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

Mallory RM-4 Mercury Hearing Aid "A" Battery

The Mallory RM-4 1.4 volt mercury hearing aid "A" battery was manufactured by the Mallory Battery Co in the USA.  It was used in vacuum tube hearing aids in the late 1940s and early 1950s.

The RM-4 mercury battery was the largest "button" battery made for use in hearing aids. 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 Mallory RM-4 mercury hearing aid battery showing the manufacturer and model number.

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

The bottom was the positive terminal of the battery.

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

 

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The Mallory RM-4 mercury hearing aid battery was the largest button battery used in hearing aids. Here you can see it contrasted with the smallest hearing aid battery used—the tiny No. 5 battery (right).

 

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Button batteries got smaller as the years went by. This picture shows the progression of button batteries from the largest to the smallest as seen from the side. They are from the left, the RM-4, RM-3, RM-1, 625. 675, 13, 312, 10 and 5. This is by no means all the button batteries made—just a sampling of the various sizes.

 

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The progression of button batteries from the largest to the smallest as seen from the top. They are from the left, the RM-4, RM-3, RM-1, 625. 675, 13, 312, 10 and 5.

 

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The picture at the right shows the three sizes of the RM series of mercury batteries. 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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