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Because they didn't' they decided HEY if 3000 cycles at 1 c.... THEN 6000 cycles at .5C! HAHAHAHA we are smart
Eve LF280K cells 6000 cycles?
- Thread starter TheJeremy
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Yes, 32 cells on 10th August.
kshopper2084
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But there's a chart! ?Because they didn't' they decided HEY if 3000 cycles at 1 c.... THEN 6000 cycles at .5C! HAHAHAHA we are smart
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I’m pretty impressed with the improvements EVE had delivered on these 280Ah cells over the past year with the new LF280K.
6000 cycles with a 300kgf fixture to 80% of initial capacity means if you treat them right, these cells will basically last forever.
Of course, there are other studies indicating that LiFePO4 cells degrade with age whether they are being cycled or not, and the ‘capacity recovery’ test/spec of >=97% after 28 days translates to degradation to 80% capacity after as little as 200 days…
Using the 0.5C charge and discharge rate along with the 30 minute test translates to a cycle time of at least 4.5 hours, so 6000 cycles translates to at least 27,000 hours or 1125 days / 3.1 years to 80% of initial capacity.
I also like that EVE is now showing discharge curves at different temperatures - you can see the ~10% capacity loss that results from discharge at 10C / 40F (pity they don’t show charge curves at a similar range of temperatures).
Of course, we’ve got no way to get ahold of these EV-class cells, but the aftermarket rejects ought to roughly embody similar levels of relative improvement (from a much lower baseline).
Did a bit of poking around and found this: https://uwspace.uwaterloo.ca/bitstream/handle/10012/12177/Catton_John.pdf
Figure 15 shows that LFP cells stored at 100% SOC @ 35C will lose ~13% of their capacity (13% capacity fade) after 28 months (note that we are talking about loss of actual capacity, not merely loss of SOC or self-discharge).
So stored at 35C, a LiFePO4 cell will fade to 80% of initial capacity after 45 months / 3.7 years whether it is cycled or not.
At 25C the capacity fade should be reduced and storing cells at 80% SOC rather than 100% SOC should decrease capacity fade as well but a capacity fade of ~4% per year whether you are cycling your LiFePO cells or not seems very realistic.
So again, without accounting for the accelerated degradation that results from cycling without a 300Kgf fixture, an EVE LF280K should fade to 80% of initial capacity after 6000 cycles or ~5 years, whichever comes first.
The punchline is don’t be shy about using those cycles - another example of ‘use it or lose it’.
Figure 15 shows that LFP cells stored at 100% SOC @ 35C will lose ~13% of their capacity (13% capacity fade) after 28 months (note that we are talking about loss of actual capacity, not merely loss of SOC or self-discharge).
So stored at 35C, a LiFePO4 cell will fade to 80% of initial capacity after 45 months / 3.7 years whether it is cycled or not.
At 25C the capacity fade should be reduced and storing cells at 80% SOC rather than 100% SOC should decrease capacity fade as well but a capacity fade of ~4% per year whether you are cycling your LiFePO cells or not seems very realistic.
So again, without accounting for the accelerated degradation that results from cycling without a 300Kgf fixture, an EVE LF280K should fade to 80% of initial capacity after 6000 cycles or ~5 years, whichever comes first.
The punchline is don’t be shy about using those cycles - another example of ‘use it or lose it’
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