Weird discharge curve of EVE LF280K V3 Grade B cell

[fl_dutch]

Living in Germany i ordered 8 Grade B EVE LF280K V3 cells from NKON in the Netherlands. One of the delivered cells show a weird discharge behavior, being tested with my EBC-A40L tester. Clamps have already been replaced by ring lugs.

This is the curve i got (just as a screener):


Okay, maybe it would have been some error in the tester or whatever. All other cells tested with a normal behavior. This cell was tested no 5 out 8 - performed 3 more cell tests without this behavior and then did a retest of this cell (internal cell number is 021):


Has anyone come across this behavior? NKON never saw something like this they claimed - me neither . Some maybe the knowledge in this forum is the place to be. Any guess if this cell may be safe to use? In my live LiFePO4 batteries i normally never go below 2.9v of cell voltage.

Yes, i bought grade b cells - capacity of all those cells is around 300Ah+, but that is not the only quality aspect of LiFePO4 cells.

Any comments and hints are highly welcome.

 

[houseofancients]

I think it is time to call NKON..show them these curves

 

[fl_dutch]

Already did that. Well, first answer seemed to start in the same direction as Aliexpress sellers, blaming the testing device ??. Time will tell how they handle this. I do have a close cell monitoring of my batteries - so i might use this cell, but that would be with a bad feeling - but also be interesting how that cell would behave in action.

 

[Zwy]

Already did that. Well, first answer seemed to start in the same direction as Aliexpress sellers, blaming the testing device ??. Time will tell how they handle this. I do have a close cell monitoring of my batteries - so i might use this cell, but that would be with a bad feeling - but also be interesting how that cell would behave in action.

It will always be higher in voltage when charging over 3.4V and then when charging ceases, it will drop below the other cells unless you can adjust balancing to compensate.

I have 4 batteries of 16S in my cabinet, all in parallel and all cells are shown in graph form on the Batrium software. I have 2 cells out of 64 that exhibit this behavior. I have changed the balancing around on the BMS and can usually get the cells to be within 0.020V of the other 62 when in float. Those 2 cells are troublesome in some respects but I don't run my cells down that often but if the bank is run down over several days, it will take a few days to get balance back within that 0.020V.

I would cycle this cell a few more times and see what results you come up with. If it doesn't improve, I'd push for a replacement as you have the proof.

 

[fl_dutch]

It will always be higher in voltage when charging over 3.4V and then when charging ceases, it will drop below the other cells unless you can adjust balancing to compensate.

I have 4 batteries of 16S in my cabinet, all in parallel and all cells are shown in graph form on the Batrium software. I have 2 cells out of 64 that exhibit this behavior. I have changed the balancing around on the BMS and can usually get the cells to be within 0.020V of the other 62 when in float. Those 2 cells are troublesome in some respects but I don't run my cells down that often but if the bank is run down over several days, it will take a few days to get balance back within that 0.020V.

I would cycle this cell a few more times and see what results you come up with. If it doesn't improve, I'd push for a replacement as you have the proof.

Thx for your reply.

I also graph all my cell volltages using dbusserialbattery on Victrons Venus OS, pushing data into a influxdb/grafana combo. Batrium would of course be the best way to go, since monitoring individual cell voltages should be possible.

I could live with 0.020V and never go below 2.9V in my working setup, only when testing. NKON seems to deny replacement because all other values are clearly within the specs of the EVE LF280K datasheet.

 

[Sam Cho TX]

Living in Germany i ordered 8 Grade B EVE LF280K V3 cells from NKON in the Netherlands. One of the delivered cells show a weird discharge behavior, being tested with my EBC-A40L tester. Clamps have already been replaced by ring lugs.

This is the curve i got (just as a screener):
View attachment 170909

Okay, maybe it would have been some error in the tester or whatever. All other cells tested with a normal behavior. This cell was tested no 5 out 8 - performed 3 more cell tests without this behavior and then did a retest of this cell (internal cell number is 021):
View attachment 170910

Has anyone come across this behavior? NKON never saw something like this they claimed - me neither . Some maybe the knowledge in this forum is the place to be. Any guess if this cell may be safe to use? In my live LiFePO4 batteries i normally never go below 2.9v of cell voltage.

Yes, i bought grade b cells - capacity of all those cells is around 300Ah+, but that is not the only quality aspect of LiFePO4 cells.

Any comments and hints are highly welcome.

Run more tests on that cell!

EVE 304 Cells from 18650batterystore & zke-40 testing.

Notice the end of discharge voltage decay drop off on cell 303. It is quite different of the other cells and is indicative of a cell that has not had enough initial cycles where the cathode and anode capacity curves have not reached their final alignment. It may gain in AH's after a few...

diysolarforum.com

I had a grade B 304 test to 306 and then after 2 cycles it crashed to 270AH!

Grade B cells can scam there way to full capacity you need to test them!

Did NKON guarantee minimum capacity?

 

[fl_dutch]

Meanwhile NKON offered to return the cell.

But after thinking into deeply: i will keep it. I ordered Grade B cells to compare them with my Grade A - in real working conditions, not only when testing. There are so many people who don‘t even do cell tests and they never get to know such a weird discharge curve of their cell, because everything work perfect.

Oh: and all other parameters are absolutely in the specs. So i‘m curious and want to see, how this cell performs.

On the capacity: NKON also offers Grade A cells. So when you buy Grade B: no need to guarantee (did not check that). I‘ll do a retest after i complete the 30 day self discharge test.

When i‘m finished i‘ll summarize in some graphs which i will upload here.

 

[Alkaline]

Looks like you had a terminal come loose on that test and was then connected back properly when the test was running.

 

[740GLE]

Looks like you had a terminal come loose on that test and was then connected back properly when the test was running.

but in both tests?

 

[Alkaline]

but in both tests?

? ur right....

 

[740GLE]

I think at least the op knows which cell to keep any eye on.

I’d be curious how the full pack behaves and if it brings down output.