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

[goboatingnow]

Originally Posted by diugo

It has now been two years since I acquired four used 260Ah ThunderSky cells from Balqon (manufactured Dec 2010). So I thought I would report on how they are holding up.

A year ago my capacity tests revealed a sharp decline to 206Ah, a 21% decline from the year before. This year the same test lasted 89 hours at 2.1A for 187Ah---less than a 10% slide, so that was encouraging.

But a second test at 39A lasted just four hours for 156Ah. Hardly bionic by any stretch of the word! At least the Peukert constant has been pretty consistent since I got them---just under 1.06. But for just $600 delivered (including the 30% solar tax credit they qualified for) they were fun to play with, and still are.

I am hoping they will continue to limp along for another twenty months, when funds become available to replace them with brand new CALBs.

So how do we square this with Mainesail and others experience. My own tests reveal year on year loss of capacity as the cell ages. Not as bad as yours however

I'm still perplexed.

Dave


Sent from my iPad using Tapatalk

[OTTCT]

Hellosaiolar

Again Not to beat a, I hope I was able to attach a clipping of the document "YOU Quoted" and it says all Lithium batteries over 100 watts and or all cells over 20ah require a Hazmat shippers contract.

not sure where your 300 watts comes from, but maybe you van attach your clipping and we can see where the misunderstanding is coming from ?

[OTTCT]

Originally Posted by offpist

I ordered the winston WB-LYP1000AHC from EV-Power | Your Complete Power Solutions
They have an limited offer now at 1,018.00$ each, and its on stock.
Still a lot of money, but it makes a huge battery pack..

(I have no relations to this company btw)

Thats a good deal, maybe ask what the date code is ? Balquon in USA current price is $1200

Cheers OTTCT

[hellosailor]

Ott-
"Your argument is that should you meet a dumb clerk - your free and clear."
NOT AT ALL. I'm not saying a dumb clerk is an opportunity of a defense. I'm saying that if the PRINTED GUIDES for the shipper say you are clear--that's sufficient to prove you had good reason to believe you were following the laws. And, that the shipper would be legally responsible for deceiving you.
The "dumb clerk" is the old game of "he said, she said" and one would hope that everyone here is old enough to know that what a clerk (employee, bureaucrat) says verbally, is worth the paper it isn't written on.


"300" comes from a page later, "Figure 4", which might be attached.

[klaus53123]

Originally Posted by transmitterdan

The consensus is that LiFePo (and other LI chemistries) will suffer shortened life if kept fully charged for extended periods of time when not being used. The general advice is when not actually in use they can be left at 50% charge. Since they have very low self discharge it might be months before they would need to be topped back to 50%.

Likewise, they will suffer reduced life if left fully discharged. Hence the recommendation to leave them stored at 50%.

This issue is one reason some have not jumped on the LiFePo bandwagon.

In my view, that is not really the answer to his question. It is well understood that you do not want to let them sit without any consumption for a longer period at eiter full or empty. But what he is asking is whether there are good experiences available with cycling the cells in the 90-100% full range. I have exactly the same problem here and right now my plan is to fill them with solar up to 13.8 V, switch solar off and start refilling at 13.4 V (same as Roetter is doing). No idea what the DOD is at 13.4V.

Would be great to hear how you do cope with your solar panels.

Klaus

[goboatingnow]

Originally Posted by klaus53123

In my view, that is not really the answer to his question. It is well understood that you do not want to let them sit without any consumption for a longer period at eiter full or empty. But what he is asking is whether there are good experiences available with cycling the cells in the 90-100% full range. I have exactly the same problem here and right now my plan is to fill them with solar up to 13.8 V, switch solar off and start refilling at 13.4 V (same as Roetter is doing). No idea what the DOD is at 13.4V.

Would be great to hear how you do cope with your solar panels.

Klaus

Because I designed GSM modems, I have investigated so called " mini-cycles", both from my own testing and by researching the various scholars articles. The results are not conclusive nor consistent. There is evidence that mini cycles are treated as full cycles in relation to cell ageing, i.e. they contribute to capacity loss over linear time.

