当没有外部负载（外电路断开）时，两极之间的电压。两极之间没有外部电流，可能有内部电流存在。

Open-circuit voltage (abbreviated as OCV or V_OC ) is the difference of electrical potential between two terminals of a device when disconnected from any circuit. There is no external load connected. No external electric current flows between the terminals. It is sometimes given the symbol V_oc. In network analysis this voltage is also known as the Thévenin voltage.