While waiting for my audiologist, I picked up some brochures to read. After 5 years of wearing a hearing aid, I discovered that zinc batteries, which I use, need air to activate and provide power. To quote from the brochure, "Once you remove the tab, you should let the battery sit for one minute before installing it in your hearing aid. This 'rest' time, allows air to reach the materials inside the battery and activate them. Batteries that are not given this time to activate may appear dead or under-powered if they are inserted immediately in the hearing aid. If this happens, remove the battery and allow it to sit for one minute before reinstalling in your hearing aids." I checked on the pkg the batteries came in and, lo and behold, on the back in small print, "For best results, let a new battery sit un-tabbed for one minute before inserting into device. I've been doing it incorrectly for 5 years. Oh, my!
My audiologist told me that - but she told me to leave them sitting without the tab (before closing the aid) for a couple of minutes. But believe she didn't share this key information for about 3 months.