Was just reading that disposable batteries can be expected to last for a shorter amount of time if used at higher altitude because the oxygen concentration is low. This shouldn’t be an issue with lithium ion batteries as they don’t rely on oxygen like zinc-air does. However I could find no specifics on how much altitude might impact zinc-air batteries. Anybody spent any significant time at high altitude (say 2500 meters or 8000 feet or higher) with zinc air batteries in their hearing aids or have any data on this. On the flip side high altitude is often accompanied by colder temperatures which I’ve heard that zinc-air batteries perform significantly better than lithium ion batteries although I haven’t found any specifics on this although low temps do impact both zinc-air and lithium ion battery performance. I’m hoping we can limit discussion to impact of altitude on zinc-air batteries and not rehash all the pluses and minuses but people will do what they do.
I wouldn’t recommend Lithium batteries in an adversely cold climate @MDB, probably more so at altitude, most if not all rechargeable aids have a Battery Management System (BMS) they have an active safety feature, which basically means the aids switch the batteries off, anything below 25 degrees Fahrenheit or around -3.8 Centigrade, the BMS will most likely kick in, and shut the aids down, they will not reboot until placed back in the the charger dock… A pain in the proverbial, if you haven’t got a charger handy! In cold weather, it is a known issue with Lithium, although very few hearing aid manufacturers divulge this information, if ever? This happened twice to me out in the sticks, with rechargeable aids in adversely cold weather… Battery runtimes will also be affected in the cold, they use more energy, this is why Lithium battery banks are sometimes heated, in colder climates, it is advisable not to charge Lithium batteries in subzero temperatures, you can damage a battery in these conditions… Cheers Kev 
These people have experience with hearing aids at high altitude:
Good thought. Audiologists living in high altitude cities like Quito, La Paz, El Alto and others should have some real experience.
I live at over 6000 ft. and have KS9 aids. I usually get 3 days from the 312 costco batteries. I do stream a fair bit. On a pack trip over 8000 ft. with no streaming they lasted 3 days without streaming. But in for 24 hours on so I could hear the bears.
In the cold I have had less than a day old batteries shut down. They come back once warmed.
FYI
Went to costco last week and had my aids cleaned. They saw I needed a new receiver. They replaced both with the new version without cost. Pretty good service if you ask me.
Thanks. I live at about 1300 feet and get 4-5 days with my KS9 aids. Sounds like in the 6-8 thousand foot range it makes a difference, but not huge.
Rayovac’s EU site has a qualitative article on zinc-air hearing aid battery performance:
I did find something interesting - they say that zinc-air batteries should not go in a hearing aid drier.
Interesting.
When I wore zinc air battery aids they went into the Dry & Store dryer every night.
No explosions or fires.
Must have been lucky??
It’s better to be lucky than good.
My take is it just shortens the useful life of the battery if it gets too dry. There was also a comment about hot/dry conditions shortening the life.
Do any of the dryer instructions also say this? Is it heat or dry air they could be an issue?
I have no idea. I live in the SW desert area of the US and here the indoor air is typically further dried by HVAC systems during a lot of the year. I’ve seen 3% RH in a lab at work with an accurate and precise temperature/RH instrument 
, None of the hearing aid providers I have dealt with in Tucson have ever suggested a drier so I’ve never used one (or apparently needed one). I would tend to go with the suggestions of the manufacturer of the batteries in question rather than the vendors of hearing aid driers. At this point, I’ve switched to aids with rechargeable batteries (Oticon Real 1) and they have worked fine for me. I guess one specification that is a bit worrying for me is the maximum operating temperature (104 F or 40 C) - I have exceeded that on numerous occasions commuting home on a bicycle in the long hot summers but with no noted issues.
I wonder if warranty claims for hearing aids are lower from those who live in dryer climates.
Operating temperature doesn’t mean they will necessarily get damaged outside that range. They could have problems operating. Desert temps plus direct sunlight might be a problem for some of the materials. Someone with an old pair could see what sort of heat and solar exposure a hearing aid can take.