Interesting. The BMS may also be measuring the total power draw or possibly the internal resistance of the module. 3.45V indicates that roughly 12Wh (22%) of the capacity is not being used. Have you tried charging the car for only a short time (1 hour) and seeing if driving it again would trigger turtle at a lower voltage?
What this means is that the 30 kWh BMS will likely not over-discharge the 40 kWh cells, so you are safe there. However, you're not getting the full possible range.
When you charge the 40 kWh modules with the 30 kWh BMS to 100%, what does Leafspy show when the charge to 100% is done? What is the min/avg/max voltage of the cells?
Good idea, I’ll try the one hour charge and drive.
Charging of the 40kWh modules with 30kWh BMS stops at 4.110/4.115/4.120 Volts. I think there might be unused capacity as well.
If I ‘ll never discharge below 22%, my battery should be very happy.
Regarding the internal resistance, it should be really different, as the Hx value with my healthy 40kWh modules is 74 according to the 30kWh BMS.