The voltage characteristics of lithium batteries are a core indicator for evaluating their performance and safety, directly affecting their charge/discharge efficiency, cycle life, and application safety. This article mainly introduces the open-circuit voltage (OCV) of lithium batteries.
Open Circuit Voltage (OCV)
Open circuit voltage (OCV) refers to the voltage value when a circuit is open, with no load connected between the terminals of a power source or component.
It reflects the electromotive force of the power source or the inherent voltage characteristic of a component when no current flows through it. For example, the open circuit voltage of a battery is usually close to its nominal voltage, while the open circuit voltage of a capacitor is consistent with its voltage after charging. Open circuit voltage is the potential difference between the positive and negative electrodes of a lithium battery in its non-operating state (no current flowing), determined by the chemical equilibrium potential difference between the positive and negative electrode materials. OCV is an important basis for evaluating the state of charge (SOC) of a battery, and its value shows a regular curve as the remaining battery capacity changes.
The OCV (Optical Capacity Value) of lithium batteries varies significantly depending on the material system:
NMC/NCA: Fully charged OCV is approximately 4.2V, dropping to 3.6-3.7V when discharged to 50% SOC;
Lithium iron phosphate Battery: Fully charged OCV is approximately 3.65V, with a stable plateau voltage around 3.2V;
Lithium Manganate Battery: OCV range is similar to ternary batteries, but the voltage plateau is slightly lower.
In practical applications, OCV should be measured after the battery has been left to stand for at least 2 hours to avoid numerical deviations caused by polarization effects after charging and discharging. For long-term storage, it is recommended to maintain a 70% SOC (corresponding to an OCV of approximately 3.8V) for lithium batteries to minimize capacity decay.
