Been using hearing aids for several weeks that run on size 312 zinc-air button batteries. They last about a week then go dead along a very sharp discharge curve.
I measured some used ones in a battery tester and their voltage has returned to normal- around 1.45v. Not sure how long they'd last if tried them back in the hearing aids- or it's a good idea to put them in there.
I might have been reading about hearing aids two or three days ago -- I do read about them at times, but maybe it was something else this time
-- and one of the things it said was to not rely on battery testers.
But I doubt they will last more than a little bit Cars start pretty reliably these days, but when they didn't, if you ran down the battery trying to start it, you could wait a few minutes, 10 minutes, and there would be enough juice in it to try once or twice more. The chemical reaction had time to catch up and provide more ions. But those extra tries were a small percentage of what a good, fully charged battery had in it.
OTOH what have you go to lose? I'm sure they're not going to catch on fire or drip or anything like that.
Not in hearing aids, but I have recharged button batteries by holding them on top of a flashlight battery completing the circuit with my finger. Like you say though, it is a hit or miss kind of thing.
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