little to no increased degradation for cells cycled upto a maximum SoC of between ~60 - ~90. Below 60% max SoC, degradation was reduced, and ~60% soC corresponds to the approximate SoC at which the cathode structural phase change occurs for an NMC or NCA cathode.
Thus, the conclusion was that if max SoC is taken below unstable levels (~90% SoC in the study), the difference that reducing max SoC further makes is negligible in comparison to the additional structural degradation induced by the regular phase changes of the cathode.
So if I understand this correctly, there is the increasing stress phenomenon for increasing SoC, and there is a”phase change” which occurs at around 60% SoC which is also bad (but is perhaps less significant)?
And if I am reading above correctly, the lowest degradation was observed for batteries charged to below 60%, and then cycled down from there (presumably not so low as to hit the low SoC stress point). So always below 60% SoC.
So with respect to daily charging limit then, if you could consistently get away with it without low SoC, wouldn’t 60% be ideal? In that case the “storage curves” from
@Zoomit provide the correct guidance.
But let’s say you wanted to have more reserve “just in case” (many people I would think):
For someone with a short commute, would it arguably be better to charge to 80% rather than 70% on a daily basis, IF it meant that you did not discharge below ~60%, thus avoiding the phase change? Would the improvement due to lack of phase change offset the slight increase in storage stress?
Understood that the exact % levels might differ from one battery technology to the next.
The warmer curves roughly depict a doubling of "stress" between 80 and 90% and doubling again between 90 and 100% absolute SoC.
Based on above questions, while these curves look qualitatively to be correct from a storage standpoint, it sounds like you’re saying the phase transition means you might want to take that into account (if you have predictable driving patterns)...so we can only look at these curves specifically for STORAGE, but not necessarily as exact guidance for what your daily charge level should be set to for optimal longevity? Is that accurate? For users with long commutes perhaps the curves are pretty good guidance since the phase transition is unavoidable, but for those with shorter commutes, slightly higher SoC might be better?
Any idea what %SoC the phase transition occurs with Model 3 battery chemistry?
These are questions, not statements...just wondering mostly how significant this phase transition is...and whether I am interpreting the qualitative behavior correctly.
A friend of mine who just got an M3 ran a cable from his stove and is getting 52Km/hour as his charge rate - this would be from a Nema 14-50 plug (see attached screen shot)
