On a 2011, the CVLI (Cell Voltage Loss Inspection) test requires that the battery be at 3.712v or less to work. That corresponds to approximately a 7% SOC for a 24 kWh battery pack. See here: https://pushevs.com/2018/01/29/2018-nissan-leaf-battery-real-specs/ (The graph is near the bottom of the post, above the comments. Do not look at the top graph--that's for a different chemistry).
I don't know what % is required for the 2018, but if the dealer didn't drain the car to approximately a 7% SOC, the CVLI test cannot be performed. If they just looked at your car and said "It's not throwing any codes", that's not sufficient. The car's BMS (battery management system) may throw a code at higher voltage levels, but without a CVLI test, you cannot rule out a mismatched or bad cell. A full CVLI must be performed to know for sure that cells are good and balanced. You know, via LeafSpy, that yours are not. The trick is getting their tools to indicate a code so they stop arguing that your car is OK.
From the service manual:
P33E6 CELL VOLTAGE DEVIATION DIAG
1.CHECK SELF-DIAGNOSIS RESULTS OF LI-ION BATTERY CONTROLLER
2.CHECK FREEZE FRAME DATA (FFD)
3.PERFORM CELL VOLTAGE LOSS INSPECTION
4.DISCHARGE OF LI-ION BATTERY
(essentially turn on the high beams, heater to full, AC to full, defrost, etc)
Check “DATA MONITOR” and let the Li-ion battery discharge until the “MINIMUM CELL VOLTAGE”
reaches 3,712 mV or less.[/b]
5.CHECK CELL OF VOLTAGE LOSS
I would also ask if they performed the module charge balance, as required in the service manual, when replacing your cells. That specifically says to balance the charge voltage of the cells with a module charge balancer.
From the service manual:
MODULE CHARGE BALANCE
1.CHECK ADJUSTMENT VOLTAGE VALUE
2.CHECK MODULE VOLTAGE
3.DISCAHRGE OF MODULE VOLTAGE (spelling intentional--it's wrong in the service manual)
4.ADJUST VOLTAGE WITH A MODULE CHARGE BALANCER
5.CHECK MODULE VOLTAGE
6.CHECK CELL VOLTAGE
I don't know what % is required for the 2018, but if the dealer didn't drain the car to approximately a 7% SOC, the CVLI test cannot be performed. If they just looked at your car and said "It's not throwing any codes", that's not sufficient. The car's BMS (battery management system) may throw a code at higher voltage levels, but without a CVLI test, you cannot rule out a mismatched or bad cell. A full CVLI must be performed to know for sure that cells are good and balanced. You know, via LeafSpy, that yours are not. The trick is getting their tools to indicate a code so they stop arguing that your car is OK.
From the service manual:
P33E6 CELL VOLTAGE DEVIATION DIAG
1.CHECK SELF-DIAGNOSIS RESULTS OF LI-ION BATTERY CONTROLLER
2.CHECK FREEZE FRAME DATA (FFD)
3.PERFORM CELL VOLTAGE LOSS INSPECTION
4.DISCHARGE OF LI-ION BATTERY
(essentially turn on the high beams, heater to full, AC to full, defrost, etc)
Check “DATA MONITOR” and let the Li-ion battery discharge until the “MINIMUM CELL VOLTAGE”
reaches 3,712 mV or less.[/b]
5.CHECK CELL OF VOLTAGE LOSS
I would also ask if they performed the module charge balance, as required in the service manual, when replacing your cells. That specifically says to balance the charge voltage of the cells with a module charge balancer.
From the service manual:
MODULE CHARGE BALANCE
1.CHECK ADJUSTMENT VOLTAGE VALUE
2.CHECK MODULE VOLTAGE
3.DISCAHRGE OF MODULE VOLTAGE (spelling intentional--it's wrong in the service manual)
4.ADJUST VOLTAGE WITH A MODULE CHARGE BALANCER
5.CHECK MODULE VOLTAGE
6.CHECK CELL VOLTAGE