The lithium battery charging curve illustrates how the battery’s voltage and current change during the charging process. Typically, it consists of several distinct phases: Constant Current (CC) Phase: In this initial phase, the charger applies a constant current to the battery until it reaches a predetermined voltage threshold.
The working voltage of the battery is used as the ordinate, discharge time, or capacity, or state of charge (SOC), or discharge depth (DOD) as the abscissa, and the curve drawn is called the discharge curve. To understand the discharge characteristic curve of a battery, we first need to understand the voltage of the battery in principle.
This charge curve of a Lithium-ion cell plots various parameters such as voltage, charging time, charging current and charged capacity. When the cells are assembled as a battery pack for an application, they must be charged using a constant current and constant voltage (CC-CV) method.
The Open Circuit Voltage (OCV) is a fundamental parameter of the cell. The OCV of a battery cell is the potential difference between the positive and negative terminals when no current flows and the cell is at rest. The typical lithium battery OCV curves versus SoC then looks like: Some points to consider:
Constant current discharge is the discharge of the same discharge current, but the battery voltage continues to drop, so the power continues to drop. Figure 5 is the voltage and current curve of the constant current discharge of lithium-ion batteries.
The lithium battery discharge curve is a curve in which the capacity of a lithium battery changes with the change of the discharge current at different discharge rates. Specifically, its discharge curve shows a gradually declining characteristic when a lithium battery is operated at a lower discharge rate (such as C/2, C/3, C/5, C/10, etc.).