What is Nominal Voltage

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7/18/20231 min read

The nominal voltage of a battery refers to an approximate value used to represent or identify the appropriate voltage of the battery. It is also known as the rated voltage, and it helps differentiate different types of batteries.

For example, the open circuit voltage of a lead-acid battery is close to 2.1V, with a nominal voltage of 2.0V. Zinc-manganese dry batteries have a nominal voltage of 1.5V, while nickel-cadmium and nickel-metal hydride batteries have a nominal voltage of 1.2V.

Lithium-ion batteries have a nominal voltage of 3.7V, and lithium iron phosphate batteries have a nominal voltage of 3.2V. The actual voltage of a battery varies based on its capacity. For commonly used lithium-ion batteries, such as 18650, 26650, and 14500, when fully charged, the voltage is approximately 4.2V or 4.3V, and when fully discharged, it drops to around 3.0V.

The discharge curve of lithium-ion batteries follows a parabolic shape (including other types of batteries), and the voltage changes rapidly when it drops from 4.3V to 3.7V and from 3.7V to 3.0V. Only in the range close to 3.7V, the discharge time is the longest, accounting for almost three-quarters of the total time.

That’s why it is designated as 3.7V.

Therefore, when designing battery packs and calculating voltage, we use the nominal voltage as the reference.