Ever Ready battery, 1957.
© Science Museum / Science & Society Picture Library
Dummy model of a combined low tension and high tension battery produced by the Ever Ready Company, cut away to show construction. Batteries like this were used to power portable radios in the 1950s. Before transistors came into use, portable radios were bulky objects. They had several valves that needed a low voltage for the valve heaters, and a high voltage, typically about 120 volts, for the other connections to the valves.