On-line Hearing Aid Museum

Hearing Aids of all types—Ear Trumpets, Carbon Hearing Aids, Vacuum Tube Hearing Aids, Transistor Hearing Aids, Body Hearing Aids, Eyeglass Hearing Aids and much more!

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General Info

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Click on the "General Information" button (top button above) for an overview and general information on this category of hearing aid.

Hearing Aid Batteries

Mallory RM-4 Mercury Hearing Aid "A" Battery

The RM-4 1.4 volt mercury hearing aid "A" battery was used in vacuum tube hearing aids in the 1940s and 1950s. The RM series of batteries was manufactured by Mallory.

The RM-4 mercury battery was the largest "button" battery made and weighed about 1½ oz. It measured ⅝" high by 1 3/16" in diameter.

Mercury batteries are no longer sold today because of the large quantities of mercury in them and the consequent environmental concerns.

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Bottom view of the Mallory RM-4 mercury hearing aid battery.

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Side view of the Mallory RM-4 mercury hearing aid battery.

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The picture at the right shows the three sizes of the RM mercury battery series. From left to right they are the RM-4, RM-3 and RM-1. There doesn’t appear to have been an RM-2 battery used in hearing aids.

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