Nominal voltage

A battery’s voltage is not one fixed figure. It starts high after a charge and slides down as the pack empties.

Makers pick one middle figure to print on the label. For lithium-ion that is about 3.6 volts per cell, so four cells in a chain are sold as a 14.4-volt pack.

Most gear stops at roughly 3.0 volts per cell, the point where about 95 percent of the energy has been used. Pushing further damages the cell, so the electronics cut it off.