LiFePO4 purchase advice needed

[expresso]

what do you mean - they are just sitting there 90% empty - i am testing and charging - they are wrapped well - nothing is exposed also they are all neg to neg - not connected in series yet

when done i will stack them same way - post neg to same post neg - from what i remember you told me thats fine that way -

[LROBBINS]

Of course you're right. Although each case is + respect to that cell, each cell in the series string is a full cell's worth different from the next one. So they run +3.4, +6.8, +10.2, +13.6, +17.0, +20.4, +23.8, +27.2. +3.4 is NEGATIVE with respect to +6.8 and so on. Imbalance in a parallel string will cause current to flow from one cell to another - a good reason to do initial top balance one battery at a time rather than wiring them in parallel as one would with lead with substantially higher internal resistance.

[Burgerman]

Thats what I suggested he did.

Imbalance when connected up in parallel is pretty hard as current flows between all cells till they are balanced rapidly. At lower than 3.4V though they can all be the same voltage and still not balanced in Ah. So pretty safe connected in parallel. But charging all of them, 8x 200Ah so a single cell of 1600Ah at 3.6 to 3.65 volts will balance them properly!

As long as they are all around the 3.3xv range, little current will flow even if they are 50Ah or more out of balance.

[Burgerman]

That glasfibre reinforced tape is thin and offers good puncture and abrasion resistance. Just a couple of layers of that around every cell would be OK.

https://www.amazon.co.uk/Crossweave-Gla ... 6095024501

[expresso]

i just received them - they are mostly all empty - i am charging one at a time full - doing a full discharge - a full recharge and discharge about 15ah and sit aside - then the next and so on - you are suggesting i should not let them touch at all till i am ready to build and add the silicone in between - i can add a sheet of paper in the meantime if thats the case -

should be good ?

[expresso]

That glasfibre reinforced tape is thin and offers good puncture and abrasion resistance. Just a couple of layers of that around every cell would be OK.

https://www.amazon.co.uk/Crossweave-Gla ... 6095024501

i have of that tape - not enough to cover the whole cell -

dont think i need too - if i use the silicone between each Cell - the sides - bottom i use the green tape - or better yet - i can put them back in the box was just about to throw them out -

[foghornleghorn]

or better yet - i can put them back in the box was just about to throw them out

Yes. Back in the packaging while just playing with them.

Have you fully charged and discharged a cell yet?

[expresso]

i will be starting on Cell 3 shortly after i eat

i remember being told that if they are all the same in order - its safe - ok if they touch each other that way -

i just got computer paper and slide one between each till i am done - once i am done with all - will wrap the bottom - locktite the screws on top - and then start to connect them -

[foghornleghorn]

What capacity are you measuring them at?

[Burgerman]

He measured the first cell correctly as specified. Got 189Ah out of a 202Ah rated cell. Thats a little less than he should get. It should give 200 or a little more.

[expresso]

actually its the 2nd cell i did correct - not much a difference but there was - so need to follow the specs to know for sure

i got a bit less than stated - its not a huge difference and i am not concerned as long as all the rest come out the same give or take

on a recharge it put back 199 and change - - if they marketed the cell as a 180ah cell - then it would have shown alot more - make the buyer happy -

i feel good about them - its way more than i will ever use - in a day - and they will outlast the chair - not much more than a set of MK gels

its possible they are Grade B New Cells - but fine with me - searching for Grade A - and if thats even true - shows a price of almost double i paid - i think i did well with these

matter of fact i would even try those varicore for $600 shipped 8 200ah cells -

i always stressed that they needed to be Brand New Cells - i didnt think of Grade A or B etc, - these may very well be Brand New Grade B -

they arrived packed very well - they look in great condition - wrapping - top sides etc, posts are M6 no dents or scratches - etc,

the QC code is scratched off - i told him why - he said something about manufacturing - commercial etc, - they will say anything really

he was very nice the whole time back and forth before the sale - during the sale shipping and now also - i email today and i get an answer tomorrow morning - he stressed that they are brand new - i emailed him today - asking about the Grade A and B etc, - wonder what he will say - either way - as long as they spec out as good as the first 2 so far - i am trilled - new chair arriving in a month -

tires are here waiting - battery pack should be done by then or shortly after - seating will be moved back - now that i know what to do - its not hard - i wont do it - but someone will for me - chair will be reprogrammed of course and ready to go this summer - i am not too aggressive with programming as much as i did the first chair 6 years ago - i toned it down some - i want to relax also - cant always be jumping at each movement

first time with a center plate - and recline - so will be interesting

[Burgerman]

