There are two types of battery failure.
Other things than worn cells, and from worn cells.
Other things than worn cells happens from time to time, andtaking care of the degradation does’nt protect from this.
Worm cells: In general the lithium battery industry do consider a cell degraded 20% as consumed. The reason is that degradation is rather predictable until that level and the degradation beyond is not.
This most probably is valid for EV cells/batteries as well as they are basically the same thing. The research shows a very good relationship between other lithium ion cells and actual EV cells.
For the normal user cyclic aging (i.e “miles) do not really mather much. Normally it will be around 0.25-0.5% or so annually.
The absolute majority of the degradation after ~ 10 years will come from calendar aging. This will be around 15% for most users, using the cars as people mostly do. More or less than 15% mostly depending on the climate/average cell temp, but also charging habits.
This means we will be close to reaching 20% after then years, and we will probably se the failure rate from high degradation (dead cells, to much imbalance etc).
As the climate ( = average cell temps) varies, these 10 years will probably also vary with shorter times in warm climatesand longer in cold.
