Just bought 16 Eve LF280K A grade; update on degradation after 15 months

[Zwy]

Ok smarty pants, show us how its done do your tests and make a video explaining process. If you don't then you can keep shouting form the peanut gallery.

I'm not the one complaining about capacity nor am I making claims about cell degradation. Proper testing would require the same parameters used as the manufacturer.

Maybe there is some value in videos such as the ones Andy put out, it shows what destroys cell cycle life and capacity.

 

[Zwy]

Thanks, I've found this thread, not got the time to read as need to get to work, if there is a better thread please let me know.

That one and the one linked in it, plus others. The very first post I ever posted in the forum was the start of this thread. https://diysolarforum.com/threads/another-cell-compression-thread-this-time-about-foam.16537/

This is the foam I have https://www.efoam.co.uk/zotefoam-plastazote.php don't know how it compares to Poron.

It's most likely similar to the original foam I used for my truck camper battery. Closed cell. I would take a sample and test flammability, the foam I used back then would only burn if you held a flame directly on it and wasn't really a burn, just a slow charring. If the flame was removed, it would stop.

 

[cajocars]

Third battery test finished

		EVE capacity	EVE shipping voltage	EVE internal resistance	my capacity measurement (mAh)	my capacity measurement (Wh)	charge cut off voltage (V)	charge/discharge current (A)	charge cut-off (A)	discharge cutoff voltage (V)
1​	04QCB76844701JC680002208	293996.9​	3.2953​	0.148​	280500​	907.38​	3.65​	40​	2​	2.5​
2​	04QCB76844701JC680001875	294316.8​	3.2957​	0.147​
3​	04QCB76844701JC680001715	293291.4​	3.2952​	0.159​
4​	04QCB76844701JC680004155	294956.3​	3.2953​	0.158​	279100​	902.65​	3.65​	40​	5​	2.5​
5​	04QCB76834001JC670000899	291631.3​	3.2941​	0.151​
6​	04QCB76844601JC670000860	292695.6​	3.2948​	0.151​
7​	04QCB76844701JC680001471	293500.9​	3.2951​	0.15​
8​	04QCB76834001JC670000644	290837​	3.2952​	0.157​
9​	04QCB76844701JC680004818	292677.8​	3.2952​	0.151​	278300​	900​	3.65​	40​	5​	2.5​
10​	04QCB76844701JC680001673	293996.9​	3.2953​	0.148​
11​	04QCB76844701JC680002498	294956.3​	3.2953​	0.158​
12​	04QCB76844601JC670005833	293937.4​	3.2958​	0.148​
13​	04QCB76844601JC660002731	292393.8​	3.2949​	0.152​
14​	04QCB76844701JC680003444	294956.3​	3.2953​	0.158​
15​	04QCB76844701JC680000264	292868.1​	3.2953​	0.152​
16​	04QCB76844701JC680002057	294316.8​	3.2957​	0.147​

I'mslightly disappointed because this was their reply when I asked about the difference between A and B grade cells, I was expecting them to be 290Ah

 

[SeaGal]

I was expecting them to be 290Ah

What is the "eve capacity" column showing?

 

[cajocars]

What is the "eve capacity" column showing?

That's the data I extracted from the big spreadsheet provided by EVE to Fogstar, as are the other 2 columns that have "EVE" in the header

 

[SeaGal]

So EVE measured just over 290Ah whereas your test is giving 280Ah - so just 3.5% difference?

Could that 3.5% difference be down to environmental conditions and accuracy of test equipment?

 

[Alkaline]

I have seen this on 280K from literally everyone the grade A with reports they always are 3-5% lower than what the list.

Here is another calculation you can according to Lampard Li from EVE: Take the watt-hours and divide it by 3.2.

So if you measured 900 WH then your reading would be 900/3.2 = 281.25 AH which technically meets the capacity.

This is how he explained this to me on Alibaba: a 280K is rated at 896WH and 3.2v nominal

so in other words if you take 896 / 3.2 = 280

but if you look at the charts the average voltage on these tests is higher like 3.24 or 3.23 so I suppose each AH is being measured at 3.24 instead of 3.2

Its not a big difference and we should not be splitting hairs to get the readings that we should.

None of this is a problem with the LF304, CATL 280, or even REPT 280, even with our "ghetto testing" as soo many like to point out we can reach AH and WH and exceed them by 3-5% of the official rating.

 

[cajocars]

I have seen this on 280K from literally everyone the grade A with reports they always are 3-5% lower than what the list.

Here is another calculation you can according to Lampard Li from EVE: Take the watt-hours and divide it by 3.2.

So if you measured 900 WH then your reading would be 900/3.2 = 281.25 AH which technically meets the capacity.

This is how he explained this to me on Alibaba: a 280K is rated at 896WH and 3.2v nominal

so in other words if you take 896 / 3.2 = 280

but if you look at the charts the average voltage on these tests is higher like 3.24 or 3.23 so I suppose each AH is being measured at 3.24 instead of 3.2

Its not a big difference and we should not be splitting hairs to get the readings that we should.

