Dr Jeff seems to only talk stress and cycles, and seldom cover* anything else but the cyclic aging.
Calendar aging causes a lot of degradation during the first 5-8 years of the battery life.
In fact, cycling aging only causes a fraction of that for the most owners.
Panasonic ncr18650 after 18 months: 100% is not the worst SOC.
View attachment 1042727
Actual model S cells:
View attachment 1042728
Charts showing cyclic aging shows that the degradation per cycle converted to miles causes about 0.5% cyclic aging per year.
—> If anything, if any owner would like to minimize degradation he/she should take the actions that reduce the calendar aging.
Doing this will also keep the cyclic aging low.
We know from research/tests that Panasonic NCA degrade less from calendar aging at or below 55% displayed on a Tesla.
The cyclic aging is also smallest between ~55 to ~30% displayed SOC so it matches good.
Actual model 3 cells cycled:
The SOC shown is true SOC, and because of Teslas buffer, the 5-15% is 0-10% displayed.
It might look bad for 5-15%, but actually those cycles 17% loss after 3000FCE is = 17% after 750K miles, so thats atound 60 years of average driving or 0.28% per year of cyclic aging.
View attachment 1042731
Calendar aging is less the lower the SOC is, down to 0% so Dr Jeff might use a ”medium” SOC as the ideal, taking in margins to ensure not to find the car empty when arriving at home.
IRL, the HV-lithium battery will degrade less the lower the SOC is, so 30% is not the sweet spot for low calendar aging - 30% might be a compromise also making Dr Jeff sure no one will sue him one day for the statements.
There is no bad thing for cyclic aging, going low in SOC. In the fine scales charts we see slightly more degradation from cycling below 20% displayed SOC but the increased wear is lower than the reduction in calendar aging, so still a win to go low.
More or less any research shows that calendar aging is doubled above 55% displayed SOC so a recommendation to charge to 65-75% will not be the best thing for degradation.
Keeping the battery at or below 55% as often as possible will be the best solution.
Things to know to do extra well with the tips above:
- Going down to 0% is safe for the HV battery. When needed, have a margin to surpress your own range anxiety.
- Charging to 100% is not that bad for the battery. You do not need to drive asap, at least no more need than when charging to 80%.
*) I recommend strongly to widen the sources for knowledge about lithium batteries.
Dr Jeff might be good, but there are several others of the same dignity that have produced research/reports.
A single source might lead to a skewed picture of this.