LiFePO4 - The future for off-grid battery banks?

[PNjunction]

"Large format lithium battery" - is that the same as large cells ? It is the only 'consumer', plug and play, LFP battery bank I've run into. It is packaged nicely - and as SK will tell you, that is all that matters

That .be domain-hack kind of freaks me out.

Still, this is what I'm talking about. And to be fair to Dax, here goes:

We don't know what the cells actually are, nor do we know what the "mppt technology" controller really is, nor do we know what sort of dc/ac inverter they are using. All of it is sight-unseen except for some pretty portable cases. I want to know what's inside before buying.

In addition, pics of some of the panels just simply ground mounted with clumps of grass across the bottom throwing shadows shows that they (or maybe just the photographers) don't know that you need to keep shadows off mono/polycrystalline panels. They really should have cleaned up in front of some of those shots. Unwary users will just plunk them down on the lawn like in the photos, and then wonder why nothing seems to charge well.

Uh, yeeeaaah, one could do much better by constructing a kit of their own.

Ignorantly, I made the mistake of buying a 155ah AGM SLA for my first 'real' toy project. Personally, I'm ready to kick lead acid to the curb. It has turned my 'solar fun' project into 'am I killing my battery' project. That 5000 year old tech is dead to me.

Actually, there is a lot to learn from a "learner project" like this, so if you take notes, it isn't money wasted. Perhaps you can still go lead-acid with a redesign. There, I said it - l love LFP, but for me, it is just one of several chemistries available to us, and not a sweeping replacement across the board.

For solar to 'really' take off, a consumer friendly, modern energy storage technology needs to rise to the challenge. At this moment, I'm putting my money on LFP. So keep their feet to the fire PNjunction

Well, with stuff like the above, if it fails to perform, the consumer will blame the battery chemistry, and not the componentry and/or build quality. Kind of like coming home with a brand new sports-car, and when asked what it is, they really don't know what's under the hood.

[inetdog]

Maybe were just talking about the semantics of manufacturing. What do you see in these pictures of this GBS battery ?? Do you not see many paralleled cells with separate cathodes and anodes for each cell ??

The normal way of describing a battery considers the cell boundary to be the boundary of the common electrolyte bath and gas space, not each pair of positive and negative plates. So each of the batteries in the picture would be one cell, or at most two if there is a boundary between the upper and lower halves.

If you consider just plates, the geometry of a stack of positive and negative plates with separators makes it hard to identify whether each plate forms one "cell" with one of the two plates next to it or one cell which shares the plates on either side with one cell.

In a typical FLA battery cell (2V nominal) there will be many positive and negative plates joined by lead bus bars at the tops but we do not consider this to be many cells in parallel.

There is a distinction of sorts that can be made between the prismatic cell with layered plates, the prismatic cell with wraparounds of the plates at the edges in a zig-zag configuration and the cylindrical cell with only two electrode sheets interleaved and wound continuously from center to outside. But I would call each of those a single cell.

[vudu]

"Large format lithium battery"

Just thought some may find this interesting.

https://youtu.be/O1jFUHcYC3U?t=5m41s

"Large format lithium battery" - is that the same as large cells ? It is the only 'consumer', plug and play, LFP battery bank I've run into. It is packaged nicely - and as SK will tell you, that is all that matters

Simon - can you book us all on some sort of LFP based corporate-retreat? You know, where we practice doing trust-falls, yurts, rope walks, that kind of thing?

I'd bet we'd all do fine in the end.

Sign me up if there is beer and hula dancers.

I little levity goes a long way. PNjunction is always knowledge seeking and courteous. When skeptical, he asks for facts without being condescending. If I knew anything about anything, I'd follow his lead .



Ignorantly, I made the mistake of buying a 155ah AGM SLA for my first 'real' toy project. Personally, I'm ready to kick lead acid to the curb. It has turned my 'solar fun' project into 'am I killing my battery' project. That 5000 year old tech is dead to me.

For solar to 'really' take off, a consumer friendly, modern energy storage technology needs to rise to the challenge. At this moment, I'm putting my money on LFP. So keep their feet to the fire PNjunction

[SunEagle]

Thinks obviously haven't changed since this post that I made http://www.solarpaneltalk.com/showth...142#post162142 over three months ago. I still stand by those comments.



I am not offended, the comments were not aimed at me. In my opinion it would have been more productive if you and Solar Pete had been more balanced with your treatment of all the antagonists.



You won't find out any new information if people are treated like dax was.

For the record I have no business dealings and never have had with dax, I don't even know who dax is or what companies he is involved with.

Simon

Simon

My misunderstanding of your relationship (or not one) with dax. It was hard to tell considering were you backing him up so strongly.

