Battery Glossary – Nominal Voltage

Nominal Voltage – what the voltage of any particular battery is called (not necessarily exactly what it is).

Most batteries actually have a voltage slightly higher than what you see on the label. A 12 volt lead acid battery is usually, in reality, a 12.6 or 12.7 volt battery. Manufacturers make batteries this way because producing units of exactly X volts is actually surprisingly hard. Voltages vary even between batches coming off the same production line. As such it is safer to have a margin of error so they cannot be accused of marketing a 12 volt battery while selling an 11.7 volt unit.

The nominal voltage is what they market the battery as and what it is generally referred to. As an example using sealed lead acid batteries –  a SLA battery that says 6 volts on the label has a nominal voltage of 6 even it its actual voltage when fully charged is 6.23. This ‘real’ voltage is known as the charge voltage – what the battery should be charged to, not what is on the label!

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