Zinc-air Cell Corrosion

For reasons that, alas, have little to do with normal age-related hearing degeneration, I’ve been wearing Etymōtic (that should be a long o symbol) MP-915 High-definition Electronic Earplugs (aka, Martian Ear Beetles) when I need a 6 dB boost for normal conversations. The key advantage: a price 10 dB under full-throttle hearing aids.

Anyhow, each one runs for about two weeks on a 312 zinc-air primary cell, so I picked up a batch from the usual eBay vendor. These were short-dated, which let me figure out how long after the rated shelf life they’d be good for, so I know what’s the largest batch I should buy.

One cell arrived with its air vent seal dislodged:

Corroded zinc-air cell
Corroded zinc-air cell

The cell in the middle is used, with several scratches from the contact point inside the earplug. The cell on the right has a good seal.

Assuming a good seal, the cells seem to work about as well as the long-dated fresh cells included with the earplugs.

Although I found several datasheets (Duracell Energizer Rayovac), there seems to be no way to relate the actual cell you purchase to any particular datasheet; the part numbers do not correspond to anything on the package and the nomenclature varies wildly both between manufacturers and within product lines.

2 thoughts on “Zinc-air Cell Corrosion

  1. It is indeed a long o symbol (at least here on my browser) but it’s supposed to come before the m, not after. :)

    (Have you heard the joke about the old riveter’s convention? WHAT DID YOU SAY? HAVE YOU HEARD THE JOKE ABOUT THE OLD RIVETER’S CONVENTION?)

    1. it’s supposed to come before the m, not after. :)


      I think that’s a leftover from my blundering around with Unicode non-spacing marks in my attempts to find the long-o symbol. Turns out that you can put an overbar atop nearly anything you like, both before and after the non-spacing character, which makes editing the outcome rather tricky.

      For what it’s worth, the overbar is called a macron and the Unicode symbol for a long lowercase o is U+014D

Comments are closed.