Hearing Aid Battery Tester: How to Test a Zinc-Air Cell

Why a multimeter can mislead you on zinc-air cells, and the two checks that actually work.

Hearing aid batteries are zinc-air cells: they only start discharging when air reaches them. A fresh sealed cell can read below 0.5V because it is still dormant — that is normal, not a dead battery.

Tester types: simple voltage testers read 1.4–1.5V on an activated cell. Better testers add a small load — a good size-10 cell holds ~1.35V under load while a worn one collapses fast. Some dispensers test on insertion and pop out weak cells, which works for the last 20% of life where failures actually happen.

The two checks that matter: (1) is the tab off? (2) is the size right? Test the NEW cell with the tab removed; compare with the old one after 1 minute of activation. A cell below 1.2V under load is finished.

We test each zinc-air batch at 20±2°C per IEC methods before packing into airtight strips — production data per batch is available with private-label orders.