There is broad agreement that charge cycles of whatever nature do contribute to cell ageing, whats in dispute is the level of effort and the nature of that effect.

dave

[transmitterdan]

Originally Posted by klaus53123

In my view, that is not really the answer to his question. It is well understood that you do not want to let them sit without any consumption for a longer period at eiter full or empty. But what he is asking is whether there are good experiences available with cycling the cells in the 90-100% full range. I have exactly the same problem here and right now my plan is to fill them with solar up to 13.8 V, switch solar off and start refilling at 13.4 V (same as Roetter is doing). No idea what the DOD is at 13.4V.

Would be great to hear how you do cope with your solar panels.

Klaus

I don't think anyone here has reported their long term (years) experience doing that. Voltage isn't the best indicator of SOC. My opinion based on reading and working with small cells is that 90-100% cycling is pretty much the same as keeping the pack fully charged all the time. It will eat into the lifetime of the pack. In your scenario I think I would set the high cutoff at about 80% and the low recharge point at about 50% based on AH counting. Then if it stays dark a long time you will always have at least 50% available to tide you over. If that's not enough AH get a bigger bank. Or be prepared to charge with fossil fuel sometimes. Every so often (quarterly at first) I would bring the pack back to full and reset the AH counter.

The pack is "aging" faster while it is almost full and almost empty. Less aging happens the further from full and empty they are. That's why the high end EV cars (e.g. Tesla) start out only running their packs at about 20%-80% charge (the exact empty/full point is a big secret). Then as the years and cycles increase they gradually start increasing the high and low charge cutoff. That's how they get 15-20 years out of a pack that would normally last 5 years if cycled fully. They can do this in an adaptive way because they accurately measure the charge and discharge profiles and keep detailed records in the onboard computer. Tesla has a "monitor only" BMS. They only have the ability to shunt milliamperes of current to rebalance the bank. So in this area Elon Musk and MaineSail are in agreement that active balancing isn't needed. Staying well away from the knees is why that works and it makes the pack last lots longer. So while we don't use batteries the way the EV cars do we can learn from them.

[OTTCT]

Originally Posted by hellosailor

Ott-
"Your argument is that should you meet a dumb clerk - your free and clear."
NOT AT ALL. I'm not saying a dumb clerk is an opportunity of a defense. I'm saying that if the PRINTED GUIDES for the shipper say you are clear--that's sufficient to prove you had good reason to believe you were following the laws. And, that the shipper would be legally responsible for deceiving you.
The "dumb clerk" is the old game of "he said, she said" and one would hope that everyone here is old enough to know that what a clerk (employee, bureaucrat) says verbally, is worth the paper it isn't written on.


"300" comes from a page later, "Figure 4", which might be attached.

Hellosailor



It appears you might be right on this point, I need to read more on my big computer, but right now I'm sick with the flue. Not sure if that helps me as the smallest cells I have are 100ah CALB but they are at least not stamped with a watt code , but reading the code number it does start with 100. My newer GBS cells have all this info Barcode stamped onto the cells.

This still leaves the big problem of how a regular Joe can legally get these into the mail ?

Thanks OTTCT

[OTTCT]

Originally Posted by diugo

Bob, you know I like LFP. Wouldn't have spent $850 on it if I didn't.


But if the lead acid battery in your car or truck died tomorrow, would you really put a $500 LFP in its place, along with all the proper charging, monitoring, and disconnect circuitry it would require?

Let me answer this question, I know a guy who put a 100 ah CALB 12v without any BMS or mods of any kind into his newer model Ford PU and it's been there for over 12 months and 12,000 miles already. I do wanna add that it usually does not get below 32F in his area. I would think most cars would start and run on 50ah liFeP04 just fine.

Now I may try this on my Tundry one day after my floods die, but I also have it where my lights auto shut off even when left on when the key is removed after a few minutes. I also plan to change to LED lights which most new cars have these days.

