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LiFePo4 Cells — how do you Really know what you’re Getting ??

SailorGolf

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Joined
Dec 14, 2019
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17
Seems like All sellers of LiFePo4 cells claim “A+ New” ... or claim nothing at all ?? So are you Really getting “New” cells and are they Really “A+” and how do you Know when you buy ?? If someone advertised “B- Really CRAPPY Cells” then I probably wouldn’t buy those !! ? But nobody says that !!
So, I recently bought 4 “New A+” 280ah cells and when they arrived they looked good ( except for the one that seemed a bit Bloated ) well packed and clean, so I balanced them and put them to work with an Overkill BMS !! They wouldn’t stay balanced, one of them ran Wild charging and discharging and was determined it was a bad cell ( wasn’t the Bloated one ... I know you were thinking that ) so ordered a Replacement “A+ New” cell and pack still won’t stay balanced and Another one seems to be a bit Suspect !!
So - how do you Know when someone really is selling good cells and when they aren’t ?? It’s not like you can ‘check them out’ first at your local Home Depot. I don’t know that it really matters Where you get them as everyone advertises the same wheather Amazon, AliExpress, EBay - they all say “New” or “A+” or similar, so ... how do you Know ???
I know you’re going to Ask so ... I got them from AliBaba, no idea what Brand they are there’s no indication on the cells - they do have serial number stickers by the vent and a generic white label on the side telling what they are - a 3.2v LiFePo4 280ah cell.

Questions that make you go ... hummmm !! ?

ps — how do you Dispose of a bad LiFePo4 cell ??
 
Unless they are sold directly by the cell manufacturer (at full price and typically only in large quantity), you are almost certainly buying cells that have failed some aspect of QC or are old/stale.

If you have an additional cell, one way you can try to salvage your pack is to double-up the two weak cells together.

A 2P-1P-1P-1P string with the two weakest cells combined in parallel will be limited by the capacity of the 3rd-weakest cell as long as the two weak cells have over 50% capacity…

But you are 100% correct - purchasing discounted cells through resellers on AliBaba is a complete crapshoot.

You can get some idea of which vendors have better ethics than others by reading the vendor review threads here on the Forum, but many/most/all? of these resellers don’t actually know what they are selling either.

The best you can hope for is to test/characterize your cells soon after you get them, and if you can document a clear deficiency in one or two cells, hope you’ve got a vendor who will send you a replacement or two at no additional cost…

They either purchase grey market cells by the palette from middlemen or at best, they may purchase surplus/not-guide-EV-grade cells directly from the factory (but that is rare because quantities are so high, as are prices if they are actually Grade-A cells).

You can make usable batteries from these cells and once the dust has cleared, they will be lower-cost than buying a turn-key battery or even securing a set of true Grade-A cells direct from the factory, but it’s a crapshoot and almost always involves some screwing around or compromise.

The old adage ‘if it sounds too good to be true, it probably is’ comes to mind…
 
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I balanced them and put them to work with an Overkill BMS !! They wouldn’t stay balanced, one of them ran Wild
I would not jump to the conclusion that the cell was bad until I knew more about the process of balancing. I assume when you say one "ran wild" that it's voltage was above the others when charging. Did you check your BMS reading independently with a known good meter? Did voltage of that same cell sag under load? I had similar readings and it turned out to be a loose connection. One way to know how a cell compares to the others is to do a capacity test on all the cells individually.
 
I would not jump to the conclusion that the cell was bad until I knew more about the process of balancing. I assume when you say one "ran wild" that it's voltage was above the others when charging. Did you check your BMS reading independently with a known good meter? Did voltage of that same cell sag under load? I had similar readings and it turned out to be a loose connection. One way to know how a cell compares to the others is to do a capacity test on all the cells individually.
I took this statement from the OP at face value: ‘one of them ran Wild charging and discharging’

If the same cell hits LVD before all of the others when discharging and also hits HVD before all of the others when charging, that’s pretty clear indication of a bad cell.

You are correct that a poor connection with high resistance will result in the same behavior, but a simple delta_V / delta_I test between the lug/Busbar and the aluminum terminal surface is an easy way to check that that is not the issue…

And yes, individually capacity testing each cell is the best way to confirm whether the cells are close to spec or not.
 
Thanks for the thoughts ...