The code is scratched of because they are used.
The terminal has a plastic part that is white on new cells. Or close to it. At least one of yours shows discolouration a brown colour. Like its been warm in use.

I would bet those were maybe 210Ah cells originally. And were used in solar or something until replaced. Is there a manufacturing date anywhere or was it scratched off? At the price I am not surprised. But myself I would rather pay more and get real A grade cells with known history. As you say these things last so long that its possible to take used ones, and sell as less Ah, and recover top and a blue plastic sleeve and ship as new. Many do.

[expresso]

i dont see this brown color - it must be the lighting from my phone camera etc, -

yes its very possible all of that - and if you and anyone here gets a hold a Brand New Grade A cells - please share - post the link to where you got them from etc, - i so far havnt been disappointed yet with the purchases i made so far with Cells - this one by far has been the best of the bunch -

if you want to pay double - thats fine - alot of users cant afford it - and with options like those Varicore Cells - its a no brainier to try them - now lets say they dont last 10 years the Varicore for $600 - they last 5 - so what - $600 is a set of MK gel that you need to replace every year - your way ahead of the game -

if i had know or realized there were Grade B or what ever - i would have given it a bit more though - i had good experience with this place on previous order for 16 100ah cells - so i felt it was best to use them again instead of someone new - maybe on my next order if i would need another - i can look around better

unless you know someone here did in fact get Brand New Grade A cells - just because they say there are - dosnt mean they really are - and once you buy them - good luck sending them back - you wont -

who ever purchased what they believe to be or really are - Brand new Grade A cells - post the link to where you got them from -

lets say they advertised these as 180ah - and you get them test them and find they have 190ah - you would feel happy knowing you the full Cap and more - i would have took them at 180ah also - for the cost - was worth it for me - but they have it as 202ah - because everyone else does it also - competition -

its a gamble - you try to pick the best between value and cost - unless you have a known source that provides them correctly as stated - and you will pay double the cost also - at least you know what your getting - thats a good thing - and what happens when you purchase Brand new Grade A cells at double the price and find out they dont get full Cap either -

have fun returning them - - live and learn - but i am not regretting getting these - just have to decide how will i arrange them in the box -

[Burgerman]

These for e.g are also reasonably cheap. And are a more modern design with the square top tabs. QR code intact. Cant really be old as they ony started making those halfway through 2020. And claimed grade A. Good feedback. So subject to asking and being damned sure they were brand new A cells, and explaing that I would be testing properly and returning is they didnt all exceed 200Ah, I would likely buy those. But theres other sellers out there on that site to look at too. This was a quick look. SA charli posted a vid on how to spot non grade A new cells. And links to reputable sellers too. And non were quite as cheap as yours. But you makes your choices! And go with whatever! This link comes out at 750? UK and so around 40 percent more expensive than a set of MK lead bricks. With 5 times the usable capacity, and maybe 5x the lifespan or more. So really around 20x cheaper than lead! https://www.aliexpress.com/item/1005001 ... web201603_

And BLS store sell A grade and Non A grade cells. And say so. The ones sold as A grade should be exactly that. And BLS have a good reputation apparently.
https://www.aliexpress.com/item/4001016 ... 2e0dtIpiUL

[LROBBINS]

FWIW I'll share some observations after doing some shopping (but not yet buying).

(1) After someone posted informative videos about testing and grade A vs. grade B, I will certainly NOT accept any cells on which the QR code has been obliterated as was the case on the cells Expresso just received, especially after his measured capacity was less than advertised. That supplier is now crossed out in my spreadsheet.