Cheers OTTCT

[OTTCT]

Originally Posted by deckofficer

The weight of those 1000 a-hr cells are higher than proportionally expected.

1000 a-hr cell 92 lbs.
700 a-hr cell 47 lbs.

I'm guessing a much thicker case?

As much as I preach for single series strings, if I was to do hybrid diesel-electric propulsion on a cat, I would go with (2) 48 volt banks of the 700 a-hr in parallel than a single bank of the 1000 a-hr.

No the 1250 cells are 92lbs - I have those, Balquon is just to lazy to correct this on their Web site, typical of how they operate.

Cheers OTTCT

[NahanniV]

I used my 400AH LifePo4 pack last season by manually connecting them for charging and use. I have a PowerLog6 (similar to CellLog) monitoring. I only ever connected the pack when I was onboard. I did about 25 charge discharge cycles to various depths of discharge. Everything worked fine, but it was a pain to monitor. My 20A Xantrex charger worked ok on GEL setting, and My 35A Leese Neville alternator did not catch on fire, although it's output did reduce to around 20A during prolonged charging; Presumably the internal regulator reduces output due to heat.

I have the pack in my basement for the winter and plan to do a capacity test in the next week or so to compare against the initial test I did.

For this season I am working on automating the system.

Can someone point me to the best price for Blue Sea 9012 relays or perhaps Tyco EV200AAANA or other equivalent ? I could have sworn that I was seeing these for around $100. last year.

Cheers,
JM.

[hellosailor]

dan-
I think you will find there is extensive commercial experience with 90-100% charging cycles. IBM (now Lenovo) offers this in their laptop (LiOn cylindrical) cells for at least a decade now. The preferred charge scheme brings the battery pack to 100%, then allows it to be used (or to self-discharge) until it has dropped to some 94% before there is any recharging. This is the "longer battery lie?" option as opposed to letting it hang on the wall charger at continuous 100% trickle charging.

I would expect that something in the subtleties of charging patterns is the reason why some users are reporting 10% annual capacity loss, others 20%, yet still others "none". It is one obvious variable that would need lab conditions to be studied properly. And one where studying all the alternatives (load, charge patterns, etc.) over a five-year base would be terribly expensive.

[diugo]

Originally Posted by goboatingnow

So how do we square this with Mainesail and others experience. My own tests reveal year on year loss of capacity as the cell ages. Not as bad as yours however

A colleague just happened to point out that my current 186Ah actually only represents an 8% per year loss over the four years, ie 186 = 260 x 0.92 x 0.92 x 0.92 x 0.92. So I'm not quite as bummed now

As to why my Balqon cells have not performed as well as Maine Sail's and DeckOfficer's... One possible explanation is that mine may have been heavily cycled/abused---whereas theirs may have just sat on a shelf unused. Samra might have perceived more PR value in giving them the best cells.

Also, I got 260Ah cells, Bob got 100s, and MS got 400s IIRC. Different sizes for different purposes?

[diugo]

Originally Posted by OTTCT

Let me answer this question, I know a guy who put a 100 ah CALB 12v without any BMS or mods of any kind into his newer model Ford PU and it's been there for over 12 months and 12,000 miles already. I do wanna add that it usually does not get below 32F in his area. I would think most cars would start and run on 50ah liFeP04 just fine.

Wow, that quote of mine was from a long time ago!

The big question is, did your guy try this with old 100Ah CALBs he was going to toss anyway---or did he buy $500 of brand new cells just for that purpose? Because even with temps in the 40s, the PU's lead acid regulator may have been charging the cells near 15V...

[OTTCT]

Originally Posted by diugo

Wow, that quote of mine was from a long time ago!

The big question is, did your guy try this with old 100Ah CALBs he was going to toss anyway---or did he buy $500 of brand new cells just for that purpose? Because even with temps in the 40s, the PU's lead acid regulator may have been charging the cells near 15V...

They were older dated cells approx 3 years old.