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:
9v mains power supply, size and shape of a PP9 battery, intended to replace the battery in portable radios. 1960s
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:
LT, typically 4 or 6.3 volts at high current to power the filaments
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.
Principle of working
Although a battery eliminator works without a battery, it has to be charged by some device, preferably a battery. The battery eliminator can also be used to charge the rechargeable automobile batteries. The cathode of a battery is attached to anode of the eliminator & battery anode to the eliminator cathode, in case of battery charging.
In case of providing the eliminator with energy, battery anode is connected to eliminator anode & battery cathode to eliminator cathode. This charges the eliminator, which can be used in place of the battery to power some external device. The connections are same as that in case of a battery.