Constancy of audio power from battery (hearing aid)

[epenguin]

I have recently had to adopt hearing aids. I shall soon be taking them back to supplier for adjustment/repair/replacement of one of them. What seems to happen is that with new (lithium) battery it gives sign of life and some amplification into the right ear, but after a few hours there is no more signal - what I hear is the same whether I wear it or not. Whereas the left aid, which must be set for a higher amplification (for less good ear) works for the 4 or 5 days asit is expected to. So it is sounding to me as if the right one is delivering just enough amplified signal to hear when battery is new, but as it is used the power soon decreases to inaudible.

It slightly surprises me. Obviously a battery can never deliver constant power for ever. But I would have thought it a fairly trivial, or at least standard and solved engineering problem to deliver a nearly constant power for a few days.
I will work this out that the supplying clinic, but would like to have some comment whether my engineering conjecture Is reasonable.

 

[anorlunda]

Are you sure that they are lithium batteries? I thought that zinc-air batteries were more common in hearing aids.

The zinc-air battery has the strange characteristic that once exposed to air, it is used up in a week or so regardless of the actual power delivered. That is why they ship with a sticker sealing the air hole.

 

[epenguin]

Yes you must be right, I don't know how I got the idea they were lithium, I haven't found the chemical nature on the manufacturer's site so far except they are proud that they are mercury-free, but they are as you describe with a sticker (you are reccomended to wait a minute after removing it for them to 'breathe' before putting them into the hearing device). The material does boast a bit of their 'high quality performance throughout the life of the battery, delivering power on demand, no matter what the hearing situation' and 'Consistent Battery Life'.

 

[jim hardy]

Sounds like one of your hearing aids draws excessive current.
Ask the supplier to check the one that's failing. It takes $150 worth of test equipment to make that measurement unless you're real handy with tiny handiwork and can make an adapter to get your meter in series with the battery.
Meter:
https://www.lightningenterprises.com/bdm.html
"Battery Pill" to go with it
https://www.lightningenterprises.com/bp1.html

Per these guys 1 or 2 milliamps is expected.
https://www.audiologyonline.com/articles/battery-life-technical-issues-and-1210

Perusing those links will arm you with some knowledge that'll hopefully disincline the supplier from just dismissing you .. Press him for a current measurement on both hearing aids.

 

[CWatters]

I have a relative with hearing aids and they sometimes suffer feedback that makes them whistle. I wonder if your right hand one is oscillating causing it to draw more current? However I think you would notice this unless it was oscillating at a frequency above your hearing range?

 

[anorlunda]

enough amplified signal to hear when battery is new, but as it is used the power soon decreases to inaudible.

My hearing aids maintain full volume until the battery is dead. They also give a beep-beep-beep warning for low battery, then cut out. You need technical help and diagnosis. I think the hearing aid suppler is the best party to provide that help.

Are you in a warm climate? Drops of sweat in the ear can significantly deteriorate hearing aid performance, and your left and right ears don't necessarily sweat alike.

Do you put the hearing aids in a dryer overnight? Accumulation of moisture also robs the aids of battery life. That too can be unbalanced left/right.

 

[epenguin]

Thank you all. I'm seeing the audio clinic tomorrow and it is good to without being the expert be able to know something about it.

RW, I didn't imagine the R one is drawing too much current, it is never loud and mostly after a short initial period at most, makes no difference whether I wear it or not.
It's the left one that is more likely to whistle, it hisses quite a lot when out in the street. And I pick up conversations at quite some distance!
With the right one working not at all it seemed a price worth paying to hear something.
I think the left one was adjusted for higher amplification because that is my worse functioning ear.
I was warned that at first things would sound strange. With normal hearing do not hear sounds proportionately to their real physical loudness because the brain over time modulates them by significance, but when you get new hearing aids the sounds are strange until the brain adjusts, and you hear loud your shoes when walking, paper rustling, water flowing etc.

 

[anorlunda]

I'm seeing the audio clinic tomorrow

So, what did the audio clinic say?

 

[epenguin]

So, what did the audio clinic say?

That it was rusted and she had never seen anything like it! I guess I must have left them on one day when washing or in the shower, though I cannot remember any occasion.

I admit I had never heard of these Zn air batteries before, and the information in the thread and links is interesting.

 

[anorlunda]

Aha.

Just as well we didn't spend too much time thinking up electrical explanations.

You should look into a dryer/dehumidifier. That might rescue it even if you did wear it in the shower. I use this.