zcskywire2
Solar Enthusiast
There is endless discussion these days here about the effects of calendar aging on cells. Even more so with cell cycle lifes hitting 15000 cycls or more. Unfortunately there is a lack large scale testing as it is both expensive and time consuming. Well through my job I was given a rare opportunity to collect good data on calendar aging over a large sample size of CALB L135F72 (CAM72) cells.
We were tasked to test over 400 cells to see if they were still valid for pack construction. These cells were still in their original shipping crates and had not been touched since they were manufactured 12/21/19. For 3 of the pallets I was able to obtain the original shipping report, containing the original capacity testing. This allows us to directly see the calendar aging after ~4 years of shipping as these were testing between Oct 23 and Feb24. Cells were stored at shipping SoC (~30%) in a heated and cooled warehouse (I believe at least).
For the actual capacity testing the cells were charged and discharged at 0.5C at at temperature ambient of 22c. This is a higher C rate on the charge (0.33C vs 0.5C) but less on the discharge (1C vs 0.5C). Current taper cutoff was kept at the same level (0.05C). Over all not quite the same but comparable enough.
Gear used was a band new B&K9115 power supply for charging and a brand new B&K 8612 electronic load for discharge. Remote sense was used for both.
Actual results are below in a image (I've done enough typing already)
Overall we saw a loss of 3.31%- 7.74% with a little less than 5% on average. This means with no cycling there is an average of ~1.25% SoH per year for CALB L135F72 cells. Much lower than many of the smaller studies out there. Giving a ~16year shelf life for cells.
Full results and original shipping documents are attached.
We were tasked to test over 400 cells to see if they were still valid for pack construction. These cells were still in their original shipping crates and had not been touched since they were manufactured 12/21/19. For 3 of the pallets I was able to obtain the original shipping report, containing the original capacity testing. This allows us to directly see the calendar aging after ~4 years of shipping as these were testing between Oct 23 and Feb24. Cells were stored at shipping SoC (~30%) in a heated and cooled warehouse (I believe at least).
For the actual capacity testing the cells were charged and discharged at 0.5C at at temperature ambient of 22c. This is a higher C rate on the charge (0.33C vs 0.5C) but less on the discharge (1C vs 0.5C). Current taper cutoff was kept at the same level (0.05C). Over all not quite the same but comparable enough.
Gear used was a band new B&K9115 power supply for charging and a brand new B&K 8612 electronic load for discharge. Remote sense was used for both.
Actual results are below in a image (I've done enough typing already)
Overall we saw a loss of 3.31%- 7.74% with a little less than 5% on average. This means with no cycling there is an average of ~1.25% SoH per year for CALB L135F72 cells. Much lower than many of the smaller studies out there. Giving a ~16year shelf life for cells.
Full results and original shipping documents are attached.