(2) Although some companies such as BLS say that they are manufacturers, and they may be in one sense or another, they do not manufacture these cells. At most they do the aging, testing, drilling and tapping and packaging for retail sales.

(3) BLS offers two different 200 Ah cells.

The ones with the rectangular posts are 1C suggested discharge rate and 1C maximum continuous discharge rate. https://blslifepo4battery.com/collections/100-200ah-lifepo4-battery/products/grade-a-3-2v-200ah-lithium-iron-phosphate-lifepo4-battery?variant=32514206072912 I have not bothered to try to figure out who actually manufactures these cells. They are cheaper than the other ones with the round posts in square bosses.

The "round post in square boss" 202 Ahr cells are not made by BLS, but by CALD, the largest battery manufacturer in China and among the world's largest, with factories in at least China, Germany and the U.S. (those are joint ventures with BMW and Tesla - but, who owns what percentage of what is hard or impossible to figure out, they are not exactly transparent about corporate arrangements). What probably explains the higher price is that they are normal discharge rate = 1C, but maximum continuous discharge rate = 3C. https://blslifepo4battery.com/collections/100-200ah-lifepo4-battery/products/3-2v-200ah-lifepo4-battery?variant=32511661637712

(4) A given supplier may sell the same batteries at different prices via different channels. Here's the BLSStore AliExpress listing for the 202 AHr round post cells: https://it.aliexpress.com/item/33019962665.html?spm=a2g0o.store_home.productList_132779083.subject_6 Delivered price to Italy for 8 cells = $1,443.95. (Shipped to the U.S. would be about $70 less, I suppose because Italy's 22% VAT is higher than the U.S. excise tax on batteries.)

Here's the same battery at BLS's own web pages: https://blslifepo4battery.com/collections/100-200ah-lifepo4-battery/products/3-2v-200ah-lifepo4-battery?variant=32511661572176 Delivered to Italy for $1,358.00.

And at Alibaba, there are two listings for the same cells with a $1 per cell difference in price:
https://www.alibaba.com/product-detail/3-2V-200AH-LiFePO4-Battery-Prismatic_1600142382534.html?spm=a2700.shop_pl.41413.18.6bbd4022X8NA3O Delivered to Italy for $1,086.00 and
https://www.alibaba.com/product-detail/Factory-price-US-Europe-stock-CATL_1600150734810.html?spm=a2700.shop_pl.41413.26.1d9440229FEjPb for $1,078.00 (Again, $70 less for shipment to the U.S. rather than Italy) In other words, the same batteries from the same supplier cost $45 per cell more on AliExpress than on Alibaba.

And, via Alibaba the rectangular connection batteries would come to $1,038.00 ($40 less for 8 than the round post batteries): https://www.alibaba.com/product-detail/Grade-A-NEW-3-2V-200Ah_1600142191594.html?spm=a2700.shop_pl.41413.14.6bbd4022X8NA3O

Of course, these are today's prices - tomorrow's will probably be different.

[expresso]

its complicated - i seen those flat tops before also and i didnt consider them for one reason - they have the screws in them already and seem higher overall - that makes a difference for me - i dont have the space - i have to stay at 9 inch high total to be safe and make it fit

those flat tops are nice - and i having the screws in already make it less work for me to do - but i cant be sure how high those will end up when in get them - didnt want to take that chance

i already know what i got now will fit - on my next set if and when i will do another - i try better to find Grade A -

i have still yet to hear from anyone here who got cells - if they were in fact Grade A brand new or not ? and links to share

seems like no one has yet gotten these Grade A cells - actually some have gotten even worse damaged Cells -

