house bank (that drives the windlass) so the alternator will always be under a constant load. Attached is the diagram of my BMS and solar connections.

I have the Cell-Log-8 as well... I power the USB side from the generator 12v start battery. It is just an extra ($15 USD cost) monitor to assure the bank is good. When 150 miles offshore, redundancy is a good thing !

The Morningstar monitoring is fantastic, and adding the Network Hub has allowed me to connect their relay that will automatically start and stop the generator to energise the AC powered LifePO4 charger. The AC charger is set to 28.1v and never activates the BMS, thus keeping the cels very happy !

I keep the LifePO4 cells out of the engine room, as well as all other charge controllers (The AC charger is in the engine room), and there has never been a issue with the temperature sensor from the bank.

I have gone down to 90% DOD several times, and the LifePO4 are more then happy and will to give a bit more before the sun came up for the panels and Morningstar to get things topped off !

I have used AGM and FLA for too many years, and I am happy to be using the LifePO4.

Speaking from experience, the Morningstar TS-60 MPPT is an outstanding solar controller for LifePO4 banks !

Alan
LPF-BMS-Relays.jpg

[SunEagle]

Now that is some funny stuff, I don't care who you are. Your solar panel got sun burned.

More likely it was heat stroke.

[Sunking]

The small dashboard PV I had on it, got sunburn. really needed to be behind a sheet of glass indoors, the plastic frame and wire insulation is all toasted.

Now that is some funny stuff, I don't care who you are. Your solar panel got sun burned.