To continue the low SOC end discussion:
This is a picture from a very good research report
Panasonic NCA calendar+cyclic aging. It was released 2017.
View attachment 875184
All cycles ended at 2.5V/ cell. Thats the manufacturers (Panasonic NCR18650PD) lower limit of discharge, which also by definition is 0% SOC.
( And as Tesla use 4.5% bottom buffer this is way below the 0% on the screen and below the limit where Tesla shut down the vehicle because of low SOC.)
Note that this is 4.5% below 0% displayed, and well in the region which people call dangerous
4.20V is 100%
4.10V is about 90%
4.00V is about 80%
My car has an average consumption of 184 Wh/km. One Full Cycle Equivalent would take my car 82000/184 = 445km.
According to the chart above, with 0.5/0.7A which is the closest C-rates to real driving, it would do 625 FCE Cycles, 278.625 km before reaching 20% degradation. This if charged to 100% and driving until the car stops, every time.
If charged to 4.1V/cell (~90%) it would do 800 cycles, or 356.000km. Driven down until it stopped, each time.
If charged to 4.0V/cell it would do 1000 FCE cycles, or 445.000km. Driven down 4.5% below 0% displayed, until the car stops in the ”very dangerous SOC region below 20%”. ( <—- Note, a joke!)
Except for the obvious fact that we can see: low SOC is safe, we also can se that it is the high SOC part that kill the battery despite the misleading name ”deep cycle”.
The deadly part of the deep cycle is in the top.
By not using the top 0.1V/cell or about 90-100% region, we increase the battery life by 25%, in miles.
By not using the top 0.2V/cell or about 80-100% we increase the life 60%, in miles driven.
I guess its clear that a battery that can do 445.000km/ 276000 miles of constant cycling down to 0%
is not very badly hurt by this:
Cycling (and storing) NCA down to 0% is very safe.
The research report I refer to in this post (link in the beginning) is not the only research report that shows these facts.
There is a lot of reports telling the same thing, this one is a very good read though.
It covers calendar aging as well, cycling cold or hot bstteries etc so if you shpuld read only one report that specifically covers NCA, this is one of these reports.