Also while you may feel that I am not "balanced" in my treatment to all antagonists, I feel I have done a pretty good job.

Also referring back to that thread you mentioned. I still stand by the decision to enforce the rule of not allowing bad information or poor suggestions concerning solar technology to be posted on this forum. People are too easily convinced of what will work just watching youtube videos. Allowing similar details with lack of backup data to be posted on this forum and not call that out would be misleading and possibly dangerous to others.

If dax and his company have developed a better battery then I would say congratulations. But words are cheap and IMO proof comes from real life data. Since I do not have this data concerning dax's battery I can't fully support it and will continue to be cautious about allowing people that I do not know to make claims without providing at least some specific data to back up their claims.

[Willy T]

If Dax reappears maybe he'll clarifiy the type of 40-50 amp hr cells he's using. I do agree that the prismatic batteries we're thinking about ( Winston, CALB, GBS and others do not use pouch cells, A123 type ), as apparent in the pictures. I thought it was time to show what they look like since someone posted they looked inside one and what was posted was totally wrong and BS.

[PNjunction]

What I mean is that they are not made of many of these types individually totally wrapped:

http://www.a123systems.com/prismatic-cell-amp20.htm

Although yes, you *could* do that, although some E-bikers / bench hackers did not get them from authorized dealers, and paid the price shortly afterwards.

[Willy T]

No - what I mean by -one- is that they are not made of many parallel discrete-stand-alone cells. Ie, not just paralleling ten, 20ah stand-alone lipo-packaged cells together internally for a 200ah battery.

Maybe were just talking about the semantics of manufacturing. What do you see in these pictures of this GBS battery ?? Do you not see many paralleled cells with separate cathodes and anodes for each cell ?? I guess I don't understand what your visualizing as stand alone and expressing. Of course there is no free electrolyte as each cell is wetted in individually. " Stand alone " ?? If separated you'd certainly have Individual cells. The Power point drawings you'v seen make you think they are all joined.

There 80 cells in this battery, two sections of 40. I don't know the amp hr capacity of the total.

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The point was / is that individual cells age and fail differently and the over all mode of failure is not always operator error. As a cell deteriorates it effects the capacity of the battery.

[PNjunction]

So, you think there is just one with one cathode and anode connected to the clamping terminals in a Winston Prismatic Battery ??

No - what I mean by -one- is that they are not made of many parallel discrete-stand-alone cells. Ie, not just paralleling ten, 20ah stand-alone lipo-packaged cells together internally for a 200ah battery.

Yeah, as for Tasman's battery, that would not be my choice. But to each his own.

Back in a galaxy far away, when I first got interested in LFP, it was to prove to myself that *under our application*, one could really use the KISS method, keep cell counts down, infrastructure simple, and most importantly not have to use a spaghetti-mess of wiring or obsession about microscopic values of top-balance differences. Later I learned that doing the microscopic top-balance with dinky / unreliable bleeder boards was more or less a mind-game in our application, and merely prolongs the time one spends near full charge - where parasitic reactions over time can negate the feel-good measures of making voltmeters line up perfectly. Reasonable-balance - yes. Going overboard - no.

Heh, but we've been down that road already.

The goal was that if I couldn't KISS my LFP batteries, and had to go totally nuts with spaghetti wiring and 3rd-party control systems, then it was a no-go and would be happy to just chuck it and go back to lead-acid. Fortunately, the LFP's are still around and I'm still amazed by them using only the same sane precautions like LVD and so forth. We'll see in a few years time if I feel the same way.

In the end, whatever floats one's boat! I prefer the KISS method since it gives me a whole lotta' latitude, but that may not suit others.

BTW, that first pic shows what appears to have been an early model Hi-Power cell with the dissimilar metal problem internally. By now, most manufacturers of high quality try not to repeat that mistake.

[lkruper]

Well from my point of View, Dax was jumped on by more than one person and the forum members have most likely missed out on a lot of good input due to a vocal minority who have justified their actions to make themselves feel good. It has been like a motorbike forum I know, but a sad week or two for this forum.

I live off grid, have done for over 9 years at my own house and lived in various different places with off grid solar or generators.

I dont want to buy cells and experiment, I have to many hobbies. My power supply is not a hobby, so if my next set of batteries is going to be anything other FLA I want to buy it as a drop in replacement with a warranty and a local service agent.

Dax has info that sounds promising, but raises more questions for me. I live above 25c most of the time with high humidity, bit hard to cool things down and a lot of circuit boards for balance etc will likely go mouldy and corrode, may just be to technical to be reliable.

But I hope he has it sorted and it is a viable option in the not to distant future.