BM - if you think you will return the Cells once you get them - it wont happen - i tell you why - it would be too costly for you to return them
you have to ship them back yourself and cover the cost -

the best you can do is work out a partial refund from the seller - for a bad cell or Cells etc, and you have to prove it - and even then they wont believe you - they will counter that proof with there own proof -

but if the seller is honest and the company is honest - like lets say BLS - or what ever - they should do the right thing - just dont count it on

i hope someone here gets a Brand New Grade A Cell at a good price - love to see them and from where -

we should make a list in a section - and list the sites we got our cells from - rate them etc, - so anyone can go to that section and review etc,

in my case - my seller - can be scratched off - based on my cells - i am happy with them and they will be fine many many years - but its still good to know before hand what your getting - i wasnt expecting my label to be scratched off - i should have told him before i dont want a cell with a scratched label - i never did

i was more focused on the fact that i wanted Brand new cells and packed well - no shipping damage - that part was good - now its questionable of they are in Face New or not - or Grade B etc,

live and learn - either way - i am still happy with the purchase - as long as the rest of them all come in at the same Cap in the end -

which seems to be 190ah - what bout others who got those 176ah - and they most likely didnt have the full Cap either - i am already ahead of those 176ah - now i see 210ah cells -

start a section for lithium Cell Sellers - from everyone who already purchased them and there experience - what the outcome of the cells where compared to what the sellers say they are - condition they arrived in etc,

then when someone is looking for Cells - can check out the section and have some sites to go on -

its an suggestion and yes i did check that one cell that has a brown color darker than the rest - not worried - its just the plastic itself color is different - - when i get to that cell - we see the outcome if its the same as others -

reason i got 9 Cells also - just in case - - also just because it says Grade A - etc, - you better hope thats what you will get - they can say anything they want - in the specs also -

[Burgerman]

Your cells are fine for the price you paid. And makes lead look rediculous.

But I really want A Grade calender new cells because I then know they have not suffered some dumb BMS for 6 months or over discharge or over voltage etc. I know that resistance and capacity and self discharge levels will all be the same across the pack. And that I am less likely to have issues down the line. Because that way it cost more but gives me peace of mind. And yes I may only get an extra 6 to 8 percent range compared to your cells. Hardly important when you can go 5 times further than lead!

Cells that are bulged, recovered and the top card replaced, scratched off or ground off QR code, or make less than advertised capacity in Ah, or are rated lower than similar physically sized cells are B grade or reused. And the only wat to tell is to look very carefully at them, and measure accurately as you did with the PL8.
Partly because I need 16 to do the Salsa and the Q700R chairs. Both have lead still. I have been stuck on bed. Neither chair has had much use.

[expresso]

i agree - and i told the seller this - i am not complaining - they are not bulged at all - flat sides bottom - very clean - the bottom is exposed and its shiny clean - wrapping is perfect all around - top sides - posts are pretty much clean also - if you look very very close and different angles you make see a scratch or two -

i may be making some myself screwing it down to test now also - but other than that - i cant say too much Neg. about them - at least not yet -

i just told the seller what i feel about that - and said as long as the rest of them all Cap out at about the same or very close to each other which looks like its 190ah - then i be fine and wont use them again in the future - other than that - not much you can really do - reason i got 9 cells just in case - hopefully i just will end up keeping it as a spare - down the line -


when you get around to doing your chairs - then you would know - test - report back and share the link to get them etc, at least this way - we wont have to guess what seller etc, -

i am excited to get this pack made - i wonder if using a breaker instead of fuse would work out better ? giving that i will have some room in the tray now i can sit in there also -

[Burgerman]

Breakers are bulky, get weak as they age, and probably less reliable than a fuse. Esp if you go up to 125 or 150A as those will never blow unless theres a short. And thats when you want them to do that! I should forget breakers.

[snaker]

In VN, lifepo4 cells are now plenty. Many import and sell them. By the time, we can identify good and honest sellers. Some only sell A grade ones. But as they confess, it is hard to distinguish A grade cells from others without testing. Because Chinese is able to recover abused cells like new, no sign of usage. QR codes are meaningless because even with genuine A grade cells, their QR codes usually show nothing. As they explain those codes are for the internal use, it is just one of strange ways Chinese does business

So all depend of the luck if we meet an honest seller or not. Expresso's 200Ah cells have 190Ah DISCHARGING capacity, that's already 95% of their claims. I think that's so good. Just to check if they are balance while charging and discharging.

