Are we all getting GRADE B cells??
- Thread starter flemmingdjensen
- Start date
Warpspeed
Solar Wizard
Almost four years ago I purchased thirty 50Ah Winston cells, and treated them very gently.
Over the first three years I had three of those cells fail short circuit from dendrite formation, and never understood the cause.
I think I will try Tom's magic break in procedure with my new Shenzhen Luyan "Amy" cells and hope for some better luck.
So, 56 amps, 47.6 amps, 39.2 amps, 30.8 amps, 2.4 amps, 14 amps, charging in six decreasing steps.
The associated discharges will be a good opportunity to check capacity.
Over the first three years I had three of those cells fail short circuit from dendrite formation, and never understood the cause.
I think I will try Tom's magic break in procedure with my new Shenzhen Luyan "Amy" cells and hope for some better luck.
So, 56 amps, 47.6 amps, 39.2 amps, 30.8 amps, 2.4 amps, 14 amps, charging in six decreasing steps.
The associated discharges will be a good opportunity to check capacity.
Remember to disconnect charge source when those currents are reached - don’t ever hold a cell at 3.65V.
There was an Australian vendor back in the day that sold cell top balancers and insisted that floating the cell at 3.65V would do no harm “as per Winston instructions”
Winston were wrong - so was he. Those cell top balancers were responsible for plenty of cell deaths due to dendrite punctures.
Warpspeed
Solar Wizard
My cells have never been over 3.45v ever, or below 3.0 volts.
I have a fairly sophisticated home brew battery monitoring system that disconnects the whole battery if any individual cell goes outside the above limits.
Yet three cells have failed dead shorted.
I have a fairly sophisticated home brew battery monitoring system that disconnects the whole battery if any individual cell goes outside the above limits.
Yet three cells have failed dead shorted.
That is very odd. I have installed hundreds of Winstons over the last decade - haven’t seen a failure yet.
edit: the other main failure mode i’ve seen is charging at temps above 35°C.
Warpspeed
Solar Wizard
Yes its very odd, and a friend of mine in another state has had the exact same experience with two dead shorted 200Ah cells.
He asked the seller what the reason might have been, was he perhaps doing something wrong ?
The seller said exactly what you say, he has sold hundreds of Winstons and never seen or heard of anything like it before.
Two people with five failed cells between them, and its never happened to anyone else ever.
So what am I supposed to think ?
All my three failed cells were perfect one day, the next day zero volts with very slight barely perceptible swelling.
When I say zero, I mean not even one measurable millivolt.
He asked the seller what the reason might have been, was he perhaps doing something wrong ?
The seller said exactly what you say, he has sold hundreds of Winstons and never seen or heard of anything like it before.
Two people with five failed cells between them, and its never happened to anyone else ever.
So what am I supposed to think ?
All my three failed cells were perfect one day, the next day zero volts with very slight barely perceptible swelling.
When I say zero, I mean not even one measurable millivolt.
Attachments
I look at it more like this: The manufacturers (EVE, for example) make several thousand cells each day. They condition and test the cells as they come off the line. During testing, they measure specific parameters such as mass, internal resistance, capacity, and possibly things like high voltage knee, low voltage knee, and things I have never thought of. They then bin each cell by its measured parameters, which means that all the cells in that "bin" are matched (within a range) in all parameters. Some of the cells are duds and don't meet one or more of the parameter specifications. Those cells are clearly not "Grade A" and probably get auctioned off.
A lot of other cells meet the standards, but are in bins with relatively few friends. Large quantity buyers who want matched cells are not interested in those cells. Nothing is wrong with them, but they just don't match enough others to sell as matched. I suspect that those are the cells we are buying since they seem to meet the specifications. It is possible that if you buy "matched and batched" you are getting cells from the fringe bins also, but somebody took the time to keep that bin's cells together and can sell you 32 from that bin. The bin may have hundreds of cells in it, but is still not interesting to the buyer who needs 20,000 cells a month, all alike.
I could be wrong, but my guess is that we will continue to see the same quality cells from the quality sellers, and they won't be marked "B" on the QR code.
