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SOK Cycle Testing

JeffofCT

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Feb 8, 2021
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I know that some people are starting to take delivery of their new SOK batteries and curious to know if anyone has done any cycle testing to judge if their claims of 4,000-8,000 cycles is correct. Obviously, nobody has had time to cycle their batteries that many times, but I understand the cells that SOK is using might already be a known variable.

I bring this question up because this fellow (
) did cycle test (45 before discontinuing) and suggested that the SOK cycle life might be as little as 1,000. He did acknowledge the main weakness in the test that the recharge capacity drops more quickly over the first 50 cycles before leveling off.
 
:cry: i attach the test result for reference ....
 

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  • SOK battery SK12V100-0915 life cycle curve.pdf
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Min, thank you. Comparing his results with your posted laboratory results are very similar if I am interpreting them directly. His test resulted in a .01105 drop in efficiency compared to your laboratory results of .01017 over the first 45 cycles. Am I comparing the results correctly?
 
Min, thank you. Comparing his results with your posted laboratory results are very similar if I am interpreting them directly. His test resulted in a .01105 drop in efficiency compared to your laboratory results of .01017 over the first 45 cycles. Am I comparing the results correctly?
you could see the bottom of the test result file.
 
if their claims of 4,000-8,000 cycles is correct. Obviously, nobody has had time to cycle their batteries that many times,
4000 to 8000 cycles claim is bs.
Most LFP batteries are claiming 2000 to 5000 cycles.
SOK is using standard prismatic cells so why the high 4000 cycle claim?
 
you could see the bottom of the test result file.
I compared your test results through 45 cycles with his test results of 45 cycles. They are comparable. If anything, his were slightly better but probably within the normal/expect error rate (+/-).
 
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4000 to 8000 cycles claim is bs.
Most LFP batteries are claiming 2000 to 5000 cycles.
SOK is using standard prismatic cells so why the high 4000 cycle claim?
It's possible that the cycle count is mathematically derived, but as far as I can tell, most manufacturers publish similar tables--even Battleborn--but I think a comparison with Min's table with a disinterested Youtube expert over 45 cycles is a fair approximation.
 
4000 to 8000 cycles claim is bs.
Most LFP batteries are claiming 2000 to 5000 cycles.
SOK is using standard prismatic cells so why the high 4000 cycle claim?
Min posted a test that shows 4000 cycles. Choose to believe it or not. It looks pretty similar to other prismatic cell tests I've seen. While the narrow temp range is optimistic, the 1C charge/discharge rate in the test is probably more abusive than typical use. The stated max by SOK is only .5c charge and 1C discharge, so it's reasonable to think the 4000+ is doable with gentler use in mild temps. 8000 cycles as best case scenario? Maybe. They don't make any promise about capacity at 8000, just say it's good for that many cycles. If I could get 60% capacity out of any battery after 8000 cycles, I'd call that a win. We're talking about full charge and discharge every day for 22 years.

Even hitting 4000 cycles before dropping to 80% capacity is just crazy to think about. I'd be happy with 1500-2000 cycles. In 10 years, I expect there will be better/cheaper options available that I'll want.

I exchanged a few emails with Min and he was very responsive and I think they have a good product. I ended up deciding to DIY my own batteries, but SOK would be my choice if I wanted to buy something off the shelf right now (assuming I could wait).
 
The problem with rapid-fire back to back cycle-testing is that it doesn't take into account the real-world aging factor that all batteries undergo. (typically internal resistance rising)

Although the video is from 2013, look into what Prof Jeffrey Dahn (Dalhousie University) did with his video "Why do Li-Ion Batteries Die ? And how to improve the situation ? "

Most of it concerns non-LFP, but there are some charts and generalities that can be followed.

Ie, there are lab results, and then there's the real world. I've been fortunate with my diy prismatic banks (small scale), but to tell the truth, my usage outlived the capability of the battery's normal aging! I should have cycled them more..
 
LFP rocks when taken care of. Like you, I might have some that will outlive me. :)

I like Will's attitude of show-me-the-data in regards to things like high-voltage floating. What makes some things tricky is that preventative measures one takes now may not show any promise right away. But it *might* several years down the road to prove it.
 
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