Button cell batteries, also known as coin cell batteries, come in various sizes and chemistries, which can result in different voltage ratings. However, one of the most common types is the alkaline button cell battery, often labeled as LR44 or AG13. These batteries typically have a nominal voltage of 1.5 volts.
Other button cell batteries, like those using silver oxide or lithium chemistries, can have different voltage ratings. For instance, silver oxide button cells usually have a nominal voltage of 1.55 volts, while lithium button cells can range from 3 volts for a CR2032 to higher voltages for specialized applications.
Always check the battery label or specifications to determine the exact voltage rating for the specific button cell battery you are using, as there can be variations based on chemistry and manufacturer.