1. 0.5C (constant current charge/discharge)
Definition: C represents the battery charge/discharge rate. 0.5C means the charge/discharge current is half of the battery's rated capacity.
Example: If the battery capacity is 100 Ah, then 0.5C corresponds to a current of 50 A.
Features:
Constant current: The current remains constant during charging and discharging (e.g., constant current charging to the cutoff voltage followed by constant voltage).
Voltage variation: The voltage plateau is relatively stable during discharge (e.g., around 3.2V for LiFePO4 batteries).
Capacity performance: At low rates (e.g., 0.5C), capacity decay is small (e.g., capacity retention can reach over 95% at 0.5C discharge), but at high rates (e.g., 2C), capacity decreases significantly due to increased polarization (e.g., down to 86.5%).
Application scenarios: laboratory testing, capacity sorting, and cycle life assessment.
2. 0.5P (constant power charge/discharge)
Definition: P represents the rated power of the battery (unit: W). 0.5P means that the charging and discharging power is half of the rated power. Example: If the rated power of the battery is 12.8 W (1.0P), then 0.5P corresponds to a power of 6.4 W.
Features:
Constant power: The power remains constant during charging and discharging, while the current is adjusted in real time according to voltage fluctuations (e.g., when the voltage drops during discharge, the current needs to be increased to maintain constant power).
Voltage variation: The discharge voltage plateau fluctuates significantly (due to dynamic current adjustment).
Capacity performance: Capacity decay is more significant at high rates (e.g., capacity retention is only 87.5% at 2.0P discharge, compared to 94.28% at constant current 2C), and energy efficiency is lower than in constant current mode.
Application scenarios: power grid dispatching and actual operation of energy storage power stations.
