Zinc Air battery voltage

[valvekits]

I measured a packet of new zinc air 1.4V hearing aid batteries and they all measured between 1.21V to 1.32V. I then re-checked the calibration of my Fluke meter with my 1.234V tester and this was okay.
So what should a new 1.4V battery measure, I haven't come across these before?

Eddie

[Michael Watterson]

They have to be activated by pulling off a tab etc. Then they wear out even if not used.
Energiser Say:

General Characteristics:
◦ Highest capacity-to-volume ratio for miniature batteries.
◦ Relatively flat discharge curve.
◦ Essentially constant internal resistance.
◦ Activated by removing covering (adhesive backed tab) from air access hole.
◦ Most effective in applications that consume battery capacity in a few weeks.
◦ Must have access to air (oxygen) to operate.
◦ Nominal voltage of 1.4
◦ Excellent service maintenance prior to tab removal.
◦ Available in common hearing aid battery sizes.
◦ Contains no added mercury.

They are 1.4V, no load immediately after activating. They quickly drop to about 1.28V (depending on temperature moisture and impurities probably)

I guess now these cells will be flat in 2 weeks now they are opened?

But it is VERY flat. Alkaline are about 1.6V fresh, no load and drop quickly to 1.5V, then average about 1.4, dropping gradually to 1.2 then rapidly to 0.9V end point.
Zinc Carbon Alkaline are almost 1.7V no load if very fresh and drop quickly to 1.4V, then average about 1.3, dropping gradually to 1.25 then rapidly to 0.9V end point.

Mercury and Silver Oxide are very flat discharge. Zinc Air are really a replacement for Mercury (toxic) and Silver Oxide (expensive!).

Most batteries it's only a "customary" nominal value that is quoted. 12V car batteries used to be 13.8 and now close to 14.2 V in a car running. The 6.3 is half a "12V" Lead Acid NOT on charge. Hence some US 6.3V valves are "7" series rather than "6" series as rated up to 7V for 6V Lead Acid supplies.

[valvekits]

Thanks for that information Michael, it turns out I was being a bit too clever for my own good.
I removed them from the packet to measure them but I didn't pull off the tab. I had incorrectly assumed that the tab was there to isolate the battery in case it was fitted to a new product. For example my new TV remote control had the batteries fitted but there was a tab isolating them from the holder.
The 1.32V battery was activated though, it was about an hour old when I measured that.

Eddie

[Refugee]

Zinc air batteries are confusing things.
There was a story in the 1970s about them being fitted to water proof watches
The watches all stopped proving that they really were waterproof

[Michael Watterson]

That's sounds good Eddie and a relief you didn't open them all!

I have a relative with an implant who needs them regularly. She thought they expensive till I showed her the Silver Oxide ones! The Silver Oxide are ideal to replace mercury in Microphones, bombs, missiles, key fobs and other long life or intermittent devices. Hearing aids are used often 16 hrs+ a day so use up the battery faster than the natural discharge.