KiwiME
Well-Known Member
Despite all the data available off OBD it's taken until now for a gen-1 owner with moderate degradation to post some numbers. Unfortunately they've accidentally missed the four cumulative values which would have allowed an accurate capacity estimate, but what has been offered at least indicates the mechanism taking place.
A new Kona battery uses a cell voltage range (defined by the manufacturer, LG Energy) of:
3.167 OCV at 0% SoC (dash)
4.166 OCV at 100% SoC(dash)
(That's "open-circuit voltage" which means measured when settled and without a load. When you measure it with an OBD app it's not really unloaded as the car must be 'on' with the traction battery supplying some 0.2 kW of power to the car, but it's close enough.)
As we've know since day one, SoC(BMS) typically lies between 95-97% at full charge and tracks proportionally downwards with SoC(dash) until they meet at 0% SoC.
This 2021 (facelift, UK) battery at 90.9% SoH has cell voltage range of:
2.84 - 3.02 OCV at 0.5% SoC (dash and BMS)
4.18 OCV at 100% SoC (dash) 96.5% SoC(BMS)
Aside noting that the cell balance was excellent at 100% but terrible at 0.5%, the bottom line is that most of the "buffer" absorbed was at the lower end of the range. But the overall mechanism is that the working cell voltage range is extended closer to the widely accepted 'safe' range of 2.5 to 4.20 OCV, so it is attempting to make up for the loss to some extent.
SoC(BMS) seems to remain at the same proportion to SoC(dash) so doesn't seem to play a part in this, as has been widely speculated.
A new Kona battery uses a cell voltage range (defined by the manufacturer, LG Energy) of:
3.167 OCV at 0% SoC (dash)
4.166 OCV at 100% SoC(dash)
(That's "open-circuit voltage" which means measured when settled and without a load. When you measure it with an OBD app it's not really unloaded as the car must be 'on' with the traction battery supplying some 0.2 kW of power to the car, but it's close enough.)
As we've know since day one, SoC(BMS) typically lies between 95-97% at full charge and tracks proportionally downwards with SoC(dash) until they meet at 0% SoC.
This 2021 (facelift, UK) battery at 90.9% SoH has cell voltage range of:
2.84 - 3.02 OCV at 0.5% SoC (dash and BMS)
4.18 OCV at 100% SoC (dash) 96.5% SoC(BMS)
Aside noting that the cell balance was excellent at 100% but terrible at 0.5%, the bottom line is that most of the "buffer" absorbed was at the lower end of the range. But the overall mechanism is that the working cell voltage range is extended closer to the widely accepted 'safe' range of 2.5 to 4.20 OCV, so it is attempting to make up for the loss to some extent.
SoC(BMS) seems to remain at the same proportion to SoC(dash) so doesn't seem to play a part in this, as has been widely speculated.