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:
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.