Alkaline
Solar Wizard
I'm sure EVE would rather sell all of there cells and get maximum price for them, I think they are forced to get rid of the cells they can't sell. Manufacturing is a ruthless business and in China of all places.
At this point if you have a sell Manufactured After March of 2022 that does not have a B on the QR code I think its as good as anything and is EV grade. If you have a B on it then its defective in someway.
EVE probably were realizing their biggest competitor is themselves. The same way the biggest competition to the IPHONE 13 is the IPHONE 12 and 11.
For me, I have played this Grade A, A++, A-, A, game long enough. I'll buy the stuff without the B on the qr code and just make sure the date is C3 or greater, I've done all this with the xuba cells back in 2019/2020 and ended up scrapping them.
At this point if you have a sell Manufactured After March of 2022 that does not have a B on the QR code I think its as good as anything and is EV grade. If you have a B on it then its defective in someway.
EVE probably were realizing their biggest competitor is themselves. The same way the biggest competition to the IPHONE 13 is the IPHONE 12 and 11.
For me, I have played this Grade A, A++, A-, A, game long enough. I'll buy the stuff without the B on the qr code and just make sure the date is C3 or greater, I've done all this with the xuba cells back in 2019/2020 and ended up scrapping them.
burgerking
New Member
In one of Seplos' videos, they claim that one of the LifePo4 cell test is the "Self-Discharge Rate" test by measuring the voltage drop after few weeks.
They could hasten the test by increasing the temperature....
ADD: Maybe this is just a test made by Seplos on their own stock of cells, and not necessarily industry wide test.
Ampster
Renewable Energy Hobbyist
I guess it depends on what one defines as defective. Outside certain parameters, sure. I understand the Automotive grades are one standard below that is the grey market which is a catch all. Perhaps with RVE's new grade B maybe we will see some consistency. There is still the translation issue and yhe difference between a Confucian thought process and a "Western" thought process that comes from ancient Greek philosophy. I am married to a Chinese girl so I live with that every day.
Yes, I think they realized the were cannibalizing their own cell sales. Now they have another market for their EV grade cells.
Ampster
Renewable Energy Hobbyist
I bought 72 Winston cells in 2012 for an EV Conversion. Through user errror I ran 36 of them down to 2 volts and all but one recovered. They are great cells. I sold the EV in 2016 and as far as I know it is still going strong.
As far as the topic of this thread, sorry if I have said this already, but going into my purchase of 54 LF280s over six months in 2020 I had no illusions that I was getting Automotive Grade cells. They were less than $125 per kWh compared to over $200 per kWh which I paid for the Winstons in 2012. My use case was a lot less aggressive than my EV conversion so I did not need automotive grade. I was putting them in a 3P16S pack so the three cells in parallel would compensate for any mismatches because they would look like an 840 Ahr cell in my configuration, The pack has been operating for a year now and is staying well balanced . I charge to 3.45 per cell and never go below 50 percent SOC. I charge at 80 Amps and the discharge rate rarely exceeds 30 Amps.
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Thanks for the answer, I go through a translator and sometimes it's surreal!
After the various initial full charge rates, at what rate do you discharge and to what depth of discharge?
burgerking
New Member
I asked (my importer to ask) Basen for the test results for my cells.
I was given "data on the sticker ..."
??
this suck.
I was given "data on the sticker ..."
??
this suck.
Thank you and sunny greetings.
Alkaline
Solar Wizard
LOL or maybe the EV companies were hey wtf why are we paying this much when Ali Sellers have it for less probably threatened
Test them and just accept them if they are between 265-280. That is like where majority of the grade B cells lie, they do ok. Although my 2 year xuba cells are starting to act very suspiciously I put them on charge now and they shoot up to 3.75 immediately when I take them off they drop to 3.23 :/ maybe I have developed runners after 2 years, will do a slow charge and see what happens.
Ampster
Renewable Energy Hobbyist
A runner could be a symptom of decreased capacity or cell drift. My BMS does not have enough balancing current for these large cells so I disabled BMS balancing and installed an active balancer. Even though I have a 3P16S pack I only used a 2 Amp balancer and it has kept the parallel cell groups within 10 millivolts.
That could be due to some resistance that has crept into your connections somewhere.
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