None of this is a problem with the LF304, CATL 280, or even REPT 280, even with our "ghetto testing" as soo many like to point out we can reach AH and WH and exceed them by 3-5% of the official rating.

I agree Wh is probably what matters the most (pure energy), but it's also subject to an error in measuring voltage (being the integral of V*A*dt) and power loss; the Ah value on the other hand should be only being subject to current measuring errors

So if we believe the Ah measurement done by my equipment to be wrong, the Wh measurement will also be wrong; Wh measurement will always be "more wrong" than Ah

Also any heat loss (due to heating of the terminals for example) won't affect the Ah capacity reading (there aren't wasted electrons, what flows from the negative pole ends up in the positive pole, no matter the resistance); there is only a voltage drop which means the charger will have to do more work to charge the battery (and affect the Wh calculation)

Having said that, if my tester underestimates the current by 3-5%, then it will underreport capacity; I have no means to calibrate it

 

[Alkaline]

the ZKE is not off by 3-5%... Eve just lies 3-5%...?

 

[billt1827]

Do you have the WH readings for your grade B fogstar cells?

No. I didn't record them at the time. I could interpolate them from the recorded data but it would be a bit of a pain as I used automatic charge/discharge/recharge so finding the start and end of discharge is somewhat difficult.

 

[cajocars]

No. I didn't record them at the time. I could interpolate them from the recorded data but it would be a bit of a pain as I used automatic charge/discharge/recharge so finding the start and end of discharge is somewhat difficult.

If you send me that csv data I can do that in 2 minutes

 

[billt1827]

I've looked at the raw data rather than the EB software display and it is easy to see.

 

[Alkaline]

1,4,9,12 pass the WH test.

 

[cajocars]

After exactly one year, I've tested the battery from fully charged (total voltage at 3.65x16V with active balancer on and Seplos BMS reset to 100% after 30 minutes above 56V) down to 2.5V on the lowest cell

The BMS measured 258Ah; voltage deviation at the end of the test was 220mV.

The inverter (but probably this isn't accurate as it's through an integration sensor in Home Assistant) measured even less, 230.36Ah.

NB: The residual capacity starts from 400Ah as I had to trick the bms into thinking the battery was bigger otherwise the inverter wouldn't let me discharge it below 10%. At the end of the test it's 142Ah, that's where the 258Ah comes from.





As it happens, my wife started running the oven at the end of the test so that may have cut it a bit short, but probably just 2-3Ah. I'll try and start discharging again once the chicken is ready and see if I can squeeze any more out of it.

 

[Ucatchmydrift]

After exactly one year, I've tested the battery from fully charged (total voltage at 3.65x16V with active balancer on and Seplos BMS reset to 100% after 30 minutes above 56V) down to 2.5V on the lowest cell

The BMS measured 258Ah; voltage deviation at the end of the test was 220mV.

The inverter (but probably this isn't accurate as it's through an integration sensor in Home Assistant) measured even less, 230.36Ah.

NB: The residual capacity starts from 400Ah as I had to trick the bms into thinking the battery was bigger otherwise the inverter wouldn't let me discharge it below 10%. At the end of the test it's 142Ah, that's where the 258Ah comes from.



View attachment 182510

As it happens, my wife started running the oven at the end of the test so that may have cut it a bit short, but probably just 2-3Ah. I'll try and start discharging again once the chicken is ready and see if I can squeeze any more out of it.

Can I ask, did you test them in this exact way a year ago when you first got them? And is the temperature different at all this time? Also, how have they been treated - what kinda voltages have you been draining them down to and charging them to regularly? Pretty much exactly a year since I installed mine too, never done any capacity testing tho, and don't notice any difference now personally, but probably wouldn't anyway unless it were significant..

 

[cajocars]

Can I ask, did you test them in this exact way a year ago when you first got them? And is the temperature different at all this time? Also, how have they been treated - what kinda voltages have you been draining them down to and charging them to regularly? Pretty much exactly a year since I installed mine too, never done any capacity testing tho, and don't notice any difference now personally, but probably wouldn't anyway unless it were significant..

Last year I tested 4 of them with the Zketech EBC-40L and they were between 278.3 and 280.5 Ah; I sold the Zketech shortly after, so I cannot repeat the same measurement.
Also, I didn't test them as a full battery when new as I hadn't worked out how to discharge them to lower than 10% with my inverter. You can probably infere something from this post where I was saying that I struggled to bring them down to 100% https://diysolarforum.com/threads/180mv-imbalance-at-13-soc.59056/#post-733615 That was one month in service, so I was proably already seeing some capacity loss back then.

Basically, I have no like for like comparison, but I think some degradation has happened.

