LiFePO4 - The future for off-grid battery banks?

[PNjunction]

Notice how all discussions seems to revolve back to commercial EV's as the only source of experience?

All discussions rapidly get out of context of OUR application of relatively low voltage / low current, something these cells laugh at, unless you have purposely used an insanely small bank to begin with, drawn to the promise of 80% DOD leaving you with no autonomy. Mistake #1.

Something not mentioned either is that in a fixed installation, these cells aren't going to be subject to physical stress / vibration etc. They are just going to sit there and laugh at the load your inverter places upon them - again of course assuming you were duly diligent in sizing your bank in the first place.

If ANYONE is going to get the rated cycles out of them, it would be US - the "Sub-C" application users.

The cycle testing HAS been done by the manufacturers, but as Prof Jeffrey Dahn has pointed out, that is just sausage-factory rapid hammer cycling. BUT, this is done typically at .3C to .5C from 10 or so to 100% SOC. WE aren't going to do that, operating PSOC, and limiting our cycle extremes. So the outlook is very good. But few consider our sub-c niche, especially coming from the so-called "lead acid mentality".

Look guys, I never said LiFepo4 was for everybody. In fact, I purposely use lead as my standby/backup because in that instance, I want to go from 100% SOC downwards, something you needn't do with LFP, nor is it recommended. To purposely have LFP sitting at 75% or so in standby means a hugely expensive bank, and just sitting there is definitely not taking advantage of it's capabilities for sure - unless you were a commercial grid supplier. That I can understand easily. My lifepo4 is used for daily cycling, and frequently leaving it in a major state of discharge without worry until I come back to it.

Thing is, there really is no point in discussing LFP, because we always get sidetracked with non-solar housebank applications, be they 48v or lowly 12v. And quite frankly, 99% of the comments come from those who will never use it, but just want to fan the flames for entertainment, and not education.

At over 72,000 reads of this thread as of this writing, there certainly is a LOT of interest. But getting to the gold amongst the dross is nearly impossible with all the sidetracks, politics, personal agendas, disgruntled CFO's, trash-hackers, and whatnot.

[donald]

As with a lot of grid connect solar systems, people will ignore logical consideration of ROI and buy it because the sales pitch says it will save them money.

The ROI will theoretically work based on many years of useful service by the battery.

Early adopters may not come out ahead financially, but they are needed to get the market moving.

[Bala]

As far as I am aware these will be a grid tied only solution unfortunately.

Although Im sure competing companies will be offering it and will sure to bring the price down.

As with a lot of grid connect solar systems, people will ignore logical consideration of ROI and buy it because the sales pitch says it will save them money.

[jedics]

Just saw on FB that telsa sets are supposed to be avail in Australia by the end of the year.

As far as I am aware these will be a grid tied only solution unfortunately.

Although Im sure competing companies will be offering it and will sure to bring the price down.

[Sunking]

THIS is what can make the up-front cost reasonable, when you look at the overall life-cycle of the product itself, the things that it powers, and the operational freedom that pays off in the end.

PN therein lies my main issue with LFP. You know the history of Chi-Com Prismatic LFP as well as I do starting with Thundersky just 8 or 9 short years ago. It is not a success story. From the start wildly exaggerated cycle life claims of 1000 to 2000 cycles. Two bankruptcies, and 5 product revisions later today and they still claim 1000 to 2000 cycles to 80% DOD. To this day I know of no documented Lithium any type that has a proven track record of 1000 to 2000 cycles. It is one thing to claim 2000 cycles with no proof or evidence vs say FLA with a 50 year history and proven track record of exceeding 1000 to 2000 cycle. 2000 cycles is about 6 to 8 years.

For EV especially DIY EV there is no other choice using Chi-Com Prismatic. It is the only game in town unless you get a chance at a salvaged EV pack. Otherwise price, availability, and thermal management are just out of reach$ of DIY. Solar you have 2 choices. Either proven Pb that is less expensive and last longer, or a gamble on Chi-Com. As of now we are still 6 to 10 years from knowing if LFP works or not as claimed.

[PNjunction]

LFP's have advantages, but if you cannot exploit them , your wasting your money.