So - if you can only buy ‘real’ cells from a manufacturer, and since they’re all in China - how does one go about Doing this if Not on AliBaba ??

OR - does anyone have another ‘reliable’ source for actual “New A+” cells ??
 
Thanks for the thoughts ...

So - if you can only buy ‘real’ cells from a manufacturer, and since they’re all in China - how does one go about Doing this if Not on AliBaba ??

OR - does anyone have another ‘reliable’ source for actual “New A+” cells ??
Ghostwriter seems very happy with a new supplier with warehouse in Texas claiming to purchase true grade A directly from Eve. Check out her thread on the subject:
 
So - if you can only buy ‘real’ cells from a manufacturer, and since they’re all in China -
real cells? These are all real cells. Some are just better than others. The best cells go to the buyers who have to ability to buy direct from the manufacturer. What we are seeing are perhaps second tier cells that fit whatever the definition that "Grade A" means. All I cared about was that the capacity was what I paid for. At a price of $125 per kWh my options were used Tesla or Nissan Leaf modules in which there were similar risks and which were a more volatile chemistry.
 
Thanks — I checked her thread and the link she has still goes to an AliBaba page ... that seemed confusing ... many different listings and pricing’s all appearing to use the same video advertisement showing all kinds of cells ??? She says pick-up in Houston ( where I actually live ) so maybe if I can find the DONCAN warehouse (haven’t found it on google maps) I can just go buy there ??? It’s all Chinese to me !!??

Just seems odd to me that it’s so Difficult to buy an actual New item ??? If I order a new tail light for my truck it too comes from China but there seems no question that it is new, works and fits properly. I guess LiFePo4 cells are just not that way ... yet. Oh Well.
 
real cells? These are all real cells. Some are just better than others. The best cells go to the buyers who have to ability to buy direct from the manufacturer. What we are seeing are perhaps second tier cells that fit whatever the definition that "Grade A" means. All I cared about was that the capacity was what I paid for. At a price of $125 per kWh my options were used Tesla or Nissan Leaf modules in which there were similar risks and which were a more volatile chemistry.
That was precisely my logic as well…

These grey-market cells from China are not the same quality as the cells passing the stringent quality (and matching) testing required for use in EVs, but they are still a bargain (and safer than used Lithium-ion cells).
 
how do you Know when someone really is selling good cells and when they aren’t ?

You search this forum and find people's experiences with vendors. Go with the ones that people have good experience with, added bonus if the vendor is also active on this forum.

how do you Dispose of a bad LiFePo4 cell ??

In my country you bring them to the sorting center as hazardous waste/e-waste or battery waste.
 
Thanks — I checked her thread and the link she has still goes to an AliBaba page ... that seemed confusing ... many different listings and pricing’s all appearing to use the same video advertisement showing all kinds of cells ??? She says pick-up in Houston ( where I actually live ) so maybe if I can find the DONCAN warehouse (haven’t found it on google maps) I can just go buy there ??? It’s all Chinese to me !!??

Just seems odd to me that it’s so Difficult to buy an actual New item ??? If I order a new tail light for my truck it too comes from China but there seems no question that it is new, works and fits properly. I guess LiFePo4 cells are just not that way ... yet. Oh Well.
I would suggest you send a PM to ghostwriter. She’ll likely explain the process by which you order through Alibaba but pick up in person in Houston 24-48 hours later…

As far as these cells, they are intended for use in EVs. They are sold in massively high volumes to EV manufacturers in China.

Selling cells in low volumes directly to end-users / DIYers is not their primary business and they have no interest in it.

They do have an interest in capturing some salvage value from cells that are unsuitable for use in EVs, hence the bulk sales to resellers.

Once Powerwall manufacturers reach the scale and the continuity to sell enough off-the-shelf batteries to meet the volume requirements of the cell manufacturers, they will be able to buy direct (as several including BYD appear to be doing now).

But as far as the cells themselves, true grade-A matched cells cost more and in the face of false advertising, th t makes it exceedingly difficult to establish the continuity of volume & demand needed to interest the manufacturers (meaning they are largely relegated to buying whatever they can get from resellers).

ghostwriter seems convinced that Doncan is selling true grade A cells they purchase directly from Eve - if you end up getting some Doncan cells yourself, we’ll all be interested in your opinion and your experience.

This market is still in the very early stage…
 
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