[MrFixr55]

Air Cells were 2.5V, non-rechargeable disposable batteries.  Since the tubes were designed for 2V rechargeable lead acid batteries, a 3 V Battery or a pair of 2 #6 dry cells put out too much voltage for these 2V tubes when new, so a variable or tapped resistor or ballast tubes had to be used.  Output voltage over the life of a 3V battery was not consistent over its life.  Eveready claimed that the air cel Model a600 did maintain its 2.5V over its life (1,000 -1,500 hours depending on tube count and total filament current.

A brochure on radio batteries is attached below:

Everready Air Cell A Battery Layerbuilt B Battery1937-2.pdf Size: 2.38 MB  Downloads: 405

Below is a link to an Antique Radio Forum thread. The author, Robert Lozier made 3 replicas of the Eveready A600 Air Cell and is making replicas of the Eveready 45V battery for his collection. An amazing build!
https://antiqueradios.com/forums/viewtop...?p=1754680