Calendar ageing tests of mixed cylindrical cells

[Pajda]

"Simple" Calendar ageing test (at nominal capacity 0.2C)

Test eqiupment:
- Precision multi-channel battery tester (accuracy ±0.02％ // 10x better than ZKE testers)
- Temperature chamber with ±0.1 °C stability
- BF-2A four-wire cell fixture (20A version with Gold plated contacts)
- Cells were stored during test period in a desk drawer, in closed carton box in room with average temperature 23 ±3 °C

Remarks and comments:
- Please don't ask why this particular selection of cells (spontaneous decision? )
- The 50% state of charge storage value is defined by performing the standard charge method of the cell and then discharging it with a current of 0.5C for 1 hour.
- After each year of storage, there is a procedure which gives "after storage" values:
1) at first values of OCV (open circiut voltage) and ACIR 1kHz are measured.
2) then the cell is discharged with a 0.2C rate. This gives values of capacity and energy which include the sum of the effect of calendar ageing and self-discharge.
3) then a nominal capacity test is performed according to the manufacturer's specification (full charge and discharge). This nominal capacity test shows the effect of calendar ageing only.
4) then cell is fully charged and discharged to 50% DoD, where the both DCIR tests are performed.
- You are probably all aware that the next values will be available in a year at the earliest.

____
All tests were performed in temperature chamber under 25°C, TC is using forced air flow to maintan consistent temp. This 25°C air flow acts as cooling force on the cell surface, so the measured temperatures under high load will be affected by this.

added Samsung INR18650 30Q6 to the table (Precision tester, cell supplier: ---)
added Samsung INR21700 50G to the table (Precision tester, cell supplier: NKON)
added LG INR21700-M50L to the table (Precision tester, cell supplier: NKON)
added Molicel INR21700-M50A to the table (Precision tester, cell supplier: NKON)

 

[Pajda]

reserved

 

[Pajda]

reserved

 

[john61ct]

doing dog's work my son

 

[Pajda]

So another year has passed and I am updating data after 2 years of ageing.

Well, see you next year.

 

[docw009]

Losing about 1-1.5% per year at 100% vs .5-1% at 50%? Pretty negligible in my opinion,

I always thought the warnings about 100% storage were overblown. Not knowing any better, I often left my ebike pikes fully charged in my early ebiking years.

 

[Stealth_Chopper]

So another year has passed and I am updating data after 2 years of ageing.

Well, see you next year.

oh 'cmon dont leave us hanging
please Pajda a one half sentence two year non conclusive comment please?
Mike
Ed: Can we say Good? I ask You ?

 

[Stealth_Chopper]

So another year has passed and I am updating data after 2 years of ageing.

Well, see you next year.

Ed:Hoo Rah!

OK since we are on the lead edge:
'What is good'?

 

[Pajda]

oh 'cmon dont leave us hanging
please Pajda a one half sentence two year non conclusive comment please?

Well, first of all, I have to point out my methodological error, which slightly affected the 2nd Year data. You may have noticed that the blue "after storage" capacity&energy data are a bit higher than in 1st Year. This is due to the fact that Pajda was in a hurry to go on vacation and did not leave enough time to equalize the cell temperature to 25°C in the temperature chamber. So the first step of the test: the 0.2C discharge started with a higher cell internal temperature. The rest of the data is fine because the temperature of the cell has managed to equalize during the first step.

With a certain amount of caution, I can give this assessment:

- The storage SoC level still plays a role. But, there is another parameter missing in this test and that is storage temperature. The general assumption is that with low storage temperature, the difference between storage SoC will decrease, while with higher storage temperature it will increase.

- This test also confirms the general assumption that High Power density (HP) cell design age faster than High Energy density (HE) design. This happens in both cycle and calendar aging. A phenomenon that further exacerbates the perception of faster aging of HP cell design is the increase in internal resistance. In a practical HP application, 0.2C nominal capacity is useless, you only count usable capacity at high C-rates.

 

[hasimcan1]

Hey there!

First off, kudos on the meticulous setup and details. It's clear you've put in some serious effort into the calendar ageing tests. The temperature consistency and precision of your testing equipment is pretty impressive. It's a nice touch to keep track of "after storage" values as it provides a clearer perspective on the cell's performance over time.

Your remarks section gave me a chuckle with the spontaneous cell selection.
Alright, class! Let's talk about the 2024 calendar. Now, as we delve into planning our year, it's essential to remember that 2024 is a special year. Can anyone tell me why? That's right, it's a leap year! This means we'll have an extra day in February, making it 29 days instead of the usual 28. This adjustment helps our calendar year stay in alignment with the Earth's revolutions around the Sun. So, as we mark down important dates, tests, and holidays, don't forget to take note of that extra day! Let's make 2024 a year of learning, growth, and, of course, excellent organization. I'll be here to guide you every step of the way!

Source: 2024 Calendar: Free Printable Calendar With Holidays


I'm particularly curious about the Samsung INR21700 50G and LG INR21700-M50L cells as I've seen mixed feedback about them in different use cases. I'll be eagerly awaiting the next set of values in a year or so. Till then, safe testing and keep us posted! 🛠

 

[fechter]

Awesome data. Thanks for sharing.