A battery eliminator is a device powered by an electrical source other than a battery, which then converts the source to a suitable DC voltage that may be used by a second device designed to be powered by batteries.
A battery eliminator eliminates the need to replace batteries but may remove the advantage of portability. A battery eliminator is also effective in replacing obsolete battery designs.
Some examples of battery eliminators:
Early commercial battery eliminators were produced by Edward S. Rogers, Sr. company in 1925, as a complement to his line of "batteryless" radio receivers. Another early producer of battery eliminators was the Galvin Manufacturing Corporation (later known as Motorola) which was opened on September 25, 1928 by Paul Galvin and his brother Joseph E. Galvin, to build battery eliminators for radio receivers installed in automobiles.
While it might seem surprising to use such a device in a car to power a radio, the first car radio receivers were based on vacuum tube technology which required two or three different voltages to function:
Batteries designed for these portable vacuum tube receivers were a combination of several different battery types and sizes, combined in a single package and intended to slowly wear out at about the same rate. The battery typically connected to the radio via a specially shaped four- or five-pin connector, keyed so that the plug must be inserted correctly.
A battery eliminator would take the typical 6-volt or 12-volt DC power from a car battery and transform it into the required LT and HT needed to power the vacuum tubes in a car radio.
Without a battery eliminator, it was necessary to occasionally replace the battery pack in the vacuum-tube car radio.