I did PM him to get a name to keep an eye one for the future, if I dont get a reply no problem, I think I have found his company. But if not I am sure he will make news in the alternative energy supply circles if his plans come good.

I have the perfect solution for you, but I won't tell you. BTW, everybody here is wrong on the subject but I can't say why

[Willy T]

For the Winston, basically just one. Inside is like pulling apart a very large post-it-note pad accordion style, but with a 3rd dimension-like fold in between.

So, you think there is just one with one cathode and anode connected to the clamping terminals in a Winston Prismatic Battery ?? How many foil tabs on each clamp ?? Where is the electrolyte contained in these cells ?? In FLA it's plate pairs that build capacity. I notice once you go above 400 amp hr in large format they go to 4 terminals per battery. The 1000 amp hr have 6 terminals.

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I will saw one apart as soon as I get one to fail, but mine are functioning at the moment. As far as pouch cells go, I have never seen one over 20 amp hr capacity, not to say there are not any. The Nissan cells have 4 cells per element, they list them as a larger capacity, but it's 4, No idea how many are in a Pouch cell.

We really need a Glossary of terms, Dax say's he uses cell's of 40-50 amp capacity, when does a number of cells become a Battery ?? I call mine unit's ( 2p2s ) to keep the size and weight down to 80 lb per unit. It also cuts down on the number of paralleled batteries and makes the compression case's easier to build.

Here is a picture of part of Tasmans bank he posted. It is 12p4s ( I think ) and he reported problems with voltage consistency and balance in the cell lines. The construction does not look bad, but with that many paralleled cells your looking for a problem.

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[PNjunction]

For the Winston, basically just one. Inside is like pulling apart a very large post-it-note pad accordion style, but with a 3rd dimension-like fold in between.

But yes, you can also put together many "pouches" if you will, like a bunch of 20ah A123 prismatic cells paralleled inside a box. The A123's are a far cry from the usual "lipo" hobby crap. Many of which are just held together with a simple heatshrink when they actually need compression to keep the elements together. Aside from over or undercharge, no compression can lead to hot spots where some of the material is close together and some not. RC hobbiests with basically loose un-compressed cells discover this pretty quickly, but they didn't really pay for a decent casing.

Another failure mode that isn't commonly discussed is poor "overhang". That is the anode and cathode are not exactly equal in dimension on purpose - but if you lose compression, and then press it back together (in extreme cases), you lose your overhang, and now dendrites and other nasties can appear. That's one reason why guys who recompress an abused cell don't get the expected life back out of them. Poor manufacturers and counterfeiters may not take the time or have the precision to do this properly. The cell doesn't immediately fail, but lives long enough to make it to market and into your hands for awhile.

I dunno' - maybe if the internet had been around in our grandfather's (or great grand-dad's) day, the situation would be the same never-ending fight between conventional lead-acid and NiFe.

[Willy T]

There are other Modes of Failure with LiFepo4 other that what was posted. Statements made to impune the Poster and diminish their credibility are not really anything new here.

Unreasonable numbers of cells in parallel cell lines ( search " Tasman " here ) are just as suspicious in LFP to me as in FLA, not to mention high resistance connections. A 100 amp hr prismatic 3.2v, cell / battery may already have 10-100, + / - prismatic envelope cells inside paralleled to the buss, the numbers add up fast. Anytime your having balance issues I would suspect individual cell failures.

Large format pouch / prismatic cells and thermal modeling. To focus on size of the format of the cells and the case they are inserted in may not be the only thing think about.

http://jes.ecsdl.org/content/162/1/A181.full

http://www.epectec.com/batteries/prismatic-pouch-packs.html

This looks like about a 100 amp hr, 3.2v Winston cell. How many prismatic envelope cells do you see inside this demo cell ??

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[Bala]

Well from my point of View, Dax was jumped on by more than one person and the forum members have most likely missed out on a lot of good input due to a vocal minority who have justified their actions to make themselves feel good. It has been like a motorbike forum I know, but a sad week or two for this forum.

I live off grid, have done for over 9 years at my own house and lived in various different places with off grid solar or generators.

I dont want to buy cells and experiment, I have to many hobbies. My power supply is not a hobby, so if my next set of batteries is going to be anything other FLA I want to buy it as a drop in replacement with a warranty and a local service agent.

Dax has info that sounds promising, but raises more questions for me. I live above 25c most of the time with high humidity, bit hard to cool things down and a lot of circuit boards for balance etc will likely go mouldy and corrode, may just be to technical to be reliable.

But I hope he has it sorted and it is a viable option in the not to distant future.

I did PM him to get a name to keep an eye one for the future, if I dont get a reply no problem, I think I have found his company. But if not I am sure he will make news in the alternative energy supply circles if his plans come good.