Willy I apologize since I didn't know you already had them.

However, I think your evaluation of LFP being nothing special means you have your blinders on. Not being surprised is a good thing actually.

OUT OF THE BOX, the extremely low IR, lower than even the best of high performance agm's, means that recharge is more efficient, especially compared to FLA, which is pretty important in my book in regards to solar.

Not having to maintain them at a high SOC to deal with sulfation issues is an out of the box plus. You can also let your hydrometer get dusty. You can walk away from them for a year or more with a relatively low to medium SOC and not worry about it and just pick up where you left off.

Higher voltage under load - again beating even the best agm's (UNLESS you are sub-freezing), means your inverters and other gear run at a higher efficiency and cooler.

Speaking of cooler, there is no temp-comp to deal with, so getting this wrong, or omitting it altogether like some might do with lead, means less chance for error.

Back to low IR - oversizing your solar array, either by accident or design, means you aren't wasting panel power by going over the typical C/8 max like you would for FLA, and the only penalty is that you are charging faster! (within reason - no more than 1C. Heh, don't make a 1C mistake with FLA). Again, 1C is for large prismatics, unless you WANT to pay even more for larger capabilities - which only means you sized your bank too small, or are taking advice from those outside our solar-storage application.

If I was retired and could live with my FLA's, maintenance could be a lot of fun and a hobby unto itself to actually wring the published cycle life out of them instead of murdering them. However, if one has a life to lead, lifepo4 done right, certainly beats a badly maintained fla bank.

This is why I don't think you have properly evaluated your bank at all. The above became immediately apparent when I used a lowly benchtop unit, so I'm at a loss as to how you could miss this, since you are better than that. While my gear isn't lab quality, I do have the means to see it and at least baseline them for performance and see the improvement over my beloved pure-lead agm's.

The most disturbing part to lifepo4 to me, is that the fact that it has become BORING. It just works without me having to nanny it, but like any reasonable battery setup, common sense monitoring and safety concerns are in place. To bring back the spice, I'm doing crazy crap like purposely abusing an SLI just for fun, questioning my sanity for not just chucking my lead.

What is also sad is that if I read between the lines, the lurker for honest information is left out of the loop trying to decide what is real, and what is a logic-trap setup that doesn't take these factors into account - mostly from outside our relatively low voltage / low current application, like hacker trash, EV and other motive-power concerns.

THIS is what can make the up-front cost reasonable, when you look at the overall life-cycle of the product itself, the things that it powers, and the operational freedom that pays off in the end. But yes, nobody has gone 10 years yet, I'll admit that. But I'll say that when that time comes, it won't be satisfactory to some unless a century has passed.

Benchtop unit indeed. Get one. Take the blinders off.

[SunEagle]

Hmm, when deciding to use LFP, it didn't occur to me that I might be picking a chemistry that in 5 years might not be available in the same format as what I bought first time, may be less in use than it is currently, etc. Seems like that may be something to consider. Going it alone has an a certain allure, but a risk.

Most of the Utility scale energy storage system are using Lithium Ion chemistry. One of those is the 30MW system that GE is installing in California's Imperial Valley.

Still for the home owner going with any Li chemistry will be very expensive and hard to justify.

[Living Large]

For commercial products, LiFePo4 really does no have much in the way of a market out there. Only one commercial EV manufacture (Fiskars) out there ever tried to use them and went bankrupt before they ever sold a car. Power tools, laptops, cell phones all pretty much use a version of LiCo.

When it comes to LiFePO4 aka LFP prismatic is still looking for a market. They will never be mainstream in EV's, Laptops, Cell Phones, Power Tools or Medical Devices because there are much better choices available today. LFP is pretty much a niche market of DIY EV and DIY Solar or Sheep being led to Slaughter.

Hmm, when deciding to use LFP, it didn't occur to me that I might be picking a chemistry that in 5 years might not be available in the same format as what I bought first time, may be less in use than it is currently, etc. Seems like that may be something to consider. Going it alone has an a certain allure, but a risk.

[Sunking]

LiFePO4 seems increasingly destined for the hobby niche.

No another Lithium type took root in hobby applications several years ago and today LiPo Pouch Cells dominate the RC market. That antiquated the NiMh and NiCd market a long time ago. For commercial products, LiFePo4 really does no have much in the way of a market out there. Only one commercial EV manufacture (Fiskars) out there ever tried to use them and went bankrupt before they ever sold a car. Power tools, laptops, cell phones all pretty much use a version of LiCo.

When it comes to LiFePO4 aka LFP prismatic is still looking for a market. They will never be mainstream in EV's, Laptops, Cell Phones, Power Tools or Medical Devices because there are much better choices available today. LFP is pretty much a niche market of DIY EV and DIY Solar or Sheep being led to Slaughter. Reason is simple DIY cannot afford the good stuff, or the required equipment like thermal management and BMS it takes to make it work. Let alone even having the knowledge to put it all together in a working package. At least not in the USA because Americans cannot spell MATH or SCIENCE let alone ever stepped foot into a Class Room. Americans are to concerned with PC and afraid of offending anyone when they should be shaming and slaughtering the PC crowd.

[donald]

It seems to me that the interest in commercial applications of LiFePO4 has decreased since this thread was started. Whatever replaces FLA in solar will include a BMS and will probably be largely "turn key".
Didn't the Chevy Volt abandon LiFePO4?
NCA appears certain to be preeminent over LiFePO4 for solar. But I suspect long term that the major technology will be something like flow batteries.
LiFePO4 seems increasingly destined for the hobby niche.
I'm glad I don't have the need to choose a large solar battery system today. Any choice available today is likely to produce regrets in a few years.

[Living Large]

yeh, I dont know about that, healthy debate and all that but I get your point that we seem to be going over the same old ground over and over but what do you do,

A sticky with a comprehensive look at all the chemistries used in solar applications, and the various considerations, limitations, etc when using each?

Since everyone agrees on, for example, cycle life vs DOD for FLA, how to balance LFP, etc, arguments would be eliminated.

Maybe a few stickies... to include dissenting opinions like the Supreme Court does Now that might be a good idea.

[Willy T]

The two best post's in the whole thread were made by Sun King, post #'s 239 & 229. While the technical side is interesting to some, it still comes down to cost and the ease of use. LFP's have advantages, but if you cannot exploit them , your wasting your money.

[Bala]

Its been a long thread with a lot of crap in it. But in between the crap there has been a lot of good info.

I live off grid and will be doing so for some time to come. My current batteries are over 9 years old and seem to be ok still but we will see how they are after this summer.

So I am preparing for new batteries and LifePO4 need to be factored in as a possibility.

If I needed to replace my batteries tomorrow I would simply get a new set of FLA just probably a little smaller than the current ones. Main reason for that is the simplicity. I would not need to change any hardware etc, learn how to look after a different type of battery and teach the wife how to.

I will however be watching and learning about Lifepo4 as if I am lucky I may get another year or two from my batteries and things can change quickly.

Just saw on FB that telsa sets are supposed to be avail in Australia by the end of the year.

[PNjunction]

I don't know either except to perhaps set up a thread or sub-forum that is filled ONLY with the technical side. Typically for lifepo4 something one would use in our solar application like a large prismatic array, and not hundreds of cylindrical laptop-pulls, crashed car batteries, or any variation that you can't get from a normal non-hacker battery dealer.

Financial, political, veiled sales, non-"Sub-C" applications can be dealt with outside the purely technical thread/subforum, where a user can make up his own mind if they want to tread through all that.

Same goes for AGM perhaps. Reserve a purely technical thread / subforum, and leave the slugfests to more general purpose cheerleading / naysaying outlets ?

[solar pete]

Agreed. I wouldn't want to take them below 32F. However, at our "Sub-C" rate, one might be able to have a bit more tolerance especially for discharge. But yep, sub-freeze is a bummer.

We're all just in an endless absorb cycle here. Same stuff every day. FLA rules. AGM and Lifepo4 suck and should be avoided at all cost.

Frankly, I'd just ban all threads about anything but FLA to keep the peace.

yeh, I dont know about that, healthy debate and all that but I get your point that we seem to be going over the same old ground over and over but what do you do,