I have always charged them to 56V (3.5V per cell) and rarely discharged down to 10% (the inverter would disconnect at 10%, with capacity set to 280Ah in the bms).
I have been running them indoor for 9 months (so never below 18 degC), compressed but not actually compressed as I was using 3mm foam which allowed for some expansion despite having used threaded rods for compression; I found this out when I disassembled the cells to move them to the garage (there was slight bloating). They are now sitting in the garage since October, still compressed, but with 0.5mm epoxy insulation. They are surrounded by 25mm polystirene insulation to keep them warmish and they are heated during charge if the temperature is lower than 9 degC up to 13 degC; they are not heated during discharge or standby.

 

[Ucatchmydrift]

Last year I tested 4 of them with the Zketech EBC-40L and they were between 278.3 and 280.5 Ah; I sold the Zketech shortly after, so I cannot repeat the same measurement.
Also, I didn't test them as a full battery when new as I hadn't worked out how to discharge them to lower than 10% with my inverter. You can probably infere something from this post where I was saying that I struggled to bring them down to 100% https://diysolarforum.com/threads/180mv-imbalance-at-13-soc.59056/#post-733615 That was one month in service, so I was proably already seeing some capacity loss back then.

Basically, I have no like for like comparison, but I think some degradation has happened.

I have always charged them to 56V (3.5V per cell) and rarely discharged down to 10% (the inverter would disconnect at 10%, with capacity set to 280Ah in the bms).
I have been running for 9 months indoor (so never below 18 degC), compressed but not actually compressed as I was using 3mm foam which allowed for some expansion despite having used threaded rods for compression; I found this out when I disassembled the cells to move them to the garage. They are now sitting in the garage since October, still compressed, but with 0.5mm epoxy insulation. They are surrounded by 25mm polystirene insulation to keep them warmish and they are heated during charge if the temperature is lower than 9 degC up to 13 degC; they are not heated during discharge or standby.

Thanks very much for the reply ?.. Sounds like you have been treating them pretty good,, be interesting to know if you tested them again for example tomorrow to see if you got the same result or not!... Also, maybe in one more years time, testing them exactly how you have just done, would also be very interesting! Ill remind you in a year ha ha.. Have you noticed any swelling? Mine have been compressed, never taken apart, dont see any swelling yet, although supposedly compressing only makes a difference when done for the first few cycles anyway, so ive read.

 

[SeaGal]

Great analysis ...

The other interesting metric in this observation is that a year ago the LF280K's were £144, now they are £119 (and were discounted to £99 for Black Friday) - so £25 reduction excluding the 'deal'.

So in Dec 2024, they should be £94
in Dec 2025 they will be £69
in Dec 2026 they will be £44
in Dec 2027 they will be £19
and in Dec 2028, if I'm still alive, @Ben@Fogstar will be paying us to have them.

Obviously I jest, but the point is that any small degradation in performance is overtaken by better purchasing power / value for money in the future - far exceeding their degradation.

So I guess we all need to work these cells as hard as we can in the meantime to save as much £££ as we can from the electricity suppliers.

I was going to say "drive them like you stole it", but as both @Ucatchmydrift and I are petrol heads, I'll refrain from using that saying

 

[cajocars]

Thanks very much for the reply ?.. Sounds like you have been treating them pretty good,, be interesting to know if you tested them again for example tomorrow to see if you got the same result or not!... Also, maybe in one more years time, testing them exactly how you have just done, would also be very interesting! Ill remind you in a year ha ha.. Have you noticed any swelling? Mine have been compressed, never taken apart, dont see any swelling yet, although supposedly compressing only makes a difference when done for the first few cycles anyway, so ive read.

Yes, I noticed some swelling when moving them to the garage.

@SeaGal, I bought them for £144 at black friday 2022; they were £99 during black friday 2023, a difference of £720 for 16 cells. Surely they dropped more than what they made me save on electricity in one year. But one year ago, I was expecting energy prices to go higher than what actually happened.

 

[Alkaline]

After exactly one year, I've tested the battery from fully charged (total voltage at 3.65x16V with active balancer on and Seplos BMS reset to 100% after 30 minutes above 56V) down to 2.5V on the lowest cell

The BMS measured 258Ah; voltage deviation at the end of the test was 220mV.

The inverter (but probably this isn't accurate as it's through an integration sensor in Home Assistant) measured even less, 230.36Ah.

NB: The residual capacity starts from 400Ah as I had to trick the bms into thinking the battery was bigger otherwise the inverter wouldn't let me discharge it below 10%. At the end of the test it's 142Ah, that's where the 258Ah comes from.



View attachment 182510

As it happens, my wife started running the oven at the end of the test so that may have cut it a bit short, but probably just 2-3Ah. I'll try and start discharging again once the chicken is ready and see if I can squeeze any more out of it.

Cajocars,

Many people have the 280 test to around 260 after a while, even the grade B usually around 258/260 I think this is basically where the v1/v2 280K likes to settle down.

Eve has released teh v3 version of this cell, its testing to 310+ but I have a feeling after a year or two in regular use it will settle down to around 280 which is what its rated for.

I suspect even if you test after a year it will still be around 258 maybe 255.