[shirley_hkg]

I'd keep an eye on Self Discharge Rate , when we get bigger and bigger capacity. My pack lasts more than a month. SD amount accumulates as recharge period lengthens. That makes re-balance difficult.

[Burgerman]

Yes thats why I always charge, remove exactly 3 or 5Ah (5000mAh) so the cells are not full. Then wait a month. And recharge each to see what we need to put back. It will be 5090 or 5030 or 5250 etc. If its 5250ma you are better using a different cell... As that will take an extra HOUR to balance after 4 months. Thats not a problem, but if theres more than 250mA difference in a month then it may start to be. You just need to do a little maths.

Do all and then you will know if you have a cell thats discharging faster than the rest. And by how much.

But all must be 100% full with say 500thC termination point charge to start with.

[expresso]

Breakers are bulky, get weak as they age, and probably less reliable than a fuse. Esp if you go up to 125 or 150A as those will never blow unless theres a short. And thats when you want them to do that! I should forget breakers.

ok i stick with a 125A fuse i have them already


thanks

[expresso]

I'd keep an eye on Self Discharge Rate , when we get bigger and bigger capacity. My pack lasts more than a month. SD amount accumulates as recharge period lengthens. That makes re-balance difficult.

yes i realized that on the previous pack i did also 200ah - it was fine after a month - then i recharged and left it 2 months - still fine - so those cells worked out good - we see with my current ones how they handle self discharge - i will wait till its built all the way - then see how it handles a month

[Burgerman]

Its not really detrimental to cells. Its just that if it goes out of balance a lot in storage it means a long time rebalancing. And the FULL cells are then held high for too long and they dont like that. So if it gets a long way out of balance set 3.5 volts, set balance only at CV (not 3.5V) and leave it for as long as it takes.

[expresso]

yes i noticed that also - takes a long time when out of balance - it happened on one of my ADD ON packs - one Cell is always out of range - when recharging it - takes longer to end - the graphs you can see it - but once in used daily or weekly etc, its fine the graphs get better with daily use -

i recommended my friend who got the pack to not let it sit too long before doing a recharge - from the testing - 2 months was still fine with her pack thats not bad

[Williamclark77]

Lenny,

I honestly haven't read the whole thread. I ordered from RJ Energy.



Quick shipping. My (15) 91ah cells were $855 plus $441 shipping. They arrived within two weeks. Well packaged. The capacity was about as advertised. All cells appeared new and in great condition. I bought one extra.

I don't capacity test mine far down to 3v, even before assembly because the voltage curves vs capacity aren't perfect between each cell (another reason to NEVER bottom balance). I pull amps to the third voltage drop only - about 3.2v per cell, which shows 45ish volts on a fully assembled pack in use. I never run my chair lower than that. On W2 (with 60ah of Headways) that's about four to five days' worth of regular use and puts back 40 to 45ah on recharge. On W3 with 91ah RJ cells that's eight days or so and puts back 60 to 70ah.

ie - Fully charged it shows 50.4v. In five minutes it shows 46.5v. It holds 46.5v for several days then drops to 45.5 to 46.0v. After a few more days the "voltage sag" under heavy load starts dipping to 44.XX volts. I then recharge. I can accurately guess how many ah it will take to recharge from this voltage sag under load. I'm usually within 3ah of being correct.

It always completely charges and balances within a day. My Graupner chargers are weaker than the Pl8. I just swap chairs while one charges.

I put a sheet of buna n rubber between each cell and under them. I don't trust the thin plastic coating they come with not to abrade away and short. I also coated the inside of the battery box with liquid electrical tape.

https://www.mcmaster.com/catalog/127/3860

I made my own "bus bars" from solid strips of Oxygen free copper. Deoxidize with sandpaper and acetone right before assembly. Use proper grease at connections and use thread locker on all fasteners.