Hugh Hetherington Hearing Aid Museum
Hugh Hetherington Hearing Aid Museum

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


Hearing Aid Batteries

No. 4 Mercury Hearing Aid "A" Battery

The No. 4 1.4 volt mercury hearing aid "A" battery was made by an unnamed manufacturer. It was used in vacuum tube hearing aids in the late 1940s and early 1950s. The No. 4 battery was the same size as the RM-4 battery manufactured by Mallory.

The No. 4 mercury battery (and the RM-4) were the largest "button" batteries made. It weighed 1˝ oz. and 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 No. 4 mercury hearing aid battery showing the model number (4) and the patent number. The bottom was the positive terminal (+) of the battery.

The small hole at the right was a pressure-relief valve that opened to relieve excess pressure that could be built up when the battery was being used.

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Side view of the No. 4 mercury hearing aid battery.

Learn more about this size of battery under the Mallory RM-4.



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