Duracell No. 675 Zinc-Air Hearing Aid Battery
The Duracell No. 675 1.4 volt zinc-air hearing aid battery is pictured
at the right.
The No. 675 hearing aid battery came out somewhere around 1957 with
the advent of behind-the-ear (BTE) and eyeglass hearing aids.
No. 675 batteries are on the way out now (2009) as most new hearing
aids use smaller batteries such as Nos. 13, 312 and 10.
The No. 675 zinc-air battery battery measured 0.455" in diameter
by 0.205" thick. |
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The bottom (positive end) of the No. 675 zinc-air battery. Note the four
little air holes
(yellow dots at the ends of the "+" arms). A blue tab seals these holes keeping the air
out until the battery is ready to be used. By doing this, zinc-air
batteries have a long shelf life. When the tab is removed, the battery
starts "working" and even if you don't use it, in a few weeks it will be
dead.
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The first No. 675 batteries were mercury batteries (shown right) and later silver-oxide batteries.
High silver prices
in the 1980s sounded the death-knell of the silver oxide battery,
coupled with the fact that the more modern silicon transistors could run
on the lower voltages supplied by the zinc-air batteries.
In 1977, in order to keep toxic mercury out of the environment,
zinc-air batteries began replacing the existing mercury batteries. Mercury batteries are no longer sold today because of their
high mercury content.
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Except for the above picture and the one to the right, the batteries shown here are
all zinc-air
batteries.
Mercury and silver-oxide batteries looked the same as modern zinc-air
batteries except that the
zinc-air batteries have 4
tiny holes on the back that let the air in. (See the difference between
a mercury battery (left) and zinc-air battery (right).
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The Duracell zinc-air batteries typically came either 4 or 8
batteries to a pack. This is a 4-pack. Notice that No. 675 batteries
have blue tabs on them, making it easy to identify them.
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Top view of the No. 675 zinc-air hearing aid battery showing its size.
(Each mark on the ruler is 1/16".) |
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Relative size of the five sizes of zinc-air hearing aid batteries as
seen from the top. From left to right they are battery numbers 5, 10,
312, 13 and 675. |
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A three-quarter view of the 5 zinc-air hearing aid batteries showing
their relative size. From left to right they are battery numbers 5, 10,
312, 13 and 675. |
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Side view of the 5 zinc-air hearing aid batteries showing their
differences in height. From left to right they are battery numbers 5,
10, 312, 13 and 675. |
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Bottom view of the 5 sizes of zinc-air batteries showing the
color-coded tabs that seal the air holes before they are used. From left
to right they are battery numbers 5 (red tab), 10 (yellow tab), 312
(brown tab), 13 (orange tab) and 675 (blue tab).
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