cell deviation is very little compared to the age of the car : the Ray EV use an SK-Innovation pack, too ?
in others sectors, cell deviation occur over ages when the builder don't really frame the cell factory (or don't have warranty to provide).
and so, you can have cell deviation and lost of capacity in the same tilt year.
example of cell deviation with a 2C discharge and 2C charge on older Lipo pack :
poor cell in orange.
that's why final voltage of the pack is a good indicator of ageing ... specially with slow charger.Example :
- good pack, 500km, 7S cell = 30v at the end of the charge (charger stop)
- bad pack, 500km, 7S cell = 27,4v at the end, same charger <-- cells problems, cell balancing fail
- cell log don't available (need to dismount the pack)
so, you see ... that's why i love this Kia product (BMS).
because members (setting torque subject) permit to draw graphic of the battery during process like charge and discharge.
only Tesla permit that (TeslaLOG) ... and deny this access when you report a charge or battery problem.