[PNjunction]

These reasons have been alluded to by dax who I would think knows far more than me. They are:
.......[*]Thermal Management: Large cells, especially if they are thick and have an insulating cover will be hotter in the middle of the cell than on the edges when charging or discharging, the heat being generated by the resistive losses in the cell . It will also be harder to dissipate this heat evenly. This will mean that the middle of the cell will degrade faster than the edges. This is not so much of a problem with low charge and discharge rates, but I am sure will still be a factor.

Not much of a factor at our rates. Not even at 1C rates. To recap a massive discharge without heat from large prismatics at about .2C for a 400ah bank. Similar to our usage:

https://www.youtube.com/watch?v=oJ8AfJsOhsM

Things start to get warmer above 1C, which we will never go to.

[*]Mechanical Stability: These cells are made up of vast numbers of microscopic particles each acting almost like an individual cell. For each of these particles to add to the total they must be in continuous intimate contact with the surrounding particles and the cell terminals. If they become disconnected the cell capacity will decrease. Encasing the cell in a thin rigid metal case I would think would lessen the chance for the particles to become disconnected from each other. Again probably more of a problem in EV use due to mechanical vibration etc.

Makes me think of Optima or Enersys/ Hawker Cyclons One aspect of cylindrical cells for the diy'er is that now you have to build a custom cylindrical housing, rather than the prismatics which more or less stack or sit aside each other with banding and strapping for physical stability. OR, the manufacturer / distributor puts the cylindricals into a box for you. Maybe you can get the holders premade, like on the smaller scale with the Headway cells.

Again you nailed it - an EV would see the most benefit. And possibly a mobile caravan doing 4x4, stuff like that. For a stationary housebank, the prismatics are sturdy enough.

[*]Cost: There is a large and growing market for electric vehicles and industrial uses which would use the smaller format metal cased cells. The off-grid market is probably still tiny compared to this market but can piggy back onto this market and befit it the scales of production.

Just be careful about piggybacking - it can go too far, although it CAN be done. For example CALB has some higher-end cells that take incredible amounts of current, but would just represent a waste of money for us. I hope Dax's cells are reasonable, considering that we will never use the high-current capability - of which we still don't know what the specs truly are!

The only problem I see with using smaller cells is the increased number of interconnections. If the benefits of the smaller cells outweigh this I would think they would be the way to go.

That is a problem all-right but there is one more: It is easier for a failing cell to "hide" amongst the mass of others, and take down their nearest neighbors. That isn't to say that you can't have a large prismatic failure too, but when you do, you have a smoking gun to point to quickly. (um, pun not intended! )

Of course the whole mass of small cells can be connected to various wiring setups and control circuitry - from a spaghetti mess to professional. I'm sure Dax is professional about it.

I really hate to go here, but Dax has kind of forced the proposed-business issue:

Will Dax be the sole-supplier for these cells, and if so, is one comfortable with a single-vendor solution? Will he sell just the cells to interested makers, including small-fry makers, or can it only be gotten as a "system"?

So there is a big factor - if my GBS bank went down tomorrow, but since I have a lot of my own infrastructure connected to it - (ie my own LVD's, monitoring, etc), I could replace the whole lot with Winston or CALB or any other manufacturer of my choosing without a lot of infrastructure changes.

I sincerely wish him the best, but it is wise to remember that NONE OF US has demonstrated a real-world calendrical lifespan reaching the mythical 2000+ cycles (ie daily cycle, not hammering them repeatedly). Ie, nobody I know that uses LFP has ever said something like "yeah, I'm on my second bank now - my first one lasted 8 years and about 2000 cycles, so I just replaced it with the same". If a cell / bank that is sitting around between 40-80% SOC on a float-standby basis, that doesn't count for us daily-cyclers.

Thing is, instead of just talking about it, get some cells from Dax, put it together and join the fun for a small experimental bank. Or any of the prismatics. 12v even with a simple 4S setup!

I tell ya' lurkers, actually doing it physically beats the pants off talking about it.

The problem is that there will never be a one-size-fits-all solution with LFP, and thus a never ending thread.

[lkruper]

Sorry, I might have missed something. Is there a question that I have not answered?

It is not that the statements are true or not, it is the intent and context that they have been used in. Now I maybe thin skinned ...
Simon

You do appear thin skinned to me. And it is of paramount interest to ME if these statements are true or not. Lets analyze your possible responses:

1) The statements are true but you don't like the way they were presented so you use that as a pretext and won't address them.
2) The statements are false and you can prove otherwise but you won't because you don't like the way they were presented.
3) The statements are false but you cannot prove otherwise.

Which is it? This not Kindergarten.