Charging Comparison: Model 3 SR – LFP vs. NCM

Vehicle and battery information

NCM Model: 2020 / 118,030 km, SOH 83.1%

LFP Model: 2022 / 121,104 km, SOH 93%

LFP (left), NCM (right):

Aspect	LFP Batteries	NCM Batteries
Voltage Curve	Flat (minimal voltage plateau)	Steep (clear voltage plateau)
CV Phase Length	Short or negligible	Pronounced and extended
Charging Implications	Faster final charge, reduced stress	Longer final charge, higher stress
SOC Calibration (OCV-based)	Difficult; requires periodic full cycles	Straightforward; frequent calibration

LFP Batteries:

• Charging Behavior:

  
  

  LFP batteries exhibit a very short or negligible constant voltage (CV) phase due to their flat voltage curve across most of the SOC range. This means the battery voltage gradually rises without a pronounced plateau.

• Implications:

  
  

  The short CV phase results in faster final charging phases and reduces stress at high states of charge (SOC), enhancing battery safety and longevity.

• Calibration Considerations (OCV-based):

  
  

  Because of the flat voltage curve and minimal CV phase, calibrating the SOC using open-circuit voltage (OCV) measurements is challenging. The battery management system (BMS) cannot rely heavily on voltage readings alone. Instead, periodic full-cycle calibrations (full charges and deep discharges) are necessary to accurately estimate SOC and battery health.

NCM Batteries:

• Charging Behavior:

  
  

  NCM batteries feature a distinct and prolonged constant voltage phase, characterized by a clearly defined voltage plateau near full charge, where voltage remains stable while charging current gradually decreases.

• Implications:

  
  

  The extended CV phase optimizes battery capacity utilization, ensuring the battery reaches its maximum charge potential. However, this prolonged stage increases charging time and can lead to higher thermal stress at elevated SOC levels, potentially affecting battery longevity.

• Calibration Considerations (OCV-based):

  
  

  The pronounced CV phase and clear voltage plateau provide ideal conditions for accurate and frequent SOC calibration using OCV. Thus, NCM BMS strategies can consistently recalibrate SOC and reliably monitor battery health through precise voltage measurements.