More interesting cycle life data

[sunshine_eggo]

Orac runs my system.

Dang... I was alive then, but that was not an option in Podunk, OK.

 

[Eber]

they represent hundreds of cycles

They likely will die of calender aging as Will said in his video, thats cool.
James, I was wondering, how EMP proof are they (EG4)? They are encased in a metal rack and the batteries themselves are in a metal casing?

 

[zcskywire2]

Since it would also benefit the office, I've got approval to test some of the CALB CAM72 and CA series cells we have nib still at the office. These would have been purchased ~2015 for a now discontinued product. Will get back on how toasted or not they are.

Our test subjects have been found. They are a CALB CA100 manufactured Jan 2014, A CALB CA180fi manufactured Oct 2013 and a Brand new CALB CAM72 manufactured April 2019. Both the CA series cells have an original testing capacity written on them. The CAM 72 cell seems to have never been used as it still has its terminal stickers attached. The plan is to simply follow the datasheet specs and see what they test. Initial voltage measurements read fine with 3.25-3.35v on each cell. Testing gear will be a B&K 9116 PSU and a B&K 8614 In battery test mode. No fancy discharge graphs this time sadly.

 

[SignatureSolarJames]

They likely will die of calender aging as Will said in his video, thats cool.
James, I was wondering, how EMP proof are they (EG4)? They are encased in a metal rack and the batteries themselves are in a metal casing?

well, full disclosure I don't have a tactical nuke in R+D
I think the rack is a good opportunity for hardening honestly, the issue is more of grid surges in the powerlines if you are grid connected

 

[Hedges]

Rather than tactical weapons, survivability was traditionally accomplished by "underground testing".
With that now banned (at least in US if not North Korea), a new facility is available:

NIF Experiments Support Warhead Life Extension

"Survivability: Researchers are using NIF to produce radiation sources to evaluate how well U.S. weapons will be able to survive—and function as expected—after traversing evolving adversary missile defenses. Without the ability to survive, these weapons would be unable to hold targets at risk, rendering the deterrent ineffective."

Yes, I agree power line surges (and coupling to PV array from nearby lightning strikes) are the threats a user might actually care about, because they will be around afterward to use the system.

 

[Sojourner1]

No offense guys but some might be interested in cycle life data than some off the wall bs being added now.

 

[mountkay]

Recently I was trying to look into what exactly causes calendar aging and what is physically happening to the battery, as most of the time people just say "calendar aging" and leave it at that.

Here is a dense article / paper that I tried to skim through, along with some charts from the article.

Assessment of the calendar aging of lithium-ion batteries for a long-term—Space missions

Energy availability is a critical challenge for space missions, especially for those missions designed to last many decades. Space satellites have depended on various combinations of radioisotope thermoelectric generators (RGTs), solar arrays, and batteries for power. For deep space missions...

www.frontiersin.org

 

[SignatureSolarJames]

Recently I was trying to look into what exactly causes calendar aging and what is physically happening to the battery, as most of the time people just say "calendar aging" and leave it at that.

Here is a dense article / paper that I tried to skim through, along with some charts from the article.

Assessment of the calendar aging of lithium-ion batteries for a long-term—Space missions

Energy availability is a critical challenge for space missions, especially for those missions designed to last many decades. Space satellites have depended on various combinations of radioisotope thermoelectric generators (RGTs), solar arrays, and batteries for power. For deep space missions...

www.frontiersin.org

View attachment 146792

View attachment 146793

we need to start a thread on this, science only. you're right, it's just a punchline too often

 

[zcskywire2]

Our test subjects have been found.
View attachment 146758

The first two results are in

Up first CALB CA100, Manufactured Jan 2014
Original testing notes read: 110.8Ah at 0.5C

Test was carried out as follows:
Charge to 3.65v at 0.3c (30A) battery is charged when current drops to under 5A
Discharge is carried out at 1C (100A), untill Cell reaches 2.5v
Test ran in open air with Tamb ~18c, remote sensing was used for both charge and discharge.

Resulting capacity was 98.704Ah for 89.56% of original tested capacity. Though this was not identical to our test today.


CALB CA180Fi, Manufactured December 2013,
Original testing notes: 189Ah -> 2.5v

Test parameters
Charge to 3.65v at 0.3C (54a), battery is charged when current falls below 9a
Discharge is carried out at 1C (180A), until battery voltage hits 2.5v
Test in open air at Tamb ~18c, Remote sense used for charge and discharge.

Resulting capacity was 177.494Ah for 93.91% of original tested capacity.


Notes. I cannot truly say how many cycles these cells have seen. Odds are it's next to zero but I can't confirm. I did not take SoC measurements of them coming out of storage, however it did seem that the CA100 was more charged than the CA180Fi. Storage conditions for these would have been some amount of time indoors in a temperature controlled house, and then at least 5-6 years in a non temperature controlled warehouse. All together I'm pretty impressed, 7%-11% SoH loss in about a decade. That loss may even be less when tested at 0.5C discharge on the cells. CAM72 tommrow. Maybe I'll go digging and find a spread of them as we have so many of them. The hard part will be confirming they are unused.

 

[MrM1]

And here I was just worrying the other day about where I'd dispose of these 40 cells I the have. If the OPs study is correct, I'll be dead, it'll be somebody else's problem ?

 

[zcskywire2]

The first two results are in

Final result in today, the the CALB CAM72

Testing was the same as the others
Charge at 0.3C (21.6A) to 3.65v, Charged when current is less than 3.6A
Discharge at 1C (72A) stop when cell reaches 2.5v.



Final result was 70.062Ah, 97.3% of rated capacity. SoH is unknown as this is the first cycle this cell has seen, sadly we have no new production CAM72 cells, if that even exists, to compare. These would have only been warehoused in non temperature controlled conditions. SoC was at the ~30% level the cells were shipped at. All together these results are better than I would have guessed. At max a loss of 10% capacity over basically a decade of rest. Further more these would have not been the ideal storage conditions. Makes me think that calendar aging may be a bit overblown. However simply slow cycling cells may change that. Hope y'all get something useful outta this. Any questions are welcome.

Edit: First I can't math properly, CAM72s are 72 ah. Not 70 doh. Has been corrected

Secondly, this shouldn't be taken as proof that there was no degradation over 4 years of storage for the CAM72 cell. There certainly was, I simply just have no way of calculating it. What it does show that the worst case numbers of that meta study referenced are not great. Four years of 3% loss would have put the cell at a original ~79Ah a reasonable level these cells could have originally tested at. A 10% loss rate would put these cells north of 100Ah originally, most certainly not real.

Lastly, looking back up at the CA cells, it is most certainly less than 3% per year averaged over a decade. Ballpark math puts it at 1%-1.25%per year averaged over 10 years. At that point it may be equivalent to cycling loss depending on your cells and setup.

 

[zcskywire2]

SoH is unknown as this is the first cycle this cell has seen, sadly we have no new production CAM72 cells, if that even exists, to compare.

While I'm thinking about it, if anyone has some original, dated testing on a CAM72 cell with the manufacturing date, we might be able